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3202 lines
75 KiB
3202 lines
75 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* Copyright (C) 2015-2017 Josh Poimboeuf <[email protected]> |
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*/ |
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|
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#include <string.h> |
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#include <stdlib.h> |
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|
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#include <arch/elf.h> |
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#include <objtool/builtin.h> |
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#include <objtool/cfi.h> |
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#include <objtool/arch.h> |
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#include <objtool/check.h> |
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#include <objtool/special.h> |
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#include <objtool/warn.h> |
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#include <objtool/endianness.h> |
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|
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#include <linux/objtool.h> |
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#include <linux/hashtable.h> |
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#include <linux/kernel.h> |
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#include <linux/static_call_types.h> |
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|
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struct alternative { |
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struct list_head list; |
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struct instruction *insn; |
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bool skip_orig; |
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}; |
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|
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struct cfi_init_state initial_func_cfi; |
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|
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struct instruction *find_insn(struct objtool_file *file, |
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struct section *sec, unsigned long offset) |
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{ |
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struct instruction *insn; |
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|
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hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) { |
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if (insn->sec == sec && insn->offset == offset) |
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return insn; |
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} |
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|
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return NULL; |
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} |
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|
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static struct instruction *next_insn_same_sec(struct objtool_file *file, |
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struct instruction *insn) |
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{ |
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struct instruction *next = list_next_entry(insn, list); |
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|
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if (!next || &next->list == &file->insn_list || next->sec != insn->sec) |
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return NULL; |
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|
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return next; |
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} |
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|
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static struct instruction *next_insn_same_func(struct objtool_file *file, |
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struct instruction *insn) |
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{ |
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struct instruction *next = list_next_entry(insn, list); |
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struct symbol *func = insn->func; |
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|
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if (!func) |
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return NULL; |
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|
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if (&next->list != &file->insn_list && next->func == func) |
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return next; |
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|
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/* Check if we're already in the subfunction: */ |
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if (func == func->cfunc) |
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return NULL; |
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|
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/* Move to the subfunction: */ |
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return find_insn(file, func->cfunc->sec, func->cfunc->offset); |
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} |
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|
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static struct instruction *prev_insn_same_sym(struct objtool_file *file, |
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struct instruction *insn) |
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{ |
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struct instruction *prev = list_prev_entry(insn, list); |
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|
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if (&prev->list != &file->insn_list && prev->func == insn->func) |
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return prev; |
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|
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return NULL; |
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} |
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|
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#define func_for_each_insn(file, func, insn) \ |
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for (insn = find_insn(file, func->sec, func->offset); \ |
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insn; \ |
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insn = next_insn_same_func(file, insn)) |
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|
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#define sym_for_each_insn(file, sym, insn) \ |
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for (insn = find_insn(file, sym->sec, sym->offset); \ |
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insn && &insn->list != &file->insn_list && \ |
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insn->sec == sym->sec && \ |
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insn->offset < sym->offset + sym->len; \ |
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insn = list_next_entry(insn, list)) |
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|
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#define sym_for_each_insn_continue_reverse(file, sym, insn) \ |
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for (insn = list_prev_entry(insn, list); \ |
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&insn->list != &file->insn_list && \ |
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insn->sec == sym->sec && insn->offset >= sym->offset; \ |
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insn = list_prev_entry(insn, list)) |
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|
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#define sec_for_each_insn_from(file, insn) \ |
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for (; insn; insn = next_insn_same_sec(file, insn)) |
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|
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#define sec_for_each_insn_continue(file, insn) \ |
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for (insn = next_insn_same_sec(file, insn); insn; \ |
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insn = next_insn_same_sec(file, insn)) |
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|
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static bool is_jump_table_jump(struct instruction *insn) |
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{ |
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struct alt_group *alt_group = insn->alt_group; |
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|
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if (insn->jump_table) |
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return true; |
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|
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/* Retpoline alternative for a jump table? */ |
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return alt_group && alt_group->orig_group && |
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alt_group->orig_group->first_insn->jump_table; |
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} |
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|
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static bool is_sibling_call(struct instruction *insn) |
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{ |
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/* |
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* Assume only ELF functions can make sibling calls. This ensures |
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* sibling call detection consistency between vmlinux.o and individual |
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* objects. |
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*/ |
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if (!insn->func) |
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return false; |
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|
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/* An indirect jump is either a sibling call or a jump to a table. */ |
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if (insn->type == INSN_JUMP_DYNAMIC) |
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return !is_jump_table_jump(insn); |
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|
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/* add_jump_destinations() sets insn->call_dest for sibling calls. */ |
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return (is_static_jump(insn) && insn->call_dest); |
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} |
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|
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/* |
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* This checks to see if the given function is a "noreturn" function. |
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* |
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* For global functions which are outside the scope of this object file, we |
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* have to keep a manual list of them. |
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* |
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* For local functions, we have to detect them manually by simply looking for |
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* the lack of a return instruction. |
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*/ |
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static bool __dead_end_function(struct objtool_file *file, struct symbol *func, |
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int recursion) |
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{ |
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int i; |
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struct instruction *insn; |
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bool empty = true; |
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|
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/* |
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* Unfortunately these have to be hard coded because the noreturn |
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* attribute isn't provided in ELF data. |
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*/ |
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static const char * const global_noreturns[] = { |
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"__stack_chk_fail", |
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"panic", |
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"do_exit", |
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"do_task_dead", |
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"__module_put_and_exit", |
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"complete_and_exit", |
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"__reiserfs_panic", |
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"lbug_with_loc", |
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"fortify_panic", |
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"usercopy_abort", |
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"machine_real_restart", |
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"rewind_stack_do_exit", |
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"kunit_try_catch_throw", |
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"xen_start_kernel", |
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}; |
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|
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if (!func) |
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return false; |
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|
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if (func->bind == STB_WEAK) |
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return false; |
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|
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if (func->bind == STB_GLOBAL) |
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for (i = 0; i < ARRAY_SIZE(global_noreturns); i++) |
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if (!strcmp(func->name, global_noreturns[i])) |
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return true; |
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|
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if (!func->len) |
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return false; |
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insn = find_insn(file, func->sec, func->offset); |
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if (!insn->func) |
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return false; |
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func_for_each_insn(file, func, insn) { |
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empty = false; |
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|
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if (insn->type == INSN_RETURN) |
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return false; |
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} |
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|
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if (empty) |
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return false; |
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|
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/* |
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* A function can have a sibling call instead of a return. In that |
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* case, the function's dead-end status depends on whether the target |
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* of the sibling call returns. |
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*/ |
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func_for_each_insn(file, func, insn) { |
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if (is_sibling_call(insn)) { |
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struct instruction *dest = insn->jump_dest; |
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|
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if (!dest) |
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/* sibling call to another file */ |
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return false; |
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|
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/* local sibling call */ |
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if (recursion == 5) { |
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/* |
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* Infinite recursion: two functions have |
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* sibling calls to each other. This is a very |
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* rare case. It means they aren't dead ends. |
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*/ |
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return false; |
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} |
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|
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return __dead_end_function(file, dest->func, recursion+1); |
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} |
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} |
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|
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return true; |
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} |
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static bool dead_end_function(struct objtool_file *file, struct symbol *func) |
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{ |
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return __dead_end_function(file, func, 0); |
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} |
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|
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static void init_cfi_state(struct cfi_state *cfi) |
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{ |
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int i; |
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|
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for (i = 0; i < CFI_NUM_REGS; i++) { |
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cfi->regs[i].base = CFI_UNDEFINED; |
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cfi->vals[i].base = CFI_UNDEFINED; |
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} |
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cfi->cfa.base = CFI_UNDEFINED; |
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cfi->drap_reg = CFI_UNDEFINED; |
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cfi->drap_offset = -1; |
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} |
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|
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static void init_insn_state(struct insn_state *state, struct section *sec) |
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{ |
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memset(state, 0, sizeof(*state)); |
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init_cfi_state(&state->cfi); |
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|
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/* |
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* We need the full vmlinux for noinstr validation, otherwise we can |
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* not correctly determine insn->call_dest->sec (external symbols do |
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* not have a section). |
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*/ |
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if (vmlinux && noinstr && sec) |
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state->noinstr = sec->noinstr; |
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} |
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|
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/* |
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* Call the arch-specific instruction decoder for all the instructions and add |
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* them to the global instruction list. |
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*/ |
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static int decode_instructions(struct objtool_file *file) |
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{ |
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struct section *sec; |
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struct symbol *func; |
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unsigned long offset; |
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struct instruction *insn; |
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unsigned long nr_insns = 0; |
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int ret; |
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for_each_sec(file, sec) { |
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|
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if (!(sec->sh.sh_flags & SHF_EXECINSTR)) |
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continue; |
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|
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if (strcmp(sec->name, ".altinstr_replacement") && |
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strcmp(sec->name, ".altinstr_aux") && |
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strncmp(sec->name, ".discard.", 9)) |
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sec->text = true; |
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|
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if (!strcmp(sec->name, ".noinstr.text") || |
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!strcmp(sec->name, ".entry.text")) |
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sec->noinstr = true; |
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for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) { |
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insn = malloc(sizeof(*insn)); |
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if (!insn) { |
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WARN("malloc failed"); |
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return -1; |
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} |
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memset(insn, 0, sizeof(*insn)); |
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INIT_LIST_HEAD(&insn->alts); |
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INIT_LIST_HEAD(&insn->stack_ops); |
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init_cfi_state(&insn->cfi); |
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insn->sec = sec; |
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insn->offset = offset; |
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ret = arch_decode_instruction(file->elf, sec, offset, |
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sec->sh.sh_size - offset, |
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&insn->len, &insn->type, |
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&insn->immediate, |
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&insn->stack_ops); |
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if (ret) |
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goto err; |
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hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset)); |
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list_add_tail(&insn->list, &file->insn_list); |
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nr_insns++; |
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} |
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list_for_each_entry(func, &sec->symbol_list, list) { |
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if (func->type != STT_FUNC || func->alias != func) |
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continue; |
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if (!find_insn(file, sec, func->offset)) { |
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WARN("%s(): can't find starting instruction", |
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func->name); |
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return -1; |
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} |
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sym_for_each_insn(file, func, insn) |
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insn->func = func; |
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} |
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} |
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if (stats) |
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printf("nr_insns: %lu\n", nr_insns); |
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return 0; |
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err: |
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free(insn); |
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return ret; |
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} |
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static struct instruction *find_last_insn(struct objtool_file *file, |
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struct section *sec) |
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{ |
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struct instruction *insn = NULL; |
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unsigned int offset; |
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unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0; |
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for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--) |
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insn = find_insn(file, sec, offset); |
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return insn; |
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} |
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/* |
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* Mark "ud2" instructions and manually annotated dead ends. |
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*/ |
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static int add_dead_ends(struct objtool_file *file) |
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{ |
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struct section *sec; |
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struct reloc *reloc; |
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struct instruction *insn; |
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|
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/* |
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* By default, "ud2" is a dead end unless otherwise annotated, because |
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* GCC 7 inserts it for certain divide-by-zero cases. |
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*/ |
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for_each_insn(file, insn) |
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if (insn->type == INSN_BUG) |
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insn->dead_end = true; |
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|
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/* |
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* Check for manually annotated dead ends. |
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*/ |
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sec = find_section_by_name(file->elf, ".rela.discard.unreachable"); |
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if (!sec) |
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goto reachable; |
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list_for_each_entry(reloc, &sec->reloc_list, list) { |
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if (reloc->sym->type != STT_SECTION) { |
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WARN("unexpected relocation symbol type in %s", sec->name); |
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return -1; |
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} |
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insn = find_insn(file, reloc->sym->sec, reloc->addend); |
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if (insn) |
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insn = list_prev_entry(insn, list); |
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else if (reloc->addend == reloc->sym->sec->sh.sh_size) { |
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insn = find_last_insn(file, reloc->sym->sec); |
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if (!insn) { |
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WARN("can't find unreachable insn at %s+0x%x", |
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reloc->sym->sec->name, reloc->addend); |
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return -1; |
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} |
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} else { |
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WARN("can't find unreachable insn at %s+0x%x", |
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reloc->sym->sec->name, reloc->addend); |
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return -1; |
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} |
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|
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insn->dead_end = true; |
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} |
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|
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reachable: |
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/* |
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* These manually annotated reachable checks are needed for GCC 4.4, |
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* where the Linux unreachable() macro isn't supported. In that case |
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* GCC doesn't know the "ud2" is fatal, so it generates code as if it's |
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* not a dead end. |
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*/ |
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sec = find_section_by_name(file->elf, ".rela.discard.reachable"); |
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if (!sec) |
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return 0; |
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|
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list_for_each_entry(reloc, &sec->reloc_list, list) { |
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if (reloc->sym->type != STT_SECTION) { |
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WARN("unexpected relocation symbol type in %s", sec->name); |
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return -1; |
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} |
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insn = find_insn(file, reloc->sym->sec, reloc->addend); |
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if (insn) |
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insn = list_prev_entry(insn, list); |
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else if (reloc->addend == reloc->sym->sec->sh.sh_size) { |
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insn = find_last_insn(file, reloc->sym->sec); |
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if (!insn) { |
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WARN("can't find reachable insn at %s+0x%x", |
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reloc->sym->sec->name, reloc->addend); |
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return -1; |
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} |
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} else { |
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WARN("can't find reachable insn at %s+0x%x", |
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reloc->sym->sec->name, reloc->addend); |
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return -1; |
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} |
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|
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insn->dead_end = false; |
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} |
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|
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return 0; |
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} |
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|
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static int create_static_call_sections(struct objtool_file *file) |
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{ |
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struct section *sec; |
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struct static_call_site *site; |
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struct instruction *insn; |
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struct symbol *key_sym; |
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char *key_name, *tmp; |
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int idx; |
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|
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sec = find_section_by_name(file->elf, ".static_call_sites"); |
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if (sec) { |
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INIT_LIST_HEAD(&file->static_call_list); |
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WARN("file already has .static_call_sites section, skipping"); |
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return 0; |
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} |
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|
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if (list_empty(&file->static_call_list)) |
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return 0; |
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|
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idx = 0; |
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list_for_each_entry(insn, &file->static_call_list, call_node) |
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idx++; |
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|
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sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE, |
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sizeof(struct static_call_site), idx); |
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if (!sec) |
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return -1; |
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|
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idx = 0; |
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list_for_each_entry(insn, &file->static_call_list, call_node) { |
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|
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site = (struct static_call_site *)sec->data->d_buf + idx; |
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memset(site, 0, sizeof(struct static_call_site)); |
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|
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/* populate reloc for 'addr' */ |
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if (elf_add_reloc_to_insn(file->elf, sec, |
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idx * sizeof(struct static_call_site), |
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R_X86_64_PC32, |
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insn->sec, insn->offset)) |
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return -1; |
|
|
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/* find key symbol */ |
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key_name = strdup(insn->call_dest->name); |
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if (!key_name) { |
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perror("strdup"); |
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return -1; |
|
} |
|
if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR, |
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STATIC_CALL_TRAMP_PREFIX_LEN)) { |
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WARN("static_call: trampoline name malformed: %s", key_name); |
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return -1; |
|
} |
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tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN; |
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memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN); |
|
|
|
key_sym = find_symbol_by_name(file->elf, tmp); |
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if (!key_sym) { |
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if (!module) { |
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WARN("static_call: can't find static_call_key symbol: %s", tmp); |
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return -1; |
|
} |
|
|
|
/* |
|
* For modules(), the key might not be exported, which |
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* means the module can make static calls but isn't |
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* allowed to change them. |
|
* |
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* In that case we temporarily set the key to be the |
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* trampoline address. This is fixed up in |
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* static_call_add_module(). |
|
*/ |
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key_sym = insn->call_dest; |
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} |
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free(key_name); |
|
|
|
/* populate reloc for 'key' */ |
|
if (elf_add_reloc(file->elf, sec, |
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idx * sizeof(struct static_call_site) + 4, |
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R_X86_64_PC32, key_sym, |
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is_sibling_call(insn) * STATIC_CALL_SITE_TAIL)) |
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return -1; |
|
|
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idx++; |
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} |
|
|
|
return 0; |
|
} |
|
|
|
static int create_mcount_loc_sections(struct objtool_file *file) |
|
{ |
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struct section *sec; |
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unsigned long *loc; |
|
struct instruction *insn; |
|
int idx; |
|
|
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sec = find_section_by_name(file->elf, "__mcount_loc"); |
|
if (sec) { |
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INIT_LIST_HEAD(&file->mcount_loc_list); |
|
WARN("file already has __mcount_loc section, skipping"); |
|
return 0; |
|
} |
|
|
|
if (list_empty(&file->mcount_loc_list)) |
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return 0; |
|
|
|
idx = 0; |
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list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node) |
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idx++; |
|
|
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sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx); |
|
if (!sec) |
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return -1; |
|
|
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idx = 0; |
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list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node) { |
|
|
|
loc = (unsigned long *)sec->data->d_buf + idx; |
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memset(loc, 0, sizeof(unsigned long)); |
|
|
|
if (elf_add_reloc_to_insn(file->elf, sec, |
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idx * sizeof(unsigned long), |
|
R_X86_64_64, |
|
insn->sec, insn->offset)) |
|
return -1; |
|
|
|
idx++; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* Warnings shouldn't be reported for ignored functions. |
|
*/ |
|
static void add_ignores(struct objtool_file *file) |
|
{ |
|
struct instruction *insn; |
|
struct section *sec; |
|
struct symbol *func; |
|
struct reloc *reloc; |
|
|
|
sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard"); |
|
if (!sec) |
|
return; |
|
|
|
list_for_each_entry(reloc, &sec->reloc_list, list) { |
|
switch (reloc->sym->type) { |
|
case STT_FUNC: |
|
func = reloc->sym; |
|
break; |
|
|
|
case STT_SECTION: |
|
func = find_func_by_offset(reloc->sym->sec, reloc->addend); |
|
if (!func) |
|
continue; |
|
break; |
|
|
|
default: |
|
WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type); |
|
continue; |
|
} |
|
|
|
func_for_each_insn(file, func, insn) |
|
insn->ignore = true; |
|
} |
|
} |
|
|
|
/* |
|
* This is a whitelist of functions that is allowed to be called with AC set. |
|
* The list is meant to be minimal and only contains compiler instrumentation |
|
* ABI and a few functions used to implement *_{to,from}_user() functions. |
|
* |
|
* These functions must not directly change AC, but may PUSHF/POPF. |
|
*/ |
|
static const char *uaccess_safe_builtin[] = { |
|
/* KASAN */ |
|
"kasan_report", |
|
"kasan_check_range", |
|
/* KASAN out-of-line */ |
|
"__asan_loadN_noabort", |
|
"__asan_load1_noabort", |
|
"__asan_load2_noabort", |
|
"__asan_load4_noabort", |
|
"__asan_load8_noabort", |
|
"__asan_load16_noabort", |
|
"__asan_storeN_noabort", |
|
"__asan_store1_noabort", |
|
"__asan_store2_noabort", |
|
"__asan_store4_noabort", |
|
"__asan_store8_noabort", |
|
"__asan_store16_noabort", |
|
"__kasan_check_read", |
|
"__kasan_check_write", |
|
/* KASAN in-line */ |
|
"__asan_report_load_n_noabort", |
|
"__asan_report_load1_noabort", |
|
"__asan_report_load2_noabort", |
|
"__asan_report_load4_noabort", |
|
"__asan_report_load8_noabort", |
|
"__asan_report_load16_noabort", |
|
"__asan_report_store_n_noabort", |
|
"__asan_report_store1_noabort", |
|
"__asan_report_store2_noabort", |
|
"__asan_report_store4_noabort", |
|
"__asan_report_store8_noabort", |
|
"__asan_report_store16_noabort", |
|
/* KCSAN */ |
|
"__kcsan_check_access", |
|
"kcsan_found_watchpoint", |
|
"kcsan_setup_watchpoint", |
|
"kcsan_check_scoped_accesses", |
|
"kcsan_disable_current", |
|
"kcsan_enable_current_nowarn", |
|
/* KCSAN/TSAN */ |
|
"__tsan_func_entry", |
|
"__tsan_func_exit", |
|
"__tsan_read_range", |
|
"__tsan_write_range", |
|
"__tsan_read1", |
|
"__tsan_read2", |
|
"__tsan_read4", |
|
"__tsan_read8", |
|
"__tsan_read16", |
|
"__tsan_write1", |
|
"__tsan_write2", |
|
"__tsan_write4", |
|
"__tsan_write8", |
|
"__tsan_write16", |
|
"__tsan_read_write1", |
|
"__tsan_read_write2", |
|
"__tsan_read_write4", |
|
"__tsan_read_write8", |
|
"__tsan_read_write16", |
|
"__tsan_atomic8_load", |
|
"__tsan_atomic16_load", |
|
"__tsan_atomic32_load", |
|
"__tsan_atomic64_load", |
|
"__tsan_atomic8_store", |
|
"__tsan_atomic16_store", |
|
"__tsan_atomic32_store", |
|
"__tsan_atomic64_store", |
|
"__tsan_atomic8_exchange", |
|
"__tsan_atomic16_exchange", |
|
"__tsan_atomic32_exchange", |
|
"__tsan_atomic64_exchange", |
|
"__tsan_atomic8_fetch_add", |
|
"__tsan_atomic16_fetch_add", |
|
"__tsan_atomic32_fetch_add", |
|
"__tsan_atomic64_fetch_add", |
|
"__tsan_atomic8_fetch_sub", |
|
"__tsan_atomic16_fetch_sub", |
|
"__tsan_atomic32_fetch_sub", |
|
"__tsan_atomic64_fetch_sub", |
|
"__tsan_atomic8_fetch_and", |
|
"__tsan_atomic16_fetch_and", |
|
"__tsan_atomic32_fetch_and", |
|
"__tsan_atomic64_fetch_and", |
|
"__tsan_atomic8_fetch_or", |
|
"__tsan_atomic16_fetch_or", |
|
"__tsan_atomic32_fetch_or", |
|
"__tsan_atomic64_fetch_or", |
|
"__tsan_atomic8_fetch_xor", |
|
"__tsan_atomic16_fetch_xor", |
|
"__tsan_atomic32_fetch_xor", |
|
"__tsan_atomic64_fetch_xor", |
|
"__tsan_atomic8_fetch_nand", |
|
"__tsan_atomic16_fetch_nand", |
|
"__tsan_atomic32_fetch_nand", |
|
"__tsan_atomic64_fetch_nand", |
|
"__tsan_atomic8_compare_exchange_strong", |
|
"__tsan_atomic16_compare_exchange_strong", |
|
"__tsan_atomic32_compare_exchange_strong", |
|
"__tsan_atomic64_compare_exchange_strong", |
|
"__tsan_atomic8_compare_exchange_weak", |
|
"__tsan_atomic16_compare_exchange_weak", |
|
"__tsan_atomic32_compare_exchange_weak", |
|
"__tsan_atomic64_compare_exchange_weak", |
|
"__tsan_atomic8_compare_exchange_val", |
|
"__tsan_atomic16_compare_exchange_val", |
|
"__tsan_atomic32_compare_exchange_val", |
|
"__tsan_atomic64_compare_exchange_val", |
|
"__tsan_atomic_thread_fence", |
|
"__tsan_atomic_signal_fence", |
|
/* KCOV */ |
|
"write_comp_data", |
|
"check_kcov_mode", |
|
"__sanitizer_cov_trace_pc", |
|
"__sanitizer_cov_trace_const_cmp1", |
|
"__sanitizer_cov_trace_const_cmp2", |
|
"__sanitizer_cov_trace_const_cmp4", |
|
"__sanitizer_cov_trace_const_cmp8", |
|
"__sanitizer_cov_trace_cmp1", |
|
"__sanitizer_cov_trace_cmp2", |
|
"__sanitizer_cov_trace_cmp4", |
|
"__sanitizer_cov_trace_cmp8", |
|
"__sanitizer_cov_trace_switch", |
|
/* UBSAN */ |
|
"ubsan_type_mismatch_common", |
|
"__ubsan_handle_type_mismatch", |
|
"__ubsan_handle_type_mismatch_v1", |
|
"__ubsan_handle_shift_out_of_bounds", |
|
/* misc */ |
|
"csum_partial_copy_generic", |
|
"copy_mc_fragile", |
|
"copy_mc_fragile_handle_tail", |
|
"copy_mc_enhanced_fast_string", |
|
"ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */ |
|
NULL |
|
}; |
|
|
|
static void add_uaccess_safe(struct objtool_file *file) |
|
{ |
|
struct symbol *func; |
|
const char **name; |
|
|
|
if (!uaccess) |
|
return; |
|
|
|
for (name = uaccess_safe_builtin; *name; name++) { |
|
func = find_symbol_by_name(file->elf, *name); |
|
if (!func) |
|
continue; |
|
|
|
func->uaccess_safe = true; |
|
} |
|
} |
|
|
|
/* |
|
* FIXME: For now, just ignore any alternatives which add retpolines. This is |
|
* a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline. |
|
* But it at least allows objtool to understand the control flow *around* the |
|
* retpoline. |
|
*/ |
|
static int add_ignore_alternatives(struct objtool_file *file) |
|
{ |
|
struct section *sec; |
|
struct reloc *reloc; |
|
struct instruction *insn; |
|
|
|
sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts"); |
|
if (!sec) |
|
return 0; |
|
|
|
list_for_each_entry(reloc, &sec->reloc_list, list) { |
|
if (reloc->sym->type != STT_SECTION) { |
|
WARN("unexpected relocation symbol type in %s", sec->name); |
|
return -1; |
|
} |
|
|
|
insn = find_insn(file, reloc->sym->sec, reloc->addend); |
|
if (!insn) { |
|
WARN("bad .discard.ignore_alts entry"); |
|
return -1; |
|
} |
|
|
|
insn->ignore_alts = true; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
__weak bool arch_is_retpoline(struct symbol *sym) |
|
{ |
|
return false; |
|
} |
|
|
|
#define NEGATIVE_RELOC ((void *)-1L) |
|
|
|
static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn) |
|
{ |
|
if (insn->reloc == NEGATIVE_RELOC) |
|
return NULL; |
|
|
|
if (!insn->reloc) { |
|
insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec, |
|
insn->offset, insn->len); |
|
if (!insn->reloc) { |
|
insn->reloc = NEGATIVE_RELOC; |
|
return NULL; |
|
} |
|
} |
|
|
|
return insn->reloc; |
|
} |
|
|
|
/* |
|
* Find the destination instructions for all jumps. |
|
*/ |
|
static int add_jump_destinations(struct objtool_file *file) |
|
{ |
|
struct instruction *insn; |
|
struct reloc *reloc; |
|
struct section *dest_sec; |
|
unsigned long dest_off; |
|
|
|
for_each_insn(file, insn) { |
|
if (!is_static_jump(insn)) |
|
continue; |
|
|
|
reloc = insn_reloc(file, insn); |
|
if (!reloc) { |
|
dest_sec = insn->sec; |
|
dest_off = arch_jump_destination(insn); |
|
} else if (reloc->sym->type == STT_SECTION) { |
|
dest_sec = reloc->sym->sec; |
|
dest_off = arch_dest_reloc_offset(reloc->addend); |
|
} else if (arch_is_retpoline(reloc->sym)) { |
|
/* |
|
* Retpoline jumps are really dynamic jumps in |
|
* disguise, so convert them accordingly. |
|
*/ |
|
if (insn->type == INSN_JUMP_UNCONDITIONAL) |
|
insn->type = INSN_JUMP_DYNAMIC; |
|
else |
|
insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL; |
|
|
|
list_add_tail(&insn->call_node, |
|
&file->retpoline_call_list); |
|
|
|
insn->retpoline_safe = true; |
|
continue; |
|
} else if (insn->func) { |
|
/* internal or external sibling call (with reloc) */ |
|
insn->call_dest = reloc->sym; |
|
if (insn->call_dest->static_call_tramp) { |
|
list_add_tail(&insn->call_node, |
|
&file->static_call_list); |
|
} |
|
continue; |
|
} else if (reloc->sym->sec->idx) { |
|
dest_sec = reloc->sym->sec; |
|
dest_off = reloc->sym->sym.st_value + |
|
arch_dest_reloc_offset(reloc->addend); |
|
} else { |
|
/* non-func asm code jumping to another file */ |
|
continue; |
|
} |
|
|
|
insn->jump_dest = find_insn(file, dest_sec, dest_off); |
|
if (!insn->jump_dest) { |
|
|
|
/* |
|
* This is a special case where an alt instruction |
|
* jumps past the end of the section. These are |
|
* handled later in handle_group_alt(). |
|
*/ |
|
if (!strcmp(insn->sec->name, ".altinstr_replacement")) |
|
continue; |
|
|
|
WARN_FUNC("can't find jump dest instruction at %s+0x%lx", |
|
insn->sec, insn->offset, dest_sec->name, |
|
dest_off); |
|
return -1; |
|
} |
|
|
|
/* |
|
* Cross-function jump. |
|
*/ |
|
if (insn->func && insn->jump_dest->func && |
|
insn->func != insn->jump_dest->func) { |
|
|
|
/* |
|
* For GCC 8+, create parent/child links for any cold |
|
* subfunctions. This is _mostly_ redundant with a |
|
* similar initialization in read_symbols(). |
|
* |
|
* If a function has aliases, we want the *first* such |
|
* function in the symbol table to be the subfunction's |
|
* parent. In that case we overwrite the |
|
* initialization done in read_symbols(). |
|
* |
|
* However this code can't completely replace the |
|
* read_symbols() code because this doesn't detect the |
|
* case where the parent function's only reference to a |
|
* subfunction is through a jump table. |
|
*/ |
|
if (!strstr(insn->func->name, ".cold") && |
|
strstr(insn->jump_dest->func->name, ".cold")) { |
|
insn->func->cfunc = insn->jump_dest->func; |
|
insn->jump_dest->func->pfunc = insn->func; |
|
|
|
} else if (insn->jump_dest->func->pfunc != insn->func->pfunc && |
|
insn->jump_dest->offset == insn->jump_dest->func->offset) { |
|
|
|
/* internal sibling call (without reloc) */ |
|
insn->call_dest = insn->jump_dest->func; |
|
if (insn->call_dest->static_call_tramp) { |
|
list_add_tail(&insn->call_node, |
|
&file->static_call_list); |
|
} |
|
} |
|
} |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static void remove_insn_ops(struct instruction *insn) |
|
{ |
|
struct stack_op *op, *tmp; |
|
|
|
list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) { |
|
list_del(&op->list); |
|
free(op); |
|
} |
|
} |
|
|
|
static struct symbol *find_call_destination(struct section *sec, unsigned long offset) |
|
{ |
|
struct symbol *call_dest; |
|
|
|
call_dest = find_func_by_offset(sec, offset); |
|
if (!call_dest) |
|
call_dest = find_symbol_by_offset(sec, offset); |
|
|
|
return call_dest; |
|
} |
|
|
|
/* |
|
* Find the destination instructions for all calls. |
|
*/ |
|
static int add_call_destinations(struct objtool_file *file) |
|
{ |
|
struct instruction *insn; |
|
unsigned long dest_off; |
|
struct reloc *reloc; |
|
|
|
for_each_insn(file, insn) { |
|
if (insn->type != INSN_CALL) |
|
continue; |
|
|
|
reloc = insn_reloc(file, insn); |
|
if (!reloc) { |
|
dest_off = arch_jump_destination(insn); |
|
insn->call_dest = find_call_destination(insn->sec, dest_off); |
|
|
|
if (insn->ignore) |
|
continue; |
|
|
|
if (!insn->call_dest) { |
|
WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset); |
|
return -1; |
|
} |
|
|
|
if (insn->func && insn->call_dest->type != STT_FUNC) { |
|
WARN_FUNC("unsupported call to non-function", |
|
insn->sec, insn->offset); |
|
return -1; |
|
} |
|
|
|
} else if (reloc->sym->type == STT_SECTION) { |
|
dest_off = arch_dest_reloc_offset(reloc->addend); |
|
insn->call_dest = find_call_destination(reloc->sym->sec, |
|
dest_off); |
|
if (!insn->call_dest) { |
|
WARN_FUNC("can't find call dest symbol at %s+0x%lx", |
|
insn->sec, insn->offset, |
|
reloc->sym->sec->name, |
|
dest_off); |
|
return -1; |
|
} |
|
|
|
} else if (arch_is_retpoline(reloc->sym)) { |
|
/* |
|
* Retpoline calls are really dynamic calls in |
|
* disguise, so convert them accordingly. |
|
*/ |
|
insn->type = INSN_CALL_DYNAMIC; |
|
insn->retpoline_safe = true; |
|
|
|
list_add_tail(&insn->call_node, |
|
&file->retpoline_call_list); |
|
|
|
remove_insn_ops(insn); |
|
continue; |
|
|
|
} else |
|
insn->call_dest = reloc->sym; |
|
|
|
if (insn->call_dest && insn->call_dest->static_call_tramp) { |
|
list_add_tail(&insn->call_node, |
|
&file->static_call_list); |
|
} |
|
|
|
/* |
|
* Many compilers cannot disable KCOV with a function attribute |
|
* so they need a little help, NOP out any KCOV calls from noinstr |
|
* text. |
|
*/ |
|
if (insn->sec->noinstr && |
|
!strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) { |
|
if (reloc) { |
|
reloc->type = R_NONE; |
|
elf_write_reloc(file->elf, reloc); |
|
} |
|
|
|
elf_write_insn(file->elf, insn->sec, |
|
insn->offset, insn->len, |
|
arch_nop_insn(insn->len)); |
|
insn->type = INSN_NOP; |
|
} |
|
|
|
if (mcount && !strcmp(insn->call_dest->name, "__fentry__")) { |
|
if (reloc) { |
|
reloc->type = R_NONE; |
|
elf_write_reloc(file->elf, reloc); |
|
} |
|
|
|
elf_write_insn(file->elf, insn->sec, |
|
insn->offset, insn->len, |
|
arch_nop_insn(insn->len)); |
|
|
|
insn->type = INSN_NOP; |
|
|
|
list_add_tail(&insn->mcount_loc_node, |
|
&file->mcount_loc_list); |
|
} |
|
|
|
/* |
|
* Whatever stack impact regular CALLs have, should be undone |
|
* by the RETURN of the called function. |
|
* |
|
* Annotated intra-function calls retain the stack_ops but |
|
* are converted to JUMP, see read_intra_function_calls(). |
|
*/ |
|
remove_insn_ops(insn); |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* The .alternatives section requires some extra special care over and above |
|
* other special sections because alternatives are patched in place. |
|
*/ |
|
static int handle_group_alt(struct objtool_file *file, |
|
struct special_alt *special_alt, |
|
struct instruction *orig_insn, |
|
struct instruction **new_insn) |
|
{ |
|
struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL; |
|
struct alt_group *orig_alt_group, *new_alt_group; |
|
unsigned long dest_off; |
|
|
|
|
|
orig_alt_group = malloc(sizeof(*orig_alt_group)); |
|
if (!orig_alt_group) { |
|
WARN("malloc failed"); |
|
return -1; |
|
} |
|
orig_alt_group->cfi = calloc(special_alt->orig_len, |
|
sizeof(struct cfi_state *)); |
|
if (!orig_alt_group->cfi) { |
|
WARN("calloc failed"); |
|
return -1; |
|
} |
|
|
|
last_orig_insn = NULL; |
|
insn = orig_insn; |
|
sec_for_each_insn_from(file, insn) { |
|
if (insn->offset >= special_alt->orig_off + special_alt->orig_len) |
|
break; |
|
|
|
insn->alt_group = orig_alt_group; |
|
last_orig_insn = insn; |
|
} |
|
orig_alt_group->orig_group = NULL; |
|
orig_alt_group->first_insn = orig_insn; |
|
orig_alt_group->last_insn = last_orig_insn; |
|
|
|
|
|
new_alt_group = malloc(sizeof(*new_alt_group)); |
|
if (!new_alt_group) { |
|
WARN("malloc failed"); |
|
return -1; |
|
} |
|
|
|
if (special_alt->new_len < special_alt->orig_len) { |
|
/* |
|
* Insert a fake nop at the end to make the replacement |
|
* alt_group the same size as the original. This is needed to |
|
* allow propagate_alt_cfi() to do its magic. When the last |
|
* instruction affects the stack, the instruction after it (the |
|
* nop) will propagate the new state to the shared CFI array. |
|
*/ |
|
nop = malloc(sizeof(*nop)); |
|
if (!nop) { |
|
WARN("malloc failed"); |
|
return -1; |
|
} |
|
memset(nop, 0, sizeof(*nop)); |
|
INIT_LIST_HEAD(&nop->alts); |
|
INIT_LIST_HEAD(&nop->stack_ops); |
|
init_cfi_state(&nop->cfi); |
|
|
|
nop->sec = special_alt->new_sec; |
|
nop->offset = special_alt->new_off + special_alt->new_len; |
|
nop->len = special_alt->orig_len - special_alt->new_len; |
|
nop->type = INSN_NOP; |
|
nop->func = orig_insn->func; |
|
nop->alt_group = new_alt_group; |
|
nop->ignore = orig_insn->ignore_alts; |
|
} |
|
|
|
if (!special_alt->new_len) { |
|
*new_insn = nop; |
|
goto end; |
|
} |
|
|
|
insn = *new_insn; |
|
sec_for_each_insn_from(file, insn) { |
|
struct reloc *alt_reloc; |
|
|
|
if (insn->offset >= special_alt->new_off + special_alt->new_len) |
|
break; |
|
|
|
last_new_insn = insn; |
|
|
|
insn->ignore = orig_insn->ignore_alts; |
|
insn->func = orig_insn->func; |
|
insn->alt_group = new_alt_group; |
|
|
|
/* |
|
* Since alternative replacement code is copy/pasted by the |
|
* kernel after applying relocations, generally such code can't |
|
* have relative-address relocation references to outside the |
|
* .altinstr_replacement section, unless the arch's |
|
* alternatives code can adjust the relative offsets |
|
* accordingly. |
|
*/ |
|
alt_reloc = insn_reloc(file, insn); |
|
if (alt_reloc && |
|
!arch_support_alt_relocation(special_alt, insn, alt_reloc)) { |
|
|
|
WARN_FUNC("unsupported relocation in alternatives section", |
|
insn->sec, insn->offset); |
|
return -1; |
|
} |
|
|
|
if (!is_static_jump(insn)) |
|
continue; |
|
|
|
if (!insn->immediate) |
|
continue; |
|
|
|
dest_off = arch_jump_destination(insn); |
|
if (dest_off == special_alt->new_off + special_alt->new_len) |
|
insn->jump_dest = next_insn_same_sec(file, last_orig_insn); |
|
|
|
if (!insn->jump_dest) { |
|
WARN_FUNC("can't find alternative jump destination", |
|
insn->sec, insn->offset); |
|
return -1; |
|
} |
|
} |
|
|
|
if (!last_new_insn) { |
|
WARN_FUNC("can't find last new alternative instruction", |
|
special_alt->new_sec, special_alt->new_off); |
|
return -1; |
|
} |
|
|
|
if (nop) |
|
list_add(&nop->list, &last_new_insn->list); |
|
end: |
|
new_alt_group->orig_group = orig_alt_group; |
|
new_alt_group->first_insn = *new_insn; |
|
new_alt_group->last_insn = nop ? : last_new_insn; |
|
new_alt_group->cfi = orig_alt_group->cfi; |
|
return 0; |
|
} |
|
|
|
/* |
|
* A jump table entry can either convert a nop to a jump or a jump to a nop. |
|
* If the original instruction is a jump, make the alt entry an effective nop |
|
* by just skipping the original instruction. |
|
*/ |
|
static int handle_jump_alt(struct objtool_file *file, |
|
struct special_alt *special_alt, |
|
struct instruction *orig_insn, |
|
struct instruction **new_insn) |
|
{ |
|
if (orig_insn->type != INSN_JUMP_UNCONDITIONAL && |
|
orig_insn->type != INSN_NOP) { |
|
|
|
WARN_FUNC("unsupported instruction at jump label", |
|
orig_insn->sec, orig_insn->offset); |
|
return -1; |
|
} |
|
|
|
if (special_alt->key_addend & 2) { |
|
struct reloc *reloc = insn_reloc(file, orig_insn); |
|
|
|
if (reloc) { |
|
reloc->type = R_NONE; |
|
elf_write_reloc(file->elf, reloc); |
|
} |
|
elf_write_insn(file->elf, orig_insn->sec, |
|
orig_insn->offset, orig_insn->len, |
|
arch_nop_insn(orig_insn->len)); |
|
orig_insn->type = INSN_NOP; |
|
} |
|
|
|
if (orig_insn->type == INSN_NOP) { |
|
if (orig_insn->len == 2) |
|
file->jl_nop_short++; |
|
else |
|
file->jl_nop_long++; |
|
|
|
return 0; |
|
} |
|
|
|
if (orig_insn->len == 2) |
|
file->jl_short++; |
|
else |
|
file->jl_long++; |
|
|
|
*new_insn = list_next_entry(orig_insn, list); |
|
return 0; |
|
} |
|
|
|
/* |
|
* Read all the special sections which have alternate instructions which can be |
|
* patched in or redirected to at runtime. Each instruction having alternate |
|
* instruction(s) has them added to its insn->alts list, which will be |
|
* traversed in validate_branch(). |
|
*/ |
|
static int add_special_section_alts(struct objtool_file *file) |
|
{ |
|
struct list_head special_alts; |
|
struct instruction *orig_insn, *new_insn; |
|
struct special_alt *special_alt, *tmp; |
|
struct alternative *alt; |
|
int ret; |
|
|
|
ret = special_get_alts(file->elf, &special_alts); |
|
if (ret) |
|
return ret; |
|
|
|
list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { |
|
|
|
orig_insn = find_insn(file, special_alt->orig_sec, |
|
special_alt->orig_off); |
|
if (!orig_insn) { |
|
WARN_FUNC("special: can't find orig instruction", |
|
special_alt->orig_sec, special_alt->orig_off); |
|
ret = -1; |
|
goto out; |
|
} |
|
|
|
new_insn = NULL; |
|
if (!special_alt->group || special_alt->new_len) { |
|
new_insn = find_insn(file, special_alt->new_sec, |
|
special_alt->new_off); |
|
if (!new_insn) { |
|
WARN_FUNC("special: can't find new instruction", |
|
special_alt->new_sec, |
|
special_alt->new_off); |
|
ret = -1; |
|
goto out; |
|
} |
|
} |
|
|
|
if (special_alt->group) { |
|
if (!special_alt->orig_len) { |
|
WARN_FUNC("empty alternative entry", |
|
orig_insn->sec, orig_insn->offset); |
|
continue; |
|
} |
|
|
|
ret = handle_group_alt(file, special_alt, orig_insn, |
|
&new_insn); |
|
if (ret) |
|
goto out; |
|
} else if (special_alt->jump_or_nop) { |
|
ret = handle_jump_alt(file, special_alt, orig_insn, |
|
&new_insn); |
|
if (ret) |
|
goto out; |
|
} |
|
|
|
alt = malloc(sizeof(*alt)); |
|
if (!alt) { |
|
WARN("malloc failed"); |
|
ret = -1; |
|
goto out; |
|
} |
|
|
|
alt->insn = new_insn; |
|
alt->skip_orig = special_alt->skip_orig; |
|
orig_insn->ignore_alts |= special_alt->skip_alt; |
|
list_add_tail(&alt->list, &orig_insn->alts); |
|
|
|
list_del(&special_alt->list); |
|
free(special_alt); |
|
} |
|
|
|
if (stats) { |
|
printf("jl\\\tNOP\tJMP\n"); |
|
printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short); |
|
printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long); |
|
} |
|
|
|
out: |
|
return ret; |
|
} |
|
|
|
static int add_jump_table(struct objtool_file *file, struct instruction *insn, |
|
struct reloc *table) |
|
{ |
|
struct reloc *reloc = table; |
|
struct instruction *dest_insn; |
|
struct alternative *alt; |
|
struct symbol *pfunc = insn->func->pfunc; |
|
unsigned int prev_offset = 0; |
|
|
|
/* |
|
* Each @reloc is a switch table relocation which points to the target |
|
* instruction. |
|
*/ |
|
list_for_each_entry_from(reloc, &table->sec->reloc_list, list) { |
|
|
|
/* Check for the end of the table: */ |
|
if (reloc != table && reloc->jump_table_start) |
|
break; |
|
|
|
/* Make sure the table entries are consecutive: */ |
|
if (prev_offset && reloc->offset != prev_offset + 8) |
|
break; |
|
|
|
/* Detect function pointers from contiguous objects: */ |
|
if (reloc->sym->sec == pfunc->sec && |
|
reloc->addend == pfunc->offset) |
|
break; |
|
|
|
dest_insn = find_insn(file, reloc->sym->sec, reloc->addend); |
|
if (!dest_insn) |
|
break; |
|
|
|
/* Make sure the destination is in the same function: */ |
|
if (!dest_insn->func || dest_insn->func->pfunc != pfunc) |
|
break; |
|
|
|
alt = malloc(sizeof(*alt)); |
|
if (!alt) { |
|
WARN("malloc failed"); |
|
return -1; |
|
} |
|
|
|
alt->insn = dest_insn; |
|
list_add_tail(&alt->list, &insn->alts); |
|
prev_offset = reloc->offset; |
|
} |
|
|
|
if (!prev_offset) { |
|
WARN_FUNC("can't find switch jump table", |
|
insn->sec, insn->offset); |
|
return -1; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* find_jump_table() - Given a dynamic jump, find the switch jump table |
|
* associated with it. |
|
*/ |
|
static struct reloc *find_jump_table(struct objtool_file *file, |
|
struct symbol *func, |
|
struct instruction *insn) |
|
{ |
|
struct reloc *table_reloc; |
|
struct instruction *dest_insn, *orig_insn = insn; |
|
|
|
/* |
|
* Backward search using the @first_jump_src links, these help avoid |
|
* much of the 'in between' code. Which avoids us getting confused by |
|
* it. |
|
*/ |
|
for (; |
|
insn && insn->func && insn->func->pfunc == func; |
|
insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) { |
|
|
|
if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC) |
|
break; |
|
|
|
/* allow small jumps within the range */ |
|
if (insn->type == INSN_JUMP_UNCONDITIONAL && |
|
insn->jump_dest && |
|
(insn->jump_dest->offset <= insn->offset || |
|
insn->jump_dest->offset > orig_insn->offset)) |
|
break; |
|
|
|
table_reloc = arch_find_switch_table(file, insn); |
|
if (!table_reloc) |
|
continue; |
|
dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend); |
|
if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func) |
|
continue; |
|
|
|
return table_reloc; |
|
} |
|
|
|
return NULL; |
|
} |
|
|
|
/* |
|
* First pass: Mark the head of each jump table so that in the next pass, |
|
* we know when a given jump table ends and the next one starts. |
|
*/ |
|
static void mark_func_jump_tables(struct objtool_file *file, |
|
struct symbol *func) |
|
{ |
|
struct instruction *insn, *last = NULL; |
|
struct reloc *reloc; |
|
|
|
func_for_each_insn(file, func, insn) { |
|
if (!last) |
|
last = insn; |
|
|
|
/* |
|
* Store back-pointers for unconditional forward jumps such |
|
* that find_jump_table() can back-track using those and |
|
* avoid some potentially confusing code. |
|
*/ |
|
if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && |
|
insn->offset > last->offset && |
|
insn->jump_dest->offset > insn->offset && |
|
!insn->jump_dest->first_jump_src) { |
|
|
|
insn->jump_dest->first_jump_src = insn; |
|
last = insn->jump_dest; |
|
} |
|
|
|
if (insn->type != INSN_JUMP_DYNAMIC) |
|
continue; |
|
|
|
reloc = find_jump_table(file, func, insn); |
|
if (reloc) { |
|
reloc->jump_table_start = true; |
|
insn->jump_table = reloc; |
|
} |
|
} |
|
} |
|
|
|
static int add_func_jump_tables(struct objtool_file *file, |
|
struct symbol *func) |
|
{ |
|
struct instruction *insn; |
|
int ret; |
|
|
|
func_for_each_insn(file, func, insn) { |
|
if (!insn->jump_table) |
|
continue; |
|
|
|
ret = add_jump_table(file, insn, insn->jump_table); |
|
if (ret) |
|
return ret; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* For some switch statements, gcc generates a jump table in the .rodata |
|
* section which contains a list of addresses within the function to jump to. |
|
* This finds these jump tables and adds them to the insn->alts lists. |
|
*/ |
|
static int add_jump_table_alts(struct objtool_file *file) |
|
{ |
|
struct section *sec; |
|
struct symbol *func; |
|
int ret; |
|
|
|
if (!file->rodata) |
|
return 0; |
|
|
|
for_each_sec(file, sec) { |
|
list_for_each_entry(func, &sec->symbol_list, list) { |
|
if (func->type != STT_FUNC) |
|
continue; |
|
|
|
mark_func_jump_tables(file, func); |
|
ret = add_func_jump_tables(file, func); |
|
if (ret) |
|
return ret; |
|
} |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static void set_func_state(struct cfi_state *state) |
|
{ |
|
state->cfa = initial_func_cfi.cfa; |
|
memcpy(&state->regs, &initial_func_cfi.regs, |
|
CFI_NUM_REGS * sizeof(struct cfi_reg)); |
|
state->stack_size = initial_func_cfi.cfa.offset; |
|
} |
|
|
|
static int read_unwind_hints(struct objtool_file *file) |
|
{ |
|
struct section *sec, *relocsec; |
|
struct reloc *reloc; |
|
struct unwind_hint *hint; |
|
struct instruction *insn; |
|
int i; |
|
|
|
sec = find_section_by_name(file->elf, ".discard.unwind_hints"); |
|
if (!sec) |
|
return 0; |
|
|
|
relocsec = sec->reloc; |
|
if (!relocsec) { |
|
WARN("missing .rela.discard.unwind_hints section"); |
|
return -1; |
|
} |
|
|
|
if (sec->sh.sh_size % sizeof(struct unwind_hint)) { |
|
WARN("struct unwind_hint size mismatch"); |
|
return -1; |
|
} |
|
|
|
file->hints = true; |
|
|
|
for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) { |
|
hint = (struct unwind_hint *)sec->data->d_buf + i; |
|
|
|
reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint)); |
|
if (!reloc) { |
|
WARN("can't find reloc for unwind_hints[%d]", i); |
|
return -1; |
|
} |
|
|
|
insn = find_insn(file, reloc->sym->sec, reloc->addend); |
|
if (!insn) { |
|
WARN("can't find insn for unwind_hints[%d]", i); |
|
return -1; |
|
} |
|
|
|
insn->hint = true; |
|
|
|
if (hint->type == UNWIND_HINT_TYPE_FUNC) { |
|
set_func_state(&insn->cfi); |
|
continue; |
|
} |
|
|
|
if (arch_decode_hint_reg(insn, hint->sp_reg)) { |
|
WARN_FUNC("unsupported unwind_hint sp base reg %d", |
|
insn->sec, insn->offset, hint->sp_reg); |
|
return -1; |
|
} |
|
|
|
insn->cfi.cfa.offset = bswap_if_needed(hint->sp_offset); |
|
insn->cfi.type = hint->type; |
|
insn->cfi.end = hint->end; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static int read_retpoline_hints(struct objtool_file *file) |
|
{ |
|
struct section *sec; |
|
struct instruction *insn; |
|
struct reloc *reloc; |
|
|
|
sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe"); |
|
if (!sec) |
|
return 0; |
|
|
|
list_for_each_entry(reloc, &sec->reloc_list, list) { |
|
if (reloc->sym->type != STT_SECTION) { |
|
WARN("unexpected relocation symbol type in %s", sec->name); |
|
return -1; |
|
} |
|
|
|
insn = find_insn(file, reloc->sym->sec, reloc->addend); |
|
if (!insn) { |
|
WARN("bad .discard.retpoline_safe entry"); |
|
return -1; |
|
} |
|
|
|
if (insn->type != INSN_JUMP_DYNAMIC && |
|
insn->type != INSN_CALL_DYNAMIC) { |
|
WARN_FUNC("retpoline_safe hint not an indirect jump/call", |
|
insn->sec, insn->offset); |
|
return -1; |
|
} |
|
|
|
insn->retpoline_safe = true; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static int read_instr_hints(struct objtool_file *file) |
|
{ |
|
struct section *sec; |
|
struct instruction *insn; |
|
struct reloc *reloc; |
|
|
|
sec = find_section_by_name(file->elf, ".rela.discard.instr_end"); |
|
if (!sec) |
|
return 0; |
|
|
|
list_for_each_entry(reloc, &sec->reloc_list, list) { |
|
if (reloc->sym->type != STT_SECTION) { |
|
WARN("unexpected relocation symbol type in %s", sec->name); |
|
return -1; |
|
} |
|
|
|
insn = find_insn(file, reloc->sym->sec, reloc->addend); |
|
if (!insn) { |
|
WARN("bad .discard.instr_end entry"); |
|
return -1; |
|
} |
|
|
|
insn->instr--; |
|
} |
|
|
|
sec = find_section_by_name(file->elf, ".rela.discard.instr_begin"); |
|
if (!sec) |
|
return 0; |
|
|
|
list_for_each_entry(reloc, &sec->reloc_list, list) { |
|
if (reloc->sym->type != STT_SECTION) { |
|
WARN("unexpected relocation symbol type in %s", sec->name); |
|
return -1; |
|
} |
|
|
|
insn = find_insn(file, reloc->sym->sec, reloc->addend); |
|
if (!insn) { |
|
WARN("bad .discard.instr_begin entry"); |
|
return -1; |
|
} |
|
|
|
insn->instr++; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static int read_intra_function_calls(struct objtool_file *file) |
|
{ |
|
struct instruction *insn; |
|
struct section *sec; |
|
struct reloc *reloc; |
|
|
|
sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls"); |
|
if (!sec) |
|
return 0; |
|
|
|
list_for_each_entry(reloc, &sec->reloc_list, list) { |
|
unsigned long dest_off; |
|
|
|
if (reloc->sym->type != STT_SECTION) { |
|
WARN("unexpected relocation symbol type in %s", |
|
sec->name); |
|
return -1; |
|
} |
|
|
|
insn = find_insn(file, reloc->sym->sec, reloc->addend); |
|
if (!insn) { |
|
WARN("bad .discard.intra_function_call entry"); |
|
return -1; |
|
} |
|
|
|
if (insn->type != INSN_CALL) { |
|
WARN_FUNC("intra_function_call not a direct call", |
|
insn->sec, insn->offset); |
|
return -1; |
|
} |
|
|
|
/* |
|
* Treat intra-function CALLs as JMPs, but with a stack_op. |
|
* See add_call_destinations(), which strips stack_ops from |
|
* normal CALLs. |
|
*/ |
|
insn->type = INSN_JUMP_UNCONDITIONAL; |
|
|
|
dest_off = insn->offset + insn->len + insn->immediate; |
|
insn->jump_dest = find_insn(file, insn->sec, dest_off); |
|
if (!insn->jump_dest) { |
|
WARN_FUNC("can't find call dest at %s+0x%lx", |
|
insn->sec, insn->offset, |
|
insn->sec->name, dest_off); |
|
return -1; |
|
} |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static int read_static_call_tramps(struct objtool_file *file) |
|
{ |
|
struct section *sec; |
|
struct symbol *func; |
|
|
|
for_each_sec(file, sec) { |
|
list_for_each_entry(func, &sec->symbol_list, list) { |
|
if (func->bind == STB_GLOBAL && |
|
!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR, |
|
strlen(STATIC_CALL_TRAMP_PREFIX_STR))) |
|
func->static_call_tramp = true; |
|
} |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static void mark_rodata(struct objtool_file *file) |
|
{ |
|
struct section *sec; |
|
bool found = false; |
|
|
|
/* |
|
* Search for the following rodata sections, each of which can |
|
* potentially contain jump tables: |
|
* |
|
* - .rodata: can contain GCC switch tables |
|
* - .rodata.<func>: same, if -fdata-sections is being used |
|
* - .rodata..c_jump_table: contains C annotated jump tables |
|
* |
|
* .rodata.str1.* sections are ignored; they don't contain jump tables. |
|
*/ |
|
for_each_sec(file, sec) { |
|
if (!strncmp(sec->name, ".rodata", 7) && |
|
!strstr(sec->name, ".str1.")) { |
|
sec->rodata = true; |
|
found = true; |
|
} |
|
} |
|
|
|
file->rodata = found; |
|
} |
|
|
|
__weak int arch_rewrite_retpolines(struct objtool_file *file) |
|
{ |
|
return 0; |
|
} |
|
|
|
static int decode_sections(struct objtool_file *file) |
|
{ |
|
int ret; |
|
|
|
mark_rodata(file); |
|
|
|
ret = decode_instructions(file); |
|
if (ret) |
|
return ret; |
|
|
|
ret = add_dead_ends(file); |
|
if (ret) |
|
return ret; |
|
|
|
add_ignores(file); |
|
add_uaccess_safe(file); |
|
|
|
ret = add_ignore_alternatives(file); |
|
if (ret) |
|
return ret; |
|
|
|
/* |
|
* Must be before add_{jump_call}_destination. |
|
*/ |
|
ret = read_static_call_tramps(file); |
|
if (ret) |
|
return ret; |
|
|
|
/* |
|
* Must be before add_special_section_alts() as that depends on |
|
* jump_dest being set. |
|
*/ |
|
ret = add_jump_destinations(file); |
|
if (ret) |
|
return ret; |
|
|
|
ret = add_special_section_alts(file); |
|
if (ret) |
|
return ret; |
|
|
|
/* |
|
* Must be before add_call_destination(); it changes INSN_CALL to |
|
* INSN_JUMP. |
|
*/ |
|
ret = read_intra_function_calls(file); |
|
if (ret) |
|
return ret; |
|
|
|
ret = add_call_destinations(file); |
|
if (ret) |
|
return ret; |
|
|
|
ret = add_jump_table_alts(file); |
|
if (ret) |
|
return ret; |
|
|
|
ret = read_unwind_hints(file); |
|
if (ret) |
|
return ret; |
|
|
|
ret = read_retpoline_hints(file); |
|
if (ret) |
|
return ret; |
|
|
|
ret = read_instr_hints(file); |
|
if (ret) |
|
return ret; |
|
|
|
/* |
|
* Must be after add_special_section_alts(), since this will emit |
|
* alternatives. Must be after add_{jump,call}_destination(), since |
|
* those create the call insn lists. |
|
*/ |
|
ret = arch_rewrite_retpolines(file); |
|
if (ret) |
|
return ret; |
|
|
|
return 0; |
|
} |
|
|
|
static bool is_fentry_call(struct instruction *insn) |
|
{ |
|
if (insn->type == INSN_CALL && insn->call_dest && |
|
insn->call_dest->type == STT_NOTYPE && |
|
!strcmp(insn->call_dest->name, "__fentry__")) |
|
return true; |
|
|
|
return false; |
|
} |
|
|
|
static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state) |
|
{ |
|
struct cfi_state *cfi = &state->cfi; |
|
int i; |
|
|
|
if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap) |
|
return true; |
|
|
|
if (cfi->cfa.offset != initial_func_cfi.cfa.offset) |
|
return true; |
|
|
|
if (cfi->stack_size != initial_func_cfi.cfa.offset) |
|
return true; |
|
|
|
for (i = 0; i < CFI_NUM_REGS; i++) { |
|
if (cfi->regs[i].base != initial_func_cfi.regs[i].base || |
|
cfi->regs[i].offset != initial_func_cfi.regs[i].offset) |
|
return true; |
|
} |
|
|
|
return false; |
|
} |
|
|
|
static bool check_reg_frame_pos(const struct cfi_reg *reg, |
|
int expected_offset) |
|
{ |
|
return reg->base == CFI_CFA && |
|
reg->offset == expected_offset; |
|
} |
|
|
|
static bool has_valid_stack_frame(struct insn_state *state) |
|
{ |
|
struct cfi_state *cfi = &state->cfi; |
|
|
|
if (cfi->cfa.base == CFI_BP && |
|
check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) && |
|
check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8)) |
|
return true; |
|
|
|
if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP) |
|
return true; |
|
|
|
return false; |
|
} |
|
|
|
static int update_cfi_state_regs(struct instruction *insn, |
|
struct cfi_state *cfi, |
|
struct stack_op *op) |
|
{ |
|
struct cfi_reg *cfa = &cfi->cfa; |
|
|
|
if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT) |
|
return 0; |
|
|
|
/* push */ |
|
if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF) |
|
cfa->offset += 8; |
|
|
|
/* pop */ |
|
if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF) |
|
cfa->offset -= 8; |
|
|
|
/* add immediate to sp */ |
|
if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD && |
|
op->dest.reg == CFI_SP && op->src.reg == CFI_SP) |
|
cfa->offset -= op->src.offset; |
|
|
|
return 0; |
|
} |
|
|
|
static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset) |
|
{ |
|
if (arch_callee_saved_reg(reg) && |
|
cfi->regs[reg].base == CFI_UNDEFINED) { |
|
cfi->regs[reg].base = base; |
|
cfi->regs[reg].offset = offset; |
|
} |
|
} |
|
|
|
static void restore_reg(struct cfi_state *cfi, unsigned char reg) |
|
{ |
|
cfi->regs[reg].base = initial_func_cfi.regs[reg].base; |
|
cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset; |
|
} |
|
|
|
/* |
|
* A note about DRAP stack alignment: |
|
* |
|
* GCC has the concept of a DRAP register, which is used to help keep track of |
|
* the stack pointer when aligning the stack. r10 or r13 is used as the DRAP |
|
* register. The typical DRAP pattern is: |
|
* |
|
* 4c 8d 54 24 08 lea 0x8(%rsp),%r10 |
|
* 48 83 e4 c0 and $0xffffffffffffffc0,%rsp |
|
* 41 ff 72 f8 pushq -0x8(%r10) |
|
* 55 push %rbp |
|
* 48 89 e5 mov %rsp,%rbp |
|
* (more pushes) |
|
* 41 52 push %r10 |
|
* ... |
|
* 41 5a pop %r10 |
|
* (more pops) |
|
* 5d pop %rbp |
|
* 49 8d 62 f8 lea -0x8(%r10),%rsp |
|
* c3 retq |
|
* |
|
* There are some variations in the epilogues, like: |
|
* |
|
* 5b pop %rbx |
|
* 41 5a pop %r10 |
|
* 41 5c pop %r12 |
|
* 41 5d pop %r13 |
|
* 41 5e pop %r14 |
|
* c9 leaveq |
|
* 49 8d 62 f8 lea -0x8(%r10),%rsp |
|
* c3 retq |
|
* |
|
* and: |
|
* |
|
* 4c 8b 55 e8 mov -0x18(%rbp),%r10 |
|
* 48 8b 5d e0 mov -0x20(%rbp),%rbx |
|
* 4c 8b 65 f0 mov -0x10(%rbp),%r12 |
|
* 4c 8b 6d f8 mov -0x8(%rbp),%r13 |
|
* c9 leaveq |
|
* 49 8d 62 f8 lea -0x8(%r10),%rsp |
|
* c3 retq |
|
* |
|
* Sometimes r13 is used as the DRAP register, in which case it's saved and |
|
* restored beforehand: |
|
* |
|
* 41 55 push %r13 |
|
* 4c 8d 6c 24 10 lea 0x10(%rsp),%r13 |
|
* 48 83 e4 f0 and $0xfffffffffffffff0,%rsp |
|
* ... |
|
* 49 8d 65 f0 lea -0x10(%r13),%rsp |
|
* 41 5d pop %r13 |
|
* c3 retq |
|
*/ |
|
static int update_cfi_state(struct instruction *insn, |
|
struct instruction *next_insn, |
|
struct cfi_state *cfi, struct stack_op *op) |
|
{ |
|
struct cfi_reg *cfa = &cfi->cfa; |
|
struct cfi_reg *regs = cfi->regs; |
|
|
|
/* stack operations don't make sense with an undefined CFA */ |
|
if (cfa->base == CFI_UNDEFINED) { |
|
if (insn->func) { |
|
WARN_FUNC("undefined stack state", insn->sec, insn->offset); |
|
return -1; |
|
} |
|
return 0; |
|
} |
|
|
|
if (cfi->type == UNWIND_HINT_TYPE_REGS || |
|
cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL) |
|
return update_cfi_state_regs(insn, cfi, op); |
|
|
|
switch (op->dest.type) { |
|
|
|
case OP_DEST_REG: |
|
switch (op->src.type) { |
|
|
|
case OP_SRC_REG: |
|
if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && |
|
cfa->base == CFI_SP && |
|
check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) { |
|
|
|
/* mov %rsp, %rbp */ |
|
cfa->base = op->dest.reg; |
|
cfi->bp_scratch = false; |
|
} |
|
|
|
else if (op->src.reg == CFI_SP && |
|
op->dest.reg == CFI_BP && cfi->drap) { |
|
|
|
/* drap: mov %rsp, %rbp */ |
|
regs[CFI_BP].base = CFI_BP; |
|
regs[CFI_BP].offset = -cfi->stack_size; |
|
cfi->bp_scratch = false; |
|
} |
|
|
|
else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
|
|
|
/* |
|
* mov %rsp, %reg |
|
* |
|
* This is needed for the rare case where GCC |
|
* does: |
|
* |
|
* mov %rsp, %rax |
|
* ... |
|
* mov %rax, %rsp |
|
*/ |
|
cfi->vals[op->dest.reg].base = CFI_CFA; |
|
cfi->vals[op->dest.reg].offset = -cfi->stack_size; |
|
} |
|
|
|
else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP && |
|
(cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) { |
|
|
|
/* |
|
* mov %rbp, %rsp |
|
* |
|
* Restore the original stack pointer (Clang). |
|
*/ |
|
cfi->stack_size = -cfi->regs[CFI_BP].offset; |
|
} |
|
|
|
else if (op->dest.reg == cfa->base) { |
|
|
|
/* mov %reg, %rsp */ |
|
if (cfa->base == CFI_SP && |
|
cfi->vals[op->src.reg].base == CFI_CFA) { |
|
|
|
/* |
|
* This is needed for the rare case |
|
* where GCC does something dumb like: |
|
* |
|
* lea 0x8(%rsp), %rcx |
|
* ... |
|
* mov %rcx, %rsp |
|
*/ |
|
cfa->offset = -cfi->vals[op->src.reg].offset; |
|
cfi->stack_size = cfa->offset; |
|
|
|
} else if (cfa->base == CFI_SP && |
|
cfi->vals[op->src.reg].base == CFI_SP_INDIRECT && |
|
cfi->vals[op->src.reg].offset == cfa->offset) { |
|
|
|
/* |
|
* Stack swizzle: |
|
* |
|
* 1: mov %rsp, (%[tos]) |
|
* 2: mov %[tos], %rsp |
|
* ... |
|
* 3: pop %rsp |
|
* |
|
* Where: |
|
* |
|
* 1 - places a pointer to the previous |
|
* stack at the Top-of-Stack of the |
|
* new stack. |
|
* |
|
* 2 - switches to the new stack. |
|
* |
|
* 3 - pops the Top-of-Stack to restore |
|
* the original stack. |
|
* |
|
* Note: we set base to SP_INDIRECT |
|
* here and preserve offset. Therefore |
|
* when the unwinder reaches ToS it |
|
* will dereference SP and then add the |
|
* offset to find the next frame, IOW: |
|
* (%rsp) + offset. |
|
*/ |
|
cfa->base = CFI_SP_INDIRECT; |
|
|
|
} else { |
|
cfa->base = CFI_UNDEFINED; |
|
cfa->offset = 0; |
|
} |
|
} |
|
|
|
else if (op->dest.reg == CFI_SP && |
|
cfi->vals[op->src.reg].base == CFI_SP_INDIRECT && |
|
cfi->vals[op->src.reg].offset == cfa->offset) { |
|
|
|
/* |
|
* The same stack swizzle case 2) as above. But |
|
* because we can't change cfa->base, case 3) |
|
* will become a regular POP. Pretend we're a |
|
* PUSH so things don't go unbalanced. |
|
*/ |
|
cfi->stack_size += 8; |
|
} |
|
|
|
|
|
break; |
|
|
|
case OP_SRC_ADD: |
|
if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) { |
|
|
|
/* add imm, %rsp */ |
|
cfi->stack_size -= op->src.offset; |
|
if (cfa->base == CFI_SP) |
|
cfa->offset -= op->src.offset; |
|
break; |
|
} |
|
|
|
if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) { |
|
|
|
/* lea disp(%rbp), %rsp */ |
|
cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset); |
|
break; |
|
} |
|
|
|
if (!cfi->drap && op->src.reg == CFI_SP && |
|
op->dest.reg == CFI_BP && cfa->base == CFI_SP && |
|
check_reg_frame_pos(®s[CFI_BP], -cfa->offset + op->src.offset)) { |
|
|
|
/* lea disp(%rsp), %rbp */ |
|
cfa->base = CFI_BP; |
|
cfa->offset -= op->src.offset; |
|
cfi->bp_scratch = false; |
|
break; |
|
} |
|
|
|
if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
|
|
|
/* drap: lea disp(%rsp), %drap */ |
|
cfi->drap_reg = op->dest.reg; |
|
|
|
/* |
|
* lea disp(%rsp), %reg |
|
* |
|
* This is needed for the rare case where GCC |
|
* does something dumb like: |
|
* |
|
* lea 0x8(%rsp), %rcx |
|
* ... |
|
* mov %rcx, %rsp |
|
*/ |
|
cfi->vals[op->dest.reg].base = CFI_CFA; |
|
cfi->vals[op->dest.reg].offset = \ |
|
-cfi->stack_size + op->src.offset; |
|
|
|
break; |
|
} |
|
|
|
if (cfi->drap && op->dest.reg == CFI_SP && |
|
op->src.reg == cfi->drap_reg) { |
|
|
|
/* drap: lea disp(%drap), %rsp */ |
|
cfa->base = CFI_SP; |
|
cfa->offset = cfi->stack_size = -op->src.offset; |
|
cfi->drap_reg = CFI_UNDEFINED; |
|
cfi->drap = false; |
|
break; |
|
} |
|
|
|
if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) { |
|
WARN_FUNC("unsupported stack register modification", |
|
insn->sec, insn->offset); |
|
return -1; |
|
} |
|
|
|
break; |
|
|
|
case OP_SRC_AND: |
|
if (op->dest.reg != CFI_SP || |
|
(cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) || |
|
(cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) { |
|
WARN_FUNC("unsupported stack pointer realignment", |
|
insn->sec, insn->offset); |
|
return -1; |
|
} |
|
|
|
if (cfi->drap_reg != CFI_UNDEFINED) { |
|
/* drap: and imm, %rsp */ |
|
cfa->base = cfi->drap_reg; |
|
cfa->offset = cfi->stack_size = 0; |
|
cfi->drap = true; |
|
} |
|
|
|
/* |
|
* Older versions of GCC (4.8ish) realign the stack |
|
* without DRAP, with a frame pointer. |
|
*/ |
|
|
|
break; |
|
|
|
case OP_SRC_POP: |
|
case OP_SRC_POPF: |
|
if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) { |
|
|
|
/* pop %rsp; # restore from a stack swizzle */ |
|
cfa->base = CFI_SP; |
|
break; |
|
} |
|
|
|
if (!cfi->drap && op->dest.reg == cfa->base) { |
|
|
|
/* pop %rbp */ |
|
cfa->base = CFI_SP; |
|
} |
|
|
|
if (cfi->drap && cfa->base == CFI_BP_INDIRECT && |
|
op->dest.reg == cfi->drap_reg && |
|
cfi->drap_offset == -cfi->stack_size) { |
|
|
|
/* drap: pop %drap */ |
|
cfa->base = cfi->drap_reg; |
|
cfa->offset = 0; |
|
cfi->drap_offset = -1; |
|
|
|
} else if (cfi->stack_size == -regs[op->dest.reg].offset) { |
|
|
|
/* pop %reg */ |
|
restore_reg(cfi, op->dest.reg); |
|
} |
|
|
|
cfi->stack_size -= 8; |
|
if (cfa->base == CFI_SP) |
|
cfa->offset -= 8; |
|
|
|
break; |
|
|
|
case OP_SRC_REG_INDIRECT: |
|
if (!cfi->drap && op->dest.reg == cfa->base && |
|
op->dest.reg == CFI_BP) { |
|
|
|
/* mov disp(%rsp), %rbp */ |
|
cfa->base = CFI_SP; |
|
cfa->offset = cfi->stack_size; |
|
} |
|
|
|
if (cfi->drap && op->src.reg == CFI_BP && |
|
op->src.offset == cfi->drap_offset) { |
|
|
|
/* drap: mov disp(%rbp), %drap */ |
|
cfa->base = cfi->drap_reg; |
|
cfa->offset = 0; |
|
cfi->drap_offset = -1; |
|
} |
|
|
|
if (cfi->drap && op->src.reg == CFI_BP && |
|
op->src.offset == regs[op->dest.reg].offset) { |
|
|
|
/* drap: mov disp(%rbp), %reg */ |
|
restore_reg(cfi, op->dest.reg); |
|
|
|
} else if (op->src.reg == cfa->base && |
|
op->src.offset == regs[op->dest.reg].offset + cfa->offset) { |
|
|
|
/* mov disp(%rbp), %reg */ |
|
/* mov disp(%rsp), %reg */ |
|
restore_reg(cfi, op->dest.reg); |
|
|
|
} else if (op->src.reg == CFI_SP && |
|
op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) { |
|
|
|
/* mov disp(%rsp), %reg */ |
|
restore_reg(cfi, op->dest.reg); |
|
} |
|
|
|
break; |
|
|
|
default: |
|
WARN_FUNC("unknown stack-related instruction", |
|
insn->sec, insn->offset); |
|
return -1; |
|
} |
|
|
|
break; |
|
|
|
case OP_DEST_PUSH: |
|
case OP_DEST_PUSHF: |
|
cfi->stack_size += 8; |
|
if (cfa->base == CFI_SP) |
|
cfa->offset += 8; |
|
|
|
if (op->src.type != OP_SRC_REG) |
|
break; |
|
|
|
if (cfi->drap) { |
|
if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) { |
|
|
|
/* drap: push %drap */ |
|
cfa->base = CFI_BP_INDIRECT; |
|
cfa->offset = -cfi->stack_size; |
|
|
|
/* save drap so we know when to restore it */ |
|
cfi->drap_offset = -cfi->stack_size; |
|
|
|
} else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) { |
|
|
|
/* drap: push %rbp */ |
|
cfi->stack_size = 0; |
|
|
|
} else { |
|
|
|
/* drap: push %reg */ |
|
save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size); |
|
} |
|
|
|
} else { |
|
|
|
/* push %reg */ |
|
save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size); |
|
} |
|
|
|
/* detect when asm code uses rbp as a scratch register */ |
|
if (!no_fp && insn->func && op->src.reg == CFI_BP && |
|
cfa->base != CFI_BP) |
|
cfi->bp_scratch = true; |
|
break; |
|
|
|
case OP_DEST_REG_INDIRECT: |
|
|
|
if (cfi->drap) { |
|
if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) { |
|
|
|
/* drap: mov %drap, disp(%rbp) */ |
|
cfa->base = CFI_BP_INDIRECT; |
|
cfa->offset = op->dest.offset; |
|
|
|
/* save drap offset so we know when to restore it */ |
|
cfi->drap_offset = op->dest.offset; |
|
} else { |
|
|
|
/* drap: mov reg, disp(%rbp) */ |
|
save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset); |
|
} |
|
|
|
} else if (op->dest.reg == cfa->base) { |
|
|
|
/* mov reg, disp(%rbp) */ |
|
/* mov reg, disp(%rsp) */ |
|
save_reg(cfi, op->src.reg, CFI_CFA, |
|
op->dest.offset - cfi->cfa.offset); |
|
|
|
} else if (op->dest.reg == CFI_SP) { |
|
|
|
/* mov reg, disp(%rsp) */ |
|
save_reg(cfi, op->src.reg, CFI_CFA, |
|
op->dest.offset - cfi->stack_size); |
|
|
|
} else if (op->src.reg == CFI_SP && op->dest.offset == 0) { |
|
|
|
/* mov %rsp, (%reg); # setup a stack swizzle. */ |
|
cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT; |
|
cfi->vals[op->dest.reg].offset = cfa->offset; |
|
} |
|
|
|
break; |
|
|
|
case OP_DEST_MEM: |
|
if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) { |
|
WARN_FUNC("unknown stack-related memory operation", |
|
insn->sec, insn->offset); |
|
return -1; |
|
} |
|
|
|
/* pop mem */ |
|
cfi->stack_size -= 8; |
|
if (cfa->base == CFI_SP) |
|
cfa->offset -= 8; |
|
|
|
break; |
|
|
|
default: |
|
WARN_FUNC("unknown stack-related instruction", |
|
insn->sec, insn->offset); |
|
return -1; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* The stack layouts of alternatives instructions can sometimes diverge when |
|
* they have stack modifications. That's fine as long as the potential stack |
|
* layouts don't conflict at any given potential instruction boundary. |
|
* |
|
* Flatten the CFIs of the different alternative code streams (both original |
|
* and replacement) into a single shared CFI array which can be used to detect |
|
* conflicts and nicely feed a linear array of ORC entries to the unwinder. |
|
*/ |
|
static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn) |
|
{ |
|
struct cfi_state **alt_cfi; |
|
int group_off; |
|
|
|
if (!insn->alt_group) |
|
return 0; |
|
|
|
alt_cfi = insn->alt_group->cfi; |
|
group_off = insn->offset - insn->alt_group->first_insn->offset; |
|
|
|
if (!alt_cfi[group_off]) { |
|
alt_cfi[group_off] = &insn->cfi; |
|
} else { |
|
if (memcmp(alt_cfi[group_off], &insn->cfi, sizeof(struct cfi_state))) { |
|
WARN_FUNC("stack layout conflict in alternatives", |
|
insn->sec, insn->offset); |
|
return -1; |
|
} |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static int handle_insn_ops(struct instruction *insn, |
|
struct instruction *next_insn, |
|
struct insn_state *state) |
|
{ |
|
struct stack_op *op; |
|
|
|
list_for_each_entry(op, &insn->stack_ops, list) { |
|
|
|
if (update_cfi_state(insn, next_insn, &state->cfi, op)) |
|
return 1; |
|
|
|
if (!insn->alt_group) |
|
continue; |
|
|
|
if (op->dest.type == OP_DEST_PUSHF) { |
|
if (!state->uaccess_stack) { |
|
state->uaccess_stack = 1; |
|
} else if (state->uaccess_stack >> 31) { |
|
WARN_FUNC("PUSHF stack exhausted", |
|
insn->sec, insn->offset); |
|
return 1; |
|
} |
|
state->uaccess_stack <<= 1; |
|
state->uaccess_stack |= state->uaccess; |
|
} |
|
|
|
if (op->src.type == OP_SRC_POPF) { |
|
if (state->uaccess_stack) { |
|
state->uaccess = state->uaccess_stack & 1; |
|
state->uaccess_stack >>= 1; |
|
if (state->uaccess_stack == 1) |
|
state->uaccess_stack = 0; |
|
} |
|
} |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2) |
|
{ |
|
struct cfi_state *cfi1 = &insn->cfi; |
|
int i; |
|
|
|
if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) { |
|
|
|
WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d", |
|
insn->sec, insn->offset, |
|
cfi1->cfa.base, cfi1->cfa.offset, |
|
cfi2->cfa.base, cfi2->cfa.offset); |
|
|
|
} else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) { |
|
for (i = 0; i < CFI_NUM_REGS; i++) { |
|
if (!memcmp(&cfi1->regs[i], &cfi2->regs[i], |
|
sizeof(struct cfi_reg))) |
|
continue; |
|
|
|
WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", |
|
insn->sec, insn->offset, |
|
i, cfi1->regs[i].base, cfi1->regs[i].offset, |
|
i, cfi2->regs[i].base, cfi2->regs[i].offset); |
|
break; |
|
} |
|
|
|
} else if (cfi1->type != cfi2->type) { |
|
|
|
WARN_FUNC("stack state mismatch: type1=%d type2=%d", |
|
insn->sec, insn->offset, cfi1->type, cfi2->type); |
|
|
|
} else if (cfi1->drap != cfi2->drap || |
|
(cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) || |
|
(cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) { |
|
|
|
WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)", |
|
insn->sec, insn->offset, |
|
cfi1->drap, cfi1->drap_reg, cfi1->drap_offset, |
|
cfi2->drap, cfi2->drap_reg, cfi2->drap_offset); |
|
|
|
} else |
|
return true; |
|
|
|
return false; |
|
} |
|
|
|
static inline bool func_uaccess_safe(struct symbol *func) |
|
{ |
|
if (func) |
|
return func->uaccess_safe; |
|
|
|
return false; |
|
} |
|
|
|
static inline const char *call_dest_name(struct instruction *insn) |
|
{ |
|
if (insn->call_dest) |
|
return insn->call_dest->name; |
|
|
|
return "{dynamic}"; |
|
} |
|
|
|
static inline bool noinstr_call_dest(struct symbol *func) |
|
{ |
|
/* |
|
* We can't deal with indirect function calls at present; |
|
* assume they're instrumented. |
|
*/ |
|
if (!func) |
|
return false; |
|
|
|
/* |
|
* If the symbol is from a noinstr section; we good. |
|
*/ |
|
if (func->sec->noinstr) |
|
return true; |
|
|
|
/* |
|
* The __ubsan_handle_*() calls are like WARN(), they only happen when |
|
* something 'BAD' happened. At the risk of taking the machine down, |
|
* let them proceed to get the message out. |
|
*/ |
|
if (!strncmp(func->name, "__ubsan_handle_", 15)) |
|
return true; |
|
|
|
return false; |
|
} |
|
|
|
static int validate_call(struct instruction *insn, struct insn_state *state) |
|
{ |
|
if (state->noinstr && state->instr <= 0 && |
|
!noinstr_call_dest(insn->call_dest)) { |
|
WARN_FUNC("call to %s() leaves .noinstr.text section", |
|
insn->sec, insn->offset, call_dest_name(insn)); |
|
return 1; |
|
} |
|
|
|
if (state->uaccess && !func_uaccess_safe(insn->call_dest)) { |
|
WARN_FUNC("call to %s() with UACCESS enabled", |
|
insn->sec, insn->offset, call_dest_name(insn)); |
|
return 1; |
|
} |
|
|
|
if (state->df) { |
|
WARN_FUNC("call to %s() with DF set", |
|
insn->sec, insn->offset, call_dest_name(insn)); |
|
return 1; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static int validate_sibling_call(struct instruction *insn, struct insn_state *state) |
|
{ |
|
if (has_modified_stack_frame(insn, state)) { |
|
WARN_FUNC("sibling call from callable instruction with modified stack frame", |
|
insn->sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
return validate_call(insn, state); |
|
} |
|
|
|
static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state) |
|
{ |
|
if (state->noinstr && state->instr > 0) { |
|
WARN_FUNC("return with instrumentation enabled", |
|
insn->sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
if (state->uaccess && !func_uaccess_safe(func)) { |
|
WARN_FUNC("return with UACCESS enabled", |
|
insn->sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
if (!state->uaccess && func_uaccess_safe(func)) { |
|
WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", |
|
insn->sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
if (state->df) { |
|
WARN_FUNC("return with DF set", |
|
insn->sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
if (func && has_modified_stack_frame(insn, state)) { |
|
WARN_FUNC("return with modified stack frame", |
|
insn->sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
if (state->cfi.bp_scratch) { |
|
WARN_FUNC("BP used as a scratch register", |
|
insn->sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static struct instruction *next_insn_to_validate(struct objtool_file *file, |
|
struct instruction *insn) |
|
{ |
|
struct alt_group *alt_group = insn->alt_group; |
|
|
|
/* |
|
* Simulate the fact that alternatives are patched in-place. When the |
|
* end of a replacement alt_group is reached, redirect objtool flow to |
|
* the end of the original alt_group. |
|
*/ |
|
if (alt_group && insn == alt_group->last_insn && alt_group->orig_group) |
|
return next_insn_same_sec(file, alt_group->orig_group->last_insn); |
|
|
|
return next_insn_same_sec(file, insn); |
|
} |
|
|
|
/* |
|
* Follow the branch starting at the given instruction, and recursively follow |
|
* any other branches (jumps). Meanwhile, track the frame pointer state at |
|
* each instruction and validate all the rules described in |
|
* tools/objtool/Documentation/stack-validation.txt. |
|
*/ |
|
static int validate_branch(struct objtool_file *file, struct symbol *func, |
|
struct instruction *insn, struct insn_state state) |
|
{ |
|
struct alternative *alt; |
|
struct instruction *next_insn; |
|
struct section *sec; |
|
u8 visited; |
|
int ret; |
|
|
|
sec = insn->sec; |
|
|
|
while (1) { |
|
next_insn = next_insn_to_validate(file, insn); |
|
|
|
if (file->c_file && func && insn->func && func != insn->func->pfunc) { |
|
WARN("%s() falls through to next function %s()", |
|
func->name, insn->func->name); |
|
return 1; |
|
} |
|
|
|
if (func && insn->ignore) { |
|
WARN_FUNC("BUG: why am I validating an ignored function?", |
|
sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
visited = 1 << state.uaccess; |
|
if (insn->visited) { |
|
if (!insn->hint && !insn_cfi_match(insn, &state.cfi)) |
|
return 1; |
|
|
|
if (insn->visited & visited) |
|
return 0; |
|
} |
|
|
|
if (state.noinstr) |
|
state.instr += insn->instr; |
|
|
|
if (insn->hint) |
|
state.cfi = insn->cfi; |
|
else |
|
insn->cfi = state.cfi; |
|
|
|
insn->visited |= visited; |
|
|
|
if (propagate_alt_cfi(file, insn)) |
|
return 1; |
|
|
|
if (!insn->ignore_alts && !list_empty(&insn->alts)) { |
|
bool skip_orig = false; |
|
|
|
list_for_each_entry(alt, &insn->alts, list) { |
|
if (alt->skip_orig) |
|
skip_orig = true; |
|
|
|
ret = validate_branch(file, func, alt->insn, state); |
|
if (ret) { |
|
if (backtrace) |
|
BT_FUNC("(alt)", insn); |
|
return ret; |
|
} |
|
} |
|
|
|
if (skip_orig) |
|
return 0; |
|
} |
|
|
|
if (handle_insn_ops(insn, next_insn, &state)) |
|
return 1; |
|
|
|
switch (insn->type) { |
|
|
|
case INSN_RETURN: |
|
return validate_return(func, insn, &state); |
|
|
|
case INSN_CALL: |
|
case INSN_CALL_DYNAMIC: |
|
ret = validate_call(insn, &state); |
|
if (ret) |
|
return ret; |
|
|
|
if (!no_fp && func && !is_fentry_call(insn) && |
|
!has_valid_stack_frame(&state)) { |
|
WARN_FUNC("call without frame pointer save/setup", |
|
sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
if (dead_end_function(file, insn->call_dest)) |
|
return 0; |
|
|
|
break; |
|
|
|
case INSN_JUMP_CONDITIONAL: |
|
case INSN_JUMP_UNCONDITIONAL: |
|
if (is_sibling_call(insn)) { |
|
ret = validate_sibling_call(insn, &state); |
|
if (ret) |
|
return ret; |
|
|
|
} else if (insn->jump_dest) { |
|
ret = validate_branch(file, func, |
|
insn->jump_dest, state); |
|
if (ret) { |
|
if (backtrace) |
|
BT_FUNC("(branch)", insn); |
|
return ret; |
|
} |
|
} |
|
|
|
if (insn->type == INSN_JUMP_UNCONDITIONAL) |
|
return 0; |
|
|
|
break; |
|
|
|
case INSN_JUMP_DYNAMIC: |
|
case INSN_JUMP_DYNAMIC_CONDITIONAL: |
|
if (is_sibling_call(insn)) { |
|
ret = validate_sibling_call(insn, &state); |
|
if (ret) |
|
return ret; |
|
} |
|
|
|
if (insn->type == INSN_JUMP_DYNAMIC) |
|
return 0; |
|
|
|
break; |
|
|
|
case INSN_CONTEXT_SWITCH: |
|
if (func && (!next_insn || !next_insn->hint)) { |
|
WARN_FUNC("unsupported instruction in callable function", |
|
sec, insn->offset); |
|
return 1; |
|
} |
|
return 0; |
|
|
|
case INSN_STAC: |
|
if (state.uaccess) { |
|
WARN_FUNC("recursive UACCESS enable", sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
state.uaccess = true; |
|
break; |
|
|
|
case INSN_CLAC: |
|
if (!state.uaccess && func) { |
|
WARN_FUNC("redundant UACCESS disable", sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
if (func_uaccess_safe(func) && !state.uaccess_stack) { |
|
WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
state.uaccess = false; |
|
break; |
|
|
|
case INSN_STD: |
|
if (state.df) { |
|
WARN_FUNC("recursive STD", sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
state.df = true; |
|
break; |
|
|
|
case INSN_CLD: |
|
if (!state.df && func) { |
|
WARN_FUNC("redundant CLD", sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
state.df = false; |
|
break; |
|
|
|
default: |
|
break; |
|
} |
|
|
|
if (insn->dead_end) |
|
return 0; |
|
|
|
if (!next_insn) { |
|
if (state.cfi.cfa.base == CFI_UNDEFINED) |
|
return 0; |
|
WARN("%s: unexpected end of section", sec->name); |
|
return 1; |
|
} |
|
|
|
insn = next_insn; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static int validate_unwind_hints(struct objtool_file *file, struct section *sec) |
|
{ |
|
struct instruction *insn; |
|
struct insn_state state; |
|
int ret, warnings = 0; |
|
|
|
if (!file->hints) |
|
return 0; |
|
|
|
init_insn_state(&state, sec); |
|
|
|
if (sec) { |
|
insn = find_insn(file, sec, 0); |
|
if (!insn) |
|
return 0; |
|
} else { |
|
insn = list_first_entry(&file->insn_list, typeof(*insn), list); |
|
} |
|
|
|
while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) { |
|
if (insn->hint && !insn->visited) { |
|
ret = validate_branch(file, insn->func, insn, state); |
|
if (ret && backtrace) |
|
BT_FUNC("<=== (hint)", insn); |
|
warnings += ret; |
|
} |
|
|
|
insn = list_next_entry(insn, list); |
|
} |
|
|
|
return warnings; |
|
} |
|
|
|
static int validate_retpoline(struct objtool_file *file) |
|
{ |
|
struct instruction *insn; |
|
int warnings = 0; |
|
|
|
for_each_insn(file, insn) { |
|
if (insn->type != INSN_JUMP_DYNAMIC && |
|
insn->type != INSN_CALL_DYNAMIC) |
|
continue; |
|
|
|
if (insn->retpoline_safe) |
|
continue; |
|
|
|
/* |
|
* .init.text code is ran before userspace and thus doesn't |
|
* strictly need retpolines, except for modules which are |
|
* loaded late, they very much do need retpoline in their |
|
* .init.text |
|
*/ |
|
if (!strcmp(insn->sec->name, ".init.text") && !module) |
|
continue; |
|
|
|
WARN_FUNC("indirect %s found in RETPOLINE build", |
|
insn->sec, insn->offset, |
|
insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); |
|
|
|
warnings++; |
|
} |
|
|
|
return warnings; |
|
} |
|
|
|
static bool is_kasan_insn(struct instruction *insn) |
|
{ |
|
return (insn->type == INSN_CALL && |
|
!strcmp(insn->call_dest->name, "__asan_handle_no_return")); |
|
} |
|
|
|
static bool is_ubsan_insn(struct instruction *insn) |
|
{ |
|
return (insn->type == INSN_CALL && |
|
!strcmp(insn->call_dest->name, |
|
"__ubsan_handle_builtin_unreachable")); |
|
} |
|
|
|
static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn) |
|
{ |
|
int i; |
|
struct instruction *prev_insn; |
|
|
|
if (insn->ignore || insn->type == INSN_NOP) |
|
return true; |
|
|
|
/* |
|
* Ignore any unused exceptions. This can happen when a whitelisted |
|
* function has an exception table entry. |
|
* |
|
* Also ignore alternative replacement instructions. This can happen |
|
* when a whitelisted function uses one of the ALTERNATIVE macros. |
|
*/ |
|
if (!strcmp(insn->sec->name, ".fixup") || |
|
!strcmp(insn->sec->name, ".altinstr_replacement") || |
|
!strcmp(insn->sec->name, ".altinstr_aux")) |
|
return true; |
|
|
|
if (!insn->func) |
|
return false; |
|
|
|
/* |
|
* CONFIG_UBSAN_TRAP inserts a UD2 when it sees |
|
* __builtin_unreachable(). The BUG() macro has an unreachable() after |
|
* the UD2, which causes GCC's undefined trap logic to emit another UD2 |
|
* (or occasionally a JMP to UD2). |
|
* |
|
* It may also insert a UD2 after calling a __noreturn function. |
|
*/ |
|
prev_insn = list_prev_entry(insn, list); |
|
if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) && |
|
(insn->type == INSN_BUG || |
|
(insn->type == INSN_JUMP_UNCONDITIONAL && |
|
insn->jump_dest && insn->jump_dest->type == INSN_BUG))) |
|
return true; |
|
|
|
/* |
|
* Check if this (or a subsequent) instruction is related to |
|
* CONFIG_UBSAN or CONFIG_KASAN. |
|
* |
|
* End the search at 5 instructions to avoid going into the weeds. |
|
*/ |
|
for (i = 0; i < 5; i++) { |
|
|
|
if (is_kasan_insn(insn) || is_ubsan_insn(insn)) |
|
return true; |
|
|
|
if (insn->type == INSN_JUMP_UNCONDITIONAL) { |
|
if (insn->jump_dest && |
|
insn->jump_dest->func == insn->func) { |
|
insn = insn->jump_dest; |
|
continue; |
|
} |
|
|
|
break; |
|
} |
|
|
|
if (insn->offset + insn->len >= insn->func->offset + insn->func->len) |
|
break; |
|
|
|
insn = list_next_entry(insn, list); |
|
} |
|
|
|
return false; |
|
} |
|
|
|
static int validate_symbol(struct objtool_file *file, struct section *sec, |
|
struct symbol *sym, struct insn_state *state) |
|
{ |
|
struct instruction *insn; |
|
int ret; |
|
|
|
if (!sym->len) { |
|
WARN("%s() is missing an ELF size annotation", sym->name); |
|
return 1; |
|
} |
|
|
|
if (sym->pfunc != sym || sym->alias != sym) |
|
return 0; |
|
|
|
insn = find_insn(file, sec, sym->offset); |
|
if (!insn || insn->ignore || insn->visited) |
|
return 0; |
|
|
|
state->uaccess = sym->uaccess_safe; |
|
|
|
ret = validate_branch(file, insn->func, insn, *state); |
|
if (ret && backtrace) |
|
BT_FUNC("<=== (sym)", insn); |
|
return ret; |
|
} |
|
|
|
static int validate_section(struct objtool_file *file, struct section *sec) |
|
{ |
|
struct insn_state state; |
|
struct symbol *func; |
|
int warnings = 0; |
|
|
|
list_for_each_entry(func, &sec->symbol_list, list) { |
|
if (func->type != STT_FUNC) |
|
continue; |
|
|
|
init_insn_state(&state, sec); |
|
set_func_state(&state.cfi); |
|
|
|
warnings += validate_symbol(file, sec, func, &state); |
|
} |
|
|
|
return warnings; |
|
} |
|
|
|
static int validate_vmlinux_functions(struct objtool_file *file) |
|
{ |
|
struct section *sec; |
|
int warnings = 0; |
|
|
|
sec = find_section_by_name(file->elf, ".noinstr.text"); |
|
if (sec) { |
|
warnings += validate_section(file, sec); |
|
warnings += validate_unwind_hints(file, sec); |
|
} |
|
|
|
sec = find_section_by_name(file->elf, ".entry.text"); |
|
if (sec) { |
|
warnings += validate_section(file, sec); |
|
warnings += validate_unwind_hints(file, sec); |
|
} |
|
|
|
return warnings; |
|
} |
|
|
|
static int validate_functions(struct objtool_file *file) |
|
{ |
|
struct section *sec; |
|
int warnings = 0; |
|
|
|
for_each_sec(file, sec) { |
|
if (!(sec->sh.sh_flags & SHF_EXECINSTR)) |
|
continue; |
|
|
|
warnings += validate_section(file, sec); |
|
} |
|
|
|
return warnings; |
|
} |
|
|
|
static int validate_reachable_instructions(struct objtool_file *file) |
|
{ |
|
struct instruction *insn; |
|
|
|
if (file->ignore_unreachables) |
|
return 0; |
|
|
|
for_each_insn(file, insn) { |
|
if (insn->visited || ignore_unreachable_insn(file, insn)) |
|
continue; |
|
|
|
WARN_FUNC("unreachable instruction", insn->sec, insn->offset); |
|
return 1; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
int check(struct objtool_file *file) |
|
{ |
|
int ret, warnings = 0; |
|
|
|
arch_initial_func_cfi_state(&initial_func_cfi); |
|
|
|
ret = decode_sections(file); |
|
if (ret < 0) |
|
goto out; |
|
warnings += ret; |
|
|
|
if (list_empty(&file->insn_list)) |
|
goto out; |
|
|
|
if (vmlinux && !validate_dup) { |
|
ret = validate_vmlinux_functions(file); |
|
if (ret < 0) |
|
goto out; |
|
|
|
warnings += ret; |
|
goto out; |
|
} |
|
|
|
if (retpoline) { |
|
ret = validate_retpoline(file); |
|
if (ret < 0) |
|
return ret; |
|
warnings += ret; |
|
} |
|
|
|
ret = validate_functions(file); |
|
if (ret < 0) |
|
goto out; |
|
warnings += ret; |
|
|
|
ret = validate_unwind_hints(file, NULL); |
|
if (ret < 0) |
|
goto out; |
|
warnings += ret; |
|
|
|
if (!warnings) { |
|
ret = validate_reachable_instructions(file); |
|
if (ret < 0) |
|
goto out; |
|
warnings += ret; |
|
} |
|
|
|
ret = create_static_call_sections(file); |
|
if (ret < 0) |
|
goto out; |
|
warnings += ret; |
|
|
|
if (mcount) { |
|
ret = create_mcount_loc_sections(file); |
|
if (ret < 0) |
|
goto out; |
|
warnings += ret; |
|
} |
|
|
|
out: |
|
/* |
|
* For now, don't fail the kernel build on fatal warnings. These |
|
* errors are still fairly common due to the growing matrix of |
|
* supported toolchains and their recent pace of change. |
|
*/ |
|
return 0; |
|
}
|
|
|