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1276 lines
30 KiB
1276 lines
30 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* core.c - Kernel Live Patching Core |
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* |
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* Copyright (C) 2014 Seth Jennings <[email protected]> |
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* Copyright (C) 2014 SUSE |
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*/ |
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|
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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|
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#include <linux/module.h> |
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#include <linux/kernel.h> |
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#include <linux/mutex.h> |
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#include <linux/slab.h> |
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#include <linux/list.h> |
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#include <linux/kallsyms.h> |
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#include <linux/livepatch.h> |
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#include <linux/elf.h> |
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#include <linux/moduleloader.h> |
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#include <linux/completion.h> |
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#include <linux/memory.h> |
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#include <linux/rcupdate.h> |
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#include <asm/cacheflush.h> |
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#include "core.h" |
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#include "patch.h" |
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#include "state.h" |
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#include "transition.h" |
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|
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/* |
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* klp_mutex is a coarse lock which serializes access to klp data. All |
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* accesses to klp-related variables and structures must have mutex protection, |
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* except within the following functions which carefully avoid the need for it: |
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* |
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* - klp_ftrace_handler() |
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* - klp_update_patch_state() |
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*/ |
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DEFINE_MUTEX(klp_mutex); |
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|
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/* |
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* Actively used patches: enabled or in transition. Note that replaced |
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* or disabled patches are not listed even though the related kernel |
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* module still can be loaded. |
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*/ |
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LIST_HEAD(klp_patches); |
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|
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static struct kobject *klp_root_kobj; |
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|
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static bool klp_is_module(struct klp_object *obj) |
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{ |
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return obj->name; |
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} |
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|
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/* sets obj->mod if object is not vmlinux and module is found */ |
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static void klp_find_object_module(struct klp_object *obj) |
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{ |
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struct module *mod; |
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|
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if (!klp_is_module(obj)) |
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return; |
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|
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rcu_read_lock_sched(); |
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/* |
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* We do not want to block removal of patched modules and therefore |
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* we do not take a reference here. The patches are removed by |
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* klp_module_going() instead. |
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*/ |
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mod = find_module(obj->name); |
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/* |
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* Do not mess work of klp_module_coming() and klp_module_going(). |
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* Note that the patch might still be needed before klp_module_going() |
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* is called. Module functions can be called even in the GOING state |
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* until mod->exit() finishes. This is especially important for |
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* patches that modify semantic of the functions. |
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*/ |
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if (mod && mod->klp_alive) |
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obj->mod = mod; |
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|
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rcu_read_unlock_sched(); |
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} |
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|
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static bool klp_initialized(void) |
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{ |
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return !!klp_root_kobj; |
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} |
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|
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static struct klp_func *klp_find_func(struct klp_object *obj, |
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struct klp_func *old_func) |
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{ |
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struct klp_func *func; |
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|
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klp_for_each_func(obj, func) { |
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if ((strcmp(old_func->old_name, func->old_name) == 0) && |
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(old_func->old_sympos == func->old_sympos)) { |
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return func; |
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} |
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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 klp_object *klp_find_object(struct klp_patch *patch, |
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struct klp_object *old_obj) |
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{ |
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struct klp_object *obj; |
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|
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klp_for_each_object(patch, obj) { |
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if (klp_is_module(old_obj)) { |
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if (klp_is_module(obj) && |
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strcmp(old_obj->name, obj->name) == 0) { |
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return obj; |
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} |
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} else if (!klp_is_module(obj)) { |
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return obj; |
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} |
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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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struct klp_find_arg { |
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const char *objname; |
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const char *name; |
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unsigned long addr; |
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unsigned long count; |
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unsigned long pos; |
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}; |
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|
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static int klp_find_callback(void *data, const char *name, |
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struct module *mod, unsigned long addr) |
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{ |
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struct klp_find_arg *args = data; |
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|
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if ((mod && !args->objname) || (!mod && args->objname)) |
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return 0; |
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|
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if (strcmp(args->name, name)) |
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return 0; |
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|
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if (args->objname && strcmp(args->objname, mod->name)) |
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return 0; |
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|
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args->addr = addr; |
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args->count++; |
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|
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/* |
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* Finish the search when the symbol is found for the desired position |
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* or the position is not defined for a non-unique symbol. |
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*/ |
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if ((args->pos && (args->count == args->pos)) || |
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(!args->pos && (args->count > 1))) |
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return 1; |
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|
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return 0; |
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} |
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|
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static int klp_find_object_symbol(const char *objname, const char *name, |
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unsigned long sympos, unsigned long *addr) |
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{ |
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struct klp_find_arg args = { |
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.objname = objname, |
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.name = name, |
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.addr = 0, |
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.count = 0, |
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.pos = sympos, |
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}; |
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|
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if (objname) |
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module_kallsyms_on_each_symbol(klp_find_callback, &args); |
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else |
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kallsyms_on_each_symbol(klp_find_callback, &args); |
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|
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/* |
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* Ensure an address was found. If sympos is 0, ensure symbol is unique; |
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* otherwise ensure the symbol position count matches sympos. |
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*/ |
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if (args.addr == 0) |
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pr_err("symbol '%s' not found in symbol table\n", name); |
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else if (args.count > 1 && sympos == 0) { |
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pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n", |
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name, objname); |
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} else if (sympos != args.count && sympos > 0) { |
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pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n", |
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sympos, name, objname ? objname : "vmlinux"); |
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} else { |
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*addr = args.addr; |
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return 0; |
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} |
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|
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*addr = 0; |
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return -EINVAL; |
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} |
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|
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static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab, |
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unsigned int symndx, Elf_Shdr *relasec, |
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const char *sec_objname) |
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{ |
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int i, cnt, ret; |
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char sym_objname[MODULE_NAME_LEN]; |
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char sym_name[KSYM_NAME_LEN]; |
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Elf_Rela *relas; |
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Elf_Sym *sym; |
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unsigned long sympos, addr; |
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bool sym_vmlinux; |
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bool sec_vmlinux = !strcmp(sec_objname, "vmlinux"); |
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|
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/* |
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* Since the field widths for sym_objname and sym_name in the sscanf() |
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* call are hard-coded and correspond to MODULE_NAME_LEN and |
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* KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN |
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* and KSYM_NAME_LEN have the values we expect them to have. |
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* |
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* Because the value of MODULE_NAME_LEN can differ among architectures, |
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* we use the smallest/strictest upper bound possible (56, based on |
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* the current definition of MODULE_NAME_LEN) to prevent overflows. |
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*/ |
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BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128); |
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|
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relas = (Elf_Rela *) relasec->sh_addr; |
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/* For each rela in this klp relocation section */ |
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for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) { |
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sym = (Elf64_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info); |
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if (sym->st_shndx != SHN_LIVEPATCH) { |
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pr_err("symbol %s is not marked as a livepatch symbol\n", |
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strtab + sym->st_name); |
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return -EINVAL; |
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} |
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|
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/* Format: .klp.sym.sym_objname.sym_name,sympos */ |
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cnt = sscanf(strtab + sym->st_name, |
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".klp.sym.%55[^.].%127[^,],%lu", |
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sym_objname, sym_name, &sympos); |
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if (cnt != 3) { |
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pr_err("symbol %s has an incorrectly formatted name\n", |
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strtab + sym->st_name); |
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return -EINVAL; |
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} |
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sym_vmlinux = !strcmp(sym_objname, "vmlinux"); |
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|
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/* |
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* Prevent module-specific KLP rela sections from referencing |
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* vmlinux symbols. This helps prevent ordering issues with |
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* module special section initializations. Presumably such |
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* symbols are exported and normal relas can be used instead. |
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*/ |
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if (!sec_vmlinux && sym_vmlinux) { |
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pr_err("invalid access to vmlinux symbol '%s' from module-specific livepatch relocation section", |
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sym_name); |
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return -EINVAL; |
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} |
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|
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/* klp_find_object_symbol() treats a NULL objname as vmlinux */ |
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ret = klp_find_object_symbol(sym_vmlinux ? NULL : sym_objname, |
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sym_name, sympos, &addr); |
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if (ret) |
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return ret; |
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|
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sym->st_value = addr; |
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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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/* |
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* At a high-level, there are two types of klp relocation sections: those which |
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* reference symbols which live in vmlinux; and those which reference symbols |
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* which live in other modules. This function is called for both types: |
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* |
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* 1) When a klp module itself loads, the module code calls this function to |
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* write vmlinux-specific klp relocations (.klp.rela.vmlinux.* sections). |
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* These relocations are written to the klp module text to allow the patched |
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* code/data to reference unexported vmlinux symbols. They're written as |
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* early as possible to ensure that other module init code (.e.g., |
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* jump_label_apply_nops) can access any unexported vmlinux symbols which |
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* might be referenced by the klp module's special sections. |
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* |
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* 2) When a to-be-patched module loads -- or is already loaded when a |
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* corresponding klp module loads -- klp code calls this function to write |
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* module-specific klp relocations (.klp.rela.{module}.* sections). These |
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* are written to the klp module text to allow the patched code/data to |
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* reference symbols which live in the to-be-patched module or one of its |
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* module dependencies. Exported symbols are supported, in addition to |
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* unexported symbols, in order to enable late module patching, which allows |
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* the to-be-patched module to be loaded and patched sometime *after* the |
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* klp module is loaded. |
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*/ |
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int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs, |
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const char *shstrtab, const char *strtab, |
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unsigned int symndx, unsigned int secndx, |
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const char *objname) |
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{ |
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int cnt, ret; |
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char sec_objname[MODULE_NAME_LEN]; |
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Elf_Shdr *sec = sechdrs + secndx; |
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|
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/* |
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* Format: .klp.rela.sec_objname.section_name |
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* See comment in klp_resolve_symbols() for an explanation |
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* of the selected field width value. |
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*/ |
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cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]", |
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sec_objname); |
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if (cnt != 1) { |
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pr_err("section %s has an incorrectly formatted name\n", |
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shstrtab + sec->sh_name); |
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return -EINVAL; |
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} |
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if (strcmp(objname ? objname : "vmlinux", sec_objname)) |
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return 0; |
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ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, sec_objname); |
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if (ret) |
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return ret; |
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return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod); |
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} |
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/* |
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* Sysfs Interface |
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* |
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* /sys/kernel/livepatch |
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* /sys/kernel/livepatch/<patch> |
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* /sys/kernel/livepatch/<patch>/enabled |
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* /sys/kernel/livepatch/<patch>/transition |
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* /sys/kernel/livepatch/<patch>/force |
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* /sys/kernel/livepatch/<patch>/<object> |
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* /sys/kernel/livepatch/<patch>/<object>/<function,sympos> |
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*/ |
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static int __klp_disable_patch(struct klp_patch *patch); |
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|
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static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr, |
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const char *buf, size_t count) |
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{ |
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struct klp_patch *patch; |
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int ret; |
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bool enabled; |
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|
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ret = kstrtobool(buf, &enabled); |
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if (ret) |
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return ret; |
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patch = container_of(kobj, struct klp_patch, kobj); |
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|
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mutex_lock(&klp_mutex); |
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|
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if (patch->enabled == enabled) { |
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/* already in requested state */ |
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ret = -EINVAL; |
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goto out; |
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} |
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|
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/* |
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* Allow to reverse a pending transition in both ways. It might be |
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* necessary to complete the transition without forcing and breaking |
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* the system integrity. |
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* |
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* Do not allow to re-enable a disabled patch. |
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*/ |
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if (patch == klp_transition_patch) |
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klp_reverse_transition(); |
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else if (!enabled) |
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ret = __klp_disable_patch(patch); |
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else |
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ret = -EINVAL; |
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|
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out: |
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mutex_unlock(&klp_mutex); |
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|
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if (ret) |
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return ret; |
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return count; |
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} |
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|
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static ssize_t enabled_show(struct kobject *kobj, |
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struct kobj_attribute *attr, char *buf) |
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{ |
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struct klp_patch *patch; |
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|
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patch = container_of(kobj, struct klp_patch, kobj); |
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return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled); |
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} |
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|
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static ssize_t transition_show(struct kobject *kobj, |
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struct kobj_attribute *attr, char *buf) |
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{ |
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struct klp_patch *patch; |
|
|
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patch = container_of(kobj, struct klp_patch, kobj); |
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return snprintf(buf, PAGE_SIZE-1, "%d\n", |
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patch == klp_transition_patch); |
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} |
|
|
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static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr, |
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const char *buf, size_t count) |
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{ |
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struct klp_patch *patch; |
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int ret; |
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bool val; |
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|
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ret = kstrtobool(buf, &val); |
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if (ret) |
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return ret; |
|
|
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if (!val) |
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return count; |
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|
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mutex_lock(&klp_mutex); |
|
|
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patch = container_of(kobj, struct klp_patch, kobj); |
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if (patch != klp_transition_patch) { |
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mutex_unlock(&klp_mutex); |
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return -EINVAL; |
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} |
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klp_force_transition(); |
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|
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mutex_unlock(&klp_mutex); |
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|
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return count; |
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} |
|
|
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static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled); |
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static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition); |
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static struct kobj_attribute force_kobj_attr = __ATTR_WO(force); |
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static struct attribute *klp_patch_attrs[] = { |
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&enabled_kobj_attr.attr, |
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&transition_kobj_attr.attr, |
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&force_kobj_attr.attr, |
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NULL |
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}; |
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ATTRIBUTE_GROUPS(klp_patch); |
|
|
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static void klp_free_object_dynamic(struct klp_object *obj) |
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{ |
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kfree(obj->name); |
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kfree(obj); |
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} |
|
|
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static void klp_init_func_early(struct klp_object *obj, |
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struct klp_func *func); |
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static void klp_init_object_early(struct klp_patch *patch, |
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struct klp_object *obj); |
|
|
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static struct klp_object *klp_alloc_object_dynamic(const char *name, |
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struct klp_patch *patch) |
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{ |
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struct klp_object *obj; |
|
|
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obj = kzalloc(sizeof(*obj), GFP_KERNEL); |
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if (!obj) |
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return NULL; |
|
|
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if (name) { |
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obj->name = kstrdup(name, GFP_KERNEL); |
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if (!obj->name) { |
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kfree(obj); |
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return NULL; |
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} |
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} |
|
|
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klp_init_object_early(patch, obj); |
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obj->dynamic = true; |
|
|
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return obj; |
|
} |
|
|
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static void klp_free_func_nop(struct klp_func *func) |
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{ |
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kfree(func->old_name); |
|
kfree(func); |
|
} |
|
|
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static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func, |
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struct klp_object *obj) |
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{ |
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struct klp_func *func; |
|
|
|
func = kzalloc(sizeof(*func), GFP_KERNEL); |
|
if (!func) |
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return NULL; |
|
|
|
if (old_func->old_name) { |
|
func->old_name = kstrdup(old_func->old_name, GFP_KERNEL); |
|
if (!func->old_name) { |
|
kfree(func); |
|
return NULL; |
|
} |
|
} |
|
|
|
klp_init_func_early(obj, func); |
|
/* |
|
* func->new_func is same as func->old_func. These addresses are |
|
* set when the object is loaded, see klp_init_object_loaded(). |
|
*/ |
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func->old_sympos = old_func->old_sympos; |
|
func->nop = true; |
|
|
|
return func; |
|
} |
|
|
|
static int klp_add_object_nops(struct klp_patch *patch, |
|
struct klp_object *old_obj) |
|
{ |
|
struct klp_object *obj; |
|
struct klp_func *func, *old_func; |
|
|
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obj = klp_find_object(patch, old_obj); |
|
|
|
if (!obj) { |
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obj = klp_alloc_object_dynamic(old_obj->name, patch); |
|
if (!obj) |
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return -ENOMEM; |
|
} |
|
|
|
klp_for_each_func(old_obj, old_func) { |
|
func = klp_find_func(obj, old_func); |
|
if (func) |
|
continue; |
|
|
|
func = klp_alloc_func_nop(old_func, obj); |
|
if (!func) |
|
return -ENOMEM; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* Add 'nop' functions which simply return to the caller to run |
|
* the original function. The 'nop' functions are added to a |
|
* patch to facilitate a 'replace' mode. |
|
*/ |
|
static int klp_add_nops(struct klp_patch *patch) |
|
{ |
|
struct klp_patch *old_patch; |
|
struct klp_object *old_obj; |
|
|
|
klp_for_each_patch(old_patch) { |
|
klp_for_each_object(old_patch, old_obj) { |
|
int err; |
|
|
|
err = klp_add_object_nops(patch, old_obj); |
|
if (err) |
|
return err; |
|
} |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static void klp_kobj_release_patch(struct kobject *kobj) |
|
{ |
|
struct klp_patch *patch; |
|
|
|
patch = container_of(kobj, struct klp_patch, kobj); |
|
complete(&patch->finish); |
|
} |
|
|
|
static struct kobj_type klp_ktype_patch = { |
|
.release = klp_kobj_release_patch, |
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.sysfs_ops = &kobj_sysfs_ops, |
|
.default_groups = klp_patch_groups, |
|
}; |
|
|
|
static void klp_kobj_release_object(struct kobject *kobj) |
|
{ |
|
struct klp_object *obj; |
|
|
|
obj = container_of(kobj, struct klp_object, kobj); |
|
|
|
if (obj->dynamic) |
|
klp_free_object_dynamic(obj); |
|
} |
|
|
|
static struct kobj_type klp_ktype_object = { |
|
.release = klp_kobj_release_object, |
|
.sysfs_ops = &kobj_sysfs_ops, |
|
}; |
|
|
|
static void klp_kobj_release_func(struct kobject *kobj) |
|
{ |
|
struct klp_func *func; |
|
|
|
func = container_of(kobj, struct klp_func, kobj); |
|
|
|
if (func->nop) |
|
klp_free_func_nop(func); |
|
} |
|
|
|
static struct kobj_type klp_ktype_func = { |
|
.release = klp_kobj_release_func, |
|
.sysfs_ops = &kobj_sysfs_ops, |
|
}; |
|
|
|
static void __klp_free_funcs(struct klp_object *obj, bool nops_only) |
|
{ |
|
struct klp_func *func, *tmp_func; |
|
|
|
klp_for_each_func_safe(obj, func, tmp_func) { |
|
if (nops_only && !func->nop) |
|
continue; |
|
|
|
list_del(&func->node); |
|
kobject_put(&func->kobj); |
|
} |
|
} |
|
|
|
/* Clean up when a patched object is unloaded */ |
|
static void klp_free_object_loaded(struct klp_object *obj) |
|
{ |
|
struct klp_func *func; |
|
|
|
obj->mod = NULL; |
|
|
|
klp_for_each_func(obj, func) { |
|
func->old_func = NULL; |
|
|
|
if (func->nop) |
|
func->new_func = NULL; |
|
} |
|
} |
|
|
|
static void __klp_free_objects(struct klp_patch *patch, bool nops_only) |
|
{ |
|
struct klp_object *obj, *tmp_obj; |
|
|
|
klp_for_each_object_safe(patch, obj, tmp_obj) { |
|
__klp_free_funcs(obj, nops_only); |
|
|
|
if (nops_only && !obj->dynamic) |
|
continue; |
|
|
|
list_del(&obj->node); |
|
kobject_put(&obj->kobj); |
|
} |
|
} |
|
|
|
static void klp_free_objects(struct klp_patch *patch) |
|
{ |
|
__klp_free_objects(patch, false); |
|
} |
|
|
|
static void klp_free_objects_dynamic(struct klp_patch *patch) |
|
{ |
|
__klp_free_objects(patch, true); |
|
} |
|
|
|
/* |
|
* This function implements the free operations that can be called safely |
|
* under klp_mutex. |
|
* |
|
* The operation must be completed by calling klp_free_patch_finish() |
|
* outside klp_mutex. |
|
*/ |
|
static void klp_free_patch_start(struct klp_patch *patch) |
|
{ |
|
if (!list_empty(&patch->list)) |
|
list_del(&patch->list); |
|
|
|
klp_free_objects(patch); |
|
} |
|
|
|
/* |
|
* This function implements the free part that must be called outside |
|
* klp_mutex. |
|
* |
|
* It must be called after klp_free_patch_start(). And it has to be |
|
* the last function accessing the livepatch structures when the patch |
|
* gets disabled. |
|
*/ |
|
static void klp_free_patch_finish(struct klp_patch *patch) |
|
{ |
|
/* |
|
* Avoid deadlock with enabled_store() sysfs callback by |
|
* calling this outside klp_mutex. It is safe because |
|
* this is called when the patch gets disabled and it |
|
* cannot get enabled again. |
|
*/ |
|
kobject_put(&patch->kobj); |
|
wait_for_completion(&patch->finish); |
|
|
|
/* Put the module after the last access to struct klp_patch. */ |
|
if (!patch->forced) |
|
module_put(patch->mod); |
|
} |
|
|
|
/* |
|
* The livepatch might be freed from sysfs interface created by the patch. |
|
* This work allows to wait until the interface is destroyed in a separate |
|
* context. |
|
*/ |
|
static void klp_free_patch_work_fn(struct work_struct *work) |
|
{ |
|
struct klp_patch *patch = |
|
container_of(work, struct klp_patch, free_work); |
|
|
|
klp_free_patch_finish(patch); |
|
} |
|
|
|
void klp_free_patch_async(struct klp_patch *patch) |
|
{ |
|
klp_free_patch_start(patch); |
|
schedule_work(&patch->free_work); |
|
} |
|
|
|
void klp_free_replaced_patches_async(struct klp_patch *new_patch) |
|
{ |
|
struct klp_patch *old_patch, *tmp_patch; |
|
|
|
klp_for_each_patch_safe(old_patch, tmp_patch) { |
|
if (old_patch == new_patch) |
|
return; |
|
klp_free_patch_async(old_patch); |
|
} |
|
} |
|
|
|
static int klp_init_func(struct klp_object *obj, struct klp_func *func) |
|
{ |
|
if (!func->old_name) |
|
return -EINVAL; |
|
|
|
/* |
|
* NOPs get the address later. The patched module must be loaded, |
|
* see klp_init_object_loaded(). |
|
*/ |
|
if (!func->new_func && !func->nop) |
|
return -EINVAL; |
|
|
|
if (strlen(func->old_name) >= KSYM_NAME_LEN) |
|
return -EINVAL; |
|
|
|
INIT_LIST_HEAD(&func->stack_node); |
|
func->patched = false; |
|
func->transition = false; |
|
|
|
/* The format for the sysfs directory is <function,sympos> where sympos |
|
* is the nth occurrence of this symbol in kallsyms for the patched |
|
* object. If the user selects 0 for old_sympos, then 1 will be used |
|
* since a unique symbol will be the first occurrence. |
|
*/ |
|
return kobject_add(&func->kobj, &obj->kobj, "%s,%lu", |
|
func->old_name, |
|
func->old_sympos ? func->old_sympos : 1); |
|
} |
|
|
|
static int klp_apply_object_relocs(struct klp_patch *patch, |
|
struct klp_object *obj) |
|
{ |
|
int i, ret; |
|
struct klp_modinfo *info = patch->mod->klp_info; |
|
|
|
for (i = 1; i < info->hdr.e_shnum; i++) { |
|
Elf_Shdr *sec = info->sechdrs + i; |
|
|
|
if (!(sec->sh_flags & SHF_RELA_LIVEPATCH)) |
|
continue; |
|
|
|
ret = klp_apply_section_relocs(patch->mod, info->sechdrs, |
|
info->secstrings, |
|
patch->mod->core_kallsyms.strtab, |
|
info->symndx, i, obj->name); |
|
if (ret) |
|
return ret; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* parts of the initialization that is done only when the object is loaded */ |
|
static int klp_init_object_loaded(struct klp_patch *patch, |
|
struct klp_object *obj) |
|
{ |
|
struct klp_func *func; |
|
int ret; |
|
|
|
if (klp_is_module(obj)) { |
|
/* |
|
* Only write module-specific relocations here |
|
* (.klp.rela.{module}.*). vmlinux-specific relocations were |
|
* written earlier during the initialization of the klp module |
|
* itself. |
|
*/ |
|
ret = klp_apply_object_relocs(patch, obj); |
|
if (ret) |
|
return ret; |
|
} |
|
|
|
klp_for_each_func(obj, func) { |
|
ret = klp_find_object_symbol(obj->name, func->old_name, |
|
func->old_sympos, |
|
(unsigned long *)&func->old_func); |
|
if (ret) |
|
return ret; |
|
|
|
ret = kallsyms_lookup_size_offset((unsigned long)func->old_func, |
|
&func->old_size, NULL); |
|
if (!ret) { |
|
pr_err("kallsyms size lookup failed for '%s'\n", |
|
func->old_name); |
|
return -ENOENT; |
|
} |
|
|
|
if (func->nop) |
|
func->new_func = func->old_func; |
|
|
|
ret = kallsyms_lookup_size_offset((unsigned long)func->new_func, |
|
&func->new_size, NULL); |
|
if (!ret) { |
|
pr_err("kallsyms size lookup failed for '%s' replacement\n", |
|
func->old_name); |
|
return -ENOENT; |
|
} |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static int klp_init_object(struct klp_patch *patch, struct klp_object *obj) |
|
{ |
|
struct klp_func *func; |
|
int ret; |
|
const char *name; |
|
|
|
if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN) |
|
return -EINVAL; |
|
|
|
obj->patched = false; |
|
obj->mod = NULL; |
|
|
|
klp_find_object_module(obj); |
|
|
|
name = klp_is_module(obj) ? obj->name : "vmlinux"; |
|
ret = kobject_add(&obj->kobj, &patch->kobj, "%s", name); |
|
if (ret) |
|
return ret; |
|
|
|
klp_for_each_func(obj, func) { |
|
ret = klp_init_func(obj, func); |
|
if (ret) |
|
return ret; |
|
} |
|
|
|
if (klp_is_object_loaded(obj)) |
|
ret = klp_init_object_loaded(patch, obj); |
|
|
|
return ret; |
|
} |
|
|
|
static void klp_init_func_early(struct klp_object *obj, |
|
struct klp_func *func) |
|
{ |
|
kobject_init(&func->kobj, &klp_ktype_func); |
|
list_add_tail(&func->node, &obj->func_list); |
|
} |
|
|
|
static void klp_init_object_early(struct klp_patch *patch, |
|
struct klp_object *obj) |
|
{ |
|
INIT_LIST_HEAD(&obj->func_list); |
|
kobject_init(&obj->kobj, &klp_ktype_object); |
|
list_add_tail(&obj->node, &patch->obj_list); |
|
} |
|
|
|
static int klp_init_patch_early(struct klp_patch *patch) |
|
{ |
|
struct klp_object *obj; |
|
struct klp_func *func; |
|
|
|
if (!patch->objs) |
|
return -EINVAL; |
|
|
|
INIT_LIST_HEAD(&patch->list); |
|
INIT_LIST_HEAD(&patch->obj_list); |
|
kobject_init(&patch->kobj, &klp_ktype_patch); |
|
patch->enabled = false; |
|
patch->forced = false; |
|
INIT_WORK(&patch->free_work, klp_free_patch_work_fn); |
|
init_completion(&patch->finish); |
|
|
|
klp_for_each_object_static(patch, obj) { |
|
if (!obj->funcs) |
|
return -EINVAL; |
|
|
|
klp_init_object_early(patch, obj); |
|
|
|
klp_for_each_func_static(obj, func) { |
|
klp_init_func_early(obj, func); |
|
} |
|
} |
|
|
|
if (!try_module_get(patch->mod)) |
|
return -ENODEV; |
|
|
|
return 0; |
|
} |
|
|
|
static int klp_init_patch(struct klp_patch *patch) |
|
{ |
|
struct klp_object *obj; |
|
int ret; |
|
|
|
ret = kobject_add(&patch->kobj, klp_root_kobj, "%s", patch->mod->name); |
|
if (ret) |
|
return ret; |
|
|
|
if (patch->replace) { |
|
ret = klp_add_nops(patch); |
|
if (ret) |
|
return ret; |
|
} |
|
|
|
klp_for_each_object(patch, obj) { |
|
ret = klp_init_object(patch, obj); |
|
if (ret) |
|
return ret; |
|
} |
|
|
|
list_add_tail(&patch->list, &klp_patches); |
|
|
|
return 0; |
|
} |
|
|
|
static int __klp_disable_patch(struct klp_patch *patch) |
|
{ |
|
struct klp_object *obj; |
|
|
|
if (WARN_ON(!patch->enabled)) |
|
return -EINVAL; |
|
|
|
if (klp_transition_patch) |
|
return -EBUSY; |
|
|
|
klp_init_transition(patch, KLP_UNPATCHED); |
|
|
|
klp_for_each_object(patch, obj) |
|
if (obj->patched) |
|
klp_pre_unpatch_callback(obj); |
|
|
|
/* |
|
* Enforce the order of the func->transition writes in |
|
* klp_init_transition() and the TIF_PATCH_PENDING writes in |
|
* klp_start_transition(). In the rare case where klp_ftrace_handler() |
|
* is called shortly after klp_update_patch_state() switches the task, |
|
* this ensures the handler sees that func->transition is set. |
|
*/ |
|
smp_wmb(); |
|
|
|
klp_start_transition(); |
|
patch->enabled = false; |
|
klp_try_complete_transition(); |
|
|
|
return 0; |
|
} |
|
|
|
static int __klp_enable_patch(struct klp_patch *patch) |
|
{ |
|
struct klp_object *obj; |
|
int ret; |
|
|
|
if (klp_transition_patch) |
|
return -EBUSY; |
|
|
|
if (WARN_ON(patch->enabled)) |
|
return -EINVAL; |
|
|
|
pr_notice("enabling patch '%s'\n", patch->mod->name); |
|
|
|
klp_init_transition(patch, KLP_PATCHED); |
|
|
|
/* |
|
* Enforce the order of the func->transition writes in |
|
* klp_init_transition() and the ops->func_stack writes in |
|
* klp_patch_object(), so that klp_ftrace_handler() will see the |
|
* func->transition updates before the handler is registered and the |
|
* new funcs become visible to the handler. |
|
*/ |
|
smp_wmb(); |
|
|
|
klp_for_each_object(patch, obj) { |
|
if (!klp_is_object_loaded(obj)) |
|
continue; |
|
|
|
ret = klp_pre_patch_callback(obj); |
|
if (ret) { |
|
pr_warn("pre-patch callback failed for object '%s'\n", |
|
klp_is_module(obj) ? obj->name : "vmlinux"); |
|
goto err; |
|
} |
|
|
|
ret = klp_patch_object(obj); |
|
if (ret) { |
|
pr_warn("failed to patch object '%s'\n", |
|
klp_is_module(obj) ? obj->name : "vmlinux"); |
|
goto err; |
|
} |
|
} |
|
|
|
klp_start_transition(); |
|
patch->enabled = true; |
|
klp_try_complete_transition(); |
|
|
|
return 0; |
|
err: |
|
pr_warn("failed to enable patch '%s'\n", patch->mod->name); |
|
|
|
klp_cancel_transition(); |
|
return ret; |
|
} |
|
|
|
/** |
|
* klp_enable_patch() - enable the livepatch |
|
* @patch: patch to be enabled |
|
* |
|
* Initializes the data structure associated with the patch, creates the sysfs |
|
* interface, performs the needed symbol lookups and code relocations, |
|
* registers the patched functions with ftrace. |
|
* |
|
* This function is supposed to be called from the livepatch module_init() |
|
* callback. |
|
* |
|
* Return: 0 on success, otherwise error |
|
*/ |
|
int klp_enable_patch(struct klp_patch *patch) |
|
{ |
|
int ret; |
|
|
|
if (!patch || !patch->mod) |
|
return -EINVAL; |
|
|
|
if (!is_livepatch_module(patch->mod)) { |
|
pr_err("module %s is not marked as a livepatch module\n", |
|
patch->mod->name); |
|
return -EINVAL; |
|
} |
|
|
|
if (!klp_initialized()) |
|
return -ENODEV; |
|
|
|
if (!klp_have_reliable_stack()) { |
|
pr_warn("This architecture doesn't have support for the livepatch consistency model.\n"); |
|
pr_warn("The livepatch transition may never complete.\n"); |
|
} |
|
|
|
mutex_lock(&klp_mutex); |
|
|
|
if (!klp_is_patch_compatible(patch)) { |
|
pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n", |
|
patch->mod->name); |
|
mutex_unlock(&klp_mutex); |
|
return -EINVAL; |
|
} |
|
|
|
ret = klp_init_patch_early(patch); |
|
if (ret) { |
|
mutex_unlock(&klp_mutex); |
|
return ret; |
|
} |
|
|
|
ret = klp_init_patch(patch); |
|
if (ret) |
|
goto err; |
|
|
|
ret = __klp_enable_patch(patch); |
|
if (ret) |
|
goto err; |
|
|
|
mutex_unlock(&klp_mutex); |
|
|
|
return 0; |
|
|
|
err: |
|
klp_free_patch_start(patch); |
|
|
|
mutex_unlock(&klp_mutex); |
|
|
|
klp_free_patch_finish(patch); |
|
|
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(klp_enable_patch); |
|
|
|
/* |
|
* This function unpatches objects from the replaced livepatches. |
|
* |
|
* We could be pretty aggressive here. It is called in the situation where |
|
* these structures are no longer accessed from the ftrace handler. |
|
* All functions are redirected by the klp_transition_patch. They |
|
* use either a new code or they are in the original code because |
|
* of the special nop function patches. |
|
* |
|
* The only exception is when the transition was forced. In this case, |
|
* klp_ftrace_handler() might still see the replaced patch on the stack. |
|
* Fortunately, it is carefully designed to work with removed functions |
|
* thanks to RCU. We only have to keep the patches on the system. Also |
|
* this is handled transparently by patch->module_put. |
|
*/ |
|
void klp_unpatch_replaced_patches(struct klp_patch *new_patch) |
|
{ |
|
struct klp_patch *old_patch; |
|
|
|
klp_for_each_patch(old_patch) { |
|
if (old_patch == new_patch) |
|
return; |
|
|
|
old_patch->enabled = false; |
|
klp_unpatch_objects(old_patch); |
|
} |
|
} |
|
|
|
/* |
|
* This function removes the dynamically allocated 'nop' functions. |
|
* |
|
* We could be pretty aggressive. NOPs do not change the existing |
|
* behavior except for adding unnecessary delay by the ftrace handler. |
|
* |
|
* It is safe even when the transition was forced. The ftrace handler |
|
* will see a valid ops->func_stack entry thanks to RCU. |
|
* |
|
* We could even free the NOPs structures. They must be the last entry |
|
* in ops->func_stack. Therefore unregister_ftrace_function() is called. |
|
* It does the same as klp_synchronize_transition() to make sure that |
|
* nobody is inside the ftrace handler once the operation finishes. |
|
* |
|
* IMPORTANT: It must be called right after removing the replaced patches! |
|
*/ |
|
void klp_discard_nops(struct klp_patch *new_patch) |
|
{ |
|
klp_unpatch_objects_dynamic(klp_transition_patch); |
|
klp_free_objects_dynamic(klp_transition_patch); |
|
} |
|
|
|
/* |
|
* Remove parts of patches that touch a given kernel module. The list of |
|
* patches processed might be limited. When limit is NULL, all patches |
|
* will be handled. |
|
*/ |
|
static void klp_cleanup_module_patches_limited(struct module *mod, |
|
struct klp_patch *limit) |
|
{ |
|
struct klp_patch *patch; |
|
struct klp_object *obj; |
|
|
|
klp_for_each_patch(patch) { |
|
if (patch == limit) |
|
break; |
|
|
|
klp_for_each_object(patch, obj) { |
|
if (!klp_is_module(obj) || strcmp(obj->name, mod->name)) |
|
continue; |
|
|
|
if (patch != klp_transition_patch) |
|
klp_pre_unpatch_callback(obj); |
|
|
|
pr_notice("reverting patch '%s' on unloading module '%s'\n", |
|
patch->mod->name, obj->mod->name); |
|
klp_unpatch_object(obj); |
|
|
|
klp_post_unpatch_callback(obj); |
|
|
|
klp_free_object_loaded(obj); |
|
break; |
|
} |
|
} |
|
} |
|
|
|
int klp_module_coming(struct module *mod) |
|
{ |
|
int ret; |
|
struct klp_patch *patch; |
|
struct klp_object *obj; |
|
|
|
if (WARN_ON(mod->state != MODULE_STATE_COMING)) |
|
return -EINVAL; |
|
|
|
if (!strcmp(mod->name, "vmlinux")) { |
|
pr_err("vmlinux.ko: invalid module name"); |
|
return -EINVAL; |
|
} |
|
|
|
mutex_lock(&klp_mutex); |
|
/* |
|
* Each module has to know that klp_module_coming() |
|
* has been called. We never know what module will |
|
* get patched by a new patch. |
|
*/ |
|
mod->klp_alive = true; |
|
|
|
klp_for_each_patch(patch) { |
|
klp_for_each_object(patch, obj) { |
|
if (!klp_is_module(obj) || strcmp(obj->name, mod->name)) |
|
continue; |
|
|
|
obj->mod = mod; |
|
|
|
ret = klp_init_object_loaded(patch, obj); |
|
if (ret) { |
|
pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n", |
|
patch->mod->name, obj->mod->name, ret); |
|
goto err; |
|
} |
|
|
|
pr_notice("applying patch '%s' to loading module '%s'\n", |
|
patch->mod->name, obj->mod->name); |
|
|
|
ret = klp_pre_patch_callback(obj); |
|
if (ret) { |
|
pr_warn("pre-patch callback failed for object '%s'\n", |
|
obj->name); |
|
goto err; |
|
} |
|
|
|
ret = klp_patch_object(obj); |
|
if (ret) { |
|
pr_warn("failed to apply patch '%s' to module '%s' (%d)\n", |
|
patch->mod->name, obj->mod->name, ret); |
|
|
|
klp_post_unpatch_callback(obj); |
|
goto err; |
|
} |
|
|
|
if (patch != klp_transition_patch) |
|
klp_post_patch_callback(obj); |
|
|
|
break; |
|
} |
|
} |
|
|
|
mutex_unlock(&klp_mutex); |
|
|
|
return 0; |
|
|
|
err: |
|
/* |
|
* If a patch is unsuccessfully applied, return |
|
* error to the module loader. |
|
*/ |
|
pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n", |
|
patch->mod->name, obj->mod->name, obj->mod->name); |
|
mod->klp_alive = false; |
|
obj->mod = NULL; |
|
klp_cleanup_module_patches_limited(mod, patch); |
|
mutex_unlock(&klp_mutex); |
|
|
|
return ret; |
|
} |
|
|
|
void klp_module_going(struct module *mod) |
|
{ |
|
if (WARN_ON(mod->state != MODULE_STATE_GOING && |
|
mod->state != MODULE_STATE_COMING)) |
|
return; |
|
|
|
mutex_lock(&klp_mutex); |
|
/* |
|
* Each module has to know that klp_module_going() |
|
* has been called. We never know what module will |
|
* get patched by a new patch. |
|
*/ |
|
mod->klp_alive = false; |
|
|
|
klp_cleanup_module_patches_limited(mod, NULL); |
|
|
|
mutex_unlock(&klp_mutex); |
|
} |
|
|
|
static int __init klp_init(void) |
|
{ |
|
klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj); |
|
if (!klp_root_kobj) |
|
return -ENOMEM; |
|
|
|
return 0; |
|
} |
|
|
|
module_init(klp_init);
|
|
|