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540 lines
13 KiB
540 lines
13 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* arch/arm/kernel/unwind.c |
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* |
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* Copyright (C) 2008 ARM Limited |
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* |
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* Stack unwinding support for ARM |
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* |
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* An ARM EABI version of gcc is required to generate the unwind |
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* tables. For information about the structure of the unwind tables, |
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* see "Exception Handling ABI for the ARM Architecture" at: |
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* |
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* http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html |
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*/ |
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|
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#ifndef __CHECKER__ |
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#if !defined (__ARM_EABI__) |
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#warning Your compiler does not have EABI support. |
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#warning ARM unwind is known to compile only with EABI compilers. |
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#warning Change compiler or disable ARM_UNWIND option. |
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#endif |
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#endif /* __CHECKER__ */ |
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#include <linux/kernel.h> |
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#include <linux/init.h> |
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#include <linux/export.h> |
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#include <linux/sched.h> |
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#include <linux/slab.h> |
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#include <linux/spinlock.h> |
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#include <linux/list.h> |
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#include <asm/stacktrace.h> |
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#include <asm/traps.h> |
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#include <asm/unwind.h> |
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/* Dummy functions to avoid linker complaints */ |
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void __aeabi_unwind_cpp_pr0(void) |
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{ |
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}; |
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EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0); |
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void __aeabi_unwind_cpp_pr1(void) |
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{ |
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}; |
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EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1); |
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void __aeabi_unwind_cpp_pr2(void) |
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{ |
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}; |
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EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2); |
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struct unwind_ctrl_block { |
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unsigned long vrs[16]; /* virtual register set */ |
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const unsigned long *insn; /* pointer to the current instructions word */ |
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unsigned long sp_high; /* highest value of sp allowed */ |
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/* |
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* 1 : check for stack overflow for each register pop. |
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* 0 : save overhead if there is plenty of stack remaining. |
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*/ |
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int check_each_pop; |
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int entries; /* number of entries left to interpret */ |
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int byte; /* current byte number in the instructions word */ |
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}; |
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enum regs { |
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#ifdef CONFIG_THUMB2_KERNEL |
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FP = 7, |
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#else |
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FP = 11, |
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#endif |
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SP = 13, |
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LR = 14, |
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PC = 15 |
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}; |
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extern const struct unwind_idx __start_unwind_idx[]; |
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static const struct unwind_idx *__origin_unwind_idx; |
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extern const struct unwind_idx __stop_unwind_idx[]; |
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static DEFINE_RAW_SPINLOCK(unwind_lock); |
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static LIST_HEAD(unwind_tables); |
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/* Convert a prel31 symbol to an absolute address */ |
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#define prel31_to_addr(ptr) \ |
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({ \ |
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/* sign-extend to 32 bits */ \ |
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long offset = (((long)*(ptr)) << 1) >> 1; \ |
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(unsigned long)(ptr) + offset; \ |
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}) |
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/* |
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* Binary search in the unwind index. The entries are |
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* guaranteed to be sorted in ascending order by the linker. |
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* |
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* start = first entry |
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* origin = first entry with positive offset (or stop if there is no such entry) |
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* stop - 1 = last entry |
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*/ |
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static const struct unwind_idx *search_index(unsigned long addr, |
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const struct unwind_idx *start, |
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const struct unwind_idx *origin, |
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const struct unwind_idx *stop) |
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{ |
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unsigned long addr_prel31; |
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pr_debug("%s(%08lx, %p, %p, %p)\n", |
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__func__, addr, start, origin, stop); |
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/* |
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* only search in the section with the matching sign. This way the |
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* prel31 numbers can be compared as unsigned longs. |
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*/ |
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if (addr < (unsigned long)start) |
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/* negative offsets: [start; origin) */ |
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stop = origin; |
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else |
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/* positive offsets: [origin; stop) */ |
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start = origin; |
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/* prel31 for address relavive to start */ |
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addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff; |
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while (start < stop - 1) { |
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const struct unwind_idx *mid = start + ((stop - start) >> 1); |
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/* |
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* As addr_prel31 is relative to start an offset is needed to |
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* make it relative to mid. |
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*/ |
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if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) < |
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mid->addr_offset) |
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stop = mid; |
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else { |
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/* keep addr_prel31 relative to start */ |
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addr_prel31 -= ((unsigned long)mid - |
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(unsigned long)start); |
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start = mid; |
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} |
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} |
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if (likely(start->addr_offset <= addr_prel31)) |
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return start; |
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else { |
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pr_warn("unwind: Unknown symbol address %08lx\n", addr); |
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return NULL; |
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} |
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} |
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static const struct unwind_idx *unwind_find_origin( |
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const struct unwind_idx *start, const struct unwind_idx *stop) |
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{ |
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pr_debug("%s(%p, %p)\n", __func__, start, stop); |
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while (start < stop) { |
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const struct unwind_idx *mid = start + ((stop - start) >> 1); |
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if (mid->addr_offset >= 0x40000000) |
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/* negative offset */ |
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start = mid + 1; |
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else |
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/* positive offset */ |
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stop = mid; |
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} |
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pr_debug("%s -> %p\n", __func__, stop); |
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return stop; |
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} |
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static const struct unwind_idx *unwind_find_idx(unsigned long addr) |
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{ |
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const struct unwind_idx *idx = NULL; |
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unsigned long flags; |
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pr_debug("%s(%08lx)\n", __func__, addr); |
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if (core_kernel_text(addr)) { |
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if (unlikely(!__origin_unwind_idx)) |
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__origin_unwind_idx = |
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unwind_find_origin(__start_unwind_idx, |
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__stop_unwind_idx); |
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/* main unwind table */ |
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idx = search_index(addr, __start_unwind_idx, |
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__origin_unwind_idx, |
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__stop_unwind_idx); |
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} else { |
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/* module unwind tables */ |
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struct unwind_table *table; |
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raw_spin_lock_irqsave(&unwind_lock, flags); |
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list_for_each_entry(table, &unwind_tables, list) { |
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if (addr >= table->begin_addr && |
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addr < table->end_addr) { |
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idx = search_index(addr, table->start, |
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table->origin, |
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table->stop); |
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/* Move-to-front to exploit common traces */ |
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list_move(&table->list, &unwind_tables); |
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break; |
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} |
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} |
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raw_spin_unlock_irqrestore(&unwind_lock, flags); |
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} |
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pr_debug("%s: idx = %p\n", __func__, idx); |
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return idx; |
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} |
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static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl) |
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{ |
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unsigned long ret; |
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if (ctrl->entries <= 0) { |
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pr_warn("unwind: Corrupt unwind table\n"); |
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return 0; |
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} |
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ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff; |
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if (ctrl->byte == 0) { |
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ctrl->insn++; |
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ctrl->entries--; |
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ctrl->byte = 3; |
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} else |
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ctrl->byte--; |
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return ret; |
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} |
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/* Before poping a register check whether it is feasible or not */ |
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static int unwind_pop_register(struct unwind_ctrl_block *ctrl, |
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unsigned long **vsp, unsigned int reg) |
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{ |
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if (unlikely(ctrl->check_each_pop)) |
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if (*vsp >= (unsigned long *)ctrl->sp_high) |
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return -URC_FAILURE; |
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/* Use READ_ONCE_NOCHECK here to avoid this memory access |
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* from being tracked by KASAN. |
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*/ |
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ctrl->vrs[reg] = READ_ONCE_NOCHECK(*(*vsp)); |
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(*vsp)++; |
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return URC_OK; |
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} |
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/* Helper functions to execute the instructions */ |
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static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl, |
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unsigned long mask) |
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{ |
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unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; |
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int load_sp, reg = 4; |
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load_sp = mask & (1 << (13 - 4)); |
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while (mask) { |
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if (mask & 1) |
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if (unwind_pop_register(ctrl, &vsp, reg)) |
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return -URC_FAILURE; |
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mask >>= 1; |
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reg++; |
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} |
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if (!load_sp) |
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ctrl->vrs[SP] = (unsigned long)vsp; |
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return URC_OK; |
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} |
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static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl, |
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unsigned long insn) |
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{ |
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unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; |
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int reg; |
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/* pop R4-R[4+bbb] */ |
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for (reg = 4; reg <= 4 + (insn & 7); reg++) |
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if (unwind_pop_register(ctrl, &vsp, reg)) |
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return -URC_FAILURE; |
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if (insn & 0x8) |
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if (unwind_pop_register(ctrl, &vsp, 14)) |
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return -URC_FAILURE; |
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ctrl->vrs[SP] = (unsigned long)vsp; |
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return URC_OK; |
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} |
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static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl, |
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unsigned long mask) |
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{ |
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unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; |
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int reg = 0; |
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/* pop R0-R3 according to mask */ |
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while (mask) { |
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if (mask & 1) |
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if (unwind_pop_register(ctrl, &vsp, reg)) |
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return -URC_FAILURE; |
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mask >>= 1; |
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reg++; |
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} |
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ctrl->vrs[SP] = (unsigned long)vsp; |
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return URC_OK; |
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} |
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/* |
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* Execute the current unwind instruction. |
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*/ |
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static int unwind_exec_insn(struct unwind_ctrl_block *ctrl) |
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{ |
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unsigned long insn = unwind_get_byte(ctrl); |
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int ret = URC_OK; |
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pr_debug("%s: insn = %08lx\n", __func__, insn); |
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if ((insn & 0xc0) == 0x00) |
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ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4; |
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else if ((insn & 0xc0) == 0x40) |
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ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4; |
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else if ((insn & 0xf0) == 0x80) { |
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unsigned long mask; |
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insn = (insn << 8) | unwind_get_byte(ctrl); |
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mask = insn & 0x0fff; |
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if (mask == 0) { |
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pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n", |
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insn); |
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return -URC_FAILURE; |
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} |
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ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask); |
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if (ret) |
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goto error; |
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} else if ((insn & 0xf0) == 0x90 && |
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(insn & 0x0d) != 0x0d) |
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ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f]; |
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else if ((insn & 0xf0) == 0xa0) { |
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ret = unwind_exec_pop_r4_to_rN(ctrl, insn); |
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if (ret) |
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goto error; |
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} else if (insn == 0xb0) { |
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if (ctrl->vrs[PC] == 0) |
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ctrl->vrs[PC] = ctrl->vrs[LR]; |
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/* no further processing */ |
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ctrl->entries = 0; |
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} else if (insn == 0xb1) { |
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unsigned long mask = unwind_get_byte(ctrl); |
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if (mask == 0 || mask & 0xf0) { |
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pr_warn("unwind: Spare encoding %04lx\n", |
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(insn << 8) | mask); |
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return -URC_FAILURE; |
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} |
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ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask); |
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if (ret) |
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goto error; |
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} else if (insn == 0xb2) { |
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unsigned long uleb128 = unwind_get_byte(ctrl); |
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ctrl->vrs[SP] += 0x204 + (uleb128 << 2); |
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} else { |
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pr_warn("unwind: Unhandled instruction %02lx\n", insn); |
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return -URC_FAILURE; |
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} |
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pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__, |
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ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]); |
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error: |
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return ret; |
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} |
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/* |
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* Unwind a single frame starting with *sp for the symbol at *pc. It |
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* updates the *pc and *sp with the new values. |
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*/ |
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int unwind_frame(struct stackframe *frame) |
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{ |
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unsigned long low; |
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const struct unwind_idx *idx; |
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struct unwind_ctrl_block ctrl; |
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/* store the highest address on the stack to avoid crossing it*/ |
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low = frame->sp; |
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ctrl.sp_high = ALIGN(low, THREAD_SIZE); |
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pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__, |
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frame->pc, frame->lr, frame->sp); |
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if (!kernel_text_address(frame->pc)) |
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return -URC_FAILURE; |
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idx = unwind_find_idx(frame->pc); |
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if (!idx) { |
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pr_warn("unwind: Index not found %08lx\n", frame->pc); |
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return -URC_FAILURE; |
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} |
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ctrl.vrs[FP] = frame->fp; |
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ctrl.vrs[SP] = frame->sp; |
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ctrl.vrs[LR] = frame->lr; |
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ctrl.vrs[PC] = 0; |
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if (idx->insn == 1) |
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/* can't unwind */ |
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return -URC_FAILURE; |
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else if ((idx->insn & 0x80000000) == 0) |
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/* prel31 to the unwind table */ |
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ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn); |
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else if ((idx->insn & 0xff000000) == 0x80000000) |
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/* only personality routine 0 supported in the index */ |
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ctrl.insn = &idx->insn; |
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else { |
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pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n", |
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idx->insn, idx); |
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return -URC_FAILURE; |
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} |
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/* check the personality routine */ |
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if ((*ctrl.insn & 0xff000000) == 0x80000000) { |
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ctrl.byte = 2; |
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ctrl.entries = 1; |
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} else if ((*ctrl.insn & 0xff000000) == 0x81000000) { |
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ctrl.byte = 1; |
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ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16); |
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} else { |
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pr_warn("unwind: Unsupported personality routine %08lx at %p\n", |
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*ctrl.insn, ctrl.insn); |
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return -URC_FAILURE; |
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} |
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ctrl.check_each_pop = 0; |
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while (ctrl.entries > 0) { |
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int urc; |
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if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs)) |
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ctrl.check_each_pop = 1; |
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urc = unwind_exec_insn(&ctrl); |
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if (urc < 0) |
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return urc; |
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if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= ctrl.sp_high) |
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return -URC_FAILURE; |
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} |
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if (ctrl.vrs[PC] == 0) |
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ctrl.vrs[PC] = ctrl.vrs[LR]; |
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/* check for infinite loop */ |
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if (frame->pc == ctrl.vrs[PC] && frame->sp == ctrl.vrs[SP]) |
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return -URC_FAILURE; |
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frame->fp = ctrl.vrs[FP]; |
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frame->sp = ctrl.vrs[SP]; |
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frame->lr = ctrl.vrs[LR]; |
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frame->pc = ctrl.vrs[PC]; |
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return URC_OK; |
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} |
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void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk, |
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const char *loglvl) |
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{ |
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struct stackframe frame; |
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pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); |
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if (!tsk) |
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tsk = current; |
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if (regs) { |
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arm_get_current_stackframe(regs, &frame); |
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/* PC might be corrupted, use LR in that case. */ |
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if (!kernel_text_address(regs->ARM_pc)) |
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frame.pc = regs->ARM_lr; |
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} else if (tsk == current) { |
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frame.fp = (unsigned long)__builtin_frame_address(0); |
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frame.sp = current_stack_pointer; |
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frame.lr = (unsigned long)__builtin_return_address(0); |
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frame.pc = (unsigned long)unwind_backtrace; |
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} else { |
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/* task blocked in __switch_to */ |
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frame.fp = thread_saved_fp(tsk); |
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frame.sp = thread_saved_sp(tsk); |
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/* |
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* The function calling __switch_to cannot be a leaf function |
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* so LR is recovered from the stack. |
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*/ |
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frame.lr = 0; |
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frame.pc = thread_saved_pc(tsk); |
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} |
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while (1) { |
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int urc; |
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unsigned long where = frame.pc; |
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urc = unwind_frame(&frame); |
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if (urc < 0) |
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break; |
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dump_backtrace_entry(where, frame.pc, frame.sp - 4, loglvl); |
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} |
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} |
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struct unwind_table *unwind_table_add(unsigned long start, unsigned long size, |
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unsigned long text_addr, |
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unsigned long text_size) |
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{ |
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unsigned long flags; |
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struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL); |
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pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size, |
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text_addr, text_size); |
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if (!tab) |
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return tab; |
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tab->start = (const struct unwind_idx *)start; |
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tab->stop = (const struct unwind_idx *)(start + size); |
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tab->origin = unwind_find_origin(tab->start, tab->stop); |
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tab->begin_addr = text_addr; |
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tab->end_addr = text_addr + text_size; |
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raw_spin_lock_irqsave(&unwind_lock, flags); |
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list_add_tail(&tab->list, &unwind_tables); |
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raw_spin_unlock_irqrestore(&unwind_lock, flags); |
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return tab; |
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} |
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void unwind_table_del(struct unwind_table *tab) |
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{ |
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unsigned long flags; |
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if (!tab) |
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return; |
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raw_spin_lock_irqsave(&unwind_lock, flags); |
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list_del(&tab->list); |
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raw_spin_unlock_irqrestore(&unwind_lock, flags); |
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kfree(tab); |
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}
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