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/*
* Copyright (C) 2012 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <dlfcn.h>
#include <execinfo.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
#include <unwind.h>
#include "private/ScopedFd.h"
struct StackState {
void** frames;
int frame_count;
int cur_frame = 0;
StackState(void** frames, int frame_count) : frames(frames), frame_count(frame_count) {}
};
static _Unwind_Reason_Code TraceFunction(_Unwind_Context* context, void* arg) {
// The instruction pointer is pointing at the instruction after the return
// call on all architectures.
// Modify the pc to point at the real function.
uintptr_t ip = _Unwind_GetIP(context);
if (ip != 0) {
#if defined(__arm__)
// If the ip is suspiciously low, do nothing to avoid a segfault trying
// to access this memory.
if (ip >= 4096) {
// Check bits [15:11] of the first halfword assuming the instruction
// is 32 bits long. If the bits are any of these values, then our
// assumption was correct:
// b11101
// b11110
// b11111
// Otherwise, this is a 16 bit instruction.
uint16_t value = (*reinterpret_cast<uint16_t*>(ip - 2)) >> 11;
if (value == 0x1f || value == 0x1e || value == 0x1d) {
ip -= 4;
} else {
ip -= 2;
}
}
#elif defined(__aarch64__)
// All instructions are 4 bytes long, skip back one instruction.
ip -= 4;
#elif defined(__i386__) || defined(__x86_64__)
// It's difficult to decode exactly where the previous instruction is,
// so subtract 1 to estimate where the instruction lives.
ip--;
#endif
}
StackState* state = static_cast<StackState*>(arg);
state->frames[state->cur_frame++] = reinterpret_cast<void*>(ip);
return (state->cur_frame >= state->frame_count) ? _URC_END_OF_STACK : _URC_NO_REASON;
}
int backtrace(void** buffer, int size) {
if (size <= 0) {
return 0;
}
StackState state(buffer, size);
_Unwind_Backtrace(TraceFunction, &state);
return state.cur_frame;
}
char** backtrace_symbols(void* const* buffer, int size) {
if (size <= 0) {
return nullptr;
}
// Do this calculation first in case the user passes in a bad value.
size_t ptr_size;
if (__builtin_mul_overflow(sizeof(char*), size, &ptr_size)) {
return nullptr;
}
ScopedFd fd(memfd_create("backtrace_symbols_fd", MFD_CLOEXEC));
if (fd.get() == -1) {
return nullptr;
}
backtrace_symbols_fd(buffer, size, fd.get());
// Get the size of the file.
off_t file_size = lseek(fd.get(), 0, SEEK_END);
if (file_size <= 0) {
return nullptr;
}
// The interface for backtrace_symbols indicates that only the single
// returned pointer must be freed by the caller. Therefore, allocate a
// buffer that includes the memory for the strings and all of the pointers.
// Add one byte at the end just in case the file didn't end with a '\n'.
size_t symbol_data_size;
if (__builtin_add_overflow(ptr_size, file_size, &symbol_data_size) ||
__builtin_add_overflow(symbol_data_size, 1, &symbol_data_size)) {
return nullptr;
}
uint8_t* symbol_data = reinterpret_cast<uint8_t*>(malloc(symbol_data_size));
if (symbol_data == nullptr) {
return nullptr;
}
// Copy the string data into the buffer.
char* cur_string = reinterpret_cast<char*>(&symbol_data[ptr_size]);
// If this fails, the read won't read back the correct number of bytes.
lseek(fd.get(), 0, SEEK_SET);
ssize_t num_read = read(fd.get(), cur_string, file_size);
fd.reset(-1);
if (num_read != file_size) {
free(symbol_data);
return nullptr;
}
// Make sure the last character in the file is '\n'.
if (cur_string[file_size] != '\n') {
cur_string[file_size++] = '\n';
}
for (int i = 0; i < size; i++) {
(reinterpret_cast<char**>(symbol_data))[i] = cur_string;
cur_string = strchr(cur_string, '\n');
if (cur_string == nullptr) {
free(symbol_data);
return nullptr;
}
cur_string[0] = '\0';
cur_string++;
}
return reinterpret_cast<char**>(symbol_data);
}
// This function should do no allocations if possible.
void backtrace_symbols_fd(void* const* buffer, int size, int fd) {
if (size <= 0 || fd < 0) {
return;
}
for (int frame_num = 0; frame_num < size; frame_num++) {
void* address = buffer[frame_num];
Dl_info info;
if (dladdr(address, &info) != 0) {
if (info.dli_fname != nullptr) {
write(fd, info.dli_fname, strlen(info.dli_fname));
}
if (info.dli_sname != nullptr) {
dprintf(fd, "(%s+0x%" PRIxPTR ") ", info.dli_sname,
reinterpret_cast<uintptr_t>(address) - reinterpret_cast<uintptr_t>(info.dli_saddr));
} else {
dprintf(fd, "(+%p) ", info.dli_saddr);
}
}
dprintf(fd, "[%p]\n", address);
}
}
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