// Copyright (c) 2006, Google Inc.
// 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.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// 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.
//
// Author: Satoru Takabayashi
// Stack-footprint reduction work done by Raksit Ashok
//
// Implementation note:
//
// We don't use heaps but only use stacks. We want to reduce the
// stack consumption so that the symbolizer can run on small stacks.
//
// Here are some numbers collected with GCC 4.1.0 on x86:
// - sizeof(Elf32_Sym) = 16
// - sizeof(Elf32_Shdr) = 40
// - sizeof(Elf64_Sym) = 24
// - sizeof(Elf64_Shdr) = 64
//
// This implementation is intended to be async-signal-safe but uses
// some functions which are not guaranteed to be so, such as memchr()
// and memmove(). We assume they are async-signal-safe.
//
// Additional header can be specified by the GLOG_BUILD_CONFIG_INCLUDE
// macro to add platform specific defines (e.g. OS_OPENBSD).
#ifdef GLOG_BUILD_CONFIG_INCLUDE
#include GLOG_BUILD_CONFIG_INCLUDE
#endif // GLOG_BUILD_CONFIG_INCLUDE
#include "utilities.h"
#if defined(HAVE_SYMBOLIZE)
#include <string.h>
#include <algorithm>
#include <limits>
#include "symbolize.h"
#include "demangle.h"
_START_GOOGLE_NAMESPACE_
// We don't use assert() since it's not guaranteed to be
// async-signal-safe. Instead we define a minimal assertion
// macro. So far, we don't need pretty printing for __FILE__, etc.
// A wrapper for abort() to make it callable in ? :.
static int AssertFail() {
abort();
return 0; // Should not reach.
}
#define SAFE_ASSERT(expr) ((expr) ? 0 : AssertFail())
static SymbolizeCallback g_symbolize_callback = NULL;
void InstallSymbolizeCallback(SymbolizeCallback callback) {
g_symbolize_callback = callback;
}
static SymbolizeOpenObjectFileCallback g_symbolize_open_object_file_callback =
NULL;
void InstallSymbolizeOpenObjectFileCallback(
SymbolizeOpenObjectFileCallback callback) {
g_symbolize_open_object_file_callback = callback;
}
// This function wraps the Demangle function to provide an interface
// where the input symbol is demangled in-place.
// To keep stack consumption low, we would like this function to not
// get inlined.
static ATTRIBUTE_NOINLINE void DemangleInplace(char *out, int out_size) {
char demangled[256]; // Big enough for sane demangled symbols.
if (Demangle(out, demangled, sizeof(demangled))) {
// Demangling succeeded. Copy to out if the space allows.
size_t len = strlen(demangled);
if (len + 1 <= (size_t)out_size) { // +1 for '\0'.
SAFE_ASSERT(len < sizeof(demangled));
memmove(out, demangled, len + 1);
}
}
}
_END_GOOGLE_NAMESPACE_
#if defined(__ELF__)
#if defined(HAVE_DLFCN_H)
#include <dlfcn.h>
#endif
#if defined(OS_OPENBSD)
#include <sys/exec_elf.h>
#else
#include <elf.h>
#endif
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include "symbolize.h"
#include "config.h"
#include "glog/raw_logging.h"
// Re-runs fn until it doesn't cause EINTR.
#define NO_INTR(fn) do {} while ((fn) < 0 && errno == EINTR)
_START_GOOGLE_NAMESPACE_
// Read up to "count" bytes from "offset" in the file pointed by file
// descriptor "fd" into the buffer starting at "buf" while handling short reads
// and EINTR. On success, return the number of bytes read. Otherwise, return
// -1.
static ssize_t ReadFromOffset(const int fd, void *buf, const size_t count,
const off_t offset) {
SAFE_ASSERT(fd >= 0);
SAFE_ASSERT(count <= std::numeric_limits<ssize_t>::max());
char *buf0 = reinterpret_cast<char *>(buf);
ssize_t num_bytes = 0;
while (num_bytes < count) {
ssize_t len;
NO_INTR(len = pread(fd, buf0 + num_bytes, count - num_bytes,
offset + num_bytes));
if (len < 0) { // There was an error other than EINTR.
return -1;
}
if (len == 0) { // Reached EOF.
break;
}
num_bytes += len;
}
SAFE_ASSERT(num_bytes <= count);
return num_bytes;
}
// Try reading exactly "count" bytes from "offset" bytes in a file
// pointed by "fd" into the buffer starting at "buf" while handling
// short reads and EINTR. On success, return true. Otherwise, return
// false.
static bool ReadFromOffsetExact(const int fd, void *buf,
const size_t count, const off_t offset) {
ssize_t len = ReadFromOffset(fd, buf, count, offset);
return len == count;
}
// Returns elf_header.e_type if the file pointed by fd is an ELF binary.
static int FileGetElfType(const int fd) {
ElfW(Ehdr) elf_header;
if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) {
return -1;
}
if (memcmp(elf_header.e_ident, ELFMAG, SELFMAG) != 0) {
return -1;
}
return elf_header.e_type;
}
// Read the section headers in the given ELF binary, and if a section
// of the specified type is found, set the output to this section header
// and return true. Otherwise, return false.
// To keep stack consumption low, we would like this function to not get
// inlined.
static ATTRIBUTE_NOINLINE bool
GetSectionHeaderByType(const int fd, ElfW(Half) sh_num, const off_t sh_offset,
ElfW(Word) type, ElfW(Shdr) *out) {
// Read at most 16 section headers at a time to save read calls.
ElfW(Shdr) buf[16];
for (int i = 0; i < sh_num;) {
const ssize_t num_bytes_left = (sh_num - i) * sizeof(buf[0]);
const ssize_t num_bytes_to_read =
(sizeof(buf) > num_bytes_left) ? num_bytes_left : sizeof(buf);
const ssize_t len = ReadFromOffset(fd, buf, num_bytes_to_read,
sh_offset + i * sizeof(buf[0]));
if (len == -1) {
return false;
}
SAFE_ASSERT(len % sizeof(buf[0]) == 0);
const ssize_t num_headers_in_buf = len / sizeof(buf[0]);
SAFE_ASSERT(num_headers_in_buf <= sizeof(buf) / sizeof(buf[0]));
for (int j = 0; j < num_headers_in_buf; ++j) {
if (buf[j].sh_type == type) {
*out = buf[j];
return true;
}
}
i += num_headers_in_buf;
}
return false;
}
// There is no particular reason to limit section name to 63 characters,
// but there has (as yet) been no need for anything longer either.
const int kMaxSectionNameLen = 64;
// name_len should include terminating '\0'.
bool GetSectionHeaderByName(int fd, const char *name, size_t name_len,
ElfW(Shdr) *out) {
ElfW(Ehdr) elf_header;
if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) {
return false;
}
ElfW(Shdr) shstrtab;
off_t shstrtab_offset = (elf_header.e_shoff +
elf_header.e_shentsize * elf_header.e_shstrndx);
if (!ReadFromOffsetExact(fd, &shstrtab, sizeof(shstrtab), shstrtab_offset)) {
return false;
}
for (int i = 0; i < elf_header.e_shnum; ++i) {
off_t section_header_offset = (elf_header.e_shoff +
elf_header.e_shentsize * i);
if (!ReadFromOffsetExact(fd, out, sizeof(*out), section_header_offset)) {
return false;
}
char header_name[kMaxSectionNameLen];
if (sizeof(header_name) < name_len) {
RAW_LOG(WARNING, "Section name '%s' is too long (%" PRIuS "); "
"section will not be found (even if present).", name, name_len);
// No point in even trying.
return false;
}
off_t name_offset = shstrtab.sh_offset + out->sh_name;
ssize_t n_read = ReadFromOffset(fd, &header_name, name_len, name_offset);
if (n_read == -1) {
return false;
} else if (n_read != name_len) {
// Short read -- name could be at end of file.
continue;
}
if (memcmp(header_name, name, name_len) == 0) {
return true;
}
}
return false;
}
// Read a symbol table and look for the symbol containing the
// pc. Iterate over symbols in a symbol table and look for the symbol
// containing "pc". On success, return true and write the symbol name
// to out. Otherwise, return false.
// To keep stack consumption low, we would like this function to not get
// inlined.
static ATTRIBUTE_NOINLINE bool
FindSymbol(uint64_t pc, const int fd, char *out, int out_size,
uint64_t symbol_offset, const ElfW(Shdr) *strtab,
const ElfW(Shdr) *symtab) {
if (symtab == NULL) {
return false;
}
const int num_symbols = symtab->sh_size / symtab->sh_entsize;
for (int i = 0; i < num_symbols;) {
off_t offset = symtab->sh_offset + i * symtab->sh_entsize;
// If we are reading Elf64_Sym's, we want to limit this array to
// 32 elements (to keep stack consumption low), otherwise we can
// have a 64 element Elf32_Sym array.
#if __WORDSIZE == 64
#define NUM_SYMBOLS 32
#else
#define NUM_SYMBOLS 64
#endif
// Read at most NUM_SYMBOLS symbols at once to save read() calls.
ElfW(Sym) buf[NUM_SYMBOLS];
int num_symbols_to_read = std::min(NUM_SYMBOLS, num_symbols - i);
const ssize_t len =
ReadFromOffset(fd, &buf, sizeof(buf[0]) * num_symbols_to_read, offset);
SAFE_ASSERT(len % sizeof(buf[0]) == 0);
const ssize_t num_symbols_in_buf = len / sizeof(buf[0]);
SAFE_ASSERT(num_symbols_in_buf <= num_symbols_to_read);
for (int j = 0; j < num_symbols_in_buf; ++j) {
const ElfW(Sym)& symbol = buf[j];
uint64_t start_address = symbol.st_value;
start_address += symbol_offset;
uint64_t end_address = start_address + symbol.st_size;
if (symbol.st_value != 0 && // Skip null value symbols.
symbol.st_shndx != 0 && // Skip undefined symbols.
start_address <= pc && pc < end_address) {
ssize_t len1 = ReadFromOffset(fd, out, out_size,
strtab->sh_offset + symbol.st_name);
if (len1 <= 0 || memchr(out, '\0', out_size) == NULL) {
memset(out, 0, out_size);
return false;
}
return true; // Obtained the symbol name.
}
}
i += num_symbols_in_buf;
}
return false;
}
// Get the symbol name of "pc" from the file pointed by "fd". Process
// both regular and dynamic symbol tables if necessary. On success,
// write the symbol name to "out" and return true. Otherwise, return
// false.
static bool GetSymbolFromObjectFile(const int fd,
uint64_t pc,
char* out,
int out_size,
uint64_t base_address) {
// Read the ELF header.
ElfW(Ehdr) elf_header;
if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) {
return false;
}
ElfW(Shdr) symtab, strtab;
// Consult a regular symbol table first.
if (GetSectionHeaderByType(fd, elf_header.e_shnum, elf_header.e_shoff,
SHT_SYMTAB, &symtab)) {
if (!ReadFromOffsetExact(fd, &strtab, sizeof(strtab), elf_header.e_shoff +
symtab.sh_link * sizeof(symtab))) {
return false;
}
if (FindSymbol(pc, fd, out, out_size, base_address, &strtab, &symtab)) {
return true; // Found the symbol in a regular symbol table.
}
}
// If the symbol is not found, then consult a dynamic symbol table.
if (GetSectionHeaderByType(fd, elf_header.e_shnum, elf_header.e_shoff,
SHT_DYNSYM, &symtab)) {
if (!ReadFromOffsetExact(fd, &strtab, sizeof(strtab), elf_header.e_shoff +
symtab.sh_link * sizeof(symtab))) {
return false;
}
if (FindSymbol(pc, fd, out, out_size, base_address, &strtab, &symtab)) {
return true; // Found the symbol in a dynamic symbol table.
}
}
return false;
}
namespace {
// Thin wrapper around a file descriptor so that the file descriptor
// gets closed for sure.
struct FileDescriptor {
const int fd_;
explicit FileDescriptor(int fd) : fd_(fd) {}
~FileDescriptor() {
if (fd_ >= 0) {
close(fd_);
}
}
int get() { return fd_; }
private:
explicit FileDescriptor(const FileDescriptor&);
void operator=(const FileDescriptor&);
};
// Helper class for reading lines from file.
//
// Note: we don't use ProcMapsIterator since the object is big (it has
// a 5k array member) and uses async-unsafe functions such as sscanf()
// and snprintf().
class LineReader {
public:
explicit LineReader(int fd, char *buf, int buf_len, off_t offset)
: fd_(fd),
buf_(buf),
buf_len_(buf_len),
offset_(offset),
bol_(buf),
eol_(buf),
eod_(buf) {}
// Read '\n'-terminated line from file. On success, modify "bol"
// and "eol", then return true. Otherwise, return false.
//
// Note: if the last line doesn't end with '\n', the line will be
// dropped. It's an intentional behavior to make the code simple.
bool ReadLine(const char **bol, const char **eol) {
if (BufferIsEmpty()) { // First time.
const ssize_t num_bytes = ReadFromOffset(fd_, buf_, buf_len_, offset_);
if (num_bytes <= 0) { // EOF or error.
return false;
}
offset_ += num_bytes;
eod_ = buf_ + num_bytes;
bol_ = buf_;
} else {
bol_ = eol_ + 1; // Advance to the next line in the buffer.
SAFE_ASSERT(bol_ <= eod_); // "bol_" can point to "eod_".
if (!HasCompleteLine()) {
const int incomplete_line_length = eod_ - bol_;
// Move the trailing incomplete line to the beginning.
memmove(buf_, bol_, incomplete_line_length);
// Read text from file and append it.
char * const append_pos = buf_ + incomplete_line_length;
const int capacity_left = buf_len_ - incomplete_line_length;
const ssize_t num_bytes =
ReadFromOffset(fd_, append_pos, capacity_left, offset_);
if (num_bytes <= 0) { // EOF or error.
return false;
}
offset_ += num_bytes;
eod_ = append_pos + num_bytes;
bol_ = buf_;
}
}
eol_ = FindLineFeed();
if (eol_ == NULL) { // '\n' not found. Malformed line.
return false;
}
*eol_ = '\0'; // Replace '\n' with '\0'.
*bol = bol_;
*eol = eol_;
return true;
}
// Beginning of line.
const char *bol() {
return bol_;
}
// End of line.
const char *eol() {
return eol_;
}
private:
explicit LineReader(const LineReader&);
void operator=(const LineReader&);
char *FindLineFeed() {
return reinterpret_cast<char *>(memchr(bol_, '\n', eod_ - bol_));
}
bool BufferIsEmpty() {
return buf_ == eod_;
}
bool HasCompleteLine() {
return !BufferIsEmpty() && FindLineFeed() != NULL;
}
const int fd_;
char * const buf_;
const int buf_len_;
off_t offset_;
char *bol_;
char *eol_;
const char *eod_; // End of data in "buf_".
};
} // namespace
// Place the hex number read from "start" into "*hex". The pointer to
// the first non-hex character or "end" is returned.
static char *GetHex(const char *start, const char *end, uint64_t *hex) {
*hex = 0;
const char *p;
for (p = start; p < end; ++p) {
int ch = *p;
if ((ch >= '0' && ch <= '9') ||
(ch >= 'A' && ch <= 'F') || (ch >= 'a' && ch <= 'f')) {
*hex = (*hex << 4) | (ch < 'A' ? ch - '0' : (ch & 0xF) + 9);
} else { // Encountered the first non-hex character.
break;
}
}
SAFE_ASSERT(p <= end);
return const_cast<char *>(p);
}
// Searches for the object file (from /proc/self/maps) that contains
// the specified pc. If found, sets |start_address| to the start address
// of where this object file is mapped in memory, sets the module base
// address into |base_address|, copies the object file name into
// |out_file_name|, and attempts to open the object file. If the object
// file is opened successfully, returns the file descriptor. Otherwise,
// returns -1. |out_file_name_size| is the size of the file name buffer
// (including the null-terminator).
static ATTRIBUTE_NOINLINE int
OpenObjectFileContainingPcAndGetStartAddress(uint64_t pc,
uint64_t &start_address,
uint64_t &base_address,
char *out_file_name,
int out_file_name_size) {
int object_fd;
int maps_fd;
NO_INTR(maps_fd = open("/proc/self/maps", O_RDONLY));
FileDescriptor wrapped_maps_fd(maps_fd);
if (wrapped_maps_fd.get() < 0) {
return -1;
}
int mem_fd;
NO_INTR(mem_fd = open("/proc/self/mem", O_RDONLY));
FileDescriptor wrapped_mem_fd(mem_fd);
if (wrapped_mem_fd.get() < 0) {
return -1;
}
// Iterate over maps and look for the map containing the pc. Then
// look into the symbol tables inside.
char buf[1024]; // Big enough for line of sane /proc/self/maps
int num_maps = 0;
LineReader reader(wrapped_maps_fd.get(), buf, sizeof(buf), 0);
while (true) {
num_maps++;
const char *cursor;
const char *eol;
if (!reader.ReadLine(&cursor, &eol)) { // EOF or malformed line.
return -1;
}
// Start parsing line in /proc/self/maps. Here is an example:
//
// 08048000-0804c000 r-xp 00000000 08:01 2142121 /bin/cat
//
// We want start address (08048000), end address (0804c000), flags
// (r-xp) and file name (/bin/cat).
// Read start address.
cursor = GetHex(cursor, eol, &start_address);
if (cursor == eol || *cursor != '-') {
return -1; // Malformed line.
}
++cursor; // Skip '-'.
// Read end address.
uint64_t end_address;
cursor = GetHex(cursor, eol, &end_address);
if (cursor == eol || *cursor != ' ') {
return -1; // Malformed line.
}
++cursor; // Skip ' '.
// Read flags. Skip flags until we encounter a space or eol.
const char * const flags_start = cursor;
while (cursor < eol && *cursor != ' ') {
++cursor;
}
// We expect at least four letters for flags (ex. "r-xp").
if (cursor == eol || cursor < flags_start + 4) {
return -1; // Malformed line.
}
// Determine the base address by reading ELF headers in process memory.
ElfW(Ehdr) ehdr;
// Skip non-readable maps.
if (flags_start[0] == 'r' &&
ReadFromOffsetExact(mem_fd, &ehdr, sizeof(ElfW(Ehdr)), start_address) &&
memcmp(ehdr.e_ident, ELFMAG, SELFMAG) == 0) {
switch (ehdr.e_type) {
case ET_EXEC:
base_address = 0;
break;
case ET_DYN:
// Find the segment containing file offset 0. This will correspond
// to the ELF header that we just read. Normally this will have
// virtual address 0, but this is not guaranteed. We must subtract
// the virtual address from the address where the ELF header was
// mapped to get the base address.
//
// If we fail to find a segment for file offset 0, use the address
// of the ELF header as the base address.
base_address = start_address;
for (unsigned i = 0; i != ehdr.e_phnum; ++i) {
ElfW(Phdr) phdr;
if (ReadFromOffsetExact(
mem_fd, &phdr, sizeof(phdr),
start_address + ehdr.e_phoff + i * sizeof(phdr)) &&
phdr.p_type == PT_LOAD && phdr.p_offset == 0) {
base_address = start_address - phdr.p_vaddr;
break;
}
}
break;
default:
// ET_REL or ET_CORE. These aren't directly executable, so they don't
// affect the base address.
break;
}
}
// Check start and end addresses.
if (!(start_address <= pc && pc < end_address)) {
continue; // We skip this map. PC isn't in this map.
}
// Check flags. We are only interested in "r*x" maps.
if (flags_start[0] != 'r' || flags_start[2] != 'x') {
continue; // We skip this map.
}
++cursor; // Skip ' '.
// Read file offset.
uint64_t file_offset;
cursor = GetHex(cursor, eol, &file_offset);
if (cursor == eol || *cursor != ' ') {
return -1; // Malformed line.
}
++cursor; // Skip ' '.
// Skip to file name. "cursor" now points to dev. We need to
// skip at least two spaces for dev and inode.
int num_spaces = 0;
while (cursor < eol) {
if (*cursor == ' ') {
++num_spaces;
} else if (num_spaces >= 2) {
// The first non-space character after skipping two spaces
// is the beginning of the file name.
break;
}
++cursor;
}
if (cursor == eol) {
return -1; // Malformed line.
}
// Finally, "cursor" now points to file name of our interest.
NO_INTR(object_fd = open(cursor, O_RDONLY));
if (object_fd < 0) {
// Failed to open object file. Copy the object file name to
// |out_file_name|.
strncpy(out_file_name, cursor, out_file_name_size);
// Making sure |out_file_name| is always null-terminated.
out_file_name[out_file_name_size - 1] = '\0';
return -1;
}
return object_fd;
}
}
// POSIX doesn't define any async-signal safe function for converting
// an integer to ASCII. We'll have to define our own version.
// itoa_r() converts a (signed) integer to ASCII. It returns "buf", if the
// conversion was successful or NULL otherwise. It never writes more than "sz"
// bytes. Output will be truncated as needed, and a NUL character is always
// appended.
// NOTE: code from sandbox/linux/seccomp-bpf/demo.cc.
static char *itoa_r(intptr_t i, char *buf, size_t sz, int base, size_t padding) {
// Make sure we can write at least one NUL byte.
size_t n = 1;
if (n > sz)
return NULL;
if (base < 2 || base > 16) {
buf[0] = '\000';
return NULL;
}
char *start = buf;
uintptr_t j = i;
// Handle negative numbers (only for base 10).
if (i < 0 && base == 10) {
// This does "j = -i" while avoiding integer overflow.
j = static_cast<uintptr_t>(-(i + 1)) + 1;
// Make sure we can write the '-' character.
if (++n > sz) {
buf[0] = '\000';
return NULL;
}
*start++ = '-';
}
// Loop until we have converted the entire number. Output at least one
// character (i.e. '0').
char *ptr = start;
do {
// Make sure there is still enough space left in our output buffer.
if (++n > sz) {
buf[0] = '\000';
return NULL;
}
// Output the next digit.
*ptr++ = "0123456789abcdef"[j % base];
j /= base;
if (padding > 0)
padding--;
} while (j > 0 || padding > 0);
// Terminate the output with a NUL character.
*ptr = '\000';
// Conversion to ASCII actually resulted in the digits being in reverse
// order. We can't easily generate them in forward order, as we can't tell
// the number of characters needed until we are done converting.
// So, now, we reverse the string (except for the possible "-" sign).
while (--ptr > start) {
char ch = *ptr;
*ptr = *start;
*start++ = ch;
}
return buf;
}
// Safely appends string |source| to string |dest|. Never writes past the
// buffer size |dest_size| and guarantees that |dest| is null-terminated.
static void SafeAppendString(const char* source, char* dest, int dest_size) {
int dest_string_length = strlen(dest);
SAFE_ASSERT(dest_string_length < dest_size);
dest += dest_string_length;
dest_size -= dest_string_length;
strncpy(dest, source, dest_size);
// Making sure |dest| is always null-terminated.
dest[dest_size - 1] = '\0';
}
// Converts a 64-bit value into a hex string, and safely appends it to |dest|.
// Never writes past the buffer size |dest_size| and guarantees that |dest| is
// null-terminated.
static void SafeAppendHexNumber(uint64_t value, char* dest, int dest_size) {
// 64-bit numbers in hex can have up to 16 digits.
char buf[17] = {'\0'};
SafeAppendString(itoa_r(value, buf, sizeof(buf), 16, 0), dest, dest_size);
}
// The implementation of our symbolization routine. If it
// successfully finds the symbol containing "pc" and obtains the
// symbol name, returns true and write the symbol name to "out".
// Otherwise, returns false. If Callback function is installed via
// InstallSymbolizeCallback(), the function is also called in this function,
// and "out" is used as its output.
// To keep stack consumption low, we would like this function to not
// get inlined.
static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
int out_size) {
uint64_t pc0 = reinterpret_cast<uintptr_t>(pc);
uint64_t start_address = 0;
uint64_t base_address = 0;
int object_fd = -1;
if (out_size < 1) {
return false;
}
out[0] = '\0';
SafeAppendString("(", out, out_size);
if (g_symbolize_open_object_file_callback) {
object_fd = g_symbolize_open_object_file_callback(pc0, start_address,
base_address, out + 1,
out_size - 1);
} else {
object_fd = OpenObjectFileContainingPcAndGetStartAddress(pc0, start_address,
base_address,
out + 1,
out_size - 1);
}
FileDescriptor wrapped_object_fd(object_fd);
#if defined(PRINT_UNSYMBOLIZED_STACK_TRACES)
{
#else
// Check whether a file name was returned.
if (object_fd < 0) {
#endif
if (out[1]) {
// The object file containing PC was determined successfully however the
// object file was not opened successfully. This is still considered
// success because the object file name and offset are known and tools
// like asan_symbolize.py can be used for the symbolization.
out[out_size - 1] = '\0'; // Making sure |out| is always null-terminated.
SafeAppendString("+0x", out, out_size);
SafeAppendHexNumber(pc0 - base_address, out, out_size);
SafeAppendString(")", out, out_size);
return true;
}
// Failed to determine the object file containing PC. Bail out.
return false;
}
int elf_type = FileGetElfType(wrapped_object_fd.get());
if (elf_type == -1) {
return false;
}
if (g_symbolize_callback) {
// Run the call back if it's installed.
// Note: relocation (and much of the rest of this code) will be
// wrong for prelinked shared libraries and PIE executables.
uint64_t relocation = (elf_type == ET_DYN) ? start_address : 0;
int num_bytes_written = g_symbolize_callback(wrapped_object_fd.get(),
pc, out, out_size,
relocation);
if (num_bytes_written > 0) {
out += num_bytes_written;
out_size -= num_bytes_written;
}
}
if (!GetSymbolFromObjectFile(wrapped_object_fd.get(), pc0,
out, out_size, base_address)) {
if (out[1] && !g_symbolize_callback) {
// The object file containing PC was opened successfully however the
// symbol was not found. The object may have been stripped. This is still
// considered success because the object file name and offset are known
// and tools like asan_symbolize.py can be used for the symbolization.
out[out_size - 1] = '\0'; // Making sure |out| is always null-terminated.
SafeAppendString("+0x", out, out_size);
SafeAppendHexNumber(pc0 - base_address, out, out_size);
SafeAppendString(")", out, out_size);
return true;
}
return false;
}
// Symbolization succeeded. Now we try to demangle the symbol.
DemangleInplace(out, out_size);
return true;
}
_END_GOOGLE_NAMESPACE_
#elif defined(OS_MACOSX) && defined(HAVE_DLADDR)
#include <dlfcn.h>
#include <string.h>
_START_GOOGLE_NAMESPACE_
static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
int out_size) {
Dl_info info;
if (dladdr(pc, &info)) {
if ((int)strlen(info.dli_sname) < out_size) {
strcpy(out, info.dli_sname);
// Symbolization succeeded. Now we try to demangle the symbol.
DemangleInplace(out, out_size);
return true;
}
}
return false;
}
_END_GOOGLE_NAMESPACE_
#elif defined(OS_WINDOWS) || defined(OS_CYGWIN)
#include <windows.h>
#include <dbghelp.h>
#ifdef _MSC_VER
#pragma comment(lib, "dbghelp")
#endif
_START_GOOGLE_NAMESPACE_
class SymInitializer {
public:
HANDLE process;
bool ready;
SymInitializer() : process(NULL), ready(false) {
// Initialize the symbol handler.
// https://msdn.microsoft.com/en-us/library/windows/desktop/ms680344(v=vs.85).aspx
process = GetCurrentProcess();
// Defer symbol loading.
// We do not request undecorated symbols with SYMOPT_UNDNAME
// because the mangling library calls UnDecorateSymbolName.
SymSetOptions(SYMOPT_DEFERRED_LOADS);
if (SymInitialize(process, NULL, true)) {
ready = true;
}
}
~SymInitializer() {
SymCleanup(process);
// We do not need to close `HANDLE process` because it's a "pseudo handle."
}
private:
SymInitializer(const SymInitializer&);
SymInitializer& operator=(const SymInitializer&);
};
static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
int out_size) {
const static SymInitializer symInitializer;
if (!symInitializer.ready) {
return false;
}
// Resolve symbol information from address.
// https://msdn.microsoft.com/en-us/library/windows/desktop/ms680578(v=vs.85).aspx
char buf[sizeof(SYMBOL_INFO) + MAX_SYM_NAME];
SYMBOL_INFO *symbol = reinterpret_cast<SYMBOL_INFO *>(buf);
symbol->SizeOfStruct = sizeof(SYMBOL_INFO);
symbol->MaxNameLen = MAX_SYM_NAME;
// We use the ANSI version to ensure the string type is always `char *`.
// This could break if a symbol has Unicode in it.
BOOL ret = SymFromAddr(symInitializer.process,
reinterpret_cast<DWORD64>(pc), 0, symbol);
if (ret == 1 && static_cast<int>(symbol->NameLen) < out_size) {
// `NameLen` does not include the null terminating character.
strncpy(out, symbol->Name, static_cast<size_t>(symbol->NameLen) + 1);
out[static_cast<size_t>(symbol->NameLen)] = '\0';
// Symbolization succeeded. Now we try to demangle the symbol.
DemangleInplace(out, out_size);
return true;
}
return false;
}
_END_GOOGLE_NAMESPACE_
#else
# error BUG: HAVE_SYMBOLIZE was wrongly set
#endif
_START_GOOGLE_NAMESPACE_
bool Symbolize(void *pc, char *out, int out_size) {
SAFE_ASSERT(out_size >= 0);
return SymbolizeAndDemangle(pc, out, out_size);
}
_END_GOOGLE_NAMESPACE_
#else /* HAVE_SYMBOLIZE */
#include <assert.h>
#include "config.h"
_START_GOOGLE_NAMESPACE_
// TODO: Support other environments.
bool Symbolize(void *pc, char *out, int out_size) {
assert(0);
return false;
}
_END_GOOGLE_NAMESPACE_
#endif
