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gecko-dev/tools/profiler/lul/LulElf.cpp

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
// Copyright (c) 2006, 2011, 2012 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.
// Restructured in 2009 by: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
// (derived from)
// dump_symbols.cc: implement google_breakpad::WriteSymbolFile:
// Find all the debugging info in a file and dump it as a Breakpad symbol file.
//
// dump_symbols.h: Read debugging information from an ELF file, and write
// it out as a Breakpad symbol file.
// This file is derived from the following files in
// toolkit/crashreporter/google-breakpad:
// src/common/linux/dump_symbols.cc
// src/common/linux/elfutils.cc
// src/common/linux/file_id.cc
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <set>
#include <string>
#include <vector>
#include "mozilla/Assertions.h"
#include "mozilla/Sprintf.h"
#include "PlatformMacros.h"
#include "LulCommonExt.h"
#include "LulDwarfExt.h"
#include "LulElfInt.h"
#include "LulMainInt.h"
#if defined(GP_PLAT_arm_android) && !defined(SHT_ARM_EXIDX)
// bionic and older glibsc don't define it
# define SHT_ARM_EXIDX (SHT_LOPROC + 1)
#endif
// This namespace contains helper functions.
namespace {
using lul::DwarfCFIToModule;
using lul::FindElfSectionByName;
using lul::GetOffset;
using lul::IsValidElf;
using lul::Module;
using lul::UniqueStringUniverse;
using lul::scoped_ptr;
using lul::Summariser;
using std::string;
using std::vector;
using std::set;
//
// FDWrapper
//
// Wrapper class to make sure opened file is closed.
//
class FDWrapper {
public:
explicit FDWrapper(int fd) :
fd_(fd) {}
~FDWrapper() {
if (fd_ != -1)
close(fd_);
}
int get() {
return fd_;
}
int release() {
int fd = fd_;
fd_ = -1;
return fd;
}
private:
int fd_;
};
//
// MmapWrapper
//
// Wrapper class to make sure mapped regions are unmapped.
//
class MmapWrapper {
public:
MmapWrapper() : is_set_(false), base_(NULL), size_(0){}
~MmapWrapper() {
if (is_set_ && base_ != NULL) {
MOZ_ASSERT(size_ > 0);
munmap(base_, size_);
}
}
void set(void *mapped_address, size_t mapped_size) {
is_set_ = true;
base_ = mapped_address;
size_ = mapped_size;
}
void release() {
MOZ_ASSERT(is_set_);
is_set_ = false;
base_ = NULL;
size_ = 0;
}
private:
bool is_set_;
void *base_;
size_t size_;
};
// Set NUM_DW_REGNAMES to be the number of Dwarf register names
// appropriate to the machine architecture given in HEADER. Return
// true on success, or false if HEADER's machine architecture is not
// supported.
template<typename ElfClass>
bool DwarfCFIRegisterNames(const typename ElfClass::Ehdr* elf_header,
unsigned int* num_dw_regnames) {
switch (elf_header->e_machine) {
case EM_386:
*num_dw_regnames = DwarfCFIToModule::RegisterNames::I386();
return true;
case EM_ARM:
*num_dw_regnames = DwarfCFIToModule::RegisterNames::ARM();
return true;
case EM_X86_64:
*num_dw_regnames = DwarfCFIToModule::RegisterNames::X86_64();
return true;
default:
MOZ_ASSERT(0);
return false;
}
}
template<typename ElfClass>
bool LoadDwarfCFI(const string& dwarf_filename,
const typename ElfClass::Ehdr* elf_header,
const char* section_name,
const typename ElfClass::Shdr* section,
const bool eh_frame,
const typename ElfClass::Shdr* got_section,
const typename ElfClass::Shdr* text_section,
const bool big_endian,
SecMap* smap,
uintptr_t text_bias,
UniqueStringUniverse* usu,
void (*log)(const char*)) {
// Find the appropriate set of register names for this file's
// architecture.
unsigned int num_dw_regs = 0;
if (!DwarfCFIRegisterNames<ElfClass>(elf_header, &num_dw_regs)) {
fprintf(stderr, "%s: unrecognized ELF machine architecture '%d';"
" cannot convert DWARF call frame information\n",
dwarf_filename.c_str(), elf_header->e_machine);
return false;
}
const lul::Endianness endianness
= big_endian ? lul::ENDIANNESS_BIG : lul::ENDIANNESS_LITTLE;
// Find the call frame information and its size.
const char* cfi =
GetOffset<ElfClass, char>(elf_header, section->sh_offset);
size_t cfi_size = section->sh_size;
// Plug together the parser, handler, and their entourages.
// Here's a summariser, which will receive the output of the
// parser, create summaries, and add them to |smap|.
Summariser summ(smap, text_bias, log);
lul::ByteReader reader(endianness);
reader.SetAddressSize(ElfClass::kAddrSize);
DwarfCFIToModule::Reporter module_reporter(log, dwarf_filename, section_name);
DwarfCFIToModule handler(num_dw_regs, &module_reporter, &reader, usu, &summ);
// Provide the base addresses for .eh_frame encoded pointers, if
// possible.
reader.SetCFIDataBase(section->sh_addr, cfi);
if (got_section)
reader.SetDataBase(got_section->sh_addr);
if (text_section)
reader.SetTextBase(text_section->sh_addr);
lul::CallFrameInfo::Reporter dwarf_reporter(log, dwarf_filename,
section_name);
lul::CallFrameInfo parser(cfi, cfi_size,
&reader, &handler, &dwarf_reporter,
eh_frame);
parser.Start();
return true;
}
bool LoadELF(const string& obj_file, MmapWrapper* map_wrapper,
void** elf_header) {
int obj_fd = open(obj_file.c_str(), O_RDONLY);
if (obj_fd < 0) {
fprintf(stderr, "Failed to open ELF file '%s': %s\n",
obj_file.c_str(), strerror(errno));
return false;
}
FDWrapper obj_fd_wrapper(obj_fd);
struct stat st;
if (fstat(obj_fd, &st) != 0 && st.st_size <= 0) {
fprintf(stderr, "Unable to fstat ELF file '%s': %s\n",
obj_file.c_str(), strerror(errno));
return false;
}
// Mapping it read-only is good enough. In any case, mapping it
// read-write confuses Valgrind's debuginfo acquire/discard
// heuristics, making it hard to profile the profiler.
void *obj_base = mmap(nullptr, st.st_size,
PROT_READ, MAP_PRIVATE, obj_fd, 0);
if (obj_base == MAP_FAILED) {
fprintf(stderr, "Failed to mmap ELF file '%s': %s\n",
obj_file.c_str(), strerror(errno));
return false;
}
map_wrapper->set(obj_base, st.st_size);
*elf_header = obj_base;
if (!IsValidElf(*elf_header)) {
fprintf(stderr, "Not a valid ELF file: %s\n", obj_file.c_str());
return false;
}
return true;
}
// Get the endianness of ELF_HEADER. If it's invalid, return false.
template<typename ElfClass>
bool ElfEndianness(const typename ElfClass::Ehdr* elf_header,
bool* big_endian) {
if (elf_header->e_ident[EI_DATA] == ELFDATA2LSB) {
*big_endian = false;
return true;
}
if (elf_header->e_ident[EI_DATA] == ELFDATA2MSB) {
*big_endian = true;
return true;
}
fprintf(stderr, "bad data encoding in ELF header: %d\n",
elf_header->e_ident[EI_DATA]);
return false;
}
//
// LoadSymbolsInfo
//
// Holds the state between the two calls to LoadSymbols() in case it's necessary
// to follow the .gnu_debuglink section and load debug information from a
// different file.
//
template<typename ElfClass>
class LoadSymbolsInfo {
public:
typedef typename ElfClass::Addr Addr;
explicit LoadSymbolsInfo(const vector<string>& dbg_dirs) :
debug_dirs_(dbg_dirs),
has_loading_addr_(false) {}
// Keeps track of which sections have been loaded so sections don't
// accidentally get loaded twice from two different files.
void LoadedSection(const string &section) {
if (loaded_sections_.count(section) == 0) {
loaded_sections_.insert(section);
} else {
fprintf(stderr, "Section %s has already been loaded.\n",
section.c_str());
}
}
string debuglink_file() const {
return debuglink_file_;
}
private:
const vector<string>& debug_dirs_; // Directories in which to
// search for the debug ELF file.
string debuglink_file_; // Full path to the debug ELF file.
bool has_loading_addr_; // Indicate if LOADING_ADDR_ is valid.
set<string> loaded_sections_; // Tracks the Loaded ELF sections
// between calls to LoadSymbols().
};
// Find the preferred loading address of the binary.
template<typename ElfClass>
typename ElfClass::Addr GetLoadingAddress(
const typename ElfClass::Phdr* program_headers,
int nheader) {
typedef typename ElfClass::Phdr Phdr;
// For non-PIC executables (e_type == ET_EXEC), the load address is
// the start address of the first PT_LOAD segment. (ELF requires
// the segments to be sorted by load address.) For PIC executables
// and dynamic libraries (e_type == ET_DYN), this address will
// normally be zero.
for (int i = 0; i < nheader; ++i) {
const Phdr& header = program_headers[i];
if (header.p_type == PT_LOAD)
return header.p_vaddr;
}
return 0;
}
template<typename ElfClass>
bool LoadSymbols(const string& obj_file,
const bool big_endian,
const typename ElfClass::Ehdr* elf_header,
const bool read_gnu_debug_link,
LoadSymbolsInfo<ElfClass>* info,
SecMap* smap,
void* rx_avma, size_t rx_size,
UniqueStringUniverse* usu,
void (*log)(const char*)) {
typedef typename ElfClass::Phdr Phdr;
typedef typename ElfClass::Shdr Shdr;
char buf[500];
SprintfLiteral(buf, "LoadSymbols: BEGIN %s\n", obj_file.c_str());
buf[sizeof(buf)-1] = 0;
log(buf);
// This is how the text bias is calculated.
// BEGIN CALCULATE BIAS
uintptr_t loading_addr = GetLoadingAddress<ElfClass>(
GetOffset<ElfClass, Phdr>(elf_header, elf_header->e_phoff),
elf_header->e_phnum);
uintptr_t text_bias = ((uintptr_t)rx_avma) - loading_addr;
SprintfLiteral(buf,
"LoadSymbols: rx_avma=%llx, text_bias=%llx",
(unsigned long long int)(uintptr_t)rx_avma,
(unsigned long long int)text_bias);
buf[sizeof(buf)-1] = 0;
log(buf);
// END CALCULATE BIAS
const Shdr* sections =
GetOffset<ElfClass, Shdr>(elf_header, elf_header->e_shoff);
const Shdr* section_names = sections + elf_header->e_shstrndx;
const char* names =
GetOffset<ElfClass, char>(elf_header, section_names->sh_offset);
const char *names_end = names + section_names->sh_size;
bool found_usable_info = false;
// Dwarf Call Frame Information (CFI) is actually independent from
// the other DWARF debugging information, and can be used alone.
const Shdr* dwarf_cfi_section =
FindElfSectionByName<ElfClass>(".debug_frame", SHT_PROGBITS,
sections, names, names_end,
elf_header->e_shnum);
if (dwarf_cfi_section) {
// Ignore the return value of this function; even without call frame
// information, the other debugging information could be perfectly
// useful.
info->LoadedSection(".debug_frame");
bool result =
LoadDwarfCFI<ElfClass>(obj_file, elf_header, ".debug_frame",
dwarf_cfi_section, false, 0, 0, big_endian,
smap, text_bias, usu, log);
found_usable_info = found_usable_info || result;
if (result)
log("LoadSymbols: read CFI from .debug_frame");
}
// Linux C++ exception handling information can also provide
// unwinding data.
const Shdr* eh_frame_section =
FindElfSectionByName<ElfClass>(".eh_frame", SHT_PROGBITS,
sections, names, names_end,
elf_header->e_shnum);
if (eh_frame_section) {
// Pointers in .eh_frame data may be relative to the base addresses of
// certain sections. Provide those sections if present.
const Shdr* got_section =
FindElfSectionByName<ElfClass>(".got", SHT_PROGBITS,
sections, names, names_end,
elf_header->e_shnum);
const Shdr* text_section =
FindElfSectionByName<ElfClass>(".text", SHT_PROGBITS,
sections, names, names_end,
elf_header->e_shnum);
info->LoadedSection(".eh_frame");
// As above, ignore the return value of this function.
bool result =
LoadDwarfCFI<ElfClass>(obj_file, elf_header, ".eh_frame",
eh_frame_section, true,
got_section, text_section, big_endian,
smap, text_bias, usu, log);
found_usable_info = found_usable_info || result;
if (result)
log("LoadSymbols: read CFI from .eh_frame");
}
SprintfLiteral(buf, "LoadSymbols: END %s\n", obj_file.c_str());
buf[sizeof(buf)-1] = 0;
log(buf);
return found_usable_info;
}
// Return the breakpad symbol file identifier for the architecture of
// ELF_HEADER.
template<typename ElfClass>
const char* ElfArchitecture(const typename ElfClass::Ehdr* elf_header) {
typedef typename ElfClass::Half Half;
Half arch = elf_header->e_machine;
switch (arch) {
case EM_386: return "x86";
case EM_ARM: return "arm";
case EM_MIPS: return "mips";
case EM_PPC64: return "ppc64";
case EM_PPC: return "ppc";
case EM_S390: return "s390";
case EM_SPARC: return "sparc";
case EM_SPARCV9: return "sparcv9";
case EM_X86_64: return "x86_64";
default: return NULL;
}
}
// Format the Elf file identifier in IDENTIFIER as a UUID with the
// dashes removed.
string FormatIdentifier(unsigned char identifier[16]) {
char identifier_str[40];
lul::FileID::ConvertIdentifierToString(
identifier,
identifier_str,
sizeof(identifier_str));
string id_no_dash;
for (int i = 0; identifier_str[i] != '\0'; ++i)
if (identifier_str[i] != '-')
id_no_dash += identifier_str[i];
// Add an extra "0" by the end. PDB files on Windows have an 'age'
// number appended to the end of the file identifier; this isn't
// really used or necessary on other platforms, but be consistent.
id_no_dash += '0';
return id_no_dash;
}
// Return the non-directory portion of FILENAME: the portion after the
// last slash, or the whole filename if there are no slashes.
string BaseFileName(const string &filename) {
// Lots of copies! basename's behavior is less than ideal.
char *c_filename = strdup(filename.c_str());
string base = basename(c_filename);
free(c_filename);
return base;
}
template<typename ElfClass>
bool ReadSymbolDataElfClass(const typename ElfClass::Ehdr* elf_header,
const string& obj_filename,
const vector<string>& debug_dirs,
SecMap* smap, void* rx_avma, size_t rx_size,
UniqueStringUniverse* usu,
void (*log)(const char*)) {
typedef typename ElfClass::Ehdr Ehdr;
unsigned char identifier[16];
if (!lul
::FileID::ElfFileIdentifierFromMappedFile(elf_header, identifier)) {
fprintf(stderr, "%s: unable to generate file identifier\n",
obj_filename.c_str());
return false;
}
const char *architecture = ElfArchitecture<ElfClass>(elf_header);
if (!architecture) {
fprintf(stderr, "%s: unrecognized ELF machine architecture: %d\n",
obj_filename.c_str(), elf_header->e_machine);
return false;
}
// Figure out what endianness this file is.
bool big_endian;
if (!ElfEndianness<ElfClass>(elf_header, &big_endian))
return false;
string name = BaseFileName(obj_filename);
string os = "Linux";
string id = FormatIdentifier(identifier);
LoadSymbolsInfo<ElfClass> info(debug_dirs);
if (!LoadSymbols<ElfClass>(obj_filename, big_endian, elf_header,
!debug_dirs.empty(), &info,
smap, rx_avma, rx_size, usu, log)) {
const string debuglink_file = info.debuglink_file();
if (debuglink_file.empty())
return false;
// Load debuglink ELF file.
fprintf(stderr, "Found debugging info in %s\n", debuglink_file.c_str());
MmapWrapper debug_map_wrapper;
Ehdr* debug_elf_header = NULL;
if (!LoadELF(debuglink_file, &debug_map_wrapper,
reinterpret_cast<void**>(&debug_elf_header)))
return false;
// Sanity checks to make sure everything matches up.
const char *debug_architecture =
ElfArchitecture<ElfClass>(debug_elf_header);
if (!debug_architecture) {
fprintf(stderr, "%s: unrecognized ELF machine architecture: %d\n",
debuglink_file.c_str(), debug_elf_header->e_machine);
return false;
}
if (strcmp(architecture, debug_architecture)) {
fprintf(stderr, "%s with ELF machine architecture %s does not match "
"%s with ELF architecture %s\n",
debuglink_file.c_str(), debug_architecture,
obj_filename.c_str(), architecture);
return false;
}
bool debug_big_endian;
if (!ElfEndianness<ElfClass>(debug_elf_header, &debug_big_endian))
return false;
if (debug_big_endian != big_endian) {
fprintf(stderr, "%s and %s does not match in endianness\n",
obj_filename.c_str(), debuglink_file.c_str());
return false;
}
if (!LoadSymbols<ElfClass>(debuglink_file, debug_big_endian,
debug_elf_header, false, &info,
smap, rx_avma, rx_size, usu, log)) {
return false;
}
}
return true;
}
} // namespace (anon)
namespace lul {
bool ReadSymbolDataInternal(const uint8_t* obj_file,
const string& obj_filename,
const vector<string>& debug_dirs,
SecMap* smap, void* rx_avma, size_t rx_size,
UniqueStringUniverse* usu,
void (*log)(const char*)) {
if (!IsValidElf(obj_file)) {
fprintf(stderr, "Not a valid ELF file: %s\n", obj_filename.c_str());
return false;
}
int elfclass = ElfClass(obj_file);
if (elfclass == ELFCLASS32) {
return ReadSymbolDataElfClass<ElfClass32>(
reinterpret_cast<const Elf32_Ehdr*>(obj_file),
obj_filename, debug_dirs, smap, rx_avma, rx_size, usu, log);
}
if (elfclass == ELFCLASS64) {
return ReadSymbolDataElfClass<ElfClass64>(
reinterpret_cast<const Elf64_Ehdr*>(obj_file),
obj_filename, debug_dirs, smap, rx_avma, rx_size, usu, log);
}
return false;
}
bool ReadSymbolData(const string& obj_file,
const vector<string>& debug_dirs,
SecMap* smap, void* rx_avma, size_t rx_size,
UniqueStringUniverse* usu,
void (*log)(const char*)) {
MmapWrapper map_wrapper;
void* elf_header = NULL;
if (!LoadELF(obj_file, &map_wrapper, &elf_header))
return false;
return ReadSymbolDataInternal(reinterpret_cast<uint8_t*>(elf_header),
obj_file, debug_dirs,
smap, rx_avma, rx_size, usu, log);
}
namespace {
template<typename ElfClass>
void FindElfClassSection(const char *elf_base,
const char *section_name,
typename ElfClass::Word section_type,
const void **section_start,
int *section_size) {
typedef typename ElfClass::Ehdr Ehdr;
typedef typename ElfClass::Shdr Shdr;
MOZ_ASSERT(elf_base);
MOZ_ASSERT(section_start);
MOZ_ASSERT(section_size);
MOZ_ASSERT(strncmp(elf_base, ELFMAG, SELFMAG) == 0);
const Ehdr* elf_header = reinterpret_cast<const Ehdr*>(elf_base);
MOZ_ASSERT(elf_header->e_ident[EI_CLASS] == ElfClass::kClass);
const Shdr* sections =
GetOffset<ElfClass,Shdr>(elf_header, elf_header->e_shoff);
const Shdr* section_names = sections + elf_header->e_shstrndx;
const char* names =
GetOffset<ElfClass,char>(elf_header, section_names->sh_offset);
const char *names_end = names + section_names->sh_size;
const Shdr* section =
FindElfSectionByName<ElfClass>(section_name, section_type,
sections, names, names_end,
elf_header->e_shnum);
if (section != NULL && section->sh_size > 0) {
*section_start = elf_base + section->sh_offset;
*section_size = section->sh_size;
}
}
template<typename ElfClass>
void FindElfClassSegment(const char *elf_base,
typename ElfClass::Word segment_type,
const void **segment_start,
int *segment_size) {
typedef typename ElfClass::Ehdr Ehdr;
typedef typename ElfClass::Phdr Phdr;
MOZ_ASSERT(elf_base);
MOZ_ASSERT(segment_start);
MOZ_ASSERT(segment_size);
MOZ_ASSERT(strncmp(elf_base, ELFMAG, SELFMAG) == 0);
const Ehdr* elf_header = reinterpret_cast<const Ehdr*>(elf_base);
MOZ_ASSERT(elf_header->e_ident[EI_CLASS] == ElfClass::kClass);
const Phdr* phdrs =
GetOffset<ElfClass,Phdr>(elf_header, elf_header->e_phoff);
for (int i = 0; i < elf_header->e_phnum; ++i) {
if (phdrs[i].p_type == segment_type) {
*segment_start = elf_base + phdrs[i].p_offset;
*segment_size = phdrs[i].p_filesz;
return;
}
}
}
} // namespace (anon)
bool IsValidElf(const void* elf_base) {
return strncmp(reinterpret_cast<const char*>(elf_base),
ELFMAG, SELFMAG) == 0;
}
int ElfClass(const void* elf_base) {
const ElfW(Ehdr)* elf_header =
reinterpret_cast<const ElfW(Ehdr)*>(elf_base);
return elf_header->e_ident[EI_CLASS];
}
bool FindElfSection(const void *elf_mapped_base,
const char *section_name,
uint32_t section_type,
const void **section_start,
int *section_size,
int *elfclass) {
MOZ_ASSERT(elf_mapped_base);
MOZ_ASSERT(section_start);
MOZ_ASSERT(section_size);
*section_start = NULL;
*section_size = 0;
if (!IsValidElf(elf_mapped_base))
return false;
int cls = ElfClass(elf_mapped_base);
if (elfclass) {
*elfclass = cls;
}
const char* elf_base =
static_cast<const char*>(elf_mapped_base);
if (cls == ELFCLASS32) {
FindElfClassSection<ElfClass32>(elf_base, section_name, section_type,
section_start, section_size);
return *section_start != NULL;
} else if (cls == ELFCLASS64) {
FindElfClassSection<ElfClass64>(elf_base, section_name, section_type,
section_start, section_size);
return *section_start != NULL;
}
return false;
}
bool FindElfSegment(const void *elf_mapped_base,
uint32_t segment_type,
const void **segment_start,
int *segment_size,
int *elfclass) {
MOZ_ASSERT(elf_mapped_base);
MOZ_ASSERT(segment_start);
MOZ_ASSERT(segment_size);
*segment_start = NULL;
*segment_size = 0;
if (!IsValidElf(elf_mapped_base))
return false;
int cls = ElfClass(elf_mapped_base);
if (elfclass) {
*elfclass = cls;
}
const char* elf_base =
static_cast<const char*>(elf_mapped_base);
if (cls == ELFCLASS32) {
FindElfClassSegment<ElfClass32>(elf_base, segment_type,
segment_start, segment_size);
return *segment_start != NULL;
} else if (cls == ELFCLASS64) {
FindElfClassSegment<ElfClass64>(elf_base, segment_type,
segment_start, segment_size);
return *segment_start != NULL;
}
return false;
}
// (derived from)
// file_id.cc: Return a unique identifier for a file
//
// See file_id.h for documentation
//
// ELF note name and desc are 32-bits word padded.
#define NOTE_PADDING(a) ((a + 3) & ~3)
// These functions are also used inside the crashed process, so be safe
// and use the syscall/libc wrappers instead of direct syscalls or libc.
template<typename ElfClass>
static bool ElfClassBuildIDNoteIdentifier(const void *section, int length,
uint8_t identifier[kMDGUIDSize]) {
typedef typename ElfClass::Nhdr Nhdr;
const void* section_end = reinterpret_cast<const char*>(section) + length;
const Nhdr* note_header = reinterpret_cast<const Nhdr*>(section);
while (reinterpret_cast<const void *>(note_header) < section_end) {
if (note_header->n_type == NT_GNU_BUILD_ID)
break;
note_header = reinterpret_cast<const Nhdr*>(
reinterpret_cast<const char*>(note_header) + sizeof(Nhdr) +
NOTE_PADDING(note_header->n_namesz) +
NOTE_PADDING(note_header->n_descsz));
}
if (reinterpret_cast<const void *>(note_header) >= section_end ||
note_header->n_descsz == 0) {
return false;
}
const char* build_id = reinterpret_cast<const char*>(note_header) +
sizeof(Nhdr) + NOTE_PADDING(note_header->n_namesz);
// Copy as many bits of the build ID as will fit
// into the GUID space.
memset(identifier, 0, kMDGUIDSize);
memcpy(identifier, build_id,
std::min(kMDGUIDSize, (size_t)note_header->n_descsz));
return true;
}
// Attempt to locate a .note.gnu.build-id section in an ELF binary
// and copy as many bytes of it as will fit into |identifier|.
static bool FindElfBuildIDNote(const void *elf_mapped_base,
uint8_t identifier[kMDGUIDSize]) {
void* note_section;
int note_size, elfclass;
if ((!FindElfSegment(elf_mapped_base, PT_NOTE,
(const void**)&note_section, &note_size, &elfclass) ||
note_size == 0) &&
(!FindElfSection(elf_mapped_base, ".note.gnu.build-id", SHT_NOTE,
(const void**)&note_section, &note_size, &elfclass) ||
note_size == 0)) {
return false;
}
if (elfclass == ELFCLASS32) {
return ElfClassBuildIDNoteIdentifier<ElfClass32>(note_section, note_size,
identifier);
} else if (elfclass == ELFCLASS64) {
return ElfClassBuildIDNoteIdentifier<ElfClass64>(note_section, note_size,
identifier);
}
return false;
}
// Attempt to locate the .text section of an ELF binary and generate
// a simple hash by XORing the first page worth of bytes into |identifier|.
static bool HashElfTextSection(const void *elf_mapped_base,
uint8_t identifier[kMDGUIDSize]) {
void* text_section;
int text_size;
if (!FindElfSection(elf_mapped_base, ".text", SHT_PROGBITS,
(const void**)&text_section, &text_size, NULL) ||
text_size == 0) {
return false;
}
memset(identifier, 0, kMDGUIDSize);
const uint8_t* ptr = reinterpret_cast<const uint8_t*>(text_section);
const uint8_t* ptr_end = ptr + std::min(text_size, 4096);
while (ptr < ptr_end) {
for (unsigned i = 0; i < kMDGUIDSize; i++)
identifier[i] ^= ptr[i];
ptr += kMDGUIDSize;
}
return true;
}
// static
bool FileID::ElfFileIdentifierFromMappedFile(const void* base,
uint8_t identifier[kMDGUIDSize]) {
// Look for a build id note first.
if (FindElfBuildIDNote(base, identifier))
return true;
// Fall back on hashing the first page of the text section.
return HashElfTextSection(base, identifier);
}
// static
void FileID::ConvertIdentifierToString(const uint8_t identifier[kMDGUIDSize],
char* buffer, int buffer_length) {
uint8_t identifier_swapped[kMDGUIDSize];
// Endian-ness swap to match dump processor expectation.
memcpy(identifier_swapped, identifier, kMDGUIDSize);
uint32_t* data1 = reinterpret_cast<uint32_t*>(identifier_swapped);
*data1 = htonl(*data1);
uint16_t* data2 = reinterpret_cast<uint16_t*>(identifier_swapped + 4);
*data2 = htons(*data2);
uint16_t* data3 = reinterpret_cast<uint16_t*>(identifier_swapped + 6);
*data3 = htons(*data3);
int buffer_idx = 0;
for (unsigned int idx = 0;
(buffer_idx < buffer_length) && (idx < kMDGUIDSize);
++idx) {
int hi = (identifier_swapped[idx] >> 4) & 0x0F;
int lo = (identifier_swapped[idx]) & 0x0F;
if (idx == 4 || idx == 6 || idx == 8 || idx == 10)
buffer[buffer_idx++] = '-';
buffer[buffer_idx++] = (hi >= 10) ? 'A' + hi - 10 : '0' + hi;
buffer[buffer_idx++] = (lo >= 10) ? 'A' + lo - 10 : '0' + lo;
}
// NULL terminate
buffer[(buffer_idx < buffer_length) ? buffer_idx : buffer_idx - 1] = 0;
}
} // namespace lul
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