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platform_system_core/libbacktrace/BacktraceOffline.cpp
Christopher Ferris 8540216028 Put BacktraceOffline code into a separate library. 
BacktraceOffline is the only code that uses libLLVM. Create
a new shared library, backtrace_offline.so, that references this
so that including libbacktrace.so doesn't wind up pulling in libLLVM.

Change-Id: I90c502d833f6c464c3810dffde52a0c6da241cce
2016-01-25 16:26:48 -08:00

666 lines
20 KiB
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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "BacktraceOffline.h"
extern "C" {
#define UNW_REMOTE_ONLY
#include <dwarf.h>
}
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <ucontext.h>
#include <unistd.h>
#include <string>
#include <vector>
#include <backtrace/Backtrace.h>
#include <backtrace/BacktraceMap.h>
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-parameter"
#include <llvm/ADT/StringRef.h>
#include <llvm/Object/Binary.h>
#include <llvm/Object/ELFObjectFile.h>
#include <llvm/Object/ObjectFile.h>
#pragma clang diagnostic pop
#include "BacktraceLog.h"
void Space::Clear() {
start = 0;
end = 0;
data = nullptr;
}
size_t Space::Read(uint64_t addr, uint8_t* buffer, size_t size) {
if (addr >= start && addr < end) {
size_t read_size = std::min(size, static_cast<size_t>(end - addr));
memcpy(buffer, data + (addr - start), read_size);
return read_size;
}
return 0;
}
static int FindProcInfo(unw_addr_space_t addr_space, unw_word_t ip, unw_proc_info* proc_info,
int need_unwind_info, void* arg) {
BacktraceOffline* backtrace = reinterpret_cast<BacktraceOffline*>(arg);
bool result = backtrace->FindProcInfo(addr_space, ip, proc_info, need_unwind_info);
return result ? 0 : -UNW_EINVAL;
}
static void PutUnwindInfo(unw_addr_space_t, unw_proc_info_t*, void*) {
}
static int GetDynInfoListAddr(unw_addr_space_t, unw_word_t*, void*) {
return -UNW_ENOINFO;
}
static int AccessMem(unw_addr_space_t, unw_word_t addr, unw_word_t* value, int write, void* arg) {
if (write == 1) {
return -UNW_EINVAL;
}
BacktraceOffline* backtrace = reinterpret_cast<BacktraceOffline*>(arg);
*value = 0;
size_t read_size = backtrace->Read(addr, reinterpret_cast<uint8_t*>(value), sizeof(unw_word_t));
// Strictly we should check if read_size matches sizeof(unw_word_t), but it is possible in
// .eh_frame_hdr that the section can end at a position not aligned in sizeof(unw_word_t), and
// we should permit the read at the end of the section.
return (read_size > 0u ? 0 : -UNW_EINVAL);
}
static int AccessReg(unw_addr_space_t, unw_regnum_t unwind_reg, unw_word_t* value, int write,
void* arg) {
if (write == 1) {
return -UNW_EINVAL;
}
BacktraceOffline* backtrace = reinterpret_cast<BacktraceOffline*>(arg);
uint64_t reg_value;
bool result = backtrace->ReadReg(unwind_reg, &reg_value);
if (result) {
*value = static_cast<unw_word_t>(reg_value);
}
return result ? 0 : -UNW_EINVAL;
}
static int AccessFpReg(unw_addr_space_t, unw_regnum_t, unw_fpreg_t*, int, void*) {
return -UNW_EINVAL;
}
static int Resume(unw_addr_space_t, unw_cursor_t*, void*) {
return -UNW_EINVAL;
}
static int GetProcName(unw_addr_space_t, unw_word_t, char*, size_t, unw_word_t*, void*) {
return -UNW_EINVAL;
}
static unw_accessors_t accessors = {
.find_proc_info = FindProcInfo,
.put_unwind_info = PutUnwindInfo,
.get_dyn_info_list_addr = GetDynInfoListAddr,
.access_mem = AccessMem,
.access_reg = AccessReg,
.access_fpreg = AccessFpReg,
.resume = Resume,
.get_proc_name = GetProcName,
};
bool BacktraceOffline::Unwind(size_t num_ignore_frames, ucontext_t* context) {
if (context == nullptr) {
BACK_LOGW("The context is needed for offline backtracing.");
return false;
}
context_ = context;
unw_addr_space_t addr_space = unw_create_addr_space(&accessors, 0);
unw_cursor_t cursor;
int ret = unw_init_remote(&cursor, addr_space, this);
if (ret != 0) {
BACK_LOGW("unw_init_remote failed %d", ret);
unw_destroy_addr_space(addr_space);
return false;
}
size_t num_frames = 0;
do {
unw_word_t pc;
ret = unw_get_reg(&cursor, UNW_REG_IP, &pc);
if (ret < 0) {
BACK_LOGW("Failed to read IP %d", ret);
break;
}
unw_word_t sp;
ret = unw_get_reg(&cursor, UNW_REG_SP, &sp);
if (ret < 0) {
BACK_LOGW("Failed to read SP %d", ret);
break;
}
if (num_ignore_frames == 0) {
frames_.resize(num_frames + 1);
backtrace_frame_data_t* frame = &frames_[num_frames];
frame->num = num_frames;
frame->pc = static_cast<uintptr_t>(pc);
frame->sp = static_cast<uintptr_t>(sp);
frame->stack_size = 0;
if (num_frames > 0) {
backtrace_frame_data_t* prev = &frames_[num_frames - 1];
prev->stack_size = frame->sp - prev->sp;
}
frame->func_name = GetFunctionName(frame->pc, &frame->func_offset);
FillInMap(frame->pc, &frame->map);
num_frames++;
} else {
num_ignore_frames--;
}
ret = unw_step(&cursor);
} while (ret > 0 && num_frames < MAX_BACKTRACE_FRAMES);
unw_destroy_addr_space(addr_space);
context_ = nullptr;
return true;
}
bool BacktraceOffline::ReadWord(uintptr_t ptr, word_t* out_value) {
size_t bytes_read = Read(ptr, reinterpret_cast<uint8_t*>(out_value), sizeof(word_t));
return bytes_read == sizeof(word_t);
}
size_t BacktraceOffline::Read(uintptr_t addr, uint8_t* buffer, size_t bytes) {
// Normally, libunwind needs stack information and call frame information to do remote unwinding.
// If call frame information is stored in .debug_frame, libunwind can read it from file
// by itself. If call frame information is stored in .eh_frame, we need to provide data in
// .eh_frame/.eh_frame_hdr sections.
// The order of readings below doesn't matter, as the spaces don't overlap with each other.
size_t read_size = eh_frame_hdr_space_.Read(addr, buffer, bytes);
if (read_size != 0) {
return read_size;
}
read_size = eh_frame_space_.Read(addr, buffer, bytes);
if (read_size != 0) {
return read_size;
}
read_size = stack_space_.Read(addr, buffer, bytes);
return read_size;
}
static bool FileOffsetToVaddr(
const std::vector<DebugFrameInfo::EhFrame::ProgramHeader>& program_headers,
uint64_t file_offset, uint64_t* vaddr) {
for (auto& header : program_headers) {
if (file_offset >= header.file_offset && file_offset < header.file_offset + header.file_size) {
// TODO: Consider load_bias?
*vaddr = file_offset - header.file_offset + header.vaddr;
return true;
}
}
return false;
}
bool BacktraceOffline::FindProcInfo(unw_addr_space_t addr_space, uint64_t ip,
unw_proc_info_t* proc_info, int need_unwind_info) {
backtrace_map_t map;
FillInMap(ip, &map);
if (!BacktraceMap::IsValid(map)) {
return false;
}
const std::string& filename = map.name;
DebugFrameInfo* debug_frame = GetDebugFrameInFile(filename);
if (debug_frame == nullptr) {
return false;
}
if (debug_frame->is_eh_frame) {
uint64_t ip_offset = ip - map.start + map.offset;
uint64_t ip_vaddr; // vaddr in the elf file.
bool result = FileOffsetToVaddr(debug_frame->eh_frame.program_headers, ip_offset, &ip_vaddr);
if (!result) {
return false;
}
// Calculate the addresses where .eh_frame_hdr and .eh_frame stay when the process was running.
eh_frame_hdr_space_.start = (ip - ip_vaddr) + debug_frame->eh_frame.eh_frame_hdr_vaddr;
eh_frame_hdr_space_.end =
eh_frame_hdr_space_.start + debug_frame->eh_frame.eh_frame_hdr_data.size();
eh_frame_hdr_space_.data = debug_frame->eh_frame.eh_frame_hdr_data.data();
eh_frame_space_.start = (ip - ip_vaddr) + debug_frame->eh_frame.eh_frame_vaddr;
eh_frame_space_.end = eh_frame_space_.start + debug_frame->eh_frame.eh_frame_data.size();
eh_frame_space_.data = debug_frame->eh_frame.eh_frame_data.data();
unw_dyn_info di;
memset(&di, '\0', sizeof(di));
di.start_ip = map.start;
di.end_ip = map.end;
di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
di.u.rti.name_ptr = 0;
di.u.rti.segbase = eh_frame_hdr_space_.start;
di.u.rti.table_data =
eh_frame_hdr_space_.start + debug_frame->eh_frame.fde_table_offset_in_eh_frame_hdr;
di.u.rti.table_len = (eh_frame_hdr_space_.end - di.u.rti.table_data) / sizeof(unw_word_t);
int ret = dwarf_search_unwind_table(addr_space, ip, &di, proc_info, need_unwind_info, this);
return ret == 0;
}
eh_frame_hdr_space_.Clear();
eh_frame_space_.Clear();
unw_dyn_info_t di;
unw_word_t segbase = map.start - map.offset;
int found = dwarf_find_debug_frame(0, &di, ip, segbase, filename.c_str(), map.start, map.end);
if (found == 1) {
int ret = dwarf_search_unwind_table(addr_space, ip, &di, proc_info, need_unwind_info, this);
return ret == 0;
}
return false;
}
bool BacktraceOffline::ReadReg(size_t reg, uint64_t* value) {
bool result = true;
#if defined(__arm__)
switch (reg) {
case UNW_ARM_R0:
*value = context_->uc_mcontext.arm_r0;
break;
case UNW_ARM_R1:
*value = context_->uc_mcontext.arm_r1;
break;
case UNW_ARM_R2:
*value = context_->uc_mcontext.arm_r2;
break;
case UNW_ARM_R3:
*value = context_->uc_mcontext.arm_r3;
break;
case UNW_ARM_R4:
*value = context_->uc_mcontext.arm_r4;
break;
case UNW_ARM_R5:
*value = context_->uc_mcontext.arm_r5;
break;
case UNW_ARM_R6:
*value = context_->uc_mcontext.arm_r6;
break;
case UNW_ARM_R7:
*value = context_->uc_mcontext.arm_r7;
break;
case UNW_ARM_R8:
*value = context_->uc_mcontext.arm_r8;
break;
case UNW_ARM_R9:
*value = context_->uc_mcontext.arm_r9;
break;
case UNW_ARM_R10:
*value = context_->uc_mcontext.arm_r10;
break;
case UNW_ARM_R11:
*value = context_->uc_mcontext.arm_fp;
break;
case UNW_ARM_R12:
*value = context_->uc_mcontext.arm_ip;
break;
case UNW_ARM_R13:
*value = context_->uc_mcontext.arm_sp;
break;
case UNW_ARM_R14:
*value = context_->uc_mcontext.arm_lr;
break;
case UNW_ARM_R15:
*value = context_->uc_mcontext.arm_pc;
break;
default:
result = false;
}
#elif defined(__aarch64__)
if (reg <= UNW_AARCH64_PC) {
*value = context_->uc_mcontext.regs[reg];
} else {
result = false;
}
#elif defined(__x86_64__)
switch (reg) {
case UNW_X86_64_R8:
*value = context_->uc_mcontext.gregs[REG_R8];
break;
case UNW_X86_64_R9:
*value = context_->uc_mcontext.gregs[REG_R9];
break;
case UNW_X86_64_R10:
*value = context_->uc_mcontext.gregs[REG_R10];
break;
case UNW_X86_64_R11:
*value = context_->uc_mcontext.gregs[REG_R11];
break;
case UNW_X86_64_R12:
*value = context_->uc_mcontext.gregs[REG_R12];
break;
case UNW_X86_64_R13:
*value = context_->uc_mcontext.gregs[REG_R13];
break;
case UNW_X86_64_R14:
*value = context_->uc_mcontext.gregs[REG_R14];
break;
case UNW_X86_64_R15:
*value = context_->uc_mcontext.gregs[REG_R15];
break;
case UNW_X86_64_RDI:
*value = context_->uc_mcontext.gregs[REG_RDI];
break;
case UNW_X86_64_RSI:
*value = context_->uc_mcontext.gregs[REG_RSI];
break;
case UNW_X86_64_RBP:
*value = context_->uc_mcontext.gregs[REG_RBP];
break;
case UNW_X86_64_RBX:
*value = context_->uc_mcontext.gregs[REG_RBX];
break;
case UNW_X86_64_RDX:
*value = context_->uc_mcontext.gregs[REG_RDX];
break;
case UNW_X86_64_RAX:
*value = context_->uc_mcontext.gregs[REG_RAX];
break;
case UNW_X86_64_RCX:
*value = context_->uc_mcontext.gregs[REG_RCX];
break;
case UNW_X86_64_RSP:
*value = context_->uc_mcontext.gregs[REG_RSP];
break;
case UNW_X86_64_RIP:
*value = context_->uc_mcontext.gregs[REG_RIP];
break;
default:
result = false;
}
#elif defined(__i386__)
switch (reg) {
case UNW_X86_GS:
*value = context_->uc_mcontext.gregs[REG_GS];
break;
case UNW_X86_FS:
*value = context_->uc_mcontext.gregs[REG_FS];
break;
case UNW_X86_ES:
*value = context_->uc_mcontext.gregs[REG_ES];
break;
case UNW_X86_DS:
*value = context_->uc_mcontext.gregs[REG_DS];
break;
case UNW_X86_EAX:
*value = context_->uc_mcontext.gregs[REG_EAX];
break;
case UNW_X86_EBX:
*value = context_->uc_mcontext.gregs[REG_EBX];
break;
case UNW_X86_ECX:
*value = context_->uc_mcontext.gregs[REG_ECX];
break;
case UNW_X86_EDX:
*value = context_->uc_mcontext.gregs[REG_EDX];
break;
case UNW_X86_ESI:
*value = context_->uc_mcontext.gregs[REG_ESI];
break;
case UNW_X86_EDI:
*value = context_->uc_mcontext.gregs[REG_EDI];
break;
case UNW_X86_EBP:
*value = context_->uc_mcontext.gregs[REG_EBP];
break;
case UNW_X86_EIP:
*value = context_->uc_mcontext.gregs[REG_EIP];
break;
case UNW_X86_ESP:
*value = context_->uc_mcontext.gregs[REG_ESP];
break;
case UNW_X86_TRAPNO:
*value = context_->uc_mcontext.gregs[REG_TRAPNO];
break;
case UNW_X86_CS:
*value = context_->uc_mcontext.gregs[REG_CS];
break;
case UNW_X86_EFLAGS:
*value = context_->uc_mcontext.gregs[REG_EFL];
break;
case UNW_X86_SS:
*value = context_->uc_mcontext.gregs[REG_SS];
break;
default:
result = false;
}
#endif
return result;
}
std::string BacktraceOffline::GetFunctionNameRaw(uintptr_t, uintptr_t* offset) {
// We don't have enough information to support this. And it is expensive.
*offset = 0;
return "";
}
std::unordered_map<std::string, std::unique_ptr<DebugFrameInfo>> BacktraceOffline::debug_frames_;
std::unordered_set<std::string> BacktraceOffline::debug_frame_missing_files_;
static DebugFrameInfo* ReadDebugFrameFromFile(const std::string& filename);
DebugFrameInfo* BacktraceOffline::GetDebugFrameInFile(const std::string& filename) {
if (cache_file_) {
auto it = debug_frames_.find(filename);
if (it != debug_frames_.end()) {
return it->second.get();
}
if (debug_frame_missing_files_.find(filename) != debug_frame_missing_files_.end()) {
return nullptr;
}
}
DebugFrameInfo* debug_frame = ReadDebugFrameFromFile(filename);
if (cache_file_) {
if (debug_frame != nullptr) {
debug_frames_.emplace(filename, std::unique_ptr<DebugFrameInfo>(debug_frame));
} else {
debug_frame_missing_files_.insert(filename);
}
} else {
if (last_debug_frame_ != nullptr) {
delete last_debug_frame_;
}
last_debug_frame_ = debug_frame;
}
return debug_frame;
}
static bool OmitEncodedValue(uint8_t encode, const uint8_t*& p) {
if (encode == DW_EH_PE_omit) {
return 0;
}
uint8_t format = encode & 0x0f;
switch (format) {
case DW_EH_PE_ptr:
p += sizeof(unw_word_t);
break;
case DW_EH_PE_uleb128:
case DW_EH_PE_sleb128:
while ((*p & 0x80) != 0) {
++p;
}
++p;
break;
case DW_EH_PE_udata2:
case DW_EH_PE_sdata2:
p += 2;
break;
case DW_EH_PE_udata4:
case DW_EH_PE_sdata4:
p += 4;
break;
case DW_EH_PE_udata8:
case DW_EH_PE_sdata8:
p += 8;
break;
default:
return false;
}
return true;
}
static bool GetFdeTableOffsetInEhFrameHdr(const std::vector<uint8_t>& data,
uint64_t* table_offset_in_eh_frame_hdr) {
const uint8_t* p = data.data();
const uint8_t* end = p + data.size();
if (p + 4 > end) {
return false;
}
uint8_t version = *p++;
if (version != 1) {
return false;
}
uint8_t eh_frame_ptr_encode = *p++;
uint8_t fde_count_encode = *p++;
uint8_t fde_table_encode = *p++;
if (fde_table_encode != (DW_EH_PE_datarel | DW_EH_PE_sdata4)) {
return false;
}
if (!OmitEncodedValue(eh_frame_ptr_encode, p) || !OmitEncodedValue(fde_count_encode, p)) {
return false;
}
if (p >= end) {
return false;
}
*table_offset_in_eh_frame_hdr = p - data.data();
return true;
}
using ProgramHeader = DebugFrameInfo::EhFrame::ProgramHeader;
template <class ELFT>
DebugFrameInfo* ReadDebugFrameFromELFFile(const llvm::object::ELFFile<ELFT>* elf) {
bool has_eh_frame_hdr = false;
uint64_t eh_frame_hdr_vaddr = 0;
std::vector<uint8_t> eh_frame_hdr_data;
bool has_eh_frame = false;
uint64_t eh_frame_vaddr = 0;
std::vector<uint8_t> eh_frame_data;
for (auto it = elf->begin_sections(); it != elf->end_sections(); ++it) {
llvm::ErrorOr<llvm::StringRef> name = elf->getSectionName(&*it);
if (name) {
if (name.get() == ".debug_frame") {
DebugFrameInfo* debug_frame = new DebugFrameInfo;
debug_frame->is_eh_frame = false;
return debug_frame;
}
if (name.get() == ".eh_frame_hdr") {
has_eh_frame_hdr = true;
eh_frame_hdr_vaddr = it->sh_addr;
llvm::ErrorOr<llvm::ArrayRef<uint8_t>> data = elf->getSectionContents(&*it);
if (data) {
eh_frame_hdr_data.insert(eh_frame_hdr_data.begin(), data->data(),
data->data() + data->size());
} else {
return nullptr;
}
} else if (name.get() == ".eh_frame") {
has_eh_frame = true;
eh_frame_vaddr = it->sh_addr;
llvm::ErrorOr<llvm::ArrayRef<uint8_t>> data = elf->getSectionContents(&*it);
if (data) {
eh_frame_data.insert(eh_frame_data.begin(), data->data(), data->data() + data->size());
} else {
return nullptr;
}
}
}
}
if (!(has_eh_frame_hdr && has_eh_frame)) {
return nullptr;
}
uint64_t fde_table_offset;
if (!GetFdeTableOffsetInEhFrameHdr(eh_frame_hdr_data, &fde_table_offset)) {
return nullptr;
}
std::vector<ProgramHeader> program_headers;
for (auto it = elf->begin_program_headers(); it != elf->end_program_headers(); ++it) {
ProgramHeader header;
header.vaddr = it->p_vaddr;
header.file_offset = it->p_offset;
header.file_size = it->p_filesz;
program_headers.push_back(header);
}
DebugFrameInfo* debug_frame = new DebugFrameInfo;
debug_frame->is_eh_frame = true;
debug_frame->eh_frame.eh_frame_hdr_vaddr = eh_frame_hdr_vaddr;
debug_frame->eh_frame.eh_frame_vaddr = eh_frame_vaddr;
debug_frame->eh_frame.fde_table_offset_in_eh_frame_hdr = fde_table_offset;
debug_frame->eh_frame.eh_frame_hdr_data = std::move(eh_frame_hdr_data);
debug_frame->eh_frame.eh_frame_data = std::move(eh_frame_data);
debug_frame->eh_frame.program_headers = program_headers;
return debug_frame;
}
static bool IsValidElfPath(const std::string& filename) {
static const char elf_magic[] = {0x7f, 'E', 'L', 'F'};
struct stat st;
if (stat(filename.c_str(), &st) != 0 || !S_ISREG(st.st_mode)) {
return false;
}
FILE* fp = fopen(filename.c_str(), "reb");
if (fp == nullptr) {
return false;
}
char buf[4];
if (fread(buf, 4, 1, fp) != 1) {
fclose(fp);
return false;
}
fclose(fp);
return memcmp(buf, elf_magic, 4) == 0;
}
static DebugFrameInfo* ReadDebugFrameFromFile(const std::string& filename) {
if (!IsValidElfPath(filename)) {
return nullptr;
}
auto owning_binary = llvm::object::createBinary(llvm::StringRef(filename));
if (owning_binary.getError()) {
return nullptr;
}
llvm::object::Binary* binary = owning_binary.get().getBinary();
auto obj = llvm::dyn_cast<llvm::object::ObjectFile>(binary);
if (obj == nullptr) {
return nullptr;
}
if (auto elf = llvm::dyn_cast<llvm::object::ELF32LEObjectFile>(obj)) {
return ReadDebugFrameFromELFFile(elf->getELFFile());
}
if (auto elf = llvm::dyn_cast<llvm::object::ELF64LEObjectFile>(obj)) {
return ReadDebugFrameFromELFFile(elf->getELFFile());
}
return nullptr;
}
Backtrace* Backtrace::CreateOffline(pid_t pid, pid_t tid, BacktraceMap* map,
const backtrace_stackinfo_t& stack, bool cache_file) {
return new BacktraceOffline(pid, tid, map, stack, cache_file);
}
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