kicad/thirdparty/sentry-native/external/libunwindstack-ndk/Symbols.cpp

246 lines
9.5 KiB
C++

/*
* Copyright (C) 2017 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 <elf.h>
#include <stdint.h>
#include <string.h>
#include <algorithm>
#include <string>
#include <vector>
#include <unwindstack/Memory.h>
#include "Check.h"
#include "Symbols.h"
namespace unwindstack {
Symbols::Symbols(uint64_t offset, uint64_t size, uint64_t entry_size, uint64_t str_offset,
uint64_t str_size)
: offset_(offset),
count_(entry_size != 0 ? ((size / entry_size > kMaxSymbols) ? kMaxSymbols : size / entry_size)
: 0),
entry_size_(entry_size),
str_offset_(str_offset) {
if (__builtin_add_overflow(str_offset_, str_size, &str_end_)) {
// Set to the max so that the code will still try to get symbol names.
// Any reads that might be invalid will simply return no data, so
// this will not result in crashes.
// The assumption is that this value might have been corrupted, but
// enough of the elf data is valid such that the code can still
// get symbol information.
str_end_ = UINT64_MAX;
}
}
template <typename SymType>
static bool IsFunc(const SymType* entry) {
return entry->st_shndx != SHN_UNDEF && ELF32_ST_TYPE(entry->st_info) == STT_FUNC;
}
// Binary search the symbol table to find function containing the given address.
// Without remap, the symbol table is assumed to be sorted and accessed directly.
// If the symbol table is not sorted this method might fail but should not crash.
// When the indices are remapped, they are guaranteed to be sorted by address.
template <typename SymType, bool RemapIndices>
Symbols::Info* Symbols::BinarySearch(uint64_t addr, Memory* elf_memory, uint64_t* func_offset) {
// Fast-path: Check if the symbol has been already read from memory.
// Otherwise use the cache iterator to constrain the binary search range.
// (the symbol must be in the gap between this and the previous iterator)
auto it = symbols_.upper_bound(addr);
if (it != symbols_.end()) {
uint64_t sym_value = (it->first - it->second.size); // Function address.
if (sym_value <= addr) {
*func_offset = addr - sym_value;
return &it->second;
}
}
uint32_t count = RemapIndices ? remap_->size() : count_;
uint32_t last = (it != symbols_.end()) ? it->second.index : count;
uint32_t first = (it != symbols_.begin()) ? std::prev(it)->second.index + 1 : 0;
while (first < last) {
uint32_t current = first + (last - first) / 2;
uint32_t symbol_index = RemapIndices ? remap_.value()[current] : current;
uint64_t offset = symbol_index * entry_size_;
if (__builtin_add_overflow(offset, offset_, &offset)) {
// The elf data might be malformed.
return nullptr;
}
SymType sym;
if (!elf_memory->ReadFully(offset, &sym, sizeof(sym))) {
return nullptr;
}
// There shouldn't be multiple symbols with same end address, but in case there are,
// overwrite the cache with the last entry, so that 'sym' and 'info' are consistent.
Info& info = symbols_[sym.st_value + sym.st_size];
info = {.size = static_cast<uint32_t>(sym.st_size), .index = current};
if (addr < sym.st_value) {
last = current;
} else if (addr < sym.st_value + sym.st_size) {
*func_offset = addr - sym.st_value;
return &info;
} else {
first = current + 1;
}
}
return nullptr;
}
// Create remapping table which allows us to access symbols as if they were sorted by address.
template <typename SymType>
void Symbols::BuildRemapTable(Memory* elf_memory) {
std::vector<uint64_t> addrs; // Addresses of all symbols (addrs[i] == symbols[i].st_value).
addrs.reserve(count_);
remap_.emplace(); // Construct the optional remap table.
remap_->reserve(count_);
for (size_t symbol_idx = 0; symbol_idx < count_;) {
// Read symbols from memory. We intentionally bypass the cache to save memory.
// Do the reads in batches so that we minimize the number of memory read calls.
uint64_t read_bytes = (count_ - symbol_idx) * entry_size_;
uint8_t buffer[1024];
read_bytes = std::min<size_t>(sizeof(buffer), read_bytes);
uint64_t offset = symbol_idx * entry_size_;
if (__builtin_add_overflow(offset, offset_, &offset)) {
// The elf data might be malformed.
break;
}
read_bytes = elf_memory->Read(offset, buffer, read_bytes);
if (read_bytes < sizeof(SymType)) {
// The elf data might be malformed.
break;
}
for (uint64_t offset = 0; offset <= read_bytes - sizeof(SymType);
offset += entry_size_, symbol_idx++) {
SymType sym;
memcpy(&sym, &buffer[offset], sizeof(SymType)); // Copy to ensure alignment.
addrs.push_back(sym.st_value); // Always insert so it is indexable by symbol index.
// NB: It is important to filter our zero-sized symbols since otherwise we can get
// duplicate end addresses in the table (e.g. if there is custom "end" symbol marker).
if (IsFunc(&sym) && sym.st_size != 0) {
remap_->push_back(symbol_idx); // Indices of function symbols only.
}
}
}
// Sort by address to make the remap list binary searchable (stable due to the a<b tie break).
auto comp = [&addrs](auto a, auto b) { return std::tie(addrs[a], a) < std::tie(addrs[b], b); };
std::sort(remap_->begin(), remap_->end(), comp);
// Remove duplicate entries (methods de-duplicated by the linker).
auto pred = [&addrs](auto a, auto b) { return addrs[a] == addrs[b]; };
remap_->erase(std::unique(remap_->begin(), remap_->end(), pred), remap_->end());
remap_->shrink_to_fit();
}
template <typename SymType>
bool Symbols::GetName(uint64_t addr, Memory* elf_memory, SharedString* name,
uint64_t* func_offset) {
Info* info;
if (!remap_.has_value()) {
// Assume the symbol table is sorted. If it is not, this will gracefully fail.
info = BinarySearch<SymType, false>(addr, elf_memory, func_offset);
if (info == nullptr) {
// Create the remapping table and retry the search.
BuildRemapTable<SymType>(elf_memory);
symbols_.clear(); // Remove cached symbols since the access pattern will be different.
info = BinarySearch<SymType, true>(addr, elf_memory, func_offset);
}
} else {
// Fast search using the previously created remap table.
info = BinarySearch<SymType, true>(addr, elf_memory, func_offset);
}
if (info == nullptr) {
return false;
}
// Read and cache the symbol name.
if (info->name.is_null()) {
SymType sym;
uint32_t symbol_index = remap_.has_value() ? remap_.value()[info->index] : info->index;
uint64_t offset = symbol_index * entry_size_;
if (__builtin_add_overflow(offset, offset_, &offset)) {
// The elf data might be malformed.
return false;
}
if (!elf_memory->ReadFully(offset, &sym, sizeof(sym))) {
return false;
}
std::string symbol_name;
uint64_t str;
if (__builtin_add_overflow(str_offset_, sym.st_name, &str) || str >= str_end_) {
return false;
}
if (!IsFunc(&sym) || !elf_memory->ReadString(str, &symbol_name, str_end_ - str)) {
return false;
}
info->name = SharedString(std::move(symbol_name));
}
*name = info->name;
return true;
}
template <typename SymType>
bool Symbols::GetGlobal(Memory* elf_memory, const std::string& name, uint64_t* memory_address) {
// Lookup from cache.
auto it = global_variables_.find(name);
if (it != global_variables_.end()) {
if (it->second.has_value()) {
*memory_address = it->second.value();
return true;
}
return false;
}
// Linear scan of all symbols.
for (uint32_t i = 0; i < count_; i++) {
uint64_t offset = i * entry_size_;
if (__builtin_add_overflow(offset_, offset, &offset)) {
// The elf data might be malformed.
return false;
}
SymType entry;
if (!elf_memory->ReadFully(offset, &entry, sizeof(entry))) {
return false;
}
if (entry.st_shndx != SHN_UNDEF && ELF32_ST_TYPE(entry.st_info) == STT_OBJECT &&
ELF32_ST_BIND(entry.st_info) == STB_GLOBAL) {
uint64_t str_offset = str_offset_ + entry.st_name;
if (__builtin_add_overflow(str_offset_, entry.st_name, &str_offset)) {
// The elf data might be malformed.
return false;
}
if (str_offset < str_end_) {
std::string symbol;
if (elf_memory->ReadString(str_offset, &symbol, str_end_ - str_offset) && symbol == name) {
global_variables_.emplace(name, entry.st_value);
*memory_address = entry.st_value;
return true;
}
}
}
}
global_variables_.emplace(name, std::optional<uint64_t>()); // Remember "not found" outcome.
return false;
}
// Instantiate all of the needed template functions.
template bool Symbols::GetName<Elf32_Sym>(uint64_t, Memory*, SharedString*, uint64_t*);
template bool Symbols::GetName<Elf64_Sym>(uint64_t, Memory*, SharedString*, uint64_t*);
template bool Symbols::GetGlobal<Elf32_Sym>(Memory*, const std::string&, uint64_t*);
template bool Symbols::GetGlobal<Elf64_Sym>(Memory*, const std::string&, uint64_t*);
} // namespace unwindstack