mirror of
https://github.com/google/sandboxed-api.git
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231 lines
7.4 KiB
C++
231 lines
7.4 KiB
C++
// Copyright 2019 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "sandboxed_api/sandbox2/unwind/unwind.h"
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#include <cxxabi.h>
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#include <cstddef>
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#include <cstdint>
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#include <cstdio>
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#include <map>
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#include <memory>
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#include <string>
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#include <vector>
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#include "absl/status/statusor.h"
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#include "absl/strings/match.h"
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#include "absl/strings/str_cat.h"
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#include "libunwind-ptrace.h"
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#include "sandboxed_api/sandbox2/comms.h"
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#include "sandboxed_api/sandbox2/unwind/ptrace_hook.h"
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#include "sandboxed_api/sandbox2/unwind/unwind.pb.h"
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#include "sandboxed_api/sandbox2/util/maps_parser.h"
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#include "sandboxed_api/sandbox2/util/minielf.h"
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#include "sandboxed_api/util/file_helpers.h"
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#include "sandboxed_api/util/raw_logging.h"
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#include "sandboxed_api/util/status_macros.h"
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#include "sandboxed_api/util/strerror.h"
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namespace sandbox2 {
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namespace {
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std::string DemangleSymbol(const std::string& maybe_mangled) {
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int status;
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size_t length;
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std::unique_ptr<char, decltype(&std::free)> symbol(
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abi::__cxa_demangle(maybe_mangled.c_str(), /*output_buffer=*/nullptr,
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&length, &status),
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std::free);
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if (symbol && status == 0) {
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return std::string(symbol.get(), length);
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}
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return maybe_mangled;
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}
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absl::StatusOr<std::vector<uintptr_t>> RunLibUnwind(pid_t pid, int max_frames) {
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unw_cursor_t cursor;
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static unw_addr_space_t as =
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unw_create_addr_space(&_UPT_accessors, 0 /* byte order */);
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if (as == nullptr) {
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return absl::InternalError("unw_create_addr_space() failed");
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}
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std::unique_ptr<struct UPT_info, void (*)(void*)> ui(
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reinterpret_cast<struct UPT_info*>(_UPT_create(pid)), _UPT_destroy);
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if (ui == nullptr) {
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return absl::InternalError("_UPT_create() failed");
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}
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int rc = unw_init_remote(&cursor, as, ui.get());
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if (rc < 0) {
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// Could be UNW_EINVAL (8), UNW_EUNSPEC (1) or UNW_EBADREG (3).
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return absl::InternalError(
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absl::StrCat("unw_init_remote() failed with error ", rc));
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}
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std::vector<uintptr_t> ips;
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for (int i = 0; i < max_frames; ++i) {
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unw_word_t ip;
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rc = unw_get_reg(&cursor, UNW_REG_IP, &ip);
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if (rc < 0) {
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// Could be UNW_EUNSPEC or UNW_EBADREG.
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SAPI_RAW_LOG(WARNING, "unw_get_reg() failed with error %d", rc);
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break;
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}
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ips.push_back(ip);
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rc = unw_step(&cursor);
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// Non-error condition: UNW_ESUCCESS (0).
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if (rc < 0) {
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// If anything but UNW_ESTOPUNWIND (-5), there has been an error.
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// However since we can't do anything about it and it appears that
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// this happens every time we don't log this.
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break;
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}
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}
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return ips;
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}
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absl::StatusOr<std::vector<std::string>> SymbolizeStacktrace(
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pid_t pid, const std::vector<uintptr_t>& ips) {
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SAPI_ASSIGN_OR_RETURN(auto addr_to_symbol, LoadSymbolsMap(pid));
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std::vector<std::string> stack_trace;
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stack_trace.reserve(ips.size());
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// Symbolize stacktrace
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for (uintptr_t ip : ips) {
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const std::string symbol =
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GetSymbolAt(addr_to_symbol, static_cast<uint64_t>(ip));
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stack_trace.push_back(absl::StrCat(symbol, "(0x", absl::Hex(ip), ")"));
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}
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return stack_trace;
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}
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} // namespace
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std::string GetSymbolAt(const SymbolMap& addr_to_symbol, uint64_t addr) {
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auto entry_for_next_symbol = addr_to_symbol.lower_bound(addr);
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if (entry_for_next_symbol != addr_to_symbol.end() &&
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entry_for_next_symbol != addr_to_symbol.begin()) {
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// Matches the addr exactly:
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if (entry_for_next_symbol->first == addr) {
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return DemangleSymbol(entry_for_next_symbol->second);
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}
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// Might be inside a function, return symbol+offset;
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const auto entry_for_previous_symbol = --entry_for_next_symbol;
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if (!entry_for_previous_symbol->second.empty()) {
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return absl::StrCat(DemangleSymbol(entry_for_previous_symbol->second),
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"+0x",
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absl::Hex(addr - entry_for_previous_symbol->first));
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}
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}
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return "";
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}
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absl::StatusOr<SymbolMap> LoadSymbolsMap(pid_t pid) {
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const std::string maps_filename = absl::StrCat("/proc/", pid, "/maps");
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std::string maps_content;
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SAPI_RETURN_IF_ERROR(sapi::file::GetContents(maps_filename, &maps_content,
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sapi::file::Defaults()));
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SAPI_ASSIGN_OR_RETURN(std::vector<MapsEntry> maps,
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ParseProcMaps(maps_content));
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// Get symbols for each file entry in the maps entry.
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// This is not a very efficient way, so we might want to optimize it.
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SymbolMap addr_to_symbol;
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for (const MapsEntry& entry : maps) {
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if (!entry.is_executable ||
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entry.inode == 0 || // Only parse file-backed entries
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entry.path.empty() ||
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absl::EndsWith(entry.path, " (deleted)") // Skip deleted files
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) {
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continue;
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}
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// Store details about start + end of this map.
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// The maps entries are ordered and thus sorted with increasing adresses.
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// This means if there is a symbol @ entry.end, it will be overwritten in
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// the next iteration.
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std::string map = absl::StrCat("map:", entry.path);
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if (entry.pgoff) {
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absl::StrAppend(&map, "+0x", absl::Hex(entry.pgoff));
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}
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addr_to_symbol[entry.start] = map;
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addr_to_symbol[entry.end] = "";
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absl::StatusOr<ElfFile> elf =
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ElfFile::ParseFromFile(entry.path, ElfFile::kLoadSymbols);
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if (!elf.ok()) {
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SAPI_RAW_LOG(WARNING, "Could not load symbols for %s: %s",
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entry.path.c_str(),
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std::string(elf.status().message()).c_str());
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continue;
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}
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for (const ElfFile::Symbol& symbol : elf->symbols()) {
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if (elf->position_independent()) {
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if (symbol.address < entry.end - entry.start) {
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addr_to_symbol[symbol.address + entry.start] = symbol.name;
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}
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} else {
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if (symbol.address >= entry.start && symbol.address < entry.end) {
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addr_to_symbol[symbol.address] = symbol.name;
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}
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}
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}
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}
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return addr_to_symbol;
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}
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bool RunLibUnwindAndSymbolizer(Comms* comms) {
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UnwindSetup setup;
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if (!comms->RecvProtoBuf(&setup)) {
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return false;
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}
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EnablePtraceEmulationWithUserRegs(setup.regs());
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absl::StatusOr<std::vector<uintptr_t>> ips =
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RunLibUnwind(setup.pid(), setup.default_max_frames());
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absl::StatusOr<std::vector<std::string>> stack_trace;
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if (ips.ok()) {
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stack_trace = SymbolizeStacktrace(setup.pid(), *ips);
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} else {
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stack_trace = ips.status();
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}
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if (!comms->SendStatus(stack_trace.status())) {
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return false;
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}
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if (!stack_trace.ok()) {
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return true;
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}
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UnwindResult msg;
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*msg.mutable_stacktrace() = {stack_trace->begin(), stack_trace->end()};
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*msg.mutable_ip() = {ips->begin(), ips->end()};
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return comms->SendProtoBuf(msg);
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}
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absl::StatusOr<std::vector<std::string>> RunLibUnwindAndSymbolizer(
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pid_t pid, int max_frames) {
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SAPI_ASSIGN_OR_RETURN(std::vector<uintptr_t> ips,
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RunLibUnwind(pid, max_frames));
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return SymbolizeStacktrace(pid, ips);
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}
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} // namespace sandbox2
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