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Expose unwind symbol helpers.

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PiperOrigin-RevId: 409391470
Change-Id: Iad14caabbada1278216e5e28ba55bae8dc8b9b2b
This commit is contained in:
Sandboxed API Team 2021-11-12 05:59:17 -08:00 committed by Copybara-Service
parent 26da6e6b0a
commit 2727714012
3 changed files with 86 additions and 77 deletions
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1
sandboxed_api/sandbox2/unwind/BUILD.bazel
View File

@ -51,6 +51,7 @@ cc_library(
"_Ux86_64_step",
]
]),
visibility = ["//visibility:public"],
deps = [
":ptrace_hook",
":unwind_cc_proto",

153
sandboxed_api/sandbox2/unwind/unwind.cc
View File

@ -54,83 +54,6 @@ std::string DemangleSymbol(const std::string& maybe_mangled) {
return maybe_mangled;
}
std::string GetSymbolAt(const std::map<uint64_t, std::string>& addr_to_symbol,
uint64_t addr) {
auto entry_for_next_symbol = addr_to_symbol.lower_bound(addr);
if (entry_for_next_symbol != addr_to_symbol.end() &&
entry_for_next_symbol != addr_to_symbol.begin()) {
// Matches the addr exactly:
if (entry_for_next_symbol->first == addr) {
return DemangleSymbol(entry_for_next_symbol->second);
}
// Might be inside a function, return symbol+offset;
const auto entry_for_previous_symbol = --entry_for_next_symbol;
if (!entry_for_previous_symbol->second.empty()) {
return absl::StrCat(DemangleSymbol(entry_for_previous_symbol->second),
"+0x",
absl::Hex(addr - entry_for_previous_symbol->first));
}
}
return "";
}
absl::StatusOr<std::map<uint64_t, std::string>> LoadSymbolsMap(pid_t pid) {
const std::string maps_filename = absl::StrCat("/proc/", pid, "/maps");
std::string maps_content;
SAPI_RETURN_IF_ERROR(sapi::file::GetContents(maps_filename, &maps_content,
sapi::file::Defaults()));
SAPI_ASSIGN_OR_RETURN(std::vector<MapsEntry> maps,
ParseProcMaps(maps_content));
// Get symbols for each file entry in the maps entry.
// This is not a very efficient way, so we might want to optimize it.
std::map<uint64_t, std::string> addr_to_symbol;
for (const MapsEntry& entry : maps) {
if (!entry.is_executable ||
entry.inode == 0 || // Only parse file-backed entries
entry.path.empty() ||
absl::EndsWith(entry.path, " (deleted)") // Skip deleted files
) {
continue;
}
// Store details about start + end of this map.
// The maps entries are ordered and thus sorted with increasing adresses.
// This means if there is a symbol @ entry.end, it will be overwritten in
// the next iteration.
std::string map = absl::StrCat("map:", entry.path);
if (entry.pgoff) {
absl::StrAppend(&map, "+0x", absl::Hex(entry.pgoff));
}
addr_to_symbol[entry.start] = map;
addr_to_symbol[entry.end] = "";
absl::StatusOr<ElfFile> elf =
ElfFile::ParseFromFile(entry.path, ElfFile::kLoadSymbols);
if (!elf.ok()) {
SAPI_RAW_LOG(WARNING, "Could not load symbols for %s: %s",
entry.path.c_str(),
std::string(elf.status().message()).c_str());
continue;
}
for (const ElfFile::Symbol& symbol : elf->symbols()) {
if (elf->position_independent()) {
if (symbol.address < entry.end - entry.start) {
addr_to_symbol[symbol.address + entry.start] = symbol.name;
}
} else {
if (symbol.address >= entry.start && symbol.address < entry.end) {
addr_to_symbol[symbol.address] = symbol.name;
}
}
}
}
return addr_to_symbol;
}
absl::StatusOr<std::vector<uintptr_t>> RunLibUnwind(pid_t pid, int max_frames) {
unw_cursor_t cursor;
static unw_addr_space_t as =
@ -190,6 +113,82 @@ absl::StatusOr<std::vector<std::string>> SymbolizeStacktrace(
} // namespace
std::string GetSymbolAt(const SymbolMap& addr_to_symbol, uint64_t addr) {
auto entry_for_next_symbol = addr_to_symbol.lower_bound(addr);
if (entry_for_next_symbol != addr_to_symbol.end() &&
entry_for_next_symbol != addr_to_symbol.begin()) {
// Matches the addr exactly:
if (entry_for_next_symbol->first == addr) {
return DemangleSymbol(entry_for_next_symbol->second);
}
// Might be inside a function, return symbol+offset;
const auto entry_for_previous_symbol = --entry_for_next_symbol;
if (!entry_for_previous_symbol->second.empty()) {
return absl::StrCat(DemangleSymbol(entry_for_previous_symbol->second),
"+0x",
absl::Hex(addr - entry_for_previous_symbol->first));
}
}
return "";
}
absl::StatusOr<SymbolMap> LoadSymbolsMap(pid_t pid) {
const std::string maps_filename = absl::StrCat("/proc/", pid, "/maps");
std::string maps_content;
SAPI_RETURN_IF_ERROR(sapi::file::GetContents(maps_filename, &maps_content,
sapi::file::Defaults()));
SAPI_ASSIGN_OR_RETURN(std::vector<MapsEntry> maps,
ParseProcMaps(maps_content));
// Get symbols for each file entry in the maps entry.
// This is not a very efficient way, so we might want to optimize it.
SymbolMap addr_to_symbol;
for (const MapsEntry& entry : maps) {
if (!entry.is_executable ||
entry.inode == 0 || // Only parse file-backed entries
entry.path.empty() ||
absl::EndsWith(entry.path, " (deleted)") // Skip deleted files
) {
continue;
}
// Store details about start + end of this map.
// The maps entries are ordered and thus sorted with increasing adresses.
// This means if there is a symbol @ entry.end, it will be overwritten in
// the next iteration.
std::string map = absl::StrCat("map:", entry.path);
if (entry.pgoff) {
absl::StrAppend(&map, "+0x", absl::Hex(entry.pgoff));
}
addr_to_symbol[entry.start] = map;
addr_to_symbol[entry.end] = "";
absl::StatusOr<ElfFile> elf =
ElfFile::ParseFromFile(entry.path, ElfFile::kLoadSymbols);
if (!elf.ok()) {
SAPI_RAW_LOG(WARNING, "Could not load symbols for %s: %s",
entry.path.c_str(),
std::string(elf.status().message()).c_str());
continue;
}
for (const ElfFile::Symbol& symbol : elf->symbols()) {
if (elf->position_independent()) {
if (symbol.address < entry.end - entry.start) {
addr_to_symbol[symbol.address + entry.start] = symbol.name;
}
} else {
if (symbol.address >= entry.start && symbol.address < entry.end) {
addr_to_symbol[symbol.address] = symbol.name;
}
}
}
}
return addr_to_symbol;
}
bool RunLibUnwindAndSymbolizer(Comms* comms) {
UnwindSetup setup;
if (!comms->RecvProtoBuf(&setup)) {

9
sandboxed_api/sandbox2/unwind/unwind.h
View File

@ -26,6 +26,15 @@
namespace sandbox2 {
// Used to map from an address to a human-readable symbol.
using SymbolMap = std::map<uint64_t, std::string>;
// Returns the symbol at `addr`, possibly with an offset into said symbol.
std::string GetSymbolAt(const SymbolMap& addr_to_symbol, uint64_t addr);
// Loads and returns a symbol map for a process with the provided `pid`.
absl::StatusOr<SymbolMap> LoadSymbolsMap(pid_t pid);
// Runs libunwind and the symbolizer and sends the results via comms.
bool RunLibUnwindAndSymbolizer(Comms* comms);