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#include <c10/macros/Macros.h>
#include <c10/util/Exception.h>
#include <torch/csrc/profiler/unwind/unwind.h>
#include <torch/csrc/utils/cpp_stacktraces.h>
#if !defined(__linux__) || !defined(__x86_64__) || !defined(__has_include) || \
!__has_include("ext/stdio_filebuf.h")
namespace torch::unwind {
std::vector<void*> unwind() {
TORCH_WARN_ONCE(
"record_context_cpp is not support on non-linux non-x86_64 platforms");
return {};
}
std::optional<std::pair<std::string, uint64_t>> libraryFor(void* addr) {
TORCH_WARN_ONCE(
"record_context_cpp is not support on non-linux non-x86_64 platforms");
return {};
}
#ifndef FBCODE_CAFFE2
std::vector<Frame> symbolize(const std::vector<void*>& frames, Mode mode) {
TORCH_WARN_ONCE(
"record_context_cpp is not support on non-linux non-x86_64 platforms");
return {};
}
#endif
Stats stats() {
TORCH_WARN_ONCE(
"record_context_cpp is not support on non-linux non-x86_64 platforms");
return {};
}
} // namespace torch::unwind
#else
#include <c10/util/flat_hash_map.h>
#include <dlfcn.h>
#include <elf.h>
#include <link.h>
#include <linux/limits.h>
#include <algorithm>
#include <climits>
#include <vector>
#include <c10/util/irange.h>
#include <cxxabi.h>
#include <torch/csrc/profiler/unwind/communicate.h>
#include <torch/csrc/profiler/unwind/dwarf_enums.h>
#include <torch/csrc/profiler/unwind/eh_frame_hdr.h>
#include <torch/csrc/profiler/unwind/fast_symbolizer.h>
#include <torch/csrc/profiler/unwind/fde.h>
#include <torch/csrc/profiler/unwind/unwinder.h>
#include <shared_mutex>
extern "C" void unwind_c(std::vector<void*>* result, int64_t rsp, int64_t rbp);
extern "C" void unwind_entry(std::vector<void*>* result);
namespace torch::unwind {
struct UpgradeExclusive {
UpgradeExclusive(std::shared_lock<std::shared_timed_mutex>& rdlock)
: rdlock_(rdlock) {
rdlock_.unlock();
rdlock_.mutex()->lock();
}
UpgradeExclusive(const UpgradeExclusive&) = delete;
UpgradeExclusive(UpgradeExclusive&&) = delete;
UpgradeExclusive& operator=(const UpgradeExclusive&) = delete;
UpgradeExclusive& operator=(UpgradeExclusive&&) = delete;
~UpgradeExclusive() {
rdlock_.mutex()->unlock();
rdlock_.lock();
}
private:
// NOLINTNEXTLINE(cppcoreguidelines-avoid-const-or-ref-data-members)
std::shared_lock<std::shared_timed_mutex>& rdlock_;
};
struct LibraryInfo {
LibraryInfo(
std::string name,
uint64_t load_bias,
uint64_t last_addr,
void* eh_frame_hdr_ptr_)
: name_(std::move(name)),
load_bias_(load_bias),
last_addr_(last_addr),
eh_frame_hdr_(eh_frame_hdr_ptr_) {}
uint64_t load_bias() const {
return load_bias_;
}
uint64_t last_addr() const {
return last_addr_;
}
Unwinder unwinderFor(uint64_t addr) const {
void* fde_data = eh_frame_hdr_.entryForAddr(addr);
FDE fde(fde_data, name().c_str(), load_bias());
TableState state = fde.readUpTo(addr);
return Unwinder(state.cfa, state.registers[D_RIP], state.registers[D_RBP]);
}
const std::string& name() const {
return name_;
}
private:
std::string name_;
uint64_t load_bias_; // addr >= load_bias_
uint64_t last_addr_; // addr < last_addr_
EHFrameHdr eh_frame_hdr_;
};
static const char* process_name() {
// NOLINTNEXTLINE(*-c-arrays*)
static char name[PATH_MAX + 1] = "";
if (*name == '\0') {
ssize_t len = readlink("/proc/self/exe", name, PATH_MAX);
TORCH_INTERNAL_ASSERT(len != -1, "can't get path to exe")
name[len] = '\0';
}
return name;
}
struct Version {
uint64_t adds_ = LLONG_MAX;
uint64_t subs_ = LLONG_MAX;
};
struct UnwindCache {
Version currentVersion() {
Version r;
dl_iterate_phdr(
[](struct dl_phdr_info* info,
size_t size [[maybe_unused]],
void* data) {
Version* v = (Version*)data;
v->adds_ = info->dlpi_adds;
v->subs_ = info->dlpi_subs;
return 1;
},
&r);
return r;
}
void refreshLibraries() {
++stats_.resets;
all_libraries_.clear();
ip_cache_.clear();
dl_iterate_phdr(
[](struct dl_phdr_info* info,
size_t size [[maybe_unused]],
void* data) {
auto self = (UnwindCache*)data;
uint64_t last_addr = 0;
auto segments = (Elf64_Phdr*)info->dlpi_phdr;
for (auto i : c10::irange(info->dlpi_phnum)) {
if (segments[i].p_type == PT_LOAD) {
auto begin = ((uint64_t)info->dlpi_addr + segments[i].p_vaddr);
auto end = (begin + segments[i].p_memsz);
last_addr = std::max(end, last_addr);
}
if (segments[i].p_type == PT_GNU_EH_FRAME) {
std::string library_name = info->dlpi_name;
if (library_name.empty()) {
library_name = process_name();
}
auto eh_frame_hdr =
// NOLINTNEXTLINE(performance-no-int-to-ptr)
(void*)(segments[i].p_vaddr + info->dlpi_addr);
self->all_libraries_.emplace_back(
std::move(library_name),
info->dlpi_addr,
last_addr,
eh_frame_hdr);
return 0;
}
}
self->libraries_with_no_unwind_.emplace_back(info->dlpi_name);
return 0;
},
this);
std::sort(
all_libraries_.begin(),
all_libraries_.end(),
[](const LibraryInfo& lhs, const LibraryInfo& rhs) {
return lhs.load_bias() < rhs.load_bias();
});
}
void checkRefresh(std::shared_lock<std::shared_timed_mutex>& rdlock) {
Version current_version = currentVersion();
if (current_version.subs_ != last_version_.subs_) {
UpgradeExclusive lock(rdlock);
refreshLibraries();
}
}
const Unwinder& unwinderFor(
uint64_t addr,
std::shared_lock<std::shared_timed_mutex>& rdlock) {
auto it = ip_cache_.find(addr);
if (it != ip_cache_.end()) {
++stats_.hits;
return it->second;
}
// we are about to modify the cache
UpgradeExclusive lock(rdlock);
++stats_.misses;
Unwinder unwinder = Unwinder::unknown();
try {
unwinder = libraryFor(addr).unwinderFor(addr);
} catch (unwind::UnwindError& err) {
// because unwinders are cached this will only print
// once per frame that cannot be unwound.
TORCH_WARN("Unsupported unwinding pattern: ", err.what());
}
auto r = ip_cache_.insert_or_assign(addr, unwinder);
return r.first->second;
}
const LibraryInfo* findLibraryFor(uint64_t addr) {
Version current_version = currentVersion();
if (current_version.subs_ != last_version_.subs_) {
refreshLibraries();
last_version_ = current_version;
}
auto* r = searchFor(addr);
if (!r) {
if (current_version.adds_ != last_version_.adds_) {
refreshLibraries();
last_version_ = current_version;
}
r = searchFor(addr);
}
return r;
}
const LibraryInfo& libraryFor(uint64_t addr) {
auto* r = findLibraryFor(addr);
if (!r) {
for ([[maybe_unused]] const auto& l : libraries_with_no_unwind_) {
TORCH_WARN("Did not find a PT_GNU_EH_FRAME segment for ", l);
}
libraries_with_no_unwind_.clear();
throw UnwindError("addr not in range of known libraries");
}
return *r;
}
torch::unwind::Stats stats() {
return stats_;
}
private:
const LibraryInfo* searchFor(uint64_t addr) {
if (all_libraries_.empty()) {
return nullptr;
}
uint64_t low = 0;
uint64_t high = all_libraries_.size();
while (low + 1 < high) {
auto mid = (low + high) / 2;
if (addr < all_libraries_.at(mid).load_bias()) {
high = mid;
} else {
low = mid;
}
}
LibraryInfo* r = &all_libraries_.at(low);
if (addr < r->load_bias() || addr >= r->last_addr()) {
return nullptr;
}
return r;
}
// sorted by load_bias
std::vector<LibraryInfo> all_libraries_;
ska::flat_hash_map<uint64_t, Unwinder> ip_cache_;
torch::unwind::Stats stats_;
// to keep track of whether we need to refresh this info
Version last_version_;
std::vector<std::string> libraries_with_no_unwind_;
};
static UnwindCache unwind_cache;
static std::shared_timed_mutex cache_mutex_;
std::vector<void*> unwind() {
std::vector<void*> frames;
unwind_entry(&frames);
return frames;
}
std::optional<std::pair<std::string, uint64_t>> libraryFor(void* addr) {
if (!addr) {
return std::nullopt;
}
std::shared_lock lock(cache_mutex_);
const LibraryInfo* library_info = unwind_cache.findLibraryFor((uint64_t)addr);
if (!library_info) {
return std::nullopt;
}
return std::make_pair(
library_info->name(), (uint64_t)addr - library_info->load_bias());
}
static std::string dladdr_lookup(void* addr) {
Dl_info dlinfo;
std::string funcname = "??";
if (dladdr(addr, &dlinfo) && dlinfo.dli_sname) {
funcname = demangle(dlinfo.dli_sname);
}
return funcname;
}
struct Symbolizer {
Symbolizer() {
auto envar = std::getenv("TORCH_ADDR2LINE_BINARY");
if (envar != nullptr) {
// currently we take user's input as is without checking
addr2line_binary_ = envar;
TORCH_WARN("Use custom addr2line binary: ", addr2line_binary_);
} else {
addr2line_binary_ = "addr2line"; // default
}
}
static std::lock_guard<std::mutex> guard() {
static std::mutex mutex;
return std::lock_guard<std::mutex>(mutex);
}
static Symbolizer& get() {
static Symbolizer singleton;
return singleton;
}
void request(void* addr) {
if (frame_map_.count(addr)) {
return;
}
auto maybe_library = libraryFor(addr);
if (!maybe_library) {
frame_map_[addr] = Frame{"??", "<unwind unsupported>", 0};
return;
}
has_pending_results_ = true;
auto& entry = getOrCreate(maybe_library->first);
entry.queried.push_back(addr);
auto libaddress = maybe_library->second - 1;
// NOLINTNEXTLINE(performance-no-int-to-ptr)
entry.comm->out() << (void*)libaddress << "\n";
// we need to make sure we don't write more than 64k bytes to
// a pipe before reading the results. Otherwise the buffer may
// get filled and block before we read the results.
// Each line is < 32 characters,
// so this limits us to < 32k bytes before we read rules.
if (entry.queried.size() - entry.completed > BLOCK) {
entry.comm->out().flush();
readPendingResults(entry);
}
}
const Frame& lookup(void* addr) {
if (has_pending_results_) {
for (auto& kv : entries_) {
kv.second.comm->out().flush();
}
for (auto& kv : entries_) {
readPendingResults(kv.second);
}
has_pending_results_ = false;
}
return frame_map_.at(addr);
}
private:
static constexpr int BLOCK = 1024;
const char* addr2line_binary_;
struct Entry {
std::unique_ptr<Communicate> comm;
std::vector<void*> queried;
size_t completed = 0;
};
ska::flat_hash_map<std::string, Entry> entries_;
ska::flat_hash_map<void*, Frame> frame_map_;
bool has_pending_results_ = true;
Entry& getOrCreate(const std::string& name) {
auto it = entries_.find(name);
if (it == entries_.end()) {
// NOLINTNEXTLINE(*-c-arrays*)
const char* args[] = {
addr2line_binary_, "-C", "-f", "-e", name.c_str(), nullptr};
it = entries_
.insert_or_assign(
name,
Entry{
std::make_unique<Communicate>(addr2line_binary_, args),
{}})
.first;
}
return it->second;
}
void readPendingResults(Entry& e) {
size_t N = e.queried.size();
for (; e.completed < N; ++e.completed) {
Frame frame;
std::getline(e.comm->in(), frame.funcname);
std::string filename_lineno;
std::getline(e.comm->in(), filename_lineno);
auto colon = filename_lineno.find_last_of(':');
frame.filename = filename_lineno.substr(0, colon);
std::string lineno_str = filename_lineno.substr(colon + 1);
frame.lineno = lineno_str == "?" ? 0 : std::stoi(lineno_str);
frame_map_[e.queried[e.completed]] = std::move(frame);
}
}
};
static std::vector<Frame> symbolize_fast(
const std::vector<void*>& frames,
Mode mode) {
static std::mutex cache_mutex;
static std::array<ska::flat_hash_map<void*, Frame>, 2> frame_maps;
auto& frame_map = frame_maps[mode == Mode::fast ? 0 : 1];
std::vector<uint32_t> indices_to_lookup;
std::vector<Frame> results;
results.reserve(frames.size());
{
std::lock_guard<std::mutex> lock(cache_mutex);
for (auto i : c10::irange(frames.size())) {
void* f = frames.at(i);
auto it = frame_map.find(f);
if (it == frame_map.end()) {
indices_to_lookup.push_back(i);
results.emplace_back(Frame{"??", "??", 0});
} else {
results.emplace_back(it->second);
}
}
}
if (!indices_to_lookup.empty()) {
// do symbolizer work
FastSymbolizer symbolizer;
for (auto i : indices_to_lookup) {
void* addr = frames.at(i);
Frame& f = results.at(i);
auto library = libraryFor(frames.at(i));
if (library) {
if (mode == Mode::fast) {
f = symbolizer.symbolize(library->first, library->second - 1);
} else {
f = Frame{library->first, "??", library->second - 1};
}
}
if (f.funcname == "??") {
f.funcname = dladdr_lookup(addr);
}
}
std::lock_guard<std::mutex> lock(cache_mutex);
for (auto i : indices_to_lookup) {
frame_map.emplace(frames.at(i), results.at(i));
}
}
return results;
}
static std::vector<Frame> symbolize_addr2line(
const std::vector<void*>& frames) {
auto guard = Symbolizer::guard();
Symbolizer& s = Symbolizer::get();
for (auto f : frames) {
s.request(f);
}
std::vector<Frame> results;
results.reserve(frames.size());
for (auto f : frames) {
results.emplace_back(s.lookup(f));
}
return results;
}
// fbcode will use llvm symbolize since there is an llvm dependency already
#ifndef FBCODE_CAFFE2
std::vector<Frame> symbolize(const std::vector<void*>& frames, Mode mode) {
if (mode == Mode::addr2line) {
return symbolize_addr2line(frames);
} else {
return symbolize_fast(frames, mode);
}
}
#endif
Stats stats() {
return unwind_cache.stats();
}
} // namespace torch::unwind
extern "C" C10_USED void unwind_c(
std::vector<void*>* result,
int64_t rsp,
int64_t rbp) {
std::shared_lock lock(torch::unwind::cache_mutex_);
torch::unwind::UnwindState state{};
// NOLINTNEXTLINE(performance-no-int-to-ptr)
state.rip = *(int64_t*)(rsp);
// +8 because we saved rsp after the return address was already pushed
// to the stack
state.rsp = rsp + 8;
state.rbp = rbp;
torch::unwind::unwind_cache.checkRefresh(lock);
while (true) { // unwind for _start sets rip as being undefined
// NOLINTNEXTLINE(performance-no-int-to-ptr)
result->push_back((void*)state.rip);
const torch::unwind::Unwinder& uw =
torch::unwind::unwind_cache.unwinderFor(state.rip, lock);
if (uw.terminator()) {
if (uw.isUnknown()) {
result->push_back(nullptr);
}
break;
}
state = uw.run(state);
}
}
// calling convention puts the first three pointer/int64_t arguments in
// rdi rsi rdx (all caller-saved)
// rdi already holds the pointer to the result vector
// we add arguments for current rsp and rbp and then tail call
// into unwind_c
__asm__(
".global unwind_entry\n"
"unwind_entry:\n"
"mov %rsp, %rsi;\n"
"mov %rbp, %rdx;\n"
"jmp unwind_c;\n");
#endif
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