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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:nil -*-
// vim: ts=8 sw=2 smarttab
#include "fatal_signal.h"
#include <csignal>
#include <iostream>
#include <string_view>
#define BOOST_STACKTRACE_USE_ADDR2LINE
#include <boost/stacktrace.hpp>
#include <seastar/core/reactor.hh>
#include "common/safe_io.h"
#include "include/scope_guard.h"
FatalSignal::FatalSignal()
{
install_oneshot_signals_handler<SIGSEGV,
SIGABRT,
SIGBUS,
SIGILL,
SIGFPE,
SIGXCPU,
SIGXFSZ,
SIGSYS>();
}
template <int... SigNums>
void FatalSignal::install_oneshot_signals_handler()
{
(install_oneshot_signal_handler<SigNums>() , ...);
}
static void reraise_fatal(const int signum)
{
// use default handler to dump core
::signal(signum, SIG_DFL);
// normally, we won't get here. if we do, something is very weird.
if (::raise(signum)) {
std::cerr << "reraise_fatal: failed to re-raise signal " << signum
<< std::endl;
} else {
std::cerr << "reraise_fatal: default handler for signal " << signum
<< " didn't terminate the process?" << std::endl;
}
std::cerr << std::flush;
::_exit(1);
}
[[gnu::noinline]] void FatalSignal::signal_entry(
const int signum,
siginfo_t* const info,
void*)
{
if (static std::atomic_bool handled{false}; handled.exchange(true)) {
return;
}
assert(info);
FatalSignal::signaled(signum, *info);
reraise_fatal(signum);
}
template <int SigNum>
void FatalSignal::install_oneshot_signal_handler()
{
struct sigaction sa;
// it's a bad idea to use a lambda here. On GCC there are `operator()`
// and `_FUN()`. Controlling their inlineability is hard (impossible?).
sa.sa_sigaction = signal_entry;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_SIGINFO | SA_RESTART | SA_NODEFER;
if constexpr (SigNum == SIGSEGV) {
sa.sa_flags |= SA_ONSTACK;
}
[[maybe_unused]] auto r = ::sigaction(SigNum, &sa, nullptr);
assert(r == 0);
}
[[gnu::noinline]] static void print_backtrace(std::string_view cause) {
std::cerr << cause;
if (seastar::engine_is_ready()) {
std::cerr << " on shard " << seastar::this_shard_id();
}
// nobody wants to see things like `FatalSignal::signaled()` or
// `print_backtrace()` in our backtraces. `+ 1` is for the extra
// frame created by kernel (signal trampoline, it will take care
// about e.g. sigreturn(2) calling; see the man page).
constexpr std::size_t FRAMES_TO_SKIP = 3 + 1;
std::cerr << ".\nBacktrace:\n";
std::cerr << boost::stacktrace::stacktrace(
FRAMES_TO_SKIP,
static_cast<std::size_t>(-1)/* max depth same as the default one */);
std::cerr << std::flush;
// TODO: dump crash related meta data to $crash_dir
// see handle_fatal_signal()
}
static void print_segv_info(const siginfo_t& siginfo)
{
std::cerr \
<< "Dump of siginfo:" << std::endl
<< " si_signo: " << siginfo.si_signo << std::endl
<< " si_errno: " << siginfo.si_errno << std::endl
<< " si_code: " << siginfo.si_code << std::endl
<< " si_pid: " << siginfo.si_pid << std::endl
<< " si_uid: " << siginfo.si_uid << std::endl
<< " si_status: " << siginfo.si_status << std::endl
<< " si_utime: " << siginfo.si_utime << std::endl
<< " si_stime: " << siginfo.si_stime << std::endl
<< " si_int: " << siginfo.si_int << std::endl
<< " si_ptr: " << siginfo.si_ptr << std::endl
<< " si_overrun: " << siginfo.si_overrun << std::endl
<< " si_timerid: " << siginfo.si_timerid << std::endl
<< " si_addr: " << siginfo.si_addr << std::endl
<< " si_band: " << siginfo.si_band << std::endl
<< " si_fd: " << siginfo.si_fd << std::endl
<< " si_addr_lsb: " << siginfo.si_addr_lsb << std::endl
<< " si_lower: " << siginfo.si_lower << std::endl
<< " si_upper: " << siginfo.si_upper << std::endl
<< " si_pkey: " << siginfo.si_pkey << std::endl
<< " si_call_addr: " << siginfo.si_call_addr << std::endl
<< " si_syscall: " << siginfo.si_syscall << std::endl
<< " si_arch: " << siginfo.si_arch << std::endl;
std::cerr << std::flush;
}
static void print_proc_maps()
{
const int fd = ::open("/proc/self/maps", O_RDONLY);
if (fd < 0) {
std::cerr << "can't open /proc/self/maps. procfs not mounted?" << std::endl;
return;
}
const auto fd_guard = make_scope_guard([fd] {
::close(fd);
});
std::cerr << "Content of /proc/self/maps:" << std::endl;
while (true) {
char chunk[4096] = {0, };
const ssize_t r = safe_read(fd, chunk, sizeof(chunk) - 1);
if (r < 0) {
std::cerr << "error while reading /proc/self/maps: " << r << std::endl;
return;
} else {
std::cerr << chunk << std::flush;
if (r < static_cast<ssize_t>(sizeof(chunk) - 1)) {
return; // eof
}
}
}
}
[[gnu::noinline]] void FatalSignal::signaled(const int signum,
const siginfo_t& siginfo)
{
switch (signum) {
case SIGSEGV:
print_backtrace("Segmentation fault");
print_segv_info(siginfo);
break;
case SIGABRT:
print_backtrace("Aborting");
break;
default:
print_backtrace(fmt::format("Signal {}", signum));
break;
}
print_proc_maps();
}
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