PageFaultHandler: Simplifications
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0240ea8b49
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@ -54,10 +54,7 @@ if(LINUX)
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endif()
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if(NOT WIN32 AND NOT APPLE)
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find_package(Libbacktrace)
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if(NOT LIBBACKTRACE_FOUND)
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message(WARNING "libbacktrace not found, crashes will not produce backtraces.")
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endif()
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find_package(Libbacktrace REQUIRED)
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endif()
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if(APPLE)
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@ -169,7 +169,7 @@ void CrashHandler::WriteDumpForCaller()
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WriteMinidumpAndCallstack(nullptr);
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}
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#elif defined(ENABLE_LIBBACKTRACE)
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#elif !defined(__APPLE__)
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#include <backtrace.h>
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#include <cstdarg>
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@ -194,15 +194,12 @@ static void AllocateBuffer(BacktraceBuffer* buf);
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static void FreeBuffer(BacktraceBuffer* buf);
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static void AppendToBuffer(BacktraceBuffer* buf, const char* format, ...);
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static int BacktraceFullCallback(void* data, uintptr_t pc, const char* filename, int lineno, const char* function);
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static void CallExistingSignalHandler(int signal, siginfo_t* siginfo, void* ctx);
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static void CrashSignalHandler(int signal, siginfo_t* siginfo, void* ctx);
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static void LogCallstack(int signal, const void* exception_pc);
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static std::recursive_mutex s_crash_mutex;
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static bool s_in_signal_handler = false;
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static backtrace_state* s_backtrace_state = nullptr;
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static struct sigaction s_old_sigbus_action;
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static struct sigaction s_old_sigsegv_action;
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} // namespace CrashHandler
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const char* CrashHandler::GetSignalName(int signal_no)
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@ -268,23 +265,25 @@ int CrashHandler::BacktraceFullCallback(void* data, uintptr_t pc, const char* fi
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return 0;
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}
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void CrashHandler::CallExistingSignalHandler(int signal, siginfo_t* siginfo, void* ctx)
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void CrashHandler::LogCallstack(int signal, const void* exception_pc)
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{
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const struct sigaction& sa = (signal == SIGBUS) ? s_old_sigbus_action : s_old_sigsegv_action;
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if (sa.sa_flags & SA_SIGINFO)
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{
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sa.sa_sigaction(signal, siginfo, ctx);
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}
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else if (sa.sa_handler == SIG_DFL)
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{
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// Re-raising the signal would just queue it, and since we'd restore the handler back to us,
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// we'd end up right back here again. So just abort, because that's probably what it'd do anyway.
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abort();
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}
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else if (sa.sa_handler != SIG_IGN)
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{
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sa.sa_handler(signal);
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}
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BacktraceBuffer buf;
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AllocateBuffer(&buf);
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if (signal != 0 || exception_pc)
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AppendToBuffer(&buf, "*************** Unhandled %s at %p ***************\n", GetSignalName(signal), exception_pc);
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else
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AppendToBuffer(&buf, "*******************************************************************\n");
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const int rc = backtrace_full(s_backtrace_state, 0, BacktraceFullCallback, nullptr, &buf);
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if (rc != 0)
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AppendToBuffer(&buf, " backtrace_full() failed: %d\n");
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AppendToBuffer(&buf, "*******************************************************************\n");
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if (buf.used > 0)
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write(STDERR_FILENO, buf.buffer, buf.used);
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FreeBuffer(&buf);
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}
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void CrashHandler::CrashSignalHandler(int signal, siginfo_t* siginfo, void* ctx)
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@ -306,27 +305,17 @@ void CrashHandler::CrashSignalHandler(int signal, siginfo_t* siginfo, void* ctx)
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void* const exception_pc = nullptr;
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#endif
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BacktraceBuffer buf;
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AllocateBuffer(&buf);
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AppendToBuffer(&buf, "*************** Unhandled %s at %p ***************\n", GetSignalName(signal), exception_pc);
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const int rc = backtrace_full(s_backtrace_state, 0, BacktraceFullCallback, nullptr, &buf);
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if (rc != 0)
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AppendToBuffer(&buf, " backtrace_full() failed: %d\n");
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AppendToBuffer(&buf, "*******************************************************************\n");
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if (buf.used > 0)
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write(STDERR_FILENO, buf.buffer, buf.used);
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FreeBuffer(&buf);
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LogCallstack(signal, exception_pc);
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s_in_signal_handler = false;
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}
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// Chances are we're not going to have anything else to call, but just in case.
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lock.unlock();
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CallExistingSignalHandler(signal, siginfo, ctx);
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// We can't continue from here. Just bail out and dump core.
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std::fputs("Aborting application.\n", stderr);
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std::fflush(stderr);
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std::abort();
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}
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bool CrashHandler::Install()
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@ -341,9 +330,9 @@ bool CrashHandler::Install()
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sigemptyset(&sa.sa_mask);
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sa.sa_flags = SA_SIGINFO | SA_NODEFER;
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sa.sa_sigaction = CrashSignalHandler;
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if (sigaction(SIGBUS, &sa, &s_old_sigbus_action) != 0)
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if (sigaction(SIGBUS, &sa, nullptr) != 0)
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return false;
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if (sigaction(SIGSEGV, &sa, &s_old_sigsegv_action) != 0)
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if (sigaction(SIGSEGV, &sa, nullptr) != 0)
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return false;
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return true;
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@ -355,6 +344,7 @@ void CrashHandler::SetWriteDirectory(std::string_view dump_directory)
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void CrashHandler::WriteDumpForCaller()
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{
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LogCallstack(0, nullptr);
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}
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#else
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@ -372,4 +362,12 @@ void CrashHandler::WriteDumpForCaller()
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{
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}
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void CrashHandler::CrashSignalHandler(int signal, siginfo_t* siginfo, void* ctx)
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{
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// We can't continue from here. Just bail out and dump core.
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std::fputs("Aborting application.\n", stderr);
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std::fflush(stderr);
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std::abort();
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}
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#endif
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@ -1,11 +1,21 @@
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// SPDX-FileCopyrightText: 2019-2023 Connor McLaughlin <stenzek@gmail.com>
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// SPDX-FileCopyrightText: 2019-2024 Connor McLaughlin <stenzek@gmail.com>
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// SPDX-License-Identifier: (GPL-3.0 OR CC-BY-NC-ND-4.0)
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#include "types.h"
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#include <string_view>
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#ifndef _WIN32
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#include <signal.h>
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#endif
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namespace CrashHandler {
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bool Install();
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void SetWriteDirectory(std::string_view dump_directory);
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void WriteDumpForCaller();
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#ifndef _WIN32
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// Allow crash handler to be invoked from a signal.
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void CrashSignalHandler(int signal, siginfo_t* siginfo, void* ctx);
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#endif
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} // namespace CrashHandler
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@ -4,6 +4,7 @@
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#include "page_fault_handler.h"
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#include "common/assert.h"
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#include "common/crash_handler.h"
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#include "common/error.h"
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#include "common/log.h"
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@ -14,7 +15,7 @@
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#if defined(_WIN32)
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#include "common/windows_headers.h"
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#elif defined(__linux__) || defined(__ANDROID__)
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#elif defined(__linux__)
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#include <signal.h>
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#include <ucontext.h>
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#include <unistd.h>
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@ -139,54 +140,11 @@ bool PageFaultHandler::Install(Error* error)
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namespace PageFaultHandler {
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static void SignalHandler(int sig, siginfo_t* info, void* ctx);
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static void CallExistingSignalHandler(int signal, siginfo_t* siginfo, void* ctx);
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static struct sigaction s_old_sigsegv_action;
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#if defined(__APPLE__) || defined(__aarch64__)
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static struct sigaction s_old_sigbus_action;
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#endif
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} // namespace PageFaultHandler
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void PageFaultHandler::CallExistingSignalHandler(int signal, siginfo_t* siginfo, void* ctx)
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{
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#if defined(__aarch64__)
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const struct sigaction& sa = (signal == SIGBUS) ? s_old_sigbus_action : s_old_sigsegv_action;
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#elif defined(__APPLE__)
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const struct sigaction& sa = s_old_sigbus_action;
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#else
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const struct sigaction& sa = s_old_sigsegv_action;
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#endif
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if (sa.sa_flags & SA_SIGINFO)
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{
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sa.sa_sigaction(signal, siginfo, ctx);
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}
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else if (sa.sa_handler == SIG_DFL)
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{
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// Re-raising the signal would just queue it, and since we'd restore the handler back to us,
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// we'd end up right back here again. So just abort, because that's probably what it'd do anyway.
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abort();
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}
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else if (sa.sa_handler != SIG_IGN)
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{
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sa.sa_handler(signal);
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}
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}
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void PageFaultHandler::SignalHandler(int sig, siginfo_t* info, void* ctx)
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{
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// Executing the handler concurrently from multiple threads wouldn't go down well.
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std::unique_lock lock(s_exception_handler_mutex);
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// Prevent recursive exception filtering.
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if (s_in_exception_handler)
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{
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lock.unlock();
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CallExistingSignalHandler(sig, info, ctx);
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return;
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}
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#if defined(__linux__) || defined(__ANDROID__)
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#if defined(__linux__)
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void* const exception_address = reinterpret_cast<void*>(info->si_addr);
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#if defined(CPU_ARCH_X64)
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@ -241,19 +199,26 @@ void PageFaultHandler::SignalHandler(int sig, siginfo_t* info, void* ctx)
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#endif
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s_in_exception_handler = true;
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// Executing the handler concurrently from multiple threads wouldn't go down well.
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s_exception_handler_mutex.lock();
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const HandlerResult result = HandlePageFault(exception_pc, exception_address, is_write);
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// Prevent recursive exception filtering.
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HandlerResult result = HandlerResult::ExecuteNextHandler;
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if (!s_in_exception_handler)
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{
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s_in_exception_handler = true;
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result = HandlePageFault(exception_pc, exception_address, is_write);
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s_in_exception_handler = false;
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}
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s_in_exception_handler = false;
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s_exception_handler_mutex.unlock();
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// Resumes execution right where we left off (re-executes instruction that caused the SIGSEGV).
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if (result == HandlerResult::ContinueExecution)
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return;
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// Call old signal handler, which will likely dump core.
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lock.unlock();
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CallExistingSignalHandler(sig, info, ctx);
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// We couldn't handle it. Pass it off to the crash dumper.
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CrashHandler::CrashSignalHandler(sig, info, ctx);
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}
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bool PageFaultHandler::Install(Error* error)
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@ -270,14 +235,14 @@ bool PageFaultHandler::Install(Error* error)
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// Don't block the signal from executing recursively, we want to fire the original handler.
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sa.sa_flags |= SA_NODEFER;
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#endif
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if (sigaction(SIGSEGV, &sa, &s_old_sigsegv_action) != 0)
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if (sigaction(SIGSEGV, &sa, nullptr) != 0)
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{
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Error::SetErrno(error, "sigaction() for SIGSEGV failed: ", errno);
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return false;
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}
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#if defined(__APPLE__) || defined(__aarch64__)
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// MacOS uses SIGBUS for memory permission violations
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if (sigaction(SIGBUS, &sa, &s_old_sigbus_action) != 0)
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if (sigaction(SIGBUS, &sa, nullptr) != 0)
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{
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Error::SetErrno(error, "sigaction() for SIGBUS failed: ", errno);
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return false;
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