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crashcatcher.cpp
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crashcatcher.cpp
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#include <algorithm>
#include <cstring>
#include <filesystem>
#include <fstream>
#include <optional>
#include <span>
#include <errno.h>
#include <limits.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
#include <sys/ptrace.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/utsname.h>
#include <sys/wait.h>
#include <unistd.h>
#include <components/debug/debuglog.hpp>
#include <components/files/conversion.hpp>
#include <SDL_messagebox.h>
#ifdef __linux__
#include <sys/prctl.h>
#include <sys/ucontext.h>
#ifndef PR_SET_PTRACER
#define PR_SET_PTRACER 0x59616d61
#endif
#elif defined(__APPLE__) || defined(__FreeBSD__) || defined(__OpenBSD__)
#include <signal.h>
#endif
#if defined(__APPLE__)
#include <cassert>
#include <libproc.h>
#include <sys/sysctl.h>
#endif
#if defined(__FreeBSD__)
#include <sys/sysctl.h>
#include <sys/user.h>
#endif
#include "crashcatcher.hpp"
static const char fatal_err[] = "\n\n*** Fatal Error ***\n";
static const char pipe_err[] = "!!! Failed to create pipe\n";
static const char fork_err[] = "!!! Failed to fork debug process\n";
static const char exec_err[] = "!!! Failed to exec debug process\n";
#ifndef PATH_MAX /* Not all platforms (GNU Hurd) have this. */
#define PATH_MAX 256
#endif
static char argv0[PATH_MAX];
static struct
{
int signum;
pid_t pid;
std::optional<siginfo_t> siginfo;
} crash_info;
namespace
{
constexpr char crash_switch[] = "--cc-handle-crash";
struct SignalInfo
{
int mCode;
const char* mDescription;
const char* mName = "";
};
constexpr SignalInfo signals[] = {
{ SIGSEGV, "Segmentation fault", "SIGSEGV" },
{ SIGILL, "Illegal instruction", "SIGILL" },
{ SIGFPE, "FPU exception", "SIGFPE" },
{ SIGBUS, "System BUS error", "SIGBUS" },
{ SIGABRT, "Abnormal termination condition", "SIGABRT" },
};
constexpr SignalInfo sigIllCodes[] = {
#if !defined(__FreeBSD__) && !defined(__FreeBSD_kernel__)
{ ILL_ILLOPC, "Illegal opcode" },
{ ILL_ILLOPN, "Illegal operand" },
{ ILL_ILLADR, "Illegal addressing mode" },
{ ILL_ILLTRP, "Illegal trap" },
{ ILL_PRVOPC, "Privileged opcode" },
{ ILL_PRVREG, "Privileged register" },
{ ILL_COPROC, "Coprocessor error" },
{ ILL_BADSTK, "Internal stack error" },
#endif
};
constexpr SignalInfo sigFpeCodes[] = {
{ FPE_INTDIV, "Integer divide by zero" },
{ FPE_INTOVF, "Integer overflow" },
{ FPE_FLTDIV, "Floating point divide by zero" },
{ FPE_FLTOVF, "Floating point overflow" },
{ FPE_FLTUND, "Floating point underflow" },
{ FPE_FLTRES, "Floating point inexact result" },
{ FPE_FLTINV, "Floating point invalid operation" },
{ FPE_FLTSUB, "Subscript out of range" },
};
constexpr SignalInfo sigSegvCodes[] = {
#ifndef __FreeBSD__
{ SEGV_MAPERR, "Address not mapped to object" },
{ SEGV_ACCERR, "Invalid permissions for mapped object" },
#endif
};
constexpr SignalInfo sigBusCodes[] = {
#ifndef __FreeBSD__
{ BUS_ADRALN, "Invalid address alignment" },
{ BUS_ADRERR, "Non-existent physical address" },
{ BUS_OBJERR, "Object specific hardware error" },
#endif
};
const char* findSignalDescription(std::span<const SignalInfo> info, int code)
{
const auto it = std::find_if(info.begin(), info.end(), [&](const SignalInfo& v) { return v.mCode == code; });
return it == info.end() ? "" : it->mDescription;
}
struct Close
{
void operator()(const int* value) { close(*value); }
};
struct CloseFile
{
void operator()(FILE* value) { fclose(value); }
};
struct Remove
{
void operator()(const char* value) { remove(value); }
};
template <class T>
bool printDebuggerInfo(pid_t pid)
{
// Create a temp file to put gdb commands into.
// Note: POSIX.1-2008 declares that the file should be already created with mode 0600 by default.
// Modern systems implement it and suggest to do not touch masks in multithreaded applications.
// So CoverityScan warning is valid only for ancient versions of stdlib.
char scriptPath[64];
std::snprintf(scriptPath, sizeof(scriptPath), "/tmp/%s-script-XXXXXX", T::sName);
#ifdef __COVERITY__
umask(0600);
#endif
const int fd = mkstemp(scriptPath);
if (fd == -1)
{
printf("Failed to call mkstemp: %s\n", std::generic_category().message(errno).c_str());
return false;
}
std::unique_ptr<const char, Remove> tempFile(scriptPath);
std::unique_ptr<const int, Close> scopedFd(&fd);
FILE* const file = fdopen(fd, "w");
if (file == nullptr)
{
printf("Failed to open file for %s output \"%s\": %s\n", T::sName, scriptPath,
std::generic_category().message(errno).c_str());
return false;
}
std::unique_ptr<FILE, CloseFile> scopedFile(file);
if (fprintf(file, "%s", T::sScript) < 0)
{
printf("Failed to write debugger script to file \"%s\": %s\n", scriptPath,
std::generic_category().message(errno).c_str());
return false;
}
scopedFile = nullptr;
scopedFd = nullptr;
char command[128];
snprintf(command, sizeof(command), T::sCommandTemplate, pid, scriptPath);
printf("Executing: %s\n", command);
fflush(stdout);
const int ret = system(command);
const bool result = (ret == 0);
if (ret == -1)
printf(
"\nFailed to create a crash report: %s.\n"
"Please make sure that '%s' is installed and present in PATH then crash again.\n"
"Current PATH: %s\n",
std::generic_category().message(errno).c_str(), T::sName, getenv("PATH"));
else if (ret != 0)
printf(
"\nFailed to create a crash report.\n"
"Please make sure that '%s' is installed and present in PATH then crash again.\n"
"Current PATH: %s\n",
T::sName, getenv("PATH"));
fflush(stdout);
return result;
}
struct Gdb
{
static constexpr char sName[] = "gdb";
static constexpr char sScript[] = R"(shell echo ""
shell echo "* Loaded Libraries"
info sharedlibrary
shell echo ""
shell echo "* Threads"
info threads
shell echo ""
shell echo "* FPU Status"
info float
shell echo ""
shell echo "* Registers"
info registers
shell echo ""
shell echo "* Backtrace"
thread apply all backtrace full 1000
detach
quit
)";
static constexpr char sCommandTemplate[] = "gdb --pid %d --quiet --batch --command %s";
};
struct Lldb
{
static constexpr char sName[] = "lldb";
static constexpr char sScript[] = R"(script print("\n* Loaded Libraries")
image list
script print('\n* Threads')
thread list
script print('\n* Registers')
register read --all
script print('\n* Backtrace')
script print(''.join(f'{t}\n' + ''.join(''.join([f' {f}\n', ''.join(f' {s}\n' for s in f.statics), ''.join(f' {v}\n' for v in f.variables)]) for f in t.frames) for t in lldb.process.threads))
detach
quit
)";
static constexpr char sCommandTemplate[] = "lldb --attach-pid %d --batch --source %s";
};
void printProcessInfo(pid_t pid)
{
if (printDebuggerInfo<Gdb>(pid))
return;
if (printDebuggerInfo<Lldb>(pid))
return;
}
}
static void printSystemInfo(void)
{
#ifdef __unix__
struct utsname info;
if (uname(&info) == -1)
printf("Failed to get system information: %s\n", std::generic_category().message(errno).c_str());
else
printf("System: %s %s %s %s %s\n", info.sysname, info.nodename, info.release, info.version, info.machine);
fflush(stdout);
#endif
}
static size_t safe_write(int fd, const void* buf, size_t len)
{
size_t ret = 0;
while (ret < len)
{
const ssize_t rem = write(fd, (const char*)buf + ret, len - ret);
if (rem == -1)
{
if (errno == EINTR)
continue;
break;
}
ret += rem;
}
return ret;
}
static void crash_catcher(int signum, siginfo_t* siginfo, void* /*context*/)
{
/* Make sure the effective uid is the real uid */
if (getuid() != geteuid())
{
raise(signum);
return;
}
safe_write(STDERR_FILENO, fatal_err, sizeof(fatal_err) - 1);
int fd[2];
if (pipe(fd) == -1)
{
safe_write(STDERR_FILENO, pipe_err, sizeof(pipe_err) - 1);
raise(signum);
return;
}
crash_info.signum = signum;
crash_info.pid = getpid();
if (siginfo == nullptr)
crash_info.siginfo = std::nullopt;
else
crash_info.siginfo = *siginfo;
const pid_t dbg_pid = fork();
/* Fork off to start a crash handler */
switch (dbg_pid)
{
/* Error */
case -1:
safe_write(STDERR_FILENO, fork_err, sizeof(fork_err) - 1);
raise(signum);
return;
case 0:
dup2(fd[0], STDIN_FILENO);
close(fd[0]);
close(fd[1]);
execl(argv0, argv0, crash_switch, nullptr);
safe_write(STDERR_FILENO, exec_err, sizeof(exec_err) - 1);
_exit(1);
default:
#ifdef __linux__
prctl(PR_SET_PTRACER, dbg_pid, 0, 0, 0);
#endif
safe_write(fd[1], &crash_info, sizeof(crash_info));
close(fd[0]);
close(fd[1]);
/* Wait; we'll be killed when gdb is done */
do
{
int status;
if (waitpid(dbg_pid, &status, 0) == dbg_pid && (WIFEXITED(status) || WIFSIGNALED(status)))
{
/* The debug process died before it could kill us */
raise(signum);
break;
}
} while (1);
}
}
[[noreturn]] static void handleCrash(const char* logfile)
{
if (fread(&crash_info, sizeof(crash_info), 1, stdin) != 1)
{
fprintf(stderr, "Failed to retrieve info from crashed process: %s\n",
std::generic_category().message(errno).c_str());
exit(1);
}
const char* sigdesc = findSignalDescription(signals, crash_info.signum);
if (crash_info.siginfo.has_value())
{
switch (crash_info.signum)
{
case SIGSEGV:
sigdesc = findSignalDescription(sigSegvCodes, crash_info.siginfo->si_code);
break;
case SIGFPE:
sigdesc = findSignalDescription(sigFpeCodes, crash_info.siginfo->si_code);
break;
case SIGILL:
sigdesc = findSignalDescription(sigIllCodes, crash_info.siginfo->si_code);
break;
case SIGBUS:
sigdesc = findSignalDescription(sigBusCodes, crash_info.siginfo->si_code);
break;
}
}
fprintf(stderr, "%s (signal %i)\n", sigdesc, crash_info.signum);
if (crash_info.siginfo.has_value())
fprintf(stderr, "Address: %p\n", crash_info.siginfo->si_addr);
fputc('\n', stderr);
/* Create crash log file and redirect shell output to it */
if (freopen(logfile, "wa", stdout) != stdout)
{
fprintf(stderr, "Could not create %s following signal: %s\n", logfile,
std::generic_category().message(errno).c_str());
exit(1);
}
fprintf(stderr, "Generating %s and killing process %d, please wait... ", logfile, crash_info.pid);
printf(
"*** Fatal Error ***\n"
"%s (signal %i)\n",
sigdesc, crash_info.signum);
if (crash_info.siginfo.has_value())
printf("Address: %p\n", crash_info.siginfo->si_addr);
fputc('\n', stdout);
fflush(stdout);
printSystemInfo();
fflush(stdout);
if (crash_info.pid > 0)
{
printProcessInfo(crash_info.pid);
kill(crash_info.pid, SIGKILL);
}
// delay between killing of the crashed process and showing the message box to
// work around occasional X server lock-up. this can only be a bug in X11 since
// even faulty applications shouldn't be able to freeze the X server.
usleep(100000);
const std::string message = "OpenMW has encountered a fatal error.\nCrash log saved to '" + std::string(logfile)
+ "'.\n Please report this to https://gitlab.com/OpenMW/openmw/issues !";
SDL_ShowSimpleMessageBox(0, "Fatal Error", message.c_str(), nullptr);
exit(0);
}
static void getExecPath(char** argv)
{
#if defined(__FreeBSD__)
int mib[4] = { CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1 };
size_t size = sizeof(argv0);
if (sysctl(mib, 4, argv0, &size, nullptr, 0) == 0)
return;
Log(Debug::Warning) << "Failed to call sysctl: " << std::generic_category().message(errno);
#endif
#if defined(__APPLE__)
if (proc_pidpath(getpid(), argv0, sizeof(argv0)) > 0)
return;
Log(Debug::Warning) << "Failed to call proc_pidpath: " << std::generic_category().message(errno);
#endif
const char* statusPaths[] = { "/proc/self/exe", "/proc/self/file", "/proc/curproc/exe", "/proc/curproc/file" };
memset(argv0, 0, sizeof(argv0));
for (const char* path : statusPaths)
{
if (readlink(path, argv0, sizeof(argv0)) != -1)
return;
Log(Debug::Warning) << "Failed to call readlink for \"" << path
<< "\": " << std::generic_category().message(errno);
}
if (argv[0][0] == '/')
{
snprintf(argv0, sizeof(argv0), "%s", argv[0]);
return;
}
if (getcwd(argv0, sizeof(argv0)) == nullptr)
{
Log(Debug::Error) << "Failed to call getcwd: " << std::generic_category().message(errno);
return;
}
const int cwdlen = strlen(argv0);
snprintf(argv0 + cwdlen, sizeof(argv0) - cwdlen, "/%s", argv[0]);
}
static bool crashCatcherInstallHandlers(char** argv)
{
getExecPath(argv);
/* Set an alternate signal stack so SIGSEGVs caused by stack overflows
* still run */
static char* altstack = new char[SIGSTKSZ];
stack_t altss;
altss.ss_sp = altstack;
altss.ss_flags = 0;
altss.ss_size = SIGSTKSZ;
if (sigaltstack(&altss, nullptr) == -1)
{
Log(Debug::Error) << "Failed to call sigaltstack: " << std::generic_category().message(errno);
return false;
}
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_sigaction = crash_catcher;
sa.sa_flags = SA_RESETHAND | SA_NODEFER | SA_SIGINFO | SA_ONSTACK;
if (sigemptyset(&sa.sa_mask) == -1)
{
Log(Debug::Error) << "Failed to call sigemptyset: " << std::generic_category().message(errno);
return false;
}
for (const SignalInfo& signal : signals)
{
if (sigaction(signal.mCode, &sa, nullptr) == -1)
{
Log(Debug::Error) << "Failed to call sigaction for signal " << signal.mName << " (" << signal.mCode
<< "): " << std::generic_category().message(errno);
return false;
}
}
return true;
}
namespace
{
#if defined(__APPLE__)
bool isDebuggerPresent(const auto& info)
{
return (info.kp_proc.p_flag & P_TRACED) != 0;
}
#elif defined(__FreeBSD__)
bool isDebuggerPresent(const auto& info)
{
return (info.ki_flag & P_TRACED) != 0;
}
#endif
}
static bool isDebuggerPresent()
{
#if defined(__linux__)
std::filesystem::path procstatus = std::filesystem::path("/proc/self/status");
if (std::filesystem::exists(procstatus))
{
std::ifstream file((procstatus));
while (!file.eof())
{
std::string word;
file >> word;
if (word == "TracerPid:")
{
file >> word;
return word != "0";
}
}
}
return false;
#elif defined(__APPLE__) || defined(__FreeBSD__)
struct kinfo_proc info;
std::memset(&info, 0, sizeof(info));
// Initialize mib, which tells sysctl the info we want, in this case
// we're looking for information about a specific process ID.
int mib[4] = { CTL_KERN, KERN_PROC, KERN_PROC_PID, getpid() };
size_t size = sizeof(info);
if (sysctl(mib, std::size(mib), &info, &size, nullptr, 0) == -1)
{
Log(Debug::Warning) << "Failed to call sysctl, assuming no debugger: "
<< std::generic_category().message(errno);
return false;
}
return isDebuggerPresent(info);
#else
return false;
#endif
}
void crashCatcherInstall(int argc, char** argv, const std::filesystem::path& crashLogPath)
{
if (argc == 2 && strcmp(argv[1], crash_switch) == 0)
handleCrash(Files::pathToUnicodeString(crashLogPath).c_str());
if (isDebuggerPresent())
return;
if (crashCatcherInstallHandlers(argv))
Log(Debug::Info) << "Crash handler installed";
else
Log(Debug::Warning) << "Installing crash handler failed";
}