static bool gdbExtendedBacktrace(int const dumpFile)
#endif
{
/*
* Pointer to the stackframe of the function containing faulting
* instruction (assuming
* -fomit-frame-pointer has *not* been used).
*
* The frame pointer register (x86: %ebp, x64: %rbp) point's to the
* local variables of the current function (which are preceded by the
* previous frame pointer and the return address). Hence the
* additions to the frame-pointer register's content.
*/
void const * const frame =
#if defined(SA_SIGINFO) && __WORDSIZE == 64
sigcontext ? (void*)(sigcontext->uc_mcontext.gregs[REG_RBP] + sizeof(greg_t) + sizeof(void (*)(void))) : NULL;
#elif defined(SA_SIGINFO) && __WORDSIZE == 32
sigcontext ? (void*)(sigcontext->uc_mcontext.gregs[REG_EBP] + sizeof(greg_t) + sizeof(void (*)(void))) : NULL;
#else
NULL;
#endif
/*
* Faulting instruction.
*/
void (*instruction)(void) =
#if defined(SA_SIGINFO) && __WORDSIZE == 64
sigcontext ? (void (*)(void))sigcontext->uc_mcontext.gregs[REG_RIP] : NULL;
#elif defined(SA_SIGINFO) && __WORDSIZE == 32
sigcontext ? (void (*)(void))sigcontext->uc_mcontext.gregs[REG_EIP] : NULL;
#else
NULL;
#endif
// Spawn a GDB instance and retrieve a pipe to its stdin
int gdbPipe;
int status;
pid_t wpid;
// Retrieve a full stack backtrace
static const char gdbCommands[] = "backtrace full\n"
// Move to the stack frame where we triggered the crash
"frame 4\n"
// Show the assembly code associated with that stack frame
"disassemble /m\n"
// Show the content of all registers
"info registers\n"
"quit\n";
const pid_t pid = execGdb(dumpFile, &gdbPipe);
if (pid == 0)
{
return false;
}
// Disassemble the faulting instruction (if we know it)
if (instruction)
{
dprintf(gdbPipe, "x/i %p\n", (void*)instruction);
}
// We have an intelligent guess for the *correct* frame, disassemble *that* one.
if (frame)
{
dprintf(gdbPipe, "frame %p\n"
"disassemble /m\n", frame);
}
write(gdbPipe, gdbCommands, strlen(gdbCommands));
/* Flush our end of the pipe to make sure that GDB has all commands
* directly available to it.
*/
fsync(gdbPipe);
// Wait for our child to terminate
wpid = waitpid(pid, &status, 0);
// Clean up our end of the pipe
close(gdbPipe);
// waitpid(): on error, -1 is returned
if (wpid == -1)
{
write(dumpFile, "GDB failed\n",
strlen("GDB failed\n"));
printf("GDB failed\n");
return false;
}
/* waitpid(): on success, returns the process ID of the child whose
* state has changed
*
* We only have one child, from our fork() call above, thus these PIDs
* should match.
*/
assert(pid == wpid);
/* Check wether our child (which presumably was GDB, but doesn't
* necessarily have to be) didn't terminate normally or had a non-zero
* return code.
*/
if (!WIFEXITED(status)
|| WEXITSTATUS(status) != 0)
{
write(dumpFile, "GDB failed\n",
strlen("GDB failed\n"));
printf("GDB failed\n");
return false;
}
return true;
}
/**
* Dumps a backtrace of the stack to the given output stream.
*
* @param dumpFile a POSIX file descriptor to write the resulting backtrace to.
*
* @return false if any failure occurred, preventing a full "extended"
* backtrace.
*/
static bool gdbExtendedBacktrace(int const dumpFile)
{
// Spawn a GDB instance and retrieve a pipe to its stdin
int gdbPipe;
int status;
pid_t wpid;
// Retrieve a full stack backtrace
static const char gdbCommands[] = "backtrace full\n"
// Move to the stack frame where we triggered the crash
"frame 4\n"
// Show the assembly code associated with that stack frame
"disassemble\n"
// Show the content of all registers
"info registers\n"
"quit\n";
const pid_t pid = execGdb(dumpFile, &gdbPipe);
if (pid == 0)
{
return false;
}
write(gdbPipe, gdbCommands, sizeof(gdbCommands));
/* Flush our end of the pipe to make sure that GDB has all commands
* directly available to it.
*/
fsync(gdbPipe);
// Wait for our child to terminate
wpid = waitpid(pid, &status, 0);
// Clean up our end of the pipe
close(gdbPipe);
// waitpid(): on error, -1 is returned
if (wpid == -1)
{
write(dumpFile, "GDB failed\n",
strlen("GDB failed\n"));
printf("GDB failed\n");
return false;
}
/* waitpid(): on success, returns the process ID of the child whose
* state has changed
*
* We only have one child, from our fork() call above, thus these PIDs
* should match.
*/
assert(pid == wpid);
/* Check wether our child (which presumably was GDB, but doesn't
* necessarily have to be) didn't terminate normally or had a non-zero
* return code.
*/
if (!WIFEXITED(status)
|| WEXITSTATUS(status) != 0)
{
write(dumpFile, "GDB failed\n",
strlen("GDB failed\n"));
printf("GDB failed\n");
return false;
}
return true;
}
