linux: improve diagnosis on exception handling

Under some circumstances, the diagnostic message in the exception signal
handler was not printed. This could happen due to a dead lock in the
console library if the console code itself produces the exception while
possessing the mutex, e.g., by exhausting a undersized stack. Now, we
directly write to the log session via the stdout_write() hook or use
raw_write_str() in core.
This commit is contained in:
Christian Helmuth 2015-10-05 15:39:36 +02:00
parent bbf8a4f2ec
commit ce354d6fd9

View File

@ -31,6 +31,19 @@ char **lx_environ;
*/
int main_thread_futex_counter __attribute__((aligned(sizeof(addr_t))));
/**
* Genode console hook
*/
extern "C" int stdout_write(char const *);
/*
* Core lacks the hook, so provide a base-linux specific weak implementation
*/
extern "C" __attribute__((weak)) int stdout_write(char const *s)
{
return raw_write_str(s);
}
/**
* Signal handler for exceptions like segmentation faults
*/
@ -46,7 +59,18 @@ static void exception_signal_handler(int signum)
default: /* unexpected signal */ return;
}
PERR("%s (signum=%d), see Linux kernel log for details", reason, signum);
/*
* We can't use Genode::printf() as the exception may have occurred in the
* Genode console library itself, which uses a mutex. Therefore, we use
* Genode::snprintf() and call the console hook directly to minimize
* overlaps with other code paths.
*/
static char msg[128];
snprintf(msg, sizeof(msg),
ESC_ERR "%s (signum=%d), see Linux kernel log for details" ESC_END "\n",
reason, signum);
stdout_write(msg);
/*
* We reset the signal handler to SIG_DFL and trigger exception again,