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catching all signals in a single handler
Post 58959 by xtrix on Monday 6th of December 2004 11:31:34 AM
12-06-2004
catching all signals in a single handler
Hi guys - got some questions... hope something helpfull will come out!!! I just want to catch every signal that can be caught and print some info by using only one handler.
I use the sigaction() function and only one instance of a sigaction struct as an argument to the sigaction() function.
1) If sigset_t sigaction.sa_mask is empty, things seem to work fine when i send signals to my process from the command line. However the shell sends an additional SIGCONT to my process for every signal that i send. Why is this happening?
2) If sigset_t sigaction.sa_mask is filled (meaning - from my point of view
- that all signals should block while sig_handler's body is being executed) i get weird results. For example the scheduler (pid=0) is repeatedly sending a SIGBUS signal to my process. Why is this happening?
Thanx in advance, please have a look at the code...
P.S. This is a simplified version of the source code. In fact the program is multi-threaded. Anyway considering just one thread of execution, would this be right?
//----------------------------------------------------------------------------------
void sig_handler(int sig, siginfo_t * info, void * context)
{
FILE *f= fopen("signal_trap", "a");
if (sig == SIGILL || sig == SIGFPE || sig == SIGSEGV || sig == SIGBUS || sig == SIGCHLD || sig == SIGTRAP || sig == SIGPOLL)
fprintf(f, "Signal = %d, subcode = %d, pid = %d, uid = %d, address = %p, errno = %d\n", sig, info->si_code, info->si_pid, info->si_uid, info->si_addr, info->si_errno);
else
fprintf(f, "Signal = %d, pid = %d, uid = %d, address = %p, errno = %d\n", sig, info->si_pid, info->si_uid, info->si_addr, info->si_errno);
fprintf(f, "\n");
fclose(f);
}
//----------------------------------------------------------------------------------
int main()
{
struct sigaction act;
sigemptyset(&act.sa_mask); // or sigfillset(&act.sa_mask);
act.sa_flags = SA_SIGINFO;
act.sa_sigaction = sig_handler;
sigaction(SIGABRT, &act, 0);
sigaction(SIGALRM, &act, 0);
sigaction(SIGFPE, &act, 0);
sigaction(SIGHUP, &act, 0);
sigaction(SIGILL, &act, 0);
sigaction(SIGINT, &act, 0);
sigaction(SIGPIPE, &act, 0);
// blah blah blah - all available signals use struct sigaction act
return 0;
}
//----------------------------------------------------------------------------------
I use the sigaction() function and only one instance of a sigaction struct as an argument to the sigaction() function.
1) If sigset_t sigaction.sa_mask is empty, things seem to work fine when i send signals to my process from the command line. However the shell sends an additional SIGCONT to my process for every signal that i send. Why is this happening?
2) If sigset_t sigaction.sa_mask is filled (meaning - from my point of view
- that all signals should block while sig_handler's body is being executed) i get weird results. For example the scheduler (pid=0) is repeatedly sending a SIGBUS signal to my process. Why is this happening?Thanx in advance, please have a look at the code...
P.S. This is a simplified version of the source code. In fact the program is multi-threaded. Anyway considering just one thread of execution, would this be right?
//----------------------------------------------------------------------------------
void sig_handler(int sig, siginfo_t * info, void * context)
{
FILE *f= fopen("signal_trap", "a");
if (sig == SIGILL || sig == SIGFPE || sig == SIGSEGV || sig == SIGBUS || sig == SIGCHLD || sig == SIGTRAP || sig == SIGPOLL)
fprintf(f, "Signal = %d, subcode = %d, pid = %d, uid = %d, address = %p, errno = %d\n", sig, info->si_code, info->si_pid, info->si_uid, info->si_addr, info->si_errno);
else
fprintf(f, "Signal = %d, pid = %d, uid = %d, address = %p, errno = %d\n", sig, info->si_pid, info->si_uid, info->si_addr, info->si_errno);
fprintf(f, "\n");
fclose(f);
}
//----------------------------------------------------------------------------------
int main()
{
struct sigaction act;
sigemptyset(&act.sa_mask); // or sigfillset(&act.sa_mask);
act.sa_flags = SA_SIGINFO;
act.sa_sigaction = sig_handler;
sigaction(SIGABRT, &act, 0);
sigaction(SIGALRM, &act, 0);
sigaction(SIGFPE, &act, 0);
sigaction(SIGHUP, &act, 0);
sigaction(SIGILL, &act, 0);
sigaction(SIGINT, &act, 0);
sigaction(SIGPIPE, &act, 0);
// blah blah blah - all available signals use struct sigaction act
return 0;
}
//----------------------------------------------------------------------------------
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LEARN ABOUT OPENSOLARIS
sigsuspend
sigsuspend(2) System Calls sigsuspend(2) NAME
sigsuspend - install a signal mask and suspend caller until signal SYNOPSIS
#include <signal.h> int sigsuspend(const sigset_t *set); DESCRIPTION
The sigsuspend() function replaces the caller's signal mask with the set of signals pointed to by the set argument and suspends the caller until delivery of a signal whose action is either to execute a signal catching function or to terminate the process. If the set argument points to an invalid address, the behavior is undefined and errno may be set to EFAULT. If the action is to terminate the process, sigsuspend() does not return. If the action is to execute a signal catching function, sigsus- pend() returns after the signal catching function returns. On return, the signal mask is restored to the set that existed before the call to sigsuspend(). It is not possible to block signals that cannot be ignored (see signal.h(3HEAD)). This restriction is silently imposed by the system. RETURN VALUES
Since sigsuspend() suspends the caller's execution indefinitely, there is no successful completion return value. On failure, it returns -1 and sets errno to indicate the error. ERRORS
The sigsuspend() function will fail if: EINTR A signal was caught by the caller and control was returned from the signal catching function. The sigsuspend() function may fail if: EFAULT The set argument points to an illegal address. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Async-Signal-Safe | +-----------------------------+-----------------------------+ SEE ALSO
sigaction(2), sigprocmask(2), sigwait(2), signal(3C), signal.h(3HEAD), sigsetops(3C), attributes(5) NOTES
If the caller specifies more than one unblocked signal in the mask to sigsuspend(), more than one signal might be processed before the call to sigsuspend() returns. While the caller is executing the signal handler that interrupted its call to sigsuspend(), its signal mask is the one passed to sigsus- pend(), modified as usual by the signal mask specification in the signal's sigaction(2) parameters. The caller's signal mask is not restored to its previous value until the caller returns from all the signal handlers that interrupted sigsuspend(). SunOS 5.11 24 Jun 2001 sigsuspend(2)