NAME

stack_violation - determine stack boundary violation event

SYNOPSIS

#include <ucontext.h>
int stack_violation(int sig, const siginfo_t *sip,


     const ucontext_t *ucp);

DESCRIPTION

The stack_violation() function returns a boolean value indicating whether the signal, sig, and accompanying signal information, sip, and saved context, ucp, represent a stack boundary violation event or a stack overflow.

RETURN VALUES

The stack_violation() function returns 0 if the signal does not represent a stack boundary violation event and 1 if the signal does represent a stack boundary violation event.

ERRORS

No errors are defined.

EXAMPLES

Example 1 Set up a signal handler to run on an alternate stack.

The following example sets up a signal handler for SIGSEGV to run on an alternate signal stack. For each signal it handles, the handler emits a message to indicate if the signal was produced due to a stack boundary violation.

#include <stdlib.h>
#include <unistd.h>
#include <ucontext.h>
#include <signal.h>
static void
handler(int sig, siginfo_t *sip, void *p)
{


        ucontext_t *ucp = p;


        const char *str;


        if (stack_violation(sig, sip, ucp))


                str = "stack violation.\n";


        else


                str = "no stack violation.\n";


        (void) write(STDERR_FILENO, str, strlen(str));


        exit(1);
}
int
main(int argc, char **argv)
{


        struct sigaction sa;


        stack_t altstack;


        altstack.ss_size = SIGSTKSZ;


        altstack.ss_sp = malloc(SIGSTKSZ);


        altstack.ss_flags = 0;


        (void) sigaltstack(&altstack, NULL);


        sa.sa_sigaction = handler;


        (void) sigfillset(&sa.sa_mask);


        sa.sa_flags = SA_ONSTACK | SA_SIGINFO;


        (void) sigaction(SIGSEGV, &sa, NULL);


        /*


         * The application is now set up to use stack_violation(3C).


         */


        return (0);
}

USAGE

An application typically uses stack_violation() in a signal handler that has been installed for SIGSEGV using sigaction(2) with the SA_SIGINFO flag set and is configured to run on an alternate signal stack.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Interface Stability	Evolving
MT-Level	Async-Signal-Safe