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/* $OpenBSD: uthread_sigaltstack.c,v 1.3 2003/01/20 19:24:24 marc Exp $ */
/* PUBLIC DOMAIN <marc@snafu.org */
#include <signal.h>
#include <errno.h>
#ifdef _THREAD_SAFE
#include <pthread.h>
#include "pthread_private.h"
/*
* IEEE Std 1003.1-2001 says:
*
* "Use of this function by library threads that are not bound to
* kernel-scheduled entities results in undefined behavior."
*
* There exists code (e.g. alpha setjmp) that uses this function
* to get information about the current stack.
*
* The "undefined behaviour" in this implementation is thus:
* o if ss is *not* null return -1 with errno set to EINVAL
* o if oss is *not* null fill it in with information about the
* current stack and return 0.
*
* This lets things like alpha setjmp work in threaded applications.
*/
int
sigaltstack(const struct sigaltstack *ss, struct sigaltstack *oss)
{
struct pthread *curthread = _get_curthread();
int ret = 0;
if (ss != NULL) {
errno = EINVAL;
ret = -1;
} else if (oss != NULL) {
/*
* get the requested info from the kernel if there is no
* thread or if the main thread (no thread stack).
*/
if (curthread == NULL || curthread->stack == NULL)
_thread_sys_sigaltstack(ss, oss);
else {
oss->ss_sp = curthread->stack->base;
oss->ss_size = curthread->stack->size;
oss->ss_flags = SS_DISABLE;
}
}
return (ret);
}
#endif /* _THREAD_SAFE */
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