#include <signal.h>
+#include <errno.h>
#include "syscall.h"
-int sigaltstack(const stack_t *ss, stack_t *old)
+int sigaltstack(const stack_t *restrict ss, stack_t *restrict old)
{
- /* depends on kernel struct matching */
- return syscall2(__NR_sigaltstack, (long)ss, (long)old);
+ if (ss) {
+ if (ss->ss_size < MINSIGSTKSZ) {
+ errno = ENOMEM;
+ return -1;
+ }
+ if (ss->ss_flags & ~SS_DISABLE) {
+ errno = EINVAL;
+ return -1;
+ }
+ }
+ return syscall(SYS_sigaltstack, ss, old);
}