text: #include <signal.h>
  #include <errno.h>
  #include <string.h>
  #include "syscall.h"
  #include "pthread_impl.h"
  #include "libc.h"
  #include "ksigaction.h"
  
  void __restore(), __restore_rt();
  
  static int unmask_done;
  static unsigned long handler_set[_NSIG/(8*sizeof(long))];
  
  void __get_handler_set(sigset_t *set)
  {
  	memcpy(set, handler_set, sizeof handler_set);
  }
  
  int __libc_sigaction(int sig, const struct sigaction *restrict sa, struct sigaction *restrict old)
  {
  	struct k_sigaction ksa, ksa_old;
  	if (sig >= (unsigned)_NSIG) {
  		errno = EINVAL;
  		return -1;
  	}
  	if (sa) {
  		if ((uintptr_t)sa->sa_handler > 1UL) {
  			a_or_l(handler_set+(sig-1)/(8*sizeof(long)),
  				1UL<<(sig-1)%(8*sizeof(long)));
  
  			/* If pthread_create has not yet been called,
  			 * implementation-internal signals might not
  			 * yet have been unblocked. They must be
  			 * unblocked before any signal handler is
  			 * installed, so that an application cannot
  			 * receive an illegal sigset_t (with them
  			 * blocked) as part of the ucontext_t passed
  			 * to the signal handler. */
  			if (!libc.threaded && !unmask_done) {
  				__syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
  					SIGPT_SET, 0, _NSIG/8);
  				unmask_done = 1;
  			}
  		}
  		ksa.handler = sa->sa_handler;
  		ksa.flags = sa->sa_flags | SA_RESTORER;
  		ksa.restorer = (sa->sa_flags & SA_SIGINFO) ? __restore_rt : __restore;
  		memcpy(&ksa.mask, &sa->sa_mask, sizeof ksa.mask);
  	}
  	if (syscall(SYS_rt_sigaction, sig, sa?&ksa:0, old?&ksa_old:0, sizeof ksa.mask))
  		return -1;
  	if (old) {
  		old->sa_handler = ksa_old.handler;
  		old->sa_flags = ksa_old.flags;
  		memcpy(&old->sa_mask, &ksa_old.mask, sizeof ksa_old.mask);
  	}
  	return 0;
  }
  
  int __sigaction(int sig, const struct sigaction *restrict sa, struct sigaction *restrict old)
  {
  	if (sig-32U < 3) {
  		errno = EINVAL;
  		return -1;
  	}
  	return __libc_sigaction(sig, sa, old);
  }
  
  weak_alias(__sigaction, sigaction);
  