Split 4.x and 5.x signal handling so that we can keep 4.x signal

handling clean and functional as 5.x evolves.  This allows some of the
nasty bandaids in the 5.x codepaths to be unwound.

Encapsulate 4.x signal handling under COMPAT_FREEBSD4 (there is an
anti-foot-shooting measure in place, 5.x folks need this for a while) and
finish encapsulating the older stuff under COMPAT_43.  Since the ancient
stuff is required on alpha (longjmp(3) passes a 'struct osigcontext *'
to the current sigreturn(2), instead of the 'ucontext_t *' that sigreturn
is supposed to take), add a compile time check to prevent foot shooting
there too.  Add uniform COMPAT_43 stubs for ia64/sparc64/powerpc.

Tested on: i386, alpha, ia64.  Compiled on sparc64 (a few days ago).
Approved by: re

1 files changed, 73 insertions, 4 deletions

diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 0d5000e..3503609 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -73,6 +73,13 @@
 
 #include <machine/cpu.h>
 
+#if !defined(COMPAT_FREEBSD4) && !defined(NO_COMPAT_FREEBSD4)
+#error "You *really* want COMPAT_FREEBSD4 on -current for a while"
+#endif
+#if defined (__alpha__) && !defined(COMPAT_43)
+#error "You *really* need COMPAT_43 on the alpha for longjmp(3)"
+#endif
+
 #define	ONSIG	32		/* NSIG for osig* syscalls.  XXX. */
 
 static int	coredump(struct thread *);
@@ -229,14 +236,15 @@ sig_ffs(sigset_t *set)
 /*
  * kern_sigaction
  * sigaction
+ * freebsd4_sigaction
  * osigaction
  */
 int
-kern_sigaction(td, sig, act, oact, old)
+kern_sigaction(td, sig, act, oact, flags)
 	struct thread *td;
 	register int sig;
 	struct sigaction *act, *oact;
-	int old;
+	int flags;
 {
 	register struct sigacts *ps;
 	struct proc *p = td->td_proc;
@@ -353,9 +361,18 @@ kern_sigaction(td, sig, act, oact, old)
 			else
 				SIGADDSET(p->p_sigcatch, sig);
 		}
+#ifdef COMPAT_FREEBSD4
+		if (ps->ps_sigact[_SIG_IDX(sig)] == SIG_IGN ||
+		    ps->ps_sigact[_SIG_IDX(sig)] == SIG_DFL ||
+		    (flags & KSA_FREEBSD4) == 0)
+			SIGDELSET(ps->ps_freebsd4, sig);
+		else
+			SIGADDSET(ps->ps_freebsd4, sig);
+#endif
 #ifdef COMPAT_43
 		if (ps->ps_sigact[_SIG_IDX(sig)] == SIG_IGN ||
-		    ps->ps_sigact[_SIG_IDX(sig)] == SIG_DFL || !old)
+		    ps->ps_sigact[_SIG_IDX(sig)] == SIG_DFL ||
+		    (flags & KSA_OSIGSET) == 0)
 			SIGDELSET(ps->ps_osigset, sig);
 		else
 			SIGADDSET(ps->ps_osigset, sig);
@@ -403,6 +420,46 @@ done2:
 	return (error);
 }
 
+#ifdef COMPAT_FREEBSD4
+#ifndef _SYS_SYSPROTO_H_
+struct freebsd4_sigaction_args {
+	int	sig;
+	struct	sigaction *act;
+	struct	sigaction *oact;
+};
+#endif
+/*
+ * MPSAFE
+ */
+/* ARGSUSED */
+int
+freebsd4_sigaction(td, uap)
+	struct thread *td;
+	register struct freebsd4_sigaction_args *uap;
+{
+	struct sigaction act, oact;
+	register struct sigaction *actp, *oactp;
+	int error;
+
+	mtx_lock(&Giant);
+
+	actp = (uap->act != NULL) ? &act : NULL;
+	oactp = (uap->oact != NULL) ? &oact : NULL;
+	if (actp) {
+		error = copyin(uap->act, actp, sizeof(act));
+		if (error)
+			goto done2;
+	}
+	error = kern_sigaction(td, uap->sig, actp, oactp, KSA_FREEBSD4);
+	if (oactp && !error) {
+		error = copyout(oactp, uap->oact, sizeof(oact));
+	}
+done2:
+	mtx_unlock(&Giant);
+	return (error);
+}
+#endif	/* COMAPT_FREEBSD4 */
+
 #ifdef COMPAT_43	/* XXX - COMPAT_FBSD3 */
 #ifndef _SYS_SYSPROTO_H_
 struct osigaction_args {
@@ -441,7 +498,7 @@ osigaction(td, uap)
 		nsap->sa_flags = sa.sa_flags;
 		OSIG2SIG(sa.sa_mask, nsap->sa_mask);
 	}
-	error = kern_sigaction(td, uap->signum, nsap, osap, 1);
+	error = kern_sigaction(td, uap->signum, nsap, osap, KSA_OSIGSET);
 	if (osap && !error) {
 		sa.sa_handler = osap->sa_handler;
 		sa.sa_flags = osap->sa_flags;
@@ -452,6 +509,18 @@ done2:
 	mtx_unlock(&Giant);
 	return (error);
 }
+
+#if !defined(__i386__) && !defined(__alpha__)
+/* Avoid replicating the same stub everywhere */
+int
+osigreturn(td, uap)
+	struct thread *td;
+	struct osigreturn_args *uap;
+{
+
+	return (nosys(td, (struct nosys_args *)uap));
+}
+#endif
 #endif /* COMPAT_43 */
 
 /*