Determine whether we're currently on the alternative signal stack

dynamically, by comparing the stack pointer against the altstack
base and size, so that you get the correct answer if you longjmp
out of the signal handler, as tested by regress/sys/kern/stackjmp/.
Also, fix alt stack handling on vax, where it was completely broken.

Testing and corrections by miod@, krw@, tobiasu@, pirofti@

3 files changed, 12 insertions, 17 deletions

diff --git a/sys/arch/m68k/include/cpu.h b/sys/arch/m68k/include/cpu.h
index c88366858b8..4a3df3f5514 100644
--- a/sys/arch/m68k/include/cpu.h
+++ b/sys/arch/m68k/include/cpu.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpu.h,v 1.25 2011/11/16 20:50:18 deraadt Exp $	*/
+/*	$OpenBSD: cpu.h,v 1.26 2012/12/02 07:03:31 guenther Exp $	*/
 /*	$NetBSD: cpu.h,v 1.3 1997/02/02 06:56:57 thorpej Exp $	*/
 
 /*
@@ -253,6 +253,7 @@ int	cachectl(struct proc *, int, vaddr_t, int);
  * This is used during profiling to integrate system time.
  */
 #define	PROC_PC(p)	(((struct trapframe *)((p)->p_md.md_regs))->tf_pc)
+#define	PROC_STACK(p)	(((struct trapframe *)((p)->p_md.md_regs))->tf_regs[15])
 
 #define	cpu_idle_enter()	do { /* nothing */ } while (0)
 #define	cpu_idle_leave()	do { /* nothing */ } while (0)
diff --git a/sys/arch/m68k/include/signal.h b/sys/arch/m68k/include/signal.h
index 731b01b0a50..9115367cfcb 100644
--- a/sys/arch/m68k/include/signal.h
+++ b/sys/arch/m68k/include/signal.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: signal.h,v 1.5 2006/01/08 14:20:17 millert Exp $	*/
+/*	$OpenBSD: signal.h,v 1.6 2012/12/02 07:03:31 guenther Exp $	*/
 /*	$NetBSD: signal.h,v 1.4 1995/01/10 19:01:31 jtc Exp $	*/
 
 /*
@@ -55,7 +55,7 @@ typedef int sig_atomic_t;
  * a non-standard exit is performed.
  */
 struct	sigcontext {
-	int	sc_onstack;		/* sigstack state to restore */
+	int	__sc_unused;
 	int	sc_mask;		/* signal mask to restore */
 	int	sc_sp;			/* sp to restore */
 	int	sc_fp;			/* fp to restore */
diff --git a/sys/arch/m68k/m68k/sig_machdep.c b/sys/arch/m68k/m68k/sig_machdep.c
index eae3162703f..f3933fdf9d4 100644
--- a/sys/arch/m68k/m68k/sig_machdep.c
+++ b/sys/arch/m68k/m68k/sig_machdep.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: sig_machdep.c,v 1.26 2012/08/22 13:33:32 okan Exp $	*/
+/*	$OpenBSD: sig_machdep.c,v 1.27 2012/12/02 07:03:31 guenther Exp $	*/
 /*	$NetBSD: sig_machdep.c,v 1.3 1997/04/30 23:28:03 gwr Exp $	*/
 
 /*
@@ -131,11 +131,10 @@ sendsig(catcher, sig, mask, code, type, val)
 	struct frame *frame;
 	struct sigacts *psp = p->p_sigacts;
 	short ft;
-	int oonstack, fsize;
+	int fsize;
 
 	frame = (struct frame *)p->p_md.md_regs;
 	ft = frame->f_format;
-	oonstack = p->p_sigstk.ss_flags & SS_ONSTACK;
 
 	/*
 	 * Allocate and validate space for the signal handler
@@ -145,22 +144,22 @@ sendsig(catcher, sig, mask, code, type, val)
 	 * the space with a `brk'.
 	 */
 	fsize = sizeof(struct sigframe);
-	if ((p->p_sigstk.ss_flags & SS_DISABLE) == 0 && !oonstack &&
-	    (psp->ps_sigonstack & sigmask(sig))) {
+	if ((p->p_sigstk.ss_flags & SS_DISABLE) == 0 &&
+	    !sigonstack(frame->f_regs[SP]) &&
+	    (psp->ps_sigonstack & sigmask(sig)))
 		fp = (struct sigframe *)(p->p_sigstk.ss_sp +
 					 p->p_sigstk.ss_size - fsize);
-		p->p_sigstk.ss_flags |= SS_ONSTACK;
-	} else
+	else
 		fp = (struct sigframe *)(frame->f_regs[SP] - fsize);
 	if ((unsigned)fp <= USRSTACK - ptoa(p->p_vmspace->vm_ssize)) 
 		(void)uvm_grow(p, (unsigned)fp);
 #ifdef DEBUG
 	if ((sigdebug & SDB_KSTACK) && p->p_pid == sigpid)
 		printf("sendsig(%d): sig %d ssp %p usp %p scp %p ft %d\n",
-		       p->p_pid, sig, &oonstack, fp, &fp->sf_sc, ft);
+		       p->p_pid, sig, &fsize, fp, &fp->sf_sc, ft);
 #endif
 	kfp = (struct sigframe *)malloc((u_long)fsize, M_TEMP,
-	    M_WAITOK | M_CANFAIL);
+	    M_WAITOK | M_CANFAIL | M_ZERO);
 	if (kfp == NULL) {
 		/* Better halt the process in its track than panicing */
 		sigexit(p, SIGILL);
@@ -226,7 +225,6 @@ sendsig(catcher, sig, mask, code, type, val)
 	/*
 	 * Build the signal context to be used by sigreturn.
 	 */
-	kfp->sf_sc.sc_onstack = oonstack;
 	kfp->sf_sc.sc_mask = mask;
 	kfp->sf_sc.sc_sp = frame->f_regs[SP];
 	kfp->sf_sc.sc_fp = frame->f_regs[A6];
@@ -320,10 +318,6 @@ sys_sigreturn(p, v, retval)
 	/*
 	 * Restore the user supplied information
 	 */
-	if (scp->sc_onstack & 1)
-		p->p_sigstk.ss_flags |= SS_ONSTACK;
-	else
-		p->p_sigstk.ss_flags &= ~SS_ONSTACK;
 	p->p_sigmask = scp->sc_mask &~ sigcantmask;
 	frame = (struct frame *) p->p_md.md_regs;
 	frame->f_regs[SP] = scp->sc_sp;