runtime: turn divide by zero, nil dereference into panics

tested on linux/amd64, linux/386, linux/arm, darwin/amd64, darwin/386.
freebsd untested; will finish in a separate CL.

for now all the panics are errorStrings.
richer structures can be added as necessary
once the mechanism is shaked out.

R=r
CC=golang-dev
http://codereview.appspot.com/906041

28 files changed, 837 insertions, 70 deletions

diff --git a/src/pkg/runtime/darwin/386/defs.h b/src/pkg/runtime/darwin/386/defs.h
index b66a5d8b4..69ccc35f7 100644
--- a/src/pkg/runtime/darwin/386/defs.h
+++ b/src/pkg/runtime/darwin/386/defs.h
@@ -1,4 +1,4 @@
-// godefs -f -m32 defs.c
+// godefs defs.c
 
 // MACHINE GENERATED - DO NOT EDIT.
 
@@ -44,6 +44,50 @@ enum {
 	SA_ONSTACK = 0x1,
 	SA_USERTRAMP = 0x100,
 	SA_64REGSET = 0x200,
+	SIGHUP = 0x1,
+	SIGINT = 0x2,
+	SIGQUIT = 0x3,
+	SIGILL = 0x4,
+	SIGTRAP = 0x5,
+	SIGABRT = 0x6,
+	SIGEMT = 0x7,
+	SIGFPE = 0x8,
+	SIGKILL = 0x9,
+	SIGBUS = 0xa,
+	SIGSEGV = 0xb,
+	SIGSYS = 0xc,
+	SIGPIPE = 0xd,
+	SIGALRM = 0xe,
+	SIGTERM = 0xf,
+	SIGURG = 0x10,
+	SIGSTOP = 0x11,
+	SIGTSTP = 0x12,
+	SIGCONT = 0x13,
+	SIGCHLD = 0x14,
+	SIGTTIN = 0x15,
+	SIGTTOU = 0x16,
+	SIGIO = 0x17,
+	SIGXCPU = 0x18,
+	SIGXFSZ = 0x19,
+	SIGVTALRM = 0x1a,
+	SIGPROF = 0x1b,
+	SIGWINCH = 0x1c,
+	SIGINFO = 0x1d,
+	SIGUSR1 = 0x1e,
+	SIGUSR2 = 0x1f,
+	FPE_INTDIV = 0x7,
+	FPE_INTOVF = 0x8,
+	FPE_FLTDIV = 0x1,
+	FPE_FLTOVF = 0x2,
+	FPE_FLTUND = 0x3,
+	FPE_FLTRES = 0x4,
+	FPE_FLTINV = 0x5,
+	FPE_FLTSUB = 0x6,
+	BUS_ADRALN = 0x1,
+	BUS_ADRERR = 0x2,
+	BUS_OBJERR = 0x3,
+	SEGV_MAPERR = 0x1,
+	SEGV_ACCERR = 0x2,
 };
 
 // Types
diff --git a/src/pkg/runtime/darwin/386/signal.c b/src/pkg/runtime/darwin/386/signal.c
index 6fe5f308f..65c217b4e 100644
--- a/src/pkg/runtime/darwin/386/signal.c
+++ b/src/pkg/runtime/darwin/386/signal.c
@@ -39,6 +39,39 @@ sighandler(int32 sig, Siginfo *info, void *context)
 	Ucontext *uc;
 	Mcontext *mc;
 	Regs *r;
+	uintptr *sp;
+	void (*fn)(void);
+	G *gp;
+	byte *pc;
+
+	uc = context;
+	mc = uc->uc_mcontext;
+	r = &mc->ss;
+
+	if((gp = m->curg) != nil && (sigtab[sig].flags & SigPanic)) {
+		// Work around Leopard bug that doesn't set FPE_INTDIV.
+		// Look at instruction to see if it is a divide.
+		// Not necessary in Snow Leopard (si_code will be != 0).
+		if(sig == SIGFPE && info->si_code == 0) {
+			pc = (byte*)r->eip;
+			if(pc[0] == 0xF7)
+				info->si_code = FPE_INTDIV;
+		}
+		
+		// Make it look like a call to the signal func.
+		// Have to pass arguments out of band since
+		// augmenting the stack frame would break
+		// the unwinding code.
+		gp->sig = sig;
+		gp->sigcode0 = info->si_code;
+		gp->sigcode1 = (uintptr)info->si_addr;
+
+		sp = (uintptr*)r->esp;
+		*--sp = r->eip;
+		r->eip = (uintptr)sigpanic;
+		r->esp = (uintptr)sp;
+		return;
+	}
 
 	if(sigtab[sig].flags & SigQueue) {
 		if(sigsend(sig) || (sigtab[sig].flags & SigIgnore))
@@ -56,11 +89,6 @@ sighandler(int32 sig, Siginfo *info, void *context)
 		printf("%s\n", sigtab[sig].name);
 	}
 
-	uc = context;
-	mc = uc->uc_mcontext;
-	r = &mc->ss;
-
-	printf("Faulting address: %p\n", info->si_addr);
 	printf("pc: %x\n", r->eip);
 	printf("\n");
 
diff --git a/src/pkg/runtime/darwin/amd64/defs.h b/src/pkg/runtime/darwin/amd64/defs.h
index 1076e4c10..0b5fde85c 100644
--- a/src/pkg/runtime/darwin/amd64/defs.h
+++ b/src/pkg/runtime/darwin/amd64/defs.h
@@ -44,6 +44,50 @@ enum {
 	SA_ONSTACK = 0x1,
 	SA_USERTRAMP = 0x100,
 	SA_64REGSET = 0x200,
+	SIGHUP = 0x1,
+	SIGINT = 0x2,
+	SIGQUIT = 0x3,
+	SIGILL = 0x4,
+	SIGTRAP = 0x5,
+	SIGABRT = 0x6,
+	SIGEMT = 0x7,
+	SIGFPE = 0x8,
+	SIGKILL = 0x9,
+	SIGBUS = 0xa,
+	SIGSEGV = 0xb,
+	SIGSYS = 0xc,
+	SIGPIPE = 0xd,
+	SIGALRM = 0xe,
+	SIGTERM = 0xf,
+	SIGURG = 0x10,
+	SIGSTOP = 0x11,
+	SIGTSTP = 0x12,
+	SIGCONT = 0x13,
+	SIGCHLD = 0x14,
+	SIGTTIN = 0x15,
+	SIGTTOU = 0x16,
+	SIGIO = 0x17,
+	SIGXCPU = 0x18,
+	SIGXFSZ = 0x19,
+	SIGVTALRM = 0x1a,
+	SIGPROF = 0x1b,
+	SIGWINCH = 0x1c,
+	SIGINFO = 0x1d,
+	SIGUSR1 = 0x1e,
+	SIGUSR2 = 0x1f,
+	FPE_INTDIV = 0x7,
+	FPE_INTOVF = 0x8,
+	FPE_FLTDIV = 0x1,
+	FPE_FLTOVF = 0x2,
+	FPE_FLTUND = 0x3,
+	FPE_FLTRES = 0x4,
+	FPE_FLTINV = 0x5,
+	FPE_FLTSUB = 0x6,
+	BUS_ADRALN = 0x1,
+	BUS_ADRERR = 0x2,
+	BUS_OBJERR = 0x3,
+	SEGV_MAPERR = 0x1,
+	SEGV_ACCERR = 0x2,
 };
 
 // Types
diff --git a/src/pkg/runtime/darwin/amd64/signal.c b/src/pkg/runtime/darwin/amd64/signal.c
index beb55decf..9c4f0dc14 100644
--- a/src/pkg/runtime/darwin/amd64/signal.c
+++ b/src/pkg/runtime/darwin/amd64/signal.c
@@ -47,6 +47,40 @@ sighandler(int32 sig, Siginfo *info, void *context)
 	Ucontext *uc;
 	Mcontext *mc;
 	Regs *r;
+	G *gp;
+	uintptr *sp;
+	byte *pc;
+
+	uc = context;
+	mc = uc->uc_mcontext;
+	r = &mc->ss;
+
+	if((gp = m->curg) != nil && (sigtab[sig].flags & SigPanic)) {
+		// Work around Leopard bug that doesn't set FPE_INTDIV.
+		// Look at instruction to see if it is a divide.
+		// Not necessary in Snow Leopard (si_code will be != 0).
+		if(sig == SIGFPE && info->si_code == 0) {
+			pc = (byte*)r->rip;
+			if((pc[0]&0xF0) == 0x40)	// 64-bit REX prefix
+				pc++;
+			if(pc[0] == 0xF7)
+				info->si_code = FPE_INTDIV;
+		}
+		
+		// Make it look like a call to the signal func.
+		// Have to pass arguments out of band since
+		// augmenting the stack frame would break
+		// the unwinding code.
+		gp->sig = sig;
+		gp->sigcode0 = info->si_code;
+		gp->sigcode1 = (uintptr)info->si_addr;
+
+		sp = (uintptr*)r->rsp;
+		*--sp = r->rip;
+		r->rip = (uintptr)sigpanic;
+		r->rsp = (uintptr)sp;
+		return;
+	}
 
 	if(sigtab[sig].flags & SigQueue) {
 		if(sigsend(sig) || (sigtab[sig].flags & SigIgnore))
@@ -64,11 +98,6 @@ sighandler(int32 sig, Siginfo *info, void *context)
 		printf("%s\n", sigtab[sig].name);
 	}
 
-	uc = context;
-	mc = uc->uc_mcontext;
-	r = &mc->ss;
-
-	printf("Faulting address: %p\n", info->si_addr);
 	printf("pc: %X\n", r->rip);
 	printf("\n");
 
diff --git a/src/pkg/runtime/darwin/defs.c b/src/pkg/runtime/darwin/defs.c
index 1ed662957..95edf7bb1 100644
--- a/src/pkg/runtime/darwin/defs.c
+++ b/src/pkg/runtime/darwin/defs.c
@@ -67,6 +67,54 @@ enum {
 	$SA_ONSTACK = SA_ONSTACK,
 	$SA_USERTRAMP = SA_USERTRAMP,
 	$SA_64REGSET = SA_64REGSET,
+	
+	$SIGHUP = SIGHUP,
+	$SIGINT = SIGINT,
+	$SIGQUIT = SIGQUIT,
+	$SIGILL = SIGILL,
+	$SIGTRAP = SIGTRAP,
+	$SIGABRT = SIGABRT,
+	$SIGEMT = SIGEMT,
+	$SIGFPE = SIGFPE,
+	$SIGKILL = SIGKILL,
+	$SIGBUS = SIGBUS,
+	$SIGSEGV = SIGSEGV,
+	$SIGSYS = SIGSYS,
+	$SIGPIPE = SIGPIPE,
+	$SIGALRM = SIGALRM,
+	$SIGTERM = SIGTERM,
+	$SIGURG = SIGURG,
+	$SIGSTOP = SIGSTOP,
+	$SIGTSTP = SIGTSTP,
+	$SIGCONT = SIGCONT,
+	$SIGCHLD = SIGCHLD,
+	$SIGTTIN = SIGTTIN,
+	$SIGTTOU = SIGTTOU,
+	$SIGIO = SIGIO,
+	$SIGXCPU = SIGXCPU,
+	$SIGXFSZ = SIGXFSZ,
+	$SIGVTALRM = SIGVTALRM,
+	$SIGPROF = SIGPROF,
+	$SIGWINCH = SIGWINCH,
+	$SIGINFO = SIGINFO,
+	$SIGUSR1 = SIGUSR1,
+	$SIGUSR2 = SIGUSR2,
+	
+	$FPE_INTDIV = FPE_INTDIV,
+	$FPE_INTOVF = FPE_INTOVF,
+	$FPE_FLTDIV = FPE_FLTDIV,
+	$FPE_FLTOVF = FPE_FLTOVF,
+	$FPE_FLTUND = FPE_FLTUND,
+	$FPE_FLTRES = FPE_FLTRES,
+	$FPE_FLTINV = FPE_FLTINV,
+	$FPE_FLTSUB = FPE_FLTSUB,
+	
+	$BUS_ADRALN = BUS_ADRALN,
+	$BUS_ADRERR = BUS_ADRERR,
+	$BUS_OBJERR = BUS_OBJERR,
+	
+	$SEGV_MAPERR = SEGV_MAPERR,
+	$SEGV_ACCERR = SEGV_ACCERR,
 };
 
 typedef mach_msg_body_t	$MachBody;
diff --git a/src/pkg/runtime/darwin/os.h b/src/pkg/runtime/darwin/os.h
index 2e493aed0..24496485c 100644
--- a/src/pkg/runtime/darwin/os.h
+++ b/src/pkg/runtime/darwin/os.h
@@ -22,3 +22,4 @@ void	sigaction(uintptr, struct Sigaction*, struct Sigaction*);
 struct StackT;
 void	sigaltstack(struct StackT*, struct StackT*);
 void	sigtramp(void);
+void	sigpanic(void);
diff --git a/src/pkg/runtime/darwin/signals.h b/src/pkg/runtime/darwin/signals.h
index c93e7fbe9..ac9e5d606 100644
--- a/src/pkg/runtime/darwin/signals.h
+++ b/src/pkg/runtime/darwin/signals.h
@@ -6,8 +6,9 @@
 #define I SigIgnore
 #define R SigRestart
 #define Q SigQueue
+#define P SigPanic
 
-static SigTab sigtab[] = {
+SigTab sigtab[] = {
 	/* 0 */	0, "SIGNONE: no trap",
 	/* 1 */	Q+R, "SIGHUP: terminal line hangup",
 	/* 2 */	Q+R, "SIGINT: interrupt",
@@ -16,10 +17,10 @@ static SigTab sigtab[] = {
 	/* 5 */	C, "SIGTRAP: trace trap",	/* used by panic and array out of bounds, etc. */
 	/* 6 */	C, "SIGABRT: abort",
 	/* 7 */	C, "SIGEMT: emulate instruction executed",
-	/* 8 */	C, "SIGFPE: floating-point exception",
+	/* 8 */	C+P, "SIGFPE: floating-point exception",
 	/* 9 */	0, "SIGKILL: kill",
-	/* 10 */	C, "SIGBUS: bus error",
-	/* 11 */	C, "SIGSEGV: segmentation violation",
+	/* 10 */	C+P, "SIGBUS: bus error",
+	/* 11 */	C+P, "SIGSEGV: segmentation violation",
 	/* 12 */	C, "SIGSYS: bad system call",
 	/* 13 */	I, "SIGPIPE: write to broken pipe",
 	/* 14 */	Q+I+R, "SIGALRM: alarm clock",
@@ -45,5 +46,6 @@ static SigTab sigtab[] = {
 #undef I
 #undef R
 #undef Q
+#undef P
 
 #define	NSIG 32
diff --git a/src/pkg/runtime/darwin/thread.c b/src/pkg/runtime/darwin/thread.c
index 38e3c23fb..d9acfa8d3 100644
--- a/src/pkg/runtime/darwin/thread.c
+++ b/src/pkg/runtime/darwin/thread.c
@@ -6,6 +6,8 @@
 #include "defs.h"
 #include "os.h"
 
+extern SigTab sigtab[];
+
 static void
 unimplemented(int8 *name)
 {
@@ -443,3 +445,26 @@ mach_semrelease(uint32 sem)
 	}
 }
 
+void
+sigpanic(void)
+{
+	switch(g->sig) {
+	case SIGBUS:
+		if(g->sigcode0 == BUS_ADRERR && g->sigcode1 < 0x1000)
+			panicstring("invalid memory address or nil pointer dereference");
+		break;
+	case SIGSEGV:
+		if((g->sigcode0 == 0 || g->sigcode0 == SEGV_MAPERR) && g->sigcode1 < 0x1000)
+			panicstring("invalid memory address or nil pointer dereference");
+		break;
+	case SIGFPE:
+		switch(g->sigcode0) {
+		case FPE_INTDIV:
+			panicstring("integer divide by zero");
+		case FPE_INTOVF:
+			panicstring("integer overflow");
+		}
+		panicstring("floating point error");
+	}
+	panicstring(sigtab[g->sig].name);
+}
diff --git a/src/pkg/runtime/freebsd/386/signal.c b/src/pkg/runtime/freebsd/386/signal.c
index 3529d1a58..2483e7d90 100644
--- a/src/pkg/runtime/freebsd/386/signal.c
+++ b/src/pkg/runtime/freebsd/386/signal.c
@@ -48,7 +48,26 @@ void
 sighandler(int32 sig, Siginfo* info, void* context)
 {
 	Ucontext *uc;
-	Mcontext *mc;
+	Mcontext *r;
+
+	uc = context;
+	r = &uc->uc_mcontext;
+
+	if((gp = m->curg) != nil && (sigtab[sig].flags & SigPanic)) {
+		// Make it look like a call to the signal func.
+		// Have to pass arguments out of band since
+		// augmenting the stack frame would break
+		// the unwinding code.
+		gp->sig = sig;
+		gp->sigcode0 = info->si_code;
+		gp->sigcode1 = (uintptr)info->si_addr;
+
+		sp = (uintptr*)r->mc_esp;
+		*--sp = r->mc_eip;
+		r->mc_eip = (uintptr)sigpanic;
+		r->mc_esp = (uintptr)sp;
+		return;
+	}
 
 	if(sigtab[sig].flags & SigQueue) {
 		if(sigsend(sig) || (sigtab[sig].flags & SigIgnore))
@@ -60,22 +79,18 @@ sighandler(int32 sig, Siginfo* info, void* context)
 		exit(2);
 	panicking = 1;
 
-	uc = context;
-	mc = &uc->uc_mcontext;
-
 	if(sig < 0 || sig >= NSIG)
 		printf("Signal %d\n", sig);
 	else
 		printf("%s\n", sigtab[sig].name);
 
-	printf("Faulting address: %p\n", info->si_addr);
-	printf("PC=%X\n", mc->mc_eip);
+	printf("PC=%X\n", r->mc_eip);
 	printf("\n");
 
 	if(gotraceback()){
-		traceback((void*)mc->mc_eip, (void*)mc->mc_esp, 0, m->curg);
+		traceback((void*)r->mc_eip, (void*)r->mc_esp, 0, m->curg);
 		tracebackothers(m->curg);
-		dumpregs(mc);
+		dumpregs(r);
 	}
 
 	breakpoint();
diff --git a/src/pkg/runtime/freebsd/amd64/signal.c b/src/pkg/runtime/freebsd/amd64/signal.c
index dc0e1eb58..ea15922c6 100644
--- a/src/pkg/runtime/freebsd/amd64/signal.c
+++ b/src/pkg/runtime/freebsd/amd64/signal.c
@@ -56,7 +56,26 @@ void
 sighandler(int32 sig, Siginfo* info, void* context)
 {
 	Ucontext *uc;
-	Mcontext *mc;
+	Mcontext *r;
+
+	uc = context;
+	r = &uc->uc_mcontext;
+
+	if((gp = m->curg) != nil && (sigtab[sig].flags & SigPanic)) {
+		// Make it look like a call to the signal func.
+		// Have to pass arguments out of band since
+		// augmenting the stack frame would break
+		// the unwinding code.
+		gp->sig = sig;
+		gp->sigcode0 = info->si_code;
+		gp->sigcode1 = (uintptr)info->si_addr;
+
+		sp = (uintptr*)r->mc_rsp;
+		*--sp = r->mc_rip;
+		r->mc_rip = (uintptr)sigpanic;
+		r->mc_rsp = (uintptr)sp;
+		return;
+	}
 
 	if(sigtab[sig].flags & SigQueue) {
 		if(sigsend(sig) || (sigtab[sig].flags & SigIgnore))
@@ -68,21 +87,17 @@ sighandler(int32 sig, Siginfo* info, void* context)
 		exit(2);
 	panicking = 1;
 
-	uc = context;
-	mc = &uc->uc_mcontext;
-
 	if(sig < 0 || sig >= NSIG)
 		printf("Signal %d\n", sig);
 	else
 		printf("%s\n", sigtab[sig].name);
 
-	printf("Faulting address: %p\n", info->si_addr);
-	printf("PC=%X\n", mc->mc_rip);
+	printf("PC=%X\n", r->mc_rip);
 	printf("\n");
 
 	if(gotraceback()){
-		traceback((void*)mc->mc_rip, (void*)mc->mc_rsp, 0, (void*)mc->mc_r15);
-		tracebackothers((void*)mc->mc_r15);
+		traceback((void*)r->mc_rip, (void*)r->mc_rsp, 0, (void*)r->mc_r15);
+		tracebackothers((void*)r->mc_r15);
 		dumpregs(mc);
 	}
 
diff --git a/src/pkg/runtime/freebsd/defs.c b/src/pkg/runtime/freebsd/defs.c
index e4d0f0068..0c75e75c4 100644
--- a/src/pkg/runtime/freebsd/defs.c
+++ b/src/pkg/runtime/freebsd/defs.c
@@ -37,6 +37,54 @@ enum {
 	$UMTX_OP_WAKE = UMTX_OP_WAKE,
 
 	$EINTR = EINTR,
+	
+	$SIGHUP = SIGHUP,
+	$SIGINT = SIGINT,
+	$SIGQUIT = SIGQUIT,
+	$SIGILL = SIGILL,
+	$SIGTRAP = SIGTRAP,
+	$SIGABRT = SIGABRT,
+	$SIGEMT = SIGEMT,
+	$SIGFPE = SIGFPE,
+	$SIGKILL = SIGKILL,
+	$SIGBUS = SIGBUS,
+	$SIGSEGV = SIGSEGV,
+	$SIGSYS = SIGSYS,
+	$SIGPIPE = SIGPIPE,
+	$SIGALRM = SIGALRM,
+	$SIGTERM = SIGTERM,
+	$SIGURG = SIGURG,
+	$SIGSTOP = SIGSTOP,
+	$SIGTSTP = SIGTSTP,
+	$SIGCONT = SIGCONT,
+	$SIGCHLD = SIGCHLD,
+	$SIGTTIN = SIGTTIN,
+	$SIGTTOU = SIGTTOU,
+	$SIGIO = SIGIO,
+	$SIGXCPU = SIGXCPU,
+	$SIGXFSZ = SIGXFSZ,
+	$SIGVTALRM = SIGVTALRM,
+	$SIGPROF = SIGPROF,
+	$SIGWINCH = SIGWINCH,
+	$SIGINFO = SIGINFO,
+	$SIGUSR1 = SIGUSR1,
+	$SIGUSR2 = SIGUSR2,
+	
+	$FPE_INTDIV = FPE_INTDIV,
+	$FPE_INTOVF = FPE_INTOVF,
+	$FPE_FLTDIV = FPE_FLTDIV,
+	$FPE_FLTOVF = FPE_FLTOVF,
+	$FPE_FLTUND = FPE_FLTUND,
+	$FPE_FLTRES = FPE_FLTRES,
+	$FPE_FLTINV = FPE_FLTINV,
+	$FPE_FLTSUB = FPE_FLTSUB,
+	
+	$BUS_ADRALN = BUS_ADRALN,
+	$BUS_ADRERR = BUS_ADRERR,
+	$BUS_OBJERR = BUS_OBJERR,
+	
+	$SEGV_MAPERR = SEGV_MAPERR,
+	$SEGV_ACCERR = SEGV_ACCERR,
 };
 
 typedef struct rtprio	$Rtprio;
diff --git a/src/pkg/runtime/freebsd/signals.h b/src/pkg/runtime/freebsd/signals.h
index 93ff7eb98..0c41daf84 100644
--- a/src/pkg/runtime/freebsd/signals.h
+++ b/src/pkg/runtime/freebsd/signals.h
@@ -6,8 +6,9 @@
 #define I SigIgnore
 #define R SigRestart
 #define Q SigQueue
+#define P SigPanic
 
-static SigTab sigtab[] = {
+SigTab sigtab[] = {
 	/* 0 */		0, "SIGNONE: no trap",
 	/* 1 */		Q+R, "SIGHUP: terminal line hangup",
 	/* 2 */		Q+R, "SIGINT: interrupt",
@@ -16,10 +17,10 @@ static SigTab sigtab[] = {
 	/* 5 */		C, "SIGTRAP: trace trap",
 	/* 6 */		C, "SIGABRT: abort",
 	/* 7 */		C, "SIGEMT: EMT instruction",
-	/* 8 */		C, "SIGFPE: floating-point exception",
+	/* 8 */		C+P, "SIGFPE: floating-point exception",
 	/* 9 */		0, "SIGKILL: kill",
-	/* 10 */	C, "SIGBUS: bus error",
-	/* 11 */	C, "SIGSEGV: segmentation violation",
+	/* 10 */	C+P, "SIGBUS: bus error",
+	/* 11 */	C+P, "SIGSEGV: segmentation violation",
 	/* 12 */	C, "SIGSYS: bad system call",
 	/* 13 */	I, "SIGPIPE: write to broken pipe",
 	/* 14 */	Q+I+R, "SIGALRM: alarm clock",
@@ -46,5 +47,6 @@ static SigTab sigtab[] = {
 #undef I
 #undef R
 #undef Q
+#undef P
 
 #define	NSIG 33
diff --git a/src/pkg/runtime/freebsd/thread.c b/src/pkg/runtime/freebsd/thread.c
index 19c14c5ab..9ee21c592 100644
--- a/src/pkg/runtime/freebsd/thread.c
+++ b/src/pkg/runtime/freebsd/thread.c
@@ -6,6 +6,8 @@
 #include "signals.h"
 #include "os.h"
 
+extern SigTab sigtab[];
+
 // FreeBSD's umtx_op syscall is effectively the same as Linux's futex, and
 // thus the code is largely similar. See linux/thread.c for comments.
 
@@ -169,3 +171,27 @@ minit(void)
 	m->gsignal = malg(32*1024);
 	signalstack(m->gsignal->stackguard, 32*1024);
 }
+
+void
+sigpanic(void)
+{
+	switch(g->sig) {
+	case SIGBUS:
+		if(g->sigcode0 == BUS_ADRERR && g->sigcode1 < 0x1000)
+			panicstring("invalid memory address or nil pointer dereference");
+		break;
+	case SIGSEGV:
+		if((g->sigcode0 == 0 || g->sigcode0 == SEGV_MAPERR) && g->sigcode1 < 0x1000)
+			panicstring("invalid memory address or nil pointer dereference");
+		break;
+	case SIGFPE:
+		switch(g->sigcode0) {
+		case FPE_INTDIV:
+			panicstring("integer divide by zero");
+		case FPE_INTOVF:
+			panicstring("integer overflow");
+		}
+		panicstring("floating point error");
+	}
+	panicstring(sigtab[g->sig].name);
+}
diff --git a/src/pkg/runtime/linux/386/defs.h b/src/pkg/runtime/linux/386/defs.h
index 94bc2b5b6..ef8ef05d0 100644
--- a/src/pkg/runtime/linux/386/defs.h
+++ b/src/pkg/runtime/linux/386/defs.h
@@ -1,4 +1,4 @@
-// godefs -f -m32 -f -D_LOOSE_KERNEL_NAMES -f -D__ARCH_SI_UID_T=__kernel_uid32_t defs2.c
+// godefs -f -m32 -f -I/home/rsc/pub/linux-2.6/arch/x86/include -f -I/home/rsc/pub/linux-2.6/include -f -D_LOOSE_KERNEL_NAMES -f -D__ARCH_SI_UID_T=__kernel_uid32_t defs2.c
 
 // MACHINE GENERATED - DO NOT EDIT.
 
@@ -14,6 +14,49 @@ enum {
 	SA_ONSTACK = 0x8000000,
 	SA_RESTORER = 0x4000000,
 	SA_SIGINFO = 0x4,
+	SIGHUP = 0x1,
+	SIGINT = 0x2,
+	SIGQUIT = 0x3,
+	SIGILL = 0x4,
+	SIGTRAP = 0x5,
+	SIGABRT = 0x6,
+	SIGBUS = 0x7,
+	SIGFPE = 0x8,
+	SIGKILL = 0x9,
+	SIGUSR1 = 0xa,
+	SIGSEGV = 0xb,
+	SIGUSR2 = 0xc,
+	SIGPIPE = 0xd,
+	SIGALRM = 0xe,
+	SIGSTKFLT = 0x10,
+	SIGCHLD = 0x11,
+	SIGCONT = 0x12,
+	SIGSTOP = 0x13,
+	SIGTSTP = 0x14,
+	SIGTTIN = 0x15,
+	SIGTTOU = 0x16,
+	SIGURG = 0x17,
+	SIGXCPU = 0x18,
+	SIGXFSZ = 0x19,
+	SIGVTALRM = 0x1a,
+	SIGPROF = 0x1b,
+	SIGWINCH = 0x1c,
+	SIGIO = 0x1d,
+	SIGPWR = 0x1e,
+	SIGSYS = 0x1f,
+	FPE_INTDIV = 0x1,
+	FPE_INTOVF = 0x2,
+	FPE_FLTDIV = 0x3,
+	FPE_FLTOVF = 0x4,
+	FPE_FLTUND = 0x5,
+	FPE_FLTRES = 0x6,
+	FPE_FLTINV = 0x7,
+	FPE_FLTSUB = 0x8,
+	BUS_ADRALN = 0x1,
+	BUS_ADRERR = 0x2,
+	BUS_OBJERR = 0x3,
+	SEGV_MAPERR = 0x1,
+	SEGV_ACCERR = 0x2,
 };
 
 // Types
diff --git a/src/pkg/runtime/linux/386/signal.c b/src/pkg/runtime/linux/386/signal.c
index 87e6779b5..fed052f63 100644
--- a/src/pkg/runtime/linux/386/signal.c
+++ b/src/pkg/runtime/linux/386/signal.c
@@ -45,7 +45,28 @@ void
 sighandler(int32 sig, Siginfo* info, void* context)
 {
 	Ucontext *uc;
-	Sigcontext *sc;
+	Sigcontext *r;
+	uintptr *sp;
+	G *gp;
+
+	uc = context;
+	r = &uc->uc_mcontext;
+
+	if((gp = m->curg) != nil && (sigtab[sig].flags & SigPanic)) {
+		// Make it look like a call to the signal func.
+		// Have to pass arguments out of band since
+		// augmenting the stack frame would break
+		// the unwinding code.
+		gp->sig = sig;
+		gp->sigcode0 = info->si_code;
+		gp->sigcode1 = ((uintptr*)info)[3];
+
+		sp = (uintptr*)r->esp;
+		*--sp = r->eip;
+		r->eip = (uintptr)sigpanic;
+		r->esp = (uintptr)sp;
+		return;
+	}
 
 	if(sigtab[sig].flags & SigQueue) {
 		if(sigsend(sig) || (sigtab[sig].flags & SigIgnore))
@@ -57,22 +78,18 @@ sighandler(int32 sig, Siginfo* info, void* context)
 		exit(2);
 	panicking = 1;
 
-	uc = context;
-	sc = &uc->uc_mcontext;
-
 	if(sig < 0 || sig >= NSIG)
 		printf("Signal %d\n", sig);
 	else
 		printf("%s\n", sigtab[sig].name);
 
-	printf("Faulting address: %p\n", *(void**)info->_sifields);
-	printf("PC=%X\n", sc->eip);
+	printf("PC=%X\n", r->eip);
 	printf("\n");
 
 	if(gotraceback()){
-		traceback((void*)sc->eip, (void*)sc->esp, 0, m->curg);
+		traceback((void*)r->eip, (void*)r->esp, 0, m->curg);
 		tracebackothers(m->curg);
-		dumpregs(sc);
+		dumpregs(r);
 	}
 
 	breakpoint();
diff --git a/src/pkg/runtime/linux/amd64/defs.h b/src/pkg/runtime/linux/amd64/defs.h
index 43b047523..c08e6b25d 100644
--- a/src/pkg/runtime/linux/amd64/defs.h
+++ b/src/pkg/runtime/linux/amd64/defs.h
@@ -14,6 +14,49 @@ enum {
 	SA_ONSTACK = 0x8000000,
 	SA_RESTORER = 0x4000000,
 	SA_SIGINFO = 0x4,
+	SIGHUP = 0x1,
+	SIGINT = 0x2,
+	SIGQUIT = 0x3,
+	SIGILL = 0x4,
+	SIGTRAP = 0x5,
+	SIGABRT = 0x6,
+	SIGBUS = 0x7,
+	SIGFPE = 0x8,
+	SIGKILL = 0x9,
+	SIGUSR1 = 0xa,
+	SIGSEGV = 0xb,
+	SIGUSR2 = 0xc,
+	SIGPIPE = 0xd,
+	SIGALRM = 0xe,
+	SIGSTKFLT = 0x10,
+	SIGCHLD = 0x11,
+	SIGCONT = 0x12,
+	SIGSTOP = 0x13,
+	SIGTSTP = 0x14,
+	SIGTTIN = 0x15,
+	SIGTTOU = 0x16,
+	SIGURG = 0x17,
+	SIGXCPU = 0x18,
+	SIGXFSZ = 0x19,
+	SIGVTALRM = 0x1a,
+	SIGPROF = 0x1b,
+	SIGWINCH = 0x1c,
+	SIGIO = 0x1d,
+	SIGPWR = 0x1e,
+	SIGSYS = 0x1f,
+	FPE_INTDIV = 0x1,
+	FPE_INTOVF = 0x2,
+	FPE_FLTDIV = 0x3,
+	FPE_FLTOVF = 0x4,
+	FPE_FLTUND = 0x5,
+	FPE_FLTRES = 0x6,
+	FPE_FLTINV = 0x7,
+	FPE_FLTSUB = 0x8,
+	BUS_ADRALN = 0x1,
+	BUS_ADRERR = 0x2,
+	BUS_OBJERR = 0x3,
+	SEGV_MAPERR = 0x1,
+	SEGV_ACCERR = 0x2,
 };
 
 // Types
@@ -116,6 +159,12 @@ struct Fpstate1 {
 	uint32 padding[24];
 };
 
+typedef struct Fpreg1 Fpreg1;
+struct Fpreg1 {
+	uint16 significand[4];
+	uint16 exponent;
+};
+
 typedef struct Sigaltstack Sigaltstack;
 struct Sigaltstack {
 	void *ss_sp;
diff --git a/src/pkg/runtime/linux/amd64/signal.c b/src/pkg/runtime/linux/amd64/signal.c
index 87a5a638b..57cdea132 100644
--- a/src/pkg/runtime/linux/amd64/signal.c
+++ b/src/pkg/runtime/linux/amd64/signal.c
@@ -54,7 +54,29 @@ sighandler(int32 sig, Siginfo* info, void* context)
 {
 	Ucontext *uc;
 	Mcontext *mc;
-	Sigcontext *sc;
+	Sigcontext *r;
+	uintptr *sp;
+	G *gp;
+
+	uc = context;
+	mc = &uc->uc_mcontext;
+	r = (Sigcontext*)mc;	// same layout, more conveient names
+
+	if((gp = m->curg) != nil && (sigtab[sig].flags & SigPanic)) {
+		// Make it look like a call to the signal func.
+		// Have to pass arguments out of band since
+		// augmenting the stack frame would break
+		// the unwinding code.
+		gp->sig = sig;
+		gp->sigcode0 = info->si_code;
+		gp->sigcode1 = ((uintptr*)info)[2];
+
+		sp = (uintptr*)r->rsp;
+		*--sp = r->rip;
+		r->rip = (uintptr)sigpanic;
+		r->rsp = (uintptr)sp;
+		return;
+	}
 
 	if(sigtab[sig].flags & SigQueue) {
 		if(sigsend(sig) || (sigtab[sig].flags & SigIgnore))
@@ -66,23 +88,18 @@ sighandler(int32 sig, Siginfo* info, void* context)
 		exit(2);
 	panicking = 1;
 
-	uc = context;
-	mc = &uc->uc_mcontext;
-	sc = (Sigcontext*)mc;	// same layout, more conveient names
-
 	if(sig < 0 || sig >= NSIG)
 		printf("Signal %d\n", sig);
 	else
 		printf("%s\n", sigtab[sig].name);
 
-	printf("Faulting address: %p\n", *(void**)info->_sifields);
-	printf("PC=%X\n", sc->rip);
+	printf("PC=%X\n", r->rip);
 	printf("\n");
 
 	if(gotraceback()){
-		traceback((void*)sc->rip, (void*)sc->rsp, 0, (void*)sc->r15);
-		tracebackothers((void*)sc->r15);
-		dumpregs(sc);
+		traceback((void*)r->rip, (void*)r->rsp, 0, (void*)r->r15);
+		tracebackothers((void*)r->r15);
+		dumpregs(r);
 	}
 
 	breakpoint();
diff --git a/src/pkg/runtime/linux/arm/defs.h b/src/pkg/runtime/linux/arm/defs.h
index 215983158..b13985171 100644
--- a/src/pkg/runtime/linux/arm/defs.h
+++ b/src/pkg/runtime/linux/arm/defs.h
@@ -14,6 +14,49 @@ enum {
 	SA_ONSTACK = 0x8000000,
 	SA_RESTORER = 0x4000000,
 	SA_SIGINFO = 0x4,
+	SIGHUP = 0x1,
+	SIGINT = 0x2,
+	SIGQUIT = 0x3,
+	SIGILL = 0x4,
+	SIGTRAP = 0x5,
+	SIGABRT = 0x6,
+	SIGBUS = 0x7,
+	SIGFPE = 0x8,
+	SIGKILL = 0x9,
+	SIGUSR1 = 0xa,
+	SIGSEGV = 0xb,
+	SIGUSR2 = 0xc,
+	SIGPIPE = 0xd,
+	SIGALRM = 0xe,
+	SIGSTKFLT = 0x10,
+	SIGCHLD = 0x11,
+	SIGCONT = 0x12,
+	SIGSTOP = 0x13,
+	SIGTSTP = 0x14,
+	SIGTTIN = 0x15,
+	SIGTTOU = 0x16,
+	SIGURG = 0x17,
+	SIGXCPU = 0x18,
+	SIGXFSZ = 0x19,
+	SIGVTALRM = 0x1a,
+	SIGPROF = 0x1b,
+	SIGWINCH = 0x1c,
+	SIGIO = 0x1d,
+	SIGPWR = 0x1e,
+	SIGSYS = 0x1f,
+	FPE_INTDIV = 0x30001,
+	FPE_INTOVF = 0x30002,
+	FPE_FLTDIV = 0x30003,
+	FPE_FLTOVF = 0x30004,
+	FPE_FLTUND = 0x30005,
+	FPE_FLTRES = 0x30006,
+	FPE_FLTINV = 0x30007,
+	FPE_FLTSUB = 0x30008,
+	BUS_ADRALN = 0x30001,
+	BUS_ADRERR = 0x30002,
+	BUS_OBJERR = 0x30003,
+	SEGV_MAPERR = 0x30001,
+	SEGV_ACCERR = 0x30002,
 };
 
 // Types
diff --git a/src/pkg/runtime/linux/arm/signal.c b/src/pkg/runtime/linux/arm/signal.c
index d1d8bc08c..6cc4ac9be 100644
--- a/src/pkg/runtime/linux/arm/signal.c
+++ b/src/pkg/runtime/linux/arm/signal.c
@@ -53,7 +53,27 @@ void
 sighandler(int32 sig, Siginfo *info, void *context)
 {
 	Ucontext *uc;
-	Sigcontext *sc;
+	Sigcontext *r;
+	G *gp;
+
+	uc = context;
+	r = &uc->uc_mcontext;
+
+	if((gp = m->curg) != nil && (sigtab[sig].flags & SigPanic)) {
+		// Make it look like a call to the signal func.
+		// Have to pass arguments out of band since
+		// augmenting the stack frame would break
+		// the unwinding code.
+		gp->sig = sig;
+		gp->sigcode0 = info->si_code;
+		gp->sigcode1 = r->fault_address;
+
+		// If this is a leaf function, we do smash LR,
+		// but we're not going back there anyway.
+		r->arm_lr = r->arm_pc;
+		r->arm_pc = (uintptr)sigpanic;
+		return;
+	}
 
 	if(sigtab[sig].flags & SigQueue) {
 		if(sigsend(sig) || (sigtab[sig].flags & SigIgnore))
@@ -70,18 +90,14 @@ sighandler(int32 sig, Siginfo *info, void *context)
 	else
 		printf("%s\n", sigtab[sig].name);
 
-	uc = context;
-	sc = &uc->uc_mcontext;
-
-	printf("Faulting address: %p\n", sc->fault_address);
-	printf("PC=%x\n", sc->arm_pc);
+	printf("PC=%x\n", r->arm_pc);
 	printf("\n");
 
 	if(gotraceback()){
-		traceback((void*)sc->arm_pc, (void*)sc->arm_sp, (void*)sc->arm_lr, m->curg);
+		traceback((void*)r->arm_pc, (void*)r->arm_sp, (void*)r->arm_lr, m->curg);
 		tracebackothers(m->curg);
 		printf("\n");
-		dumpregs(sc);
+		dumpregs(r);
 	}
 
 //	breakpoint();
diff --git a/src/pkg/runtime/linux/defs.c b/src/pkg/runtime/linux/defs.c
index 35fa02953..f3bdb61fa 100644
--- a/src/pkg/runtime/linux/defs.c
+++ b/src/pkg/runtime/linux/defs.c
@@ -32,6 +32,53 @@ enum {
 	$SA_ONSTACK = SA_ONSTACK,
 	$SA_RESTORER = SA_RESTORER,
 	$SA_SIGINFO = SA_SIGINFO,
+	
+	$SIGHUP = SIGHUP,
+	$SIGINT = SIGINT,
+	$SIGQUIT = SIGQUIT,
+	$SIGILL = SIGILL,
+	$SIGTRAP = SIGTRAP,
+	$SIGABRT = SIGABRT,
+	$SIGBUS = SIGBUS,
+	$SIGFPE = SIGFPE,
+	$SIGKILL = SIGKILL,
+	$SIGUSR1 = SIGUSR1,
+	$SIGSEGV = SIGSEGV,
+	$SIGUSR2 = SIGUSR2,
+	$SIGPIPE = SIGPIPE,
+	$SIGALRM = SIGALRM,
+	$SIGSTKFLT = SIGSTKFLT,
+	$SIGCHLD = SIGCHLD,
+	$SIGCONT = SIGCONT,
+	$SIGSTOP = SIGSTOP,
+	$SIGTSTP = SIGTSTP,
+	$SIGTTIN = SIGTTIN,
+	$SIGTTOU = SIGTTOU,
+	$SIGURG = SIGURG,
+	$SIGXCPU = SIGXCPU,
+	$SIGXFSZ = SIGXFSZ,
+	$SIGVTALRM = SIGVTALRM,
+	$SIGPROF = SIGPROF,
+	$SIGWINCH = SIGWINCH,
+	$SIGIO = SIGIO,
+	$SIGPWR = SIGPWR,
+	$SIGSYS = SIGSYS,
+	
+	$FPE_INTDIV = FPE_INTDIV,
+	$FPE_INTOVF = FPE_INTOVF,
+	$FPE_FLTDIV = FPE_FLTDIV,
+	$FPE_FLTOVF = FPE_FLTOVF,
+	$FPE_FLTUND = FPE_FLTUND,
+	$FPE_FLTRES = FPE_FLTRES,
+	$FPE_FLTINV = FPE_FLTINV,
+	$FPE_FLTSUB = FPE_FLTSUB,
+	
+	$BUS_ADRALN = BUS_ADRALN,
+	$BUS_ADRERR = BUS_ADRERR,
+	$BUS_OBJERR = BUS_OBJERR,
+	
+	$SEGV_MAPERR = SEGV_MAPERR,
+	$SEGV_ACCERR = SEGV_ACCERR,
 };
 
 typedef struct timespec $Timespec;
diff --git a/src/pkg/runtime/linux/defs1.c b/src/pkg/runtime/linux/defs1.c
index 0fe3506ad..e737f8e9e 100644
--- a/src/pkg/runtime/linux/defs1.c
+++ b/src/pkg/runtime/linux/defs1.c
@@ -14,7 +14,6 @@ typedef __sigset_t $Usigset;
 typedef struct _libc_fpxreg $Fpxreg;
 typedef struct _libc_xmmreg $Xmmreg;
 typedef struct _libc_fpstate $Fpstate;
-typedef struct _libc_fpreg $Fpreg;
 typedef struct _fpxreg $Fpxreg1;
 typedef struct _xmmreg $Xmmreg1;
 typedef struct _fpstate $Fpstate1;
diff --git a/src/pkg/runtime/linux/defs2.c b/src/pkg/runtime/linux/defs2.c
index a91086aa5..4cfe4a7ed 100644
--- a/src/pkg/runtime/linux/defs2.c
+++ b/src/pkg/runtime/linux/defs2.c
@@ -4,7 +4,12 @@
 
 /*
  * Input to godefs
-	godefs -f -m32 -f -I/home/rsc/pub/linux-2.6/arch/x86/include -f -I/home/rsc/pub/linux-2.6/include defs2.c >386/defs.h
+	godefs -f -m32 \
+		-f -I/home/rsc/pub/linux-2.6/arch/x86/include \
+		-f -I/home/rsc/pub/linux-2.6/include \
+		-f -D_LOOSE_KERNEL_NAMES \
+		-f -D__ARCH_SI_UID_T=__kernel_uid32_t \
+		defs2.c >386/defs.h
 
  * The asm header tricks we have to use for Linux on amd64
  * (see defs.c and defs1.c) don't work here, so this is yet another
@@ -47,6 +52,53 @@ enum {
 	$SA_ONSTACK = SA_ONSTACK,
 	$SA_RESTORER = SA_RESTORER,
 	$SA_SIGINFO = SA_SIGINFO,
+
+	$SIGHUP = SIGHUP,
+	$SIGINT = SIGINT,
+	$SIGQUIT = SIGQUIT,
+	$SIGILL = SIGILL,
+	$SIGTRAP = SIGTRAP,
+	$SIGABRT = SIGABRT,
+	$SIGBUS = SIGBUS,
+	$SIGFPE = SIGFPE,
+	$SIGKILL = SIGKILL,
+	$SIGUSR1 = SIGUSR1,
+	$SIGSEGV = SIGSEGV,
+	$SIGUSR2 = SIGUSR2,
+	$SIGPIPE = SIGPIPE,
+	$SIGALRM = SIGALRM,
+	$SIGSTKFLT = SIGSTKFLT,
+	$SIGCHLD = SIGCHLD,
+	$SIGCONT = SIGCONT,
+	$SIGSTOP = SIGSTOP,
+	$SIGTSTP = SIGTSTP,
+	$SIGTTIN = SIGTTIN,
+	$SIGTTOU = SIGTTOU,
+	$SIGURG = SIGURG,
+	$SIGXCPU = SIGXCPU,
+	$SIGXFSZ = SIGXFSZ,
+	$SIGVTALRM = SIGVTALRM,
+	$SIGPROF = SIGPROF,
+	$SIGWINCH = SIGWINCH,
+	$SIGIO = SIGIO,
+	$SIGPWR = SIGPWR,
+	$SIGSYS = SIGSYS,
+	
+	$FPE_INTDIV = FPE_INTDIV,
+	$FPE_INTOVF = FPE_INTOVF,
+	$FPE_FLTDIV = FPE_FLTDIV,
+	$FPE_FLTOVF = FPE_FLTOVF,
+	$FPE_FLTUND = FPE_FLTUND,
+	$FPE_FLTRES = FPE_FLTRES,
+	$FPE_FLTINV = FPE_FLTINV,
+	$FPE_FLTSUB = FPE_FLTSUB,
+	
+	$BUS_ADRALN = BUS_ADRALN,
+	$BUS_ADRERR = BUS_ADRERR,
+	$BUS_OBJERR = BUS_OBJERR,
+	
+	$SEGV_MAPERR = SEGV_MAPERR,
+	$SEGV_ACCERR = SEGV_ACCERR,
 };
 
 typedef struct _fpreg $Fpreg;
diff --git a/src/pkg/runtime/linux/defs_arm.c b/src/pkg/runtime/linux/defs_arm.c
index 01d6bfcdc..2b197272c 100644
--- a/src/pkg/runtime/linux/defs_arm.c
+++ b/src/pkg/runtime/linux/defs_arm.c
@@ -35,7 +35,54 @@ enum {
 	$SA_RESTART = SA_RESTART,
 	$SA_ONSTACK = SA_ONSTACK,
 	$SA_RESTORER = SA_RESTORER,
-	$SA_SIGINFO = SA_SIGINFO
+	$SA_SIGINFO = SA_SIGINFO,
+
+	$SIGHUP = SIGHUP,
+	$SIGINT = SIGINT,
+	$SIGQUIT = SIGQUIT,
+	$SIGILL = SIGILL,
+	$SIGTRAP = SIGTRAP,
+	$SIGABRT = SIGABRT,
+	$SIGBUS = SIGBUS,
+	$SIGFPE = SIGFPE,
+	$SIGKILL = SIGKILL,
+	$SIGUSR1 = SIGUSR1,
+	$SIGSEGV = SIGSEGV,
+	$SIGUSR2 = SIGUSR2,
+	$SIGPIPE = SIGPIPE,
+	$SIGALRM = SIGALRM,
+	$SIGSTKFLT = SIGSTKFLT,
+	$SIGCHLD = SIGCHLD,
+	$SIGCONT = SIGCONT,
+	$SIGSTOP = SIGSTOP,
+	$SIGTSTP = SIGTSTP,
+	$SIGTTIN = SIGTTIN,
+	$SIGTTOU = SIGTTOU,
+	$SIGURG = SIGURG,
+	$SIGXCPU = SIGXCPU,
+	$SIGXFSZ = SIGXFSZ,
+	$SIGVTALRM = SIGVTALRM,
+	$SIGPROF = SIGPROF,
+	$SIGWINCH = SIGWINCH,
+	$SIGIO = SIGIO,
+	$SIGPWR = SIGPWR,
+	$SIGSYS = SIGSYS,
+	
+	$FPE_INTDIV = FPE_INTDIV,
+	$FPE_INTOVF = FPE_INTOVF,
+	$FPE_FLTDIV = FPE_FLTDIV,
+	$FPE_FLTOVF = FPE_FLTOVF,
+	$FPE_FLTUND = FPE_FLTUND,
+	$FPE_FLTRES = FPE_FLTRES,
+	$FPE_FLTINV = FPE_FLTINV,
+	$FPE_FLTSUB = FPE_FLTSUB,
+	
+	$BUS_ADRALN = BUS_ADRALN,
+	$BUS_ADRERR = BUS_ADRERR,
+	$BUS_OBJERR = BUS_OBJERR,
+	
+	$SEGV_MAPERR = SEGV_MAPERR,
+	$SEGV_ACCERR = SEGV_ACCERR,
 };
 
 typedef sigset_t $Sigset;
diff --git a/src/pkg/runtime/linux/os.h b/src/pkg/runtime/linux/os.h
index 387fd4321..8ca26b748 100644
--- a/src/pkg/runtime/linux/os.h
+++ b/src/pkg/runtime/linux/os.h
@@ -10,3 +10,4 @@ struct Sigaction;
 void	rt_sigaction(uintptr, struct Sigaction*, void*, uintptr);
 
 void	sigaltstack(Sigaltstack*, Sigaltstack*);
+void	sigpanic(void);
diff --git a/src/pkg/runtime/linux/signals.h b/src/pkg/runtime/linux/signals.h
index dbc87db25..788f68240 100644
--- a/src/pkg/runtime/linux/signals.h
+++ b/src/pkg/runtime/linux/signals.h
@@ -6,8 +6,9 @@
 #define I SigIgnore
 #define R SigRestart
 #define Q SigQueue
+#define P SigPanic
 
-static SigTab sigtab[] = {
+SigTab sigtab[] = {
 	/* 0 */	0, "SIGNONE: no trap",
 	/* 1 */	Q+R, "SIGHUP: terminal line hangup",
 	/* 2 */	Q+R, "SIGINT: interrupt",
@@ -15,11 +16,11 @@ static SigTab sigtab[] = {
 	/* 4 */	C, "SIGILL: illegal instruction",
 	/* 5 */	C, "SIGTRAP: trace trap",
 	/* 6 */	C, "SIGABRT: abort",
-	/* 7 */	C, "SIGBUS: bus error",
-	/* 8 */	C, "SIGFPE: floating-point exception",
+	/* 7 */	C+P, "SIGBUS: bus error",
+	/* 8 */	C+P, "SIGFPE: floating-point exception",
 	/* 9 */	0, "SIGKILL: kill",
 	/* 10 */	Q+I+R, "SIGUSR1: user-defined signal 1",
-	/* 11 */	C, "SIGSEGV: segmentation violation",
+	/* 11 */	C+P, "SIGSEGV: segmentation violation",
 	/* 12 */	Q+I+R, "SIGUSR2: user-defined signal 2",
 	/* 13 */	I, "SIGPIPE: write to broken pipe",
 	/* 14 */	Q+I+R, "SIGALRM: alarm clock",
@@ -45,5 +46,6 @@ static SigTab sigtab[] = {
 #undef I
 #undef R
 #undef Q
+#undef P
 
 #define	NSIG 32
diff --git a/src/pkg/runtime/linux/thread.c b/src/pkg/runtime/linux/thread.c
index d6811eb37..a849125f9 100644
--- a/src/pkg/runtime/linux/thread.c
+++ b/src/pkg/runtime/linux/thread.c
@@ -4,9 +4,10 @@
 
 #include "runtime.h"
 #include "defs.h"
-#include "signals.h"
 #include "os.h"
 
+extern SigTab sigtab[];
+
 // Linux futex.
 //
 //	futexsleep(uint32 *addr, uint32 val)
@@ -270,3 +271,27 @@ minit(void)
 	m->gsignal = malg(32*1024);	// OS X wants >=8K, Linux >=2K
 	signalstack(m->gsignal->stackguard, 32*1024);
 }
+
+void
+sigpanic(void)
+{
+	switch(g->sig) {
+	case SIGBUS:
+		if(g->sigcode0 == BUS_ADRERR && g->sigcode1 < 0x1000)
+			panicstring("invalid memory address or nil pointer dereference");
+		break;
+	case SIGSEGV:
+		if((g->sigcode0 == 0 || g->sigcode0 == SEGV_MAPERR) && g->sigcode1 < 0x1000)
+			panicstring("invalid memory address or nil pointer dereference");
+		break;
+	case SIGFPE:
+		switch(g->sigcode0) {
+		case FPE_INTDIV:
+			panicstring("integer divide by zero");
+		case FPE_INTOVF:
+			panicstring("integer overflow");
+		}
+		panicstring("floating point error");
+	}
+	panicstring(sigtab[g->sig].name);
+}
diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index 26ce4b635..f3297e7e0 100644
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -198,6 +198,9 @@ struct	G
 	M*	lockedm;
 	void	(*cgofn)(void*);	// for cgo/ffi
 	void	*cgoarg;
+	int32	sig;
+	uintptr	sigcode0;
+	uintptr	sigcode1;
 };
 struct	M
 {
@@ -268,6 +271,7 @@ enum
 	SigIgnore = 1<<1,
 	SigRestart = 1<<2,
 	SigQueue = 1<<3,
+	SigPanic = 1<<4,
 };
 
 // NOTE(rsc): keep in sync with extern.go:/type.Func.
diff --git a/test/recover3.go b/test/recover3.go
new file mode 100644
index 000000000..f719b0ced
--- /dev/null
+++ b/test/recover3.go
@@ -0,0 +1,78 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"runtime"
+	"strings"
+	"syscall"
+)
+
+var didbug bool
+
+func bug() {
+	if didbug {
+		return
+	}
+	println("BUG")
+	didbug = true
+}
+
+func check(name string, f func(), err string) {
+	defer func() {
+		v := recover()
+		if v == nil {
+			bug()
+			println(name, "did not panic")
+			return
+		}
+		runt, ok := v.(runtime.Error)
+		if !ok {
+			bug()
+			println(name, "panicked but not with runtime.Error")
+			return
+		}
+		s := runt.String()
+		if strings.Index(s, err) < 0 {
+			bug()
+			println(name, "panicked with", s, "not", err)
+			return
+		}
+	}()
+	
+	f()
+}
+
+func main() {
+	var x int
+	var x64 int64
+	var p *[10]int
+	var q *[10000]int
+	var i int
+
+	// not catching divide by zero on the arm.  is that even possible?
+	if syscall.ARCH != "arm" {
+		check("int-div-zero", func() { println(1/x) }, "integer divide by zero")
+		check("int64-div-zero", func() { println(1/x64) }, "integer divide by zero")
+	}
+
+	check("nil-deref", func() { println(p[0]) }, "nil pointer dereference")
+	check("nil-deref-1", func() { println(p[1]) }, "nil pointer dereference")
+	check("nil-deref-big", func() { println(q[5000]) }, "nil pointer dereference")
+
+	i = 99999
+	var sl []int
+	check("array-bounds", func() { println(p[i]) }, "index out of range")
+	check("slice-bounds", func() { println(sl[i]) }, "index out of range")
+	
+	var inter interface{}
+	inter = 1
+	check("type-concrete", func() { println(inter.(string)) }, "int, not string")
+	check("type-interface", func() { println(inter.(m)) }, "missing method m")
+}
+
+type m interface{ m() }