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

5 files changed, 126 insertions, 20 deletions

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);
+}