Tidy/update signal handling code for linux/riscv

src/runtime/signal_riscv.go

@@ -69,18 +69,8 @@ func (c *sigctxt) preparePanic(sig uint32, gp *g) {
 
 	pc := gp.sigpc
 
-	// If we don't recognize the PC as code
-	// but we do recognize the RA register as code,
-	// then assume this was a call to non-code and treat like
-	// pc == 0, to make unwinding show the context.
-	if pc != 0 && !findfunc(pc).valid() && findfunc(uintptr(c.ra())).valid() {
-		pc = 0
-	}
-
-	// Don't bother saving PC if it's zero, which is
-	// probably a call to a nil func: the RA
-	// is more useful in the stack trace.
-	if pc != 0 {
+	if shouldPushSigpanic(gp, pc, uintptr(c.ra())) {
+		// Make it look the like faulting PC called sigpanic.
 		c.set_ra(uint64(pc))
 	}
 

src/runtime/sys_linux_riscv.s

@@ -266,18 +266,18 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
 	JALR	RA, T1
 	RET
 
-// func sigtramp(ureg, note unsafe.Pointer)
-TEXT runtime·sigtramp(SB),NOSPLIT,$24
+// func sigtramp(signo, ureg, ctxt unsafe.Pointer)
+TEXT runtime·sigtramp(SB),NOSPLIT,$64
+	MOVW	A0, 8(X2)
+	MOV	A1, 16(X2)
+	MOV	A2, 24(X2)
+
 	// this might be called in external code context,
 	// where g is not set.
-	// first save R0, because runtime·load_g will clobber it
-	MOVW	A0, 8(X2)
 	MOVBU	runtime·iscgo(SB), A0
 	BEQ	A0, ZERO, 2(PC)
 	CALL	runtime·load_g(SB)
 
-	MOV	A1, 16(X2)
-	MOV	A2, 24(X2)
 	MOV	$runtime·sigtrampgo(SB), A0
 	JALR	RA, A0
 	RET