runtime: add crash stack support for riscv64

Change-Id: Ib89a71e20f9c6b86c97814c75cb427e9bd7075e5
Reviewed-on: https://go-review.googlesource.com/c/go/+/538735
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Joel Sing <joel@sing.id.au>

src/runtime/asm.s

@@ -15,8 +15,10 @@ TEXT ·mapinitnoop<ABIInternal>(SB),NOSPLIT,$0-0
 
 #ifndef GOARCH_amd64
 #ifndef GOARCH_arm64
+#ifndef GOARCH_riscv64
 // stub to appease shared build mode.
 TEXT ·switchToCrashStack0<ABIInternal>(SB),NOSPLIT,$0-0
 	UNDEF
 #endif
 #endif
+#endif

src/runtime/asm_riscv64.s

@@ -153,6 +153,30 @@ TEXT runtime·getcallerpc(SB),NOSPLIT|NOFRAME,$0-8
 	MOV	T0, ret+0(FP)
 	RET
 
+// func switchToCrashStack0(fn func())
+TEXT runtime·switchToCrashStack0<ABIInternal>(SB), NOSPLIT, $0-8
+	MOV	X10, CTXT			// context register
+	MOV	g_m(g), X11			// curm
+
+	// set g to gcrash
+	MOV	$runtime·gcrash(SB), g	// g = &gcrash
+	CALL	runtime·save_g(SB)	// clobbers X31
+	MOV	X11, g_m(g)			// g.m = curm
+	MOV	g, m_g0(X11)			// curm.g0 = g
+
+	// switch to crashstack
+	MOV	(g_stack+stack_hi)(g), X11
+	ADD	$(-4*8), X11
+	MOV	X11, X2
+
+	// call target function
+	MOV	0(CTXT), X10
+	JALR	X1, X10
+
+	// should never return
+	CALL	runtime·abort(SB)
+	UNDEF
+
 /*
  * support for morestack
  */
@@ -168,6 +192,13 @@ TEXT runtime·getcallerpc(SB),NOSPLIT|NOFRAME,$0-8
 
 // func morestack()
 TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
+	// Called from f.
+	// Set g->sched to context in f.
+	MOV	X2, (g_sched+gobuf_sp)(g)
+	MOV	T0, (g_sched+gobuf_pc)(g)
+	MOV	RA, (g_sched+gobuf_lr)(g)
+	MOV	CTXT, (g_sched+gobuf_ctxt)(g)
+
 	// Cannot grow scheduler stack (m->g0).
 	MOV	g_m(g), A0
 	MOV	m_g0(A0), A1
@@ -181,13 +212,6 @@ TEXT runtime·morestack(SB),NOSPLIT|NOFRAME,$0-0
 	CALL	runtime·badmorestackgsignal(SB)
 	CALL	runtime·abort(SB)
 
-	// Called from f.
-	// Set g->sched to context in f.
-	MOV	X2, (g_sched+gobuf_sp)(g)
-	MOV	T0, (g_sched+gobuf_pc)(g)
-	MOV	RA, (g_sched+gobuf_lr)(g)
-	MOV	CTXT, (g_sched+gobuf_ctxt)(g)
-
 	// Called from f.
 	// Set m->morebuf to f's caller.
 	MOV	RA, (m_morebuf+gobuf_pc)(A0)	// f's caller's PC

src/runtime/crash_test.go

@@ -804,7 +804,7 @@ func TestG0StackOverflow(t *testing.T) {
 		if n := strings.Count(string(out), "morestack on g0\n"); n != 1 {
 			t.Fatalf("%s\n(exit status %v)", out, err)
 		}
-		if runtime.GOARCH == "amd64" || runtime.GOARCH == "arm64" {
+		if runtime.CrashStackImplemented {
 			// check for a stack trace
 			want := "runtime.stackOverflow"
 			if n := strings.Count(string(out), want); n < 5 {

src/runtime/export_test.go

@@ -50,6 +50,8 @@ var MemclrNoHeapPointers = memclrNoHeapPointers
 
 var CgoCheckPointer = cgoCheckPointer
 
+const CrashStackImplemented = crashStackImplemented
+
 const TracebackInnerFrames = tracebackInnerFrames
 const TracebackOuterFrames = tracebackOuterFrames
 

src/runtime/proc.go

@@ -574,7 +574,7 @@ func switchToCrashStack(fn func()) {
 	abort()
 }
 
-const crashStackImplemented = GOARCH == "amd64" || GOARCH == "arm64"
+const crashStackImplemented = GOARCH == "amd64" || GOARCH == "arm64" || GOARCH == "riscv64"
 
 //go:noescape
 func switchToCrashStack0(func()) // in assembly