src/runtime: mark asanread and asanwrite functions as NOSPLIT

The asan runtime functions may run on stacks that cannot grow, and
they do not have large local variables, so it is safe to mark them
as NOSPLIT.

Add test case.

Fixes #50391

Change-Id: Iadcbf1ae0c837d9b64da5be208c7f424e6ba11de
Reviewed-on: https://go-review.googlesource.com/c/go/+/374398
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
Trust: Fannie Zhang <Fannie.Zhang@arm.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

misc/cgo/testsanitizers/asan_test.go

@@ -39,6 +39,7 @@ func TestASAN(t *testing.T) {
 		{src: "asan2_fail.go", memoryAccessError: "heap-buffer-overflow", errorLocation: "asan2_fail.go:31"},
 		{src: "asan3_fail.go", memoryAccessError: "use-after-poison", errorLocation: "asan3_fail.go:13"},
 		{src: "asan4_fail.go", memoryAccessError: "use-after-poison", errorLocation: "asan4_fail.go:13"},
+		{src: "asan5_fail.go", memoryAccessError: "use-after-poison", errorLocation: "asan5_fail.go:18"},
 		{src: "asan_useAfterReturn.go"},
 	}
 	for _, tc := range cases {

misc/cgo/testsanitizers/testdata/asan5_fail.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"runtime"
+	"unsafe"
+)
+
+func main() {
+	p := new([1024 * 1000]int)
+	p[0] = 10
+	r := bar(&p[1024*1000-1])
+	fmt.Printf("r value is %d", r)
+}
+
+func bar(a *int) int {
+	p := unsafe.Add(unsafe.Pointer(a), 2*unsafe.Sizeof(int(1)))
+	runtime.ASanWrite(p, 8) // BOOM
+	*((*int)(p)) = 10
+	return *((*int)(p))
+}

src/runtime/asan.go

@@ -26,12 +26,16 @@ func ASanWrite(addr unsafe.Pointer, len int) {
 // Private interface for the runtime.
 const asanenabled = true
 
+// Mark asan(read, write) as NOSPLIT, because they may run
+// on stacks that cannot grow. See issue #50391.
+//go:nosplit
 func asanread(addr unsafe.Pointer, sz uintptr) {
 	sp := getcallersp()
 	pc := getcallerpc()
 	doasanread(addr, sz, sp, pc)
 }
 
+//go:nosplit
 func asanwrite(addr unsafe.Pointer, sz uintptr) {
 	sp := getcallersp()
 	pc := getcallerpc()