runtime: implement stackcheck for riscv64

Author: mauri870

src/runtime/asm_riscv64.s

@@ -64,6 +64,7 @@ nocgo:
 	ADD	$16, X2
 
 	// start this M
+	CALL	runtime·stackcheck(SB)	// fault if stack check is wrong
 	CALL	runtime·mstart(SB)
 
 	WORD $0 // crash if reached
@@ -253,6 +254,17 @@ TEXT runtime·return0(SB), NOSPLIT, $0
 	MOV	$0, A0
 	RET
 
+// check that SP is in range [g->stack.lo, g->stack.hi)
+TEXT runtime·stackcheck(SB), NOSPLIT|NOFRAME, $0-0
+	MOV	(g_stack+stack_hi)(g), A0
+	BGT	A0, X2, 2(PC)
+	CALL	runtime·abort(SB)
+
+	MOV	(g_stack+stack_lo)(g), A0
+	BGT	X2, A0, 2(PC)
+	CALL	runtime·abort(SB)
+	RET
+
 // restore state from Gobuf; longjmp
 
 // func gogo(buf *gobuf)

src/runtime/sys_freebsd_riscv64.s

@@ -79,7 +79,7 @@ TEXT runtime·thr_start(SB),NOSPLIT,$0
 	// set up g
 	MOV	m_g0(A0), g
 	MOV	A0, g_m(g)
-	CALL	emptyfunc<>(SB)	 // fault if stack check is wrong
+	CALL	runtime·stackcheck(SB)	// fault if stack check is wrong
 	CALL	runtime·mstart(SB)
 
 	WORD	$0	// crash

src/runtime/sys_linux_riscv64.s

@@ -536,6 +536,7 @@ good:
 	// In child, set up new stack
 	MOV	T0, g_m(T1)
 	MOV	T1, g
+	CALL	runtime·stackcheck(SB)	// fault if stack check is wrong
 
 nog:
 	// Call fn

src/runtime/sys_openbsd_riscv64.s

@@ -50,6 +50,7 @@ TEXT runtime·mstart_stub(SB),NOSPLIT,$200
 	MOV	m_g0(X10), g
 	CALL	runtime·save_g(SB)
 
+	CALL	runtime·stackcheck(SB)	// fault if stack check is wrong
 	CALL	runtime·mstart(SB)
 
 	// Restore callee-save registers.