From: Keith Randall <khr@golang.org>
Date: Thu, 29 Aug 2013 22:53:34 +0000 (-0700)
Subject: runtime: jump to badmcall instead of calling it.
X-Git-Tag: go1.2rc2~382
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=32b770b2c05d69c41f0ab6719dc028cf4c79e334;p=gostls13.git

runtime: jump to badmcall instead of calling it.
This replaces the mcall frame with the badmcall frame instead of
leaving the mcall frame on the stack and adding the badmcall frame.
Because mcall is no longer on the stack, traceback will now report what
called mcall, which is what we would like to see in this situation.

R=golang-dev, cshapiro
CC=golang-dev
https://golang.org/cl/13012044
---

diff --git a/src/pkg/runtime/asm_386.s b/src/pkg/runtime/asm_386.s
index c61b75cfb2..79f2e79296 100644
--- a/src/pkg/runtime/asm_386.s
+++ b/src/pkg/runtime/asm_386.s
@@ -181,14 +181,16 @@ TEXT runtime·mcall(SB), NOSPLIT, $0-4
 	MOVL	m(CX), BX
 	MOVL	m_g0(BX), SI
 	CMPL	SI, AX	// if g == m->g0 call badmcall
-	JNE	2(PC)
-	CALL	runtime·badmcall(SB)
+	JNE	3(PC)
+	MOVL	$runtime·badmcall(SB), AX
+	JMP	AX
 	MOVL	SI, g(CX)	// g = m->g0
 	MOVL	(g_sched+gobuf_sp)(SI), SP	// sp = m->g0->sched.sp
 	PUSHL	AX
 	CALL	DI
 	POPL	AX
-	CALL	runtime·badmcall2(SB)
+	MOVL	$runtime·badmcall2(SB), AX
+	JMP	AX
 	RET
 
 /*
diff --git a/src/pkg/runtime/asm_amd64.s b/src/pkg/runtime/asm_amd64.s
index fcc75a9229..a85056c9ea 100644
--- a/src/pkg/runtime/asm_amd64.s
+++ b/src/pkg/runtime/asm_amd64.s
@@ -169,16 +169,16 @@ TEXT runtime·mcall(SB), NOSPLIT, $0-8
 	MOVQ	m_g0(BX), SI
 	CMPQ	SI, AX	// if g == m->g0 call badmcall
 	JNE	3(PC)
-	ARGSIZE(0)
-	CALL	runtime·badmcall(SB)
+	MOVQ	$runtime·badmcall(SB), AX
+	JMP	AX
 	MOVQ	SI, g(CX)	// g = m->g0
 	MOVQ	(g_sched+gobuf_sp)(SI), SP	// sp = m->g0->sched.sp
 	PUSHQ	AX
 	ARGSIZE(8)
 	CALL	DI
 	POPQ	AX
-	ARGSIZE(0)
-	CALL	runtime·badmcall2(SB)
+	MOVQ	$runtime·badmcall2(SB), AX
+	JMP	AX
 	RET
 
 /*
diff --git a/src/pkg/runtime/asm_arm.s b/src/pkg/runtime/asm_arm.s
index 0d12b6a0d8..b66f80e2c6 100644
--- a/src/pkg/runtime/asm_arm.s
+++ b/src/pkg/runtime/asm_arm.s
@@ -157,12 +157,13 @@ TEXT runtime·mcall(SB), NOSPLIT, $-4-4
 	MOVW	g, R1
 	MOVW	m_g0(m), g
 	CMP	g, R1
-	BL.EQ	runtime·badmcall(SB)
+	B.NE	2(PC)
+	B	runtime·badmcall(SB)
 	MOVW	(g_sched+gobuf_sp)(g), SP
 	SUB	$8, SP
 	MOVW	R1, 4(SP)
 	BL	(R0)
-	BL	runtime·badmcall2(SB)
+	B	runtime·badmcall2(SB)
 	RET
 
 /*
diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index dab62ad69b..d37014f3a5 100644
--- a/src/pkg/runtime/proc.c
+++ b/src/pkg/runtime/proc.c
@@ -1997,14 +1997,16 @@ runtime·mcount(void)
 }
 
 void
-runtime·badmcall(void)  // called from assembly
+runtime·badmcall(void (*fn)(G*))  // called from assembly
 {
+	USED(fn); // TODO: print fn?
 	runtime·throw("runtime: mcall called on m->g0 stack");
 }
 
 void
-runtime·badmcall2(void)  // called from assembly
+runtime·badmcall2(void (*fn)(G*))  // called from assembly
 {
+	USED(fn);
 	runtime·throw("runtime: mcall function returned");
 }