runtime: print a message on bad morestack
If morestack runs on the g0 or gsignal stack, it currently performs
some abort operation that typically produces a signal (e.g., it does
an INT $3 on x86). This is useful if you're running in a debugger, but
if you're not, the runtime tries to trap this signal, which is likely
to send the program into a deeper spiral of collapse and lead to very
confusing diagnostic output.
Help out people trying to debug without a debugger by making morestack
print an informative message before blowing up.
Change-Id: I2814c64509b137bfe20a00091d8551d18c2c4749
Reviewed-on: https://go-review.googlesource.com/31133
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/src/runtime/asm_386.s b/src/runtime/asm_386.s
index 56d495a..4ef738e 100644
--- a/src/runtime/asm_386.s
+++ b/src/runtime/asm_386.s
@@ -354,13 +354,15 @@
MOVL g_m(BX), BX
MOVL m_g0(BX), SI
CMPL g(CX), SI
- JNE 2(PC)
+ JNE 3(PC)
+ CALL runtime·badmorestackg0(SB)
INT $3
// Cannot grow signal stack.
MOVL m_gsignal(BX), SI
CMPL g(CX), SI
- JNE 2(PC)
+ JNE 3(PC)
+ CALL runtime·badmorestackgsignal(SB)
INT $3
// Called from f.
diff --git a/src/runtime/asm_amd64.s b/src/runtime/asm_amd64.s
index 8d99218..34da3bd 100644
--- a/src/runtime/asm_amd64.s
+++ b/src/runtime/asm_amd64.s
@@ -331,13 +331,15 @@
MOVQ g_m(BX), BX
MOVQ m_g0(BX), SI
CMPQ g(CX), SI
- JNE 2(PC)
+ JNE 3(PC)
+ CALL runtime·badmorestackg0(SB)
INT $3
// Cannot grow signal stack (m->gsignal).
MOVQ m_gsignal(BX), SI
CMPQ g(CX), SI
- JNE 2(PC)
+ JNE 3(PC)
+ CALL runtime·badmorestackgsignal(SB)
INT $3
// Called from f.
diff --git a/src/runtime/asm_amd64p32.s b/src/runtime/asm_amd64p32.s
index 0b42c66..4e3c0cd 100644
--- a/src/runtime/asm_amd64p32.s
+++ b/src/runtime/asm_amd64p32.s
@@ -249,13 +249,15 @@
// Cannot grow scheduler stack (m->g0).
MOVL m_g0(BX), SI
CMPL g(CX), SI
- JNE 2(PC)
+ JNE 3(PC)
+ CALL runtime·badmorestackg0(SB)
MOVL 0, AX
// Cannot grow signal stack (m->gsignal).
MOVL m_gsignal(BX), SI
CMPL g(CX), SI
- JNE 2(PC)
+ JNE 3(PC)
+ CALL runtime·badmorestackgsignal(SB)
MOVL 0, AX
// Called from f.
diff --git a/src/runtime/asm_arm.s b/src/runtime/asm_arm.s
index d768060..0c7d580 100644
--- a/src/runtime/asm_arm.s
+++ b/src/runtime/asm_arm.s
@@ -281,12 +281,16 @@
MOVW g_m(g), R8
MOVW m_g0(R8), R4
CMP g, R4
- BL.EQ runtime·abort(SB)
+ BNE 3(PC)
+ BL runtime·badmorestackg0(SB)
+ B runtime·abort(SB)
// Cannot grow signal stack (m->gsignal).
MOVW m_gsignal(R8), R4
CMP g, R4
- BL.EQ runtime·abort(SB)
+ BNE 3(PC)
+ BL runtime·badmorestackgsignal(SB)
+ B runtime·abort(SB)
// Called from f.
// Set g->sched to context in f.
diff --git a/src/runtime/asm_arm64.s b/src/runtime/asm_arm64.s
index c46569f..bd2b183 100644
--- a/src/runtime/asm_arm64.s
+++ b/src/runtime/asm_arm64.s
@@ -256,13 +256,15 @@
MOVD g_m(g), R8
MOVD m_g0(R8), R4
CMP g, R4
- BNE 2(PC)
+ BNE 3(PC)
+ BL runtime·badmorestackg0(SB)
B runtime·abort(SB)
// Cannot grow signal stack (m->gsignal).
MOVD m_gsignal(R8), R4
CMP g, R4
- BNE 2(PC)
+ BNE 3(PC)
+ BL runtime·badmorestackgsignal(SB)
B runtime·abort(SB)
// Called from f.
diff --git a/src/runtime/asm_mips64x.s b/src/runtime/asm_mips64x.s
index 1381818..e295223 100644
--- a/src/runtime/asm_mips64x.s
+++ b/src/runtime/asm_mips64x.s
@@ -231,12 +231,14 @@
// Cannot grow scheduler stack (m->g0).
MOVV g_m(g), R7
MOVV m_g0(R7), R8
- BNE g, R8, 2(PC)
+ BNE g, R8, 3(PC)
+ JAL runtime·badmorestackg0(SB)
JAL runtime·abort(SB)
// Cannot grow signal stack (m->gsignal).
MOVV m_gsignal(R7), R8
- BNE g, R8, 2(PC)
+ BNE g, R8, 3(PC)
+ JAL runtime·badmorestackgsignal(SB)
JAL runtime·abort(SB)
// Called from f.
diff --git a/src/runtime/asm_ppc64x.s b/src/runtime/asm_ppc64x.s
index 8b5ea45..251dc1b 100644
--- a/src/runtime/asm_ppc64x.s
+++ b/src/runtime/asm_ppc64x.s
@@ -284,13 +284,15 @@
MOVD g_m(g), R7
MOVD m_g0(R7), R8
CMP g, R8
- BNE 2(PC)
+ BNE 3(PC)
+ BL runtime·badmorestackg0(SB)
BL runtime·abort(SB)
// Cannot grow signal stack (m->gsignal).
MOVD m_gsignal(R7), R8
CMP g, R8
- BNE 2(PC)
+ BNE 3(PC)
+ BL runtime·badmorestackgsignal(SB)
BL runtime·abort(SB)
// Called from f.
diff --git a/src/runtime/asm_s390x.s b/src/runtime/asm_s390x.s
index 70e3b5e..9ed4d91 100644
--- a/src/runtime/asm_s390x.s
+++ b/src/runtime/asm_s390x.s
@@ -279,13 +279,15 @@
// Cannot grow scheduler stack (m->g0).
MOVD g_m(g), R7
MOVD m_g0(R7), R8
- CMPBNE g, R8, 2(PC)
+ CMPBNE g, R8, 3(PC)
+ BL runtime·badmorestackg0(SB)
BL runtime·abort(SB)
// Cannot grow signal stack (m->gsignal).
MOVD m_gsignal(R7), R8
CMP g, R8
- BNE 2(PC)
+ BNE 3(PC)
+ BL runtime·badmorestackgsignal(SB)
BL runtime·abort(SB)
// Called from f.
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index cb0004d..9371359 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -381,6 +381,24 @@
panic(plainError("arg size to reflect.call more than 1GB"))
}
+var badmorestackg0Msg = "fatal: morestack on g0\n"
+
+//go:nosplit
+//go:nowritebarrierrec
+func badmorestackg0() {
+ sp := stringStructOf(&badmorestackg0Msg)
+ write(2, sp.str, int32(sp.len))
+}
+
+var badmorestackgsignalMsg = "fatal: morestack on gsignal\n"
+
+//go:nosplit
+//go:nowritebarrierrec
+func badmorestackgsignal() {
+ sp := stringStructOf(&badmorestackgsignalMsg)
+ write(2, sp.str, int32(sp.len))
+}
+
func lockedOSThread() bool {
gp := getg()
return gp.lockedm != nil && gp.m.lockedg != nil
