runtime: align stack in sigfwd for darwin/386

We might be forwarding to a C signal handler.  C code expects the stack
to be aligned.  Should fix darwin/386 build: the testcarchive tests were
hanging as the program got an endless series of SIGSEGV signals.

Change-Id: Ia02485d3736a3c40e12259f02d25f842cf8e4d29
Reviewed-on: https://go-review.googlesource.com/19025
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/runtime/sys_darwin_386.s b/src/runtime/sys_darwin_386.s
index c516ef2da81a8195be1d10d37a0f1d93c9465ab0..ad3dca444a830cf0028b07473e1cb7b80bf8eeb1 100644 (file)
--- a/src/runtime/sys_darwin_386.s
+++ b/src/runtime/sys_darwin_386.s
@@ -242,15 +242,21 @@ TEXT runtime·sigaction(SB),NOSPLIT,$0
        MOVL    $0xf1, 0xf1  // crash
        RET
 
-TEXT runtime·sigfwd(SB),NOSPLIT,$12-16
-       MOVL    sig+4(FP), AX
-       MOVL    AX, 0(SP)
-       MOVL    info+8(FP), AX
-       MOVL    AX, 4(SP)
-       MOVL    ctx+12(FP), AX
-       MOVL    AX, 8(SP)
+TEXT runtime·sigfwd(SB),NOSPLIT,$0-16
        MOVL    fn+0(FP), AX
+       MOVL    sig+4(FP), BX
+       MOVL    info+8(FP), CX
+       MOVL    ctx+12(FP), DX
+       MOVL    SP, SI
+       SUBL    $32, SP         // align stack; handler might be C code
+       ANDL    $~15, SP
+       MOVL    BX, 0(SP)
+       MOVL    CX, 4(SP)
+       MOVL    DX, 8(SP)
+       MOVL    SI, 12(SP)
        CALL    AX
+       MOVL    12(SP), AX
+       MOVL    AX, SP
        RET
 
 TEXT runtime·sigreturn(SB),NOSPLIT,$12-8