windows/svc: align stack in servicemain before calling syscall
I noticed that we call syscall in servicemain without aligning stack.
That is against Windows rules, so align the stack as required.
I tried running this code with specifically non-aligned stack (I aligned
stack, and then subtracted 1 from SP) on my Windows 10 to test this
change. But it makes no difference on my Windows 10 PC - I built and run
golang.org/x/sys/windows/svc/example, and it runs successfully
regardless of stack alignment. But alignment might make difference on
other computers.
Maybe fixes golang/go#40160
Change-Id: I351f7f730fba4aa6dc409a79de4ad737b4a0a7d4
Reviewed-on: https://go-review.googlesource.com/c/sys/+/246317
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/windows/svc/sys_amd64.s b/windows/svc/sys_amd64.s
index 2f7609c..3d4df0c 100644
--- a/windows/svc/sys_amd64.s
+++ b/windows/svc/sys_amd64.s
@@ -6,11 +6,15 @@
// func servicemain(argc uint32, argv **uint16)
TEXT ·servicemain(SB),7,$0
+ MOVQ SP, AX
+ ANDQ $~15, SP // alignment as per Windows requirement
+ SUBQ $48, SP // room for SP and 4 args as per Windows requirement
+ // plus one extra word to keep stack 16 bytes aligned
+ MOVQ AX, 32(SP)
+
MOVL CX, ·sArgc(SB)
MOVQ DX, ·sArgv(SB)
- SUBQ $32, SP // stack for the first 4 syscall params
-
MOVQ ·sName(SB), CX
MOVQ $·servicectlhandler(SB), DX
// BUG(pastarmovj): Figure out a way to pass in context in R8.
@@ -32,7 +36,7 @@
CALL AX
exit:
- ADDQ $32, SP
+ MOVQ 32(SP), SP
RET
// I do not know why, but this seems to be the only way to call
