runtime: provide room for first 4 syscall parameters in windows usleep2

Windows amd64 requires all syscall callers to provide room for first
4 parameters on stack. We do that for all our syscalls, except inside
of usleep2. In https://codereview.appspot.com/7563043#msg3 rsc says:

"We don't need the stack alignment and first 4 parameters on amd64
because it's just a system call, not an ordinary function call."

He seems to be wrong on both counts. But alignment is already fixed.
Fix parameter space now too.

Fixes #12444

Change-Id: I66a2a18d2f2c3846e3aa556cc3acc8ec6240bea0
Reviewed-on: https://go-review.googlesource.com/14282
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/runtime/sys_windows_amd64.s b/src/runtime/sys_windows_amd64.s
index ea4f3e03563a2aa2082e2808e2b56ff40ec4f0eb..b15eacbf3294978fc63a8ddda402cd06ccffa0b1 100644 (file)
--- a/src/runtime/sys_windows_amd64.s
+++ b/src/runtime/sys_windows_amd64.s
@@ -428,19 +428,21 @@ ret:
        RET
 
 // Runs on OS stack. duration (in 100ns units) is in BX.
-TEXT runtime·usleep2(SB),NOSPLIT,$16
+// The function leaves room for 4 syscall parameters
+// (as per windows amd64 calling convention).
+TEXT runtime·usleep2(SB),NOSPLIT,$48
        MOVQ    SP, AX
        ANDQ    $~15, SP        // alignment as per Windows requirement
-       MOVQ    AX, 8(SP)
+       MOVQ    AX, 40(SP)
        // Want negative 100ns units.
        NEGQ    BX
-       MOVQ    SP, R8 // ptime
+       LEAQ    32(SP), R8  // ptime
        MOVQ    BX, (R8)
        MOVQ    $-1, CX // handle
        MOVQ    $0, DX // alertable
        MOVQ    runtime·_NtWaitForSingleObject(SB), AX
        CALL    AX
-       MOVQ    8(SP), SP
+       MOVQ    40(SP), SP
        RET
 
 // func now() (sec int64, nsec int32)