From: qmuntal Date: Tue, 18 Jul 2023 14:55:26 +0000 (+0200) Subject: runtime: ensure stack is aligned in _rt0_amd64_windows_lib X-Git-Tag: go1.22rc1~1600 X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=5fe3f0a265c90a9c0346403742c6cafeb154503b;p=gostls13.git runtime: ensure stack is aligned in _rt0_amd64_windows_lib The Windows DLL loader may call a DLL entry point, in our case _rt0_amd64_windows_lib, with a stack that is not 16-byte aligned. In theory, it shouldn't, but under some circumstances, it does (see below how to reproduce it). Having an unaligned stack can, and probably will, cause problems down the line, for example if a movaps instruction tries to store a value in an unaligned address it throws an Access Violation exception (code 0xc0000005). I managed to consistently reproduce this issue by loading a Go DLL into a C program that has the Page Heap Verification diagnostic enabled [1]. Updates #54187 (and potentially fixes) [1] https://learn.microsoft.com/en-us/windows-hardware/drivers/debugger/example-12---using-page-heap-verification-to-find-a-bug Change-Id: Id0fea7f407e024c9b8cdce10ce4802d7535e7542 Reviewed-on: https://go-review.googlesource.com/c/go/+/510755 TryBot-Result: Gopher Robot Reviewed-by: Cherry Mui Reviewed-by: Than McIntosh Run-TryBot: Quim Muntal --- diff --git a/src/runtime/rt0_windows_amd64.s b/src/runtime/rt0_windows_amd64.s index d5f0940540..bd18bdd311 100644 --- a/src/runtime/rt0_windows_amd64.s +++ b/src/runtime/rt0_windows_amd64.s @@ -16,12 +16,17 @@ TEXT _rt0_amd64_windows(SB),NOSPLIT|NOFRAME,$-8 // phase. // Leave space for four pointers on the stack as required // by the Windows amd64 calling convention. -TEXT _rt0_amd64_windows_lib(SB),NOSPLIT|NOFRAME,$0x20 +TEXT _rt0_amd64_windows_lib(SB),NOSPLIT|NOFRAME,$40 // Create a new thread to do the runtime initialization and return. + MOVQ BX, 32(SP) // callee-saved, preserved across the CALL + MOVQ SP, BX + ANDQ $~15, SP // alignment as per Windows requirement MOVQ _cgo_sys_thread_create(SB), AX MOVQ $_rt0_amd64_windows_lib_go(SB), CX MOVQ $0, DX CALL AX + MOVQ BX, SP + MOVQ 32(SP), BX RET TEXT _rt0_amd64_windows_lib_go(SB),NOSPLIT|NOFRAME,$0