[x86/Linux] Port gmsasm.asm (#8456)

src/vm/CMakeLists.txt

@@ -375,6 +375,10 @@ else(WIN32)
  ${ARCH_SOURCES_DIR}/umthunkstub.S
  ${ARCH_SOURCES_DIR}/virtualcallstubamd64.S
  )
+ elseif(CLR_CMAKE_TARGET_ARCH_I386)
+ set(VM_SOURCES_WKS_ARCH_ASM
+ ${ARCH_SOURCES_DIR}/gmsasm.S
+ )
  elseif(CLR_CMAKE_TARGET_ARCH_ARM)
  set(VM_SOURCES_WKS_ARCH_ASM
  ${ARCH_SOURCES_DIR}/asmhelpers.S

src/vm/i386/gmsasm.S

@@ -0,0 +1,28 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+.intel_syntax noprefix
+#include "unixasmmacros.inc"
+#include "asmconstants.h"
+
+// int __fastcall LazyMachStateCaptureState(struct LazyMachState *pState);
+LEAF_ENTRY LazyMachStateCaptureState, _TEXT
+ // marks that this is not yet valid
+ mov dword ptr [ecx+MachState__pRetAddr], 0
+
+ // remember register values
+ mov [ecx+MachState__edi], edi
+ mov [ecx+MachState__esi], esi
+ mov [ecx+MachState__ebx], ebx
+ mov [ecx+LazyMachState_captureEbp], ebp
+ mov [ecx+LazyMachState_captureEsp], esp
+
+ // capture return address
+ mov eax, [esp]
+ mov dword ptr [ecx+LazyMachState_captureEip], eax
+
+ // return 0
+ xor eax, eax
+ ret
+LEAF_END LazyMachStateCaptureState, _TEXT