From: lgao4 <lgao4@6f19259b-4bc3-4df7-8a09-765794883524>
Date: Fri, 10 Nov 2006 09:01:25 +0000 (+0000)
Subject: Fix to pre-allocate 32bytes in stack to Load X64 Image.
X-Git-Tag: edk2-stable201903~23948
X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=commitdiff_plain;h=9723bdde15bfa46251c7a5440b034e80f11d192f

Fix to pre-allocate 32bytes in stack to Load X64 Image.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@1929 6f19259b-4bc3-4df7-8a09-765794883524
---

diff --git a/EdkModulePkg/Core/DxeIplX64Peim/DxeLoadX64.c b/EdkModulePkg/Core/DxeIplX64Peim/DxeLoadX64.c
index d011858cb9..7b293ef0c2 100644
--- a/EdkModulePkg/Core/DxeIplX64Peim/DxeLoadX64.c
+++ b/EdkModulePkg/Core/DxeIplX64Peim/DxeLoadX64.c
@@ -260,10 +260,14 @@ Returns:
 
   //
   // Compute the top of the stack we were allocated. Pre-allocate a 32 bytes
-  // for safety (PpisNeededByDxe and DxeCore).
+  // for x64 calling convention.
   //
-  TopOfStack = BaseOfStack + EFI_SIZE_TO_PAGES (STACK_SIZE) * EFI_PAGE_SIZE - CPU_STACK_ALIGNMENT;
-  TopOfStack = (EFI_PHYSICAL_ADDRESS) ALIGN_POINTER (TopOfStack, CPU_STACK_ALIGNMENT);
+  // The first four parameters to a function are passed in rcx, rdx, r8 and r9. 
+  // Any further parameters are pushed on the stack. Furthermore, space (4 * 8bytes) for the 
+  // register parameters is reserved on the stack, in case the called function 
+  // wants to spill them; this is important if the function is variadic. 
+  //
+  TopOfStack = BaseOfStack + EFI_SIZE_TO_PAGES (STACK_SIZE) * EFI_PAGE_SIZE - 32;
 
   //
   // Add architecture-specifc HOBs (including the BspStore HOB)