[PATCH] i386/relocator: Align stack in grub_relocator64_efi relocator

[Daniel Kiper]

Unified Extensible Firmware Interface Specification, Version 2.6,
section 2.3.4, x64 Platforms, boot services, says among others:
The stack must be 16-byte aligned. So, do it. Otherwise OS may
boot only by chance as it happens right now.

Signed-off-by: Daniel Kiper <address@hidden>
---
 grub-core/lib/i386/relocator64.S |   16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/grub-core/lib/i386/relocator64.S b/grub-core/lib/i386/relocator64.S
index 75725cf..148f38a 100644
--- a/grub-core/lib/i386/relocator64.S
+++ b/grub-core/lib/i386/relocator64.S
@@ -73,14 +73,22 @@ VARIABLE(grub_relocator64_rsp)
 
        movq    %rax, %rsp
 
+#ifdef GRUB_MACHINE_EFI
+       jmp     LOCAL(skip_efi_stack_align)
+
        /*
-        * Here is grub_relocator64_efi_start() entry point.
-        * Following code is shared between grub_relocator64_efi_start()
+        * Here is grub_relocator64_efi_start() entry point. Most of the
+        * code below is shared between grub_relocator64_efi_start()
         * and grub_relocator64_start().
         *
-        * Think twice before changing anything below!!!
+        * Think twice before changing anything there!!!
         */
 VARIABLE(grub_relocator64_efi_start)
+       /* Align the stack as UEFI spec requires. */
+       andq    $~15, %rsp
+
+LOCAL(skip_efi_stack_align):
+#endif
        /* mov imm64, %rax */
        .byte   0x48
        .byte   0xb8
@@ -128,8 +136,10 @@ LOCAL(jump_addr):
 VARIABLE(grub_relocator64_rip)
        .quad   0
 
+#ifdef GRUB_MACHINE_EFI
        /* Here grub_relocator64_efi_start() ends. Ufff... */
 VARIABLE(grub_relocator64_efi_end)
+#endif
 
 #ifndef __x86_64__
        .p2align        4
-- 
1.7.10.4