From: Arvind Sankar <nivedita@alum.mit.edu>
Date: Sun, 8 Mar 2020 09:08:41 +0100
Subject: efi/x86: Respect 32-bit ABI in efi32_pe_entry()
Patch-mainline: v5.7-rc1
Git-commit: 71ff44ac6cfaa1d8d3dff6c73636f4fb97b2be10
References: jsc#SLE-16407

verify_cpu() clobbers BX and DI. In case we have to return error, we need
to preserve them to respect the 32-bit calling convention.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200301230436.2246909-3-nivedita@alum.mit.edu
Link: https://lore.kernel.org/r/20200308080859.21568-11-ardb@kernel.org
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
 arch/x86/boot/compressed/head_64.S |    4 ++++
 1 file changed, 4 insertions(+)

--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -658,7 +658,11 @@ SYM_DATA(efi_is64, .byte 1)
 SYM_FUNC_START(efi32_pe_entry)
 	pushl	%ebp
 
+	pushl	%ebx
+	pushl	%edi
 	call	verify_cpu			// check for long mode support
+	popl	%edi
+	popl	%ebx
 	testl	%eax, %eax
 	movl	$0x80000003, %eax		// EFI_UNSUPPORTED
 	jnz	3f