linux-kernel - [PATCH 10/28] efi/x86: Respect 32-bit ABI in efi32_pe

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Date:   Sun,  8 Mar 2020 09:08:41 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-efi@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Ard Biesheuvel <ardb@...nel.org>, linux-kernel@...r.kernel.org,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Christoph Hellwig <hch@....de>,
        David Hildenbrand <david@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Guenter Roeck <linux@...ck-us.net>,
        Heinrich Schuchardt <xypron.glpk@....de>,
        Jonathan Corbet <corbet@....net>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nikolai Merinov <n.merinov@...ngo-systems.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Vladis Dronov <vdronov@...hat.com>
Subject: [PATCH 10/28] efi/x86: Respect 32-bit ABI in efi32_pe_entry

From: Arvind Sankar <nivedita@...m.mit.edu>

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

Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
Link: https://lore.kernel.org/r/20200301230436.2246909-3-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/boot/compressed/head_64.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 86c97797bf78..25fa763f4e83 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -660,7 +660,11 @@ 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
-- 
2.17.1