lkml.org 
[lkml]   [2019]   [Dec]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip: efi/urgent] x86/efistub: Disable paging at mixed mode entry
The following commit has been merged into the efi/urgent branch of tip:

Commit-ID: 4911ee401b7ceff8f38e0ac597cbf503d71e690c
Gitweb: https://git.kernel.org/tip/4911ee401b7ceff8f38e0ac597cbf503d71e690c
Author: Ard Biesheuvel <ardb@kernel.org>
AuthorDate: Tue, 24 Dec 2019 14:29:09 +01:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 25 Dec 2019 10:46:07 +01:00

x86/efistub: Disable paging at mixed mode entry

The EFI mixed mode entry code goes through the ordinary startup_32()
routine before jumping into the kernel's EFI boot code in 64-bit
mode. The 32-bit startup code must be entered with paging disabled,
but this is not documented as a requirement for the EFI handover
protocol, and so we should disable paging explicitly when entering
the kernel from 32-bit EFI firmware.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Cc: <stable@vger.kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191224132909.102540-4-ardb@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/boot/compressed/head_64.S | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 58a512e..ee60b81 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -244,6 +244,11 @@ SYM_FUNC_START(efi32_stub_entry)
leal efi32_config(%ebp), %eax
movl %eax, efi_config(%ebp)

+ /* Disable paging */
+ movl %cr0, %eax
+ btrl $X86_CR0_PG_BIT, %eax
+ movl %eax, %cr0
+
jmp startup_32
SYM_FUNC_END(efi32_stub_entry)
#endif
\
 
 \ /
  Last update: 2019-12-25 11:41    [W:0.049 / U:3.928 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site