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Message-Id: <6aada664ff70ec913faae672bb3c16db14b36049.1668958803.git.baskov@ispras.ru>
Date: Tue, 22 Nov 2022 14:12:12 +0300
From: Evgeniy Baskov <baskov@...ras.ru>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Evgeniy Baskov <baskov@...ras.ru>, Borislav Petkov <bp@...en8.de>,
Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Alexey Khoroshilov <khoroshilov@...ras.ru>,
Peter Jones <pjones@...hat.com>,
"Limonciello, Mario" <mario.limonciello@....com>,
joeyli <jlee@...e.com>, lvc-project@...uxtesting.org,
x86@...nel.org, linux-efi@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v3 03/24] x86/boot: Set cr0 to known state in trampoline
Ensure WP bit to be set to prevent boot code from writing to
non-writable memory pages.
Tested-by: Mario Limonciello <mario.limonciello@....com>
Signed-off-by: Evgeniy Baskov <baskov@...ras.ru>
---
arch/x86/boot/compressed/head_64.S | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index d33f060900d2..2a4372b84fc8 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -684,9 +684,8 @@ SYM_CODE_START(trampoline_32bit_src)
pushl $__KERNEL_CS
pushl %eax
- /* Enable paging again. */
- movl %cr0, %eax
- btsl $X86_CR0_PG_BIT, %eax
+ /* Enable paging and set CR0 to known state (this also sets WP flag) */
+ movl $CR0_STATE, %eax
movl %eax, %cr0
lret
--
2.37.4
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