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Message-Id: <a155c20eec6343d34b3bdf40c024ce8b35a90e02.1662459668.git.baskov@ispras.ru> Date: Tue, 6 Sep 2022 13:41:07 +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>, lvc-project@...uxtesting.org, x86@...nel.org, linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: [PATCH 03/16] 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. 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..5273367283b7 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -619,9 +619,8 @@ SYM_CODE_START(trampoline_32bit_src) /* Set up new stack */ leal TRAMPOLINE_32BIT_STACK_END(%ecx), %esp - /* Disable paging */ - movl %cr0, %eax - btrl $X86_CR0_PG_BIT, %eax + /* Disable paging and setup CR0 */ + movl $(CR0_STATE & ~X86_CR0_PG), %eax movl %eax, %cr0 /* Check what paging mode we want to be in after the trampoline */ -- 2.35.1
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