path: root/arch
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authorArd Biesheuvel <ardb@kernel.org>2019-12-24 14:29:09 +0100
committerIngo Molnar <mingo@kernel.org>2019-12-25 10:46:07 +0100
commit4911ee401b7ceff8f38e0ac597cbf503d71e690c (patch)
treee7aac326086466d51f3d67b74ea3f76cdf771f47 /arch
parent818c7ce724770fbcdcd43725c81f2b3535f82b76 (diff)
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>
Diffstat (limited to 'arch')
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 58a512e33d8d..ee60b81944a7 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