Commit 4911ee40 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Ingo Molnar

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: default avatarArd 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.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 818c7ce7
...@@ -244,6 +244,11 @@ SYM_FUNC_START(efi32_stub_entry) ...@@ -244,6 +244,11 @@ SYM_FUNC_START(efi32_stub_entry)
leal efi32_config(%ebp), %eax leal efi32_config(%ebp), %eax
movl %eax, efi_config(%ebp) movl %eax, efi_config(%ebp)
/* Disable paging */
movl %cr0, %eax
btrl $X86_CR0_PG_BIT, %eax
movl %eax, %cr0
jmp startup_32 jmp startup_32
SYM_FUNC_END(efi32_stub_entry) SYM_FUNC_END(efi32_stub_entry)
#endif #endif
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment