From: Ard Biesheuvel <ardb@kernel.org> To: linux-efi@vger.kernel.org, Ingo Molnar <mingo@kernel.org>, Thomas Gleixner <tglx@linutronix.de> Cc: Ard Biesheuvel <ardb@kernel.org>, linux-kernel@vger.kernel.org, Arvind Sankar <nivedita@alum.mit.edu>, Hans de Goede <hdegoede@redhat.com> Subject: [PATCH 3/3] x86/efistub: disable paging at mixed mode entry Date: Tue, 24 Dec 2019 14:29:09 +0100 Message-ID: <20191224132909.102540-4-ardb@kernel.org> (raw) In-Reply-To: <20191224132909.102540-1-ardb@kernel.org> 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. Cc: <stable@vger.kernel.org> Signed-off-by: Ard Biesheuvel <ardb@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 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 SYM_FUNC_END(efi32_stub_entry) #endif -- 2.20.1
next prev parent reply index Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-12-24 13:29 [GIT PULL 0/3] EFI fixes for v5.5 Ard Biesheuvel 2019-12-24 13:29 ` [PATCH 1/3] efi/earlycon: Fix write-combine mapping on x86 Ard Biesheuvel 2019-12-25 10:38 ` [tip: efi/urgent] " tip-bot2 for Arvind Sankar 2019-12-24 13:29 ` [PATCH 2/3] efi/libstub/random: Initialize pointer variables to zero for mixed mode Ard Biesheuvel 2019-12-25 10:38 ` [tip: efi/urgent] " tip-bot2 for Hans de Goede 2019-12-24 13:29 ` Ard Biesheuvel [this message] 2019-12-25 10:38 ` [tip: efi/urgent] x86/efistub: Disable paging at mixed mode entry tip-bot2 for Ard Biesheuvel 2019-12-25 9:50 ` [GIT PULL 0/3] EFI fixes for v5.5 Ingo Molnar
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