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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>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	Matthew Garrett <mjg59@google.com>
Subject: [PATCH 19/20] efi/x86: don't map the entire kernel text RW for mixed mode
Date: Fri,  3 Jan 2020 12:39:52 +0100
Message-ID: <20200103113953.9571-20-ardb@kernel.org> (raw)
In-Reply-To: <20200103113953.9571-1-ardb@kernel.org>

The mixed mode thunking routine requires a part of it to be
mapped 1:1, and for this reason, we currently map the entire
kernel .text read/write in the EFI page tables, which is bad.

In fact, the kernel_map_pages_in_pgd() invocation that installs
this mapping is entirely redundant, since all of DRAM is already
1:1 mapped read/write in the EFI page tables when we reach this
point, which means that .rodata is mapped read-write as well.

So let's remap both .text and .rodata read-only in the EFI
page tables.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/platform/efi/efi_64.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index c13fa2150976..6ec58ff60b56 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -391,11 +391,11 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
 
 	efi_scratch.phys_stack = page_to_phys(page + 1); /* stack grows down */
 
-	npages = (_etext - _text) >> PAGE_SHIFT;
+	npages = (__end_rodata_aligned - _text) >> PAGE_SHIFT;
 	text = __pa(_text);
 	pfn = text >> PAGE_SHIFT;
 
-	pf = _PAGE_RW | _PAGE_ENC;
+	pf = _PAGE_ENC;
 	if (kernel_map_pages_in_pgd(pgd, pfn, text, npages, pf)) {
 		pr_err("Failed to map kernel text 1:1\n");
 		return 1;
-- 
2.20.1


  parent reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-03 11:39 [GIT PULL 00/20] More EFI updates for v5.6 Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 01/20] efi/libstub: fix boot argument handling in mixed mode entry code Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 02/20] efi/libstub/x86: force 'hidden' visibility for extern declarations Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 03/20] efi/x86: re-disable RT services for 32-bit kernels running on 64-bit EFI Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 04/20] efi/x86: map the entire EFI vendor string before copying it Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 05/20] efi/x86: avoid redundant cast of EFI firmware service pointer Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 06/20] efi/x86: split off some old memmap handling into separate routines Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 07/20] efi/x86: split SetVirtualAddresMap() wrappers into 32 and 64 bit versions Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 08/20] efi/x86: simplify i386 efi_call_phys() firmware call wrapper Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 09/20] efi/x86: simplify 64-bit EFI " Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 10/20] efi/x86: simplify mixed mode " Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 11/20] efi/x86: drop two near identical versions of efi_runtime_init() Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 12/20] efi/x86: clean up efi_systab_init() routine for legibility Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 13/20] efi/x86: don't panic or BUG() on non-critical error conditions Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 14/20] efi/x86: remove unreachable code in kexec_enter_virtual_mode() Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 15/20] efi/x86: Check number of arguments to variadic functions Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 16/20] efi/x86: Allow translating 64-bit arguments for mixed mode calls Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 17/20] efi: Allow disabling PCI busmastering on bridges during boot Ard Biesheuvel
2020-01-03 11:39 ` [PATCH 18/20] x86/mm: fix NX bit clearing issue in kernel_map_pages_in_pgd Ard Biesheuvel
2020-01-03 11:39 ` Ard Biesheuvel [this message]
2020-01-03 11:39 ` [PATCH 20/20] efi/x86: avoid RWX mappings for all of DRAM Ard Biesheuvel
2020-01-09  9:37 ` [GIT PULL 00/20] More EFI updates for v5.6 Ard Biesheuvel
2020-01-10 18:13   ` Ingo Molnar
2020-01-13  7:29     ` Ard Biesheuvel

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