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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>,
	linux-kernel@vger.kernel.org,
	Anshuman Khandual <anshuman.khandual@arm.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Dan Williams <dan.j.williams@intel.com>,
	Dave Young <dyoung@redhat.com>,
	Saravana Kannan <saravanak@google.com>
Subject: [PATCH 05/13] efi/x86: don't map the entire kernel text RW for mixed mode
Date: Mon, 13 Jan 2020 18:22:37 +0100
Message-ID: <20200113172245.27925-6-ardb@kernel.org> (raw)
In-Reply-To: <20200113172245.27925-1-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: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-13 17:22 [GIT PULL 00/13] More EFI updates for v5.6 Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 01/13] efi/libstub/x86: use const attribute for efi_is_64bit() Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 02/13] efi/libstub/x86: use mandatory 16-byte stack alignment in mixed mode Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 03/13] efi/libstub/x86: fix unused-variable warning Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 04/13] x86/mm: fix NX bit clearing issue in kernel_map_pages_in_pgd Ard Biesheuvel
2020-01-13 17:22 ` Ard Biesheuvel [this message]
2020-01-13 17:22 ` [PATCH 06/13] efi/x86: avoid RWX mappings for all of DRAM Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 07/13] efi/x86: limit EFI old memory map to SGI UV machines Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 08/13] efi/arm: defer probe of PCIe backed efifb on DT systems Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 09/13] efi: Fix comment for efi_mem_type() wrt absent physical addresses Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 10/13] efi: Add a flags parameter to efi_memory_map Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 11/13] efi: Add tracking for dynamically allocated memmaps Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 12/13] efi: Fix efi_memmap_alloc() leaks Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 13/13] efi: Fix handling of multiple efi_fake_mem= entries Ard Biesheuvel

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