Date: Wed, 15 Feb 2017 15:37:58 +0000 From: Ard Biesheuvel <ard.biesheuvel@...aro.org> To: linux-arm-kernel@...ts.infradead.org, mark.rutland@....com, will.deacon@....com, catalin.marinas@....com, keescook@...omium.org, labbott@...oraproject.org, james.morse@....com Cc: kernel-hardening@...ts.openwall.com, Ard Biesheuvel <ard.biesheuvel@...aro.org> Subject: [RFC PATCH 0/3] arm64: eliminate early RWX mappings This series is a proof of concept that eliminates the RWX mappings from the early kernel mapping. I realize I got carried away a bit while hacking on this, and I am not convinced this is something we should merge, but since I did the work already, I am sharing this mostly as a discussion piece. Patch #1 updates the early mapping routines to map the kernel image non-executable initially, and selectively update permissions on regions that contain executable code. Patch #2 tweaks the text offset of relocatable kernels so that the init section (which could require a RWX mapping otherwise) appears at a swapper block boundary. Patch #3 updates the image loader in the EFI stub to take the modified text offset into account. Note that this approach interferes with the ability of external debuggers to set software breakpoints, but the early mapping is not very long lived anyway. Ard Biesheuvel (3): arm64: mmu: restrict permissions of early kernel mappings arm64: boot: align __inittext with swapper block on relocatable kernels arm64: efi: use effective text offset when allocating Image arch/arm64/include/asm/kernel-pgtable.h | 3 ++ arch/arm64/kernel/efi-entry.S | 5 ++ arch/arm64/kernel/head.S | 53 +++++++++++++++++++- arch/arm64/kernel/image.h | 24 +++++++-- arch/arm64/kernel/vmlinux.lds.S | 14 +++--- drivers/firmware/efi/libstub/Makefile | 1 - drivers/firmware/efi/libstub/arm64-stub.c | 13 +++-- 7 files changed, 96 insertions(+), 17 deletions(-) -- 2.7.4
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