From mboxrd@z Thu Jan 1 00:00:00 1970 From: ard.biesheuvel@linaro.org (Ard Biesheuvel) Date: Wed, 14 Feb 2018 11:36:42 +0000 Subject: [RFC PATCH v3 0/3] arm64/kernel: get rid of GCC large model code Message-ID: <20180214113645.16793-1-ard.biesheuvel@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi all, I am resending this as an RFC, because I'd like to understand whether anyone else shares my concern, or whether I am being overly paranoid. v2 blurb: GCC's large model uses literal pools to emit cross object symbol references rather than movz/movk sequences, resulting in data items mixed in the with executable code in modules' .text segments, reducing cache utilization, but also potentially resulting in the creation of code gadgets that are exploitable under speculative execution. We are using GCC's large model for two separate reasons, both of which can be worked around rather easily: - KASLR uses it to move modules and the kernel very far apart, which is not really needed, - the Cortex-A53 erratum code uses it to avoid ADRP instruction altogether, which can be replaced by selective patching of only the ADRP instructions that are affected by the erratum Ard Biesheuvel (3): arm64/kernel: kaslr: reduce module randomization range to 4 GB arm64/kernel: don't ban ADRP to work around Cortex-A53 erratum #843419 arm64/kernel: enable A53 erratum #8434319 handling at runtime arch/arm64/Kconfig | 18 ++--- arch/arm64/Makefile | 5 -- arch/arm64/include/asm/cpucaps.h | 3 +- arch/arm64/include/asm/module.h | 2 + arch/arm64/kernel/cpu_errata.c | 26 +++++++ arch/arm64/kernel/kaslr.c | 20 +++-- arch/arm64/kernel/module-plts.c | 77 +++++++++++++++++++- arch/arm64/kernel/module.c | 40 ++++++++-- arch/arm64/kernel/reloc_test_core.c | 4 +- arch/arm64/kernel/reloc_test_syms.S | 12 ++- include/linux/sizes.h | 2 + 11 files changed, 171 insertions(+), 38 deletions(-) -- 2.11.0