From b799a09f639beeda105fe8a9ab440d80fdabd3b3 Mon Sep 17 00:00:00 2001 From: AKASHI Takahiro Date: Fri, 13 Apr 2018 15:35:45 -0700 Subject: kexec_file: make use of purgatory optional Patch series "kexec_file, x86, powerpc: refactoring for other architecutres", v2. This is a preparatory patchset for adding kexec_file support on arm64. It was originally included in a arm64 patch set[1], but Philipp is also working on their kexec_file support on s390[2] and some changes are now conflicting. So these common parts were extracted and put into a separate patch set for better integration. What's more, my original patch#4 was split into a few small chunks for easier review after Dave's comment. As such, the resulting code is basically identical with my original, and the only *visible* differences are: - renaming of _kexec_kernel_image_probe() and _kimage_file_post_load_cleanup() - change one of types of arguments at prepare_elf64_headers() Those, unfortunately, require a couple of trivial changes on the rest (#1, #6 to #13) of my arm64 kexec_file patch set[1]. Patch #1 allows making a use of purgatory optional, particularly useful for arm64. Patch #2 commonalizes arch_kexec_kernel_{image_probe, image_load, verify_sig}() and arch_kimage_file_post_load_cleanup() across architectures. Patches #3-#7 are also intended to generalize parse_elf64_headers(), along with exclude_mem_range(), to be made best re-use of. [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-February/561182.html [2] http://lkml.iu.edu//hypermail/linux/kernel/1802.1/02596.html This patch (of 7): On arm64, crash dump kernel's usable memory is protected by *unmapping* it from kernel virtual space unlike other architectures where the region is just made read-only. It is highly unlikely that the region is accidentally corrupted and this observation rationalizes that digest check code can also be dropped from purgatory. The resulting code is so simple as it doesn't require a bit ugly re-linking/relocation stuff, i.e. arch_kexec_apply_relocations_add(). Please see: http://lists.infradead.org/pipermail/linux-arm-kernel/2017-December/545428.html All that the purgatory does is to shuffle arguments and jump into a new kernel, while we still need to have some space for a hash value (purgatory_sha256_digest) which is never checked against. As such, it doesn't make sense to have trampline code between old kernel and new kernel on arm64. This patch introduces a new configuration, ARCH_HAS_KEXEC_PURGATORY, and allows related code to be compiled in only if necessary. [takahiro.akashi@linaro.org: fix trivial screwup] Link: http://lkml.kernel.org/r/20180309093346.GF25863@linaro.org Link: http://lkml.kernel.org/r/20180306102303.9063-2-takahiro.akashi@linaro.org Signed-off-by: AKASHI Takahiro Acked-by: Dave Young Tested-by: Dave Young Cc: Vivek Goyal Cc: Baoquan He Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/powerpc/Kconfig | 3 +++ arch/x86/Kconfig | 3 +++ 2 files changed, 6 insertions(+) (limited to 'arch') diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 73ce5dd07642..c32a181a7cbb 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -552,6 +552,9 @@ config KEXEC_FILE for kernel and initramfs as opposed to a list of segments as is the case for the older kexec call. +config ARCH_HAS_KEXEC_PURGATORY + def_bool KEXEC_FILE + config RELOCATABLE bool "Build a relocatable kernel" depends on PPC64 || (FLATMEM && (44x || FSL_BOOKE)) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index d234cca296db..7fe107f5990b 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2008,6 +2008,9 @@ config KEXEC_FILE for kernel and initramfs as opposed to list of segments as accepted by previous system call. +config ARCH_HAS_KEXEC_PURGATORY + def_bool KEXEC_FILE + config KEXEC_VERIFY_SIG bool "Verify kernel signature during kexec_file_load() syscall" depends on KEXEC_FILE -- cgit v1.2.3