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. Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> Cc: Dave Young <dyoung@xxxxxxxxxx> Cc: Vivek Goyal <vgoyal@xxxxxxxxxx> Cc: Baoquan He <bhe@xxxxxxxxxx> --- arch/powerpc/Kconfig | 3 +++ arch/x86/Kconfig | 3 +++ kernel/kexec_file.c | 6 ++++++ 3 files changed, 12 insertions(+) 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 c1236b187824..f031c3efe47e 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2019,6 +2019,9 @@ 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 diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index e5bcd94c1efb..990adae52151 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -26,7 +26,11 @@ #include <linux/vmalloc.h> #include "kexec_internal.h" +#ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY static int kexec_calculate_store_digests(struct kimage *image); +#else +static int kexec_calculate_store_digests(struct kimage *image) { return 0; }; +#endif /* Architectures can provide this probe function */ int __weak arch_kexec_kernel_image_probe(struct kimage *image, void *buf, @@ -520,6 +524,7 @@ int kexec_add_buffer(struct kexec_buf *kbuf) return 0; } +#ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY /* Calculate and store the digest of segments */ static int kexec_calculate_store_digests(struct kimage *image) { @@ -1022,3 +1027,4 @@ int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name, return 0; } +#endif /* CONFIG_ARCH_HAS_KEXEC_PURGATORY */ -- 2.16.2 -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
