On 02/27/18 at 01:48pm, AKASHI Takahiro wrote: > 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 > For this one, I think purgatory digest verification is still good to have, but I do not insist since this is arch specific. If nobody else objects then I think I can ack the series after some testing passed. Thanks Dave -- 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
