2015-08-28 17:43 GMT+03:00 Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>: > On Fri, 28 Aug, at 02:09:59PM, Andrey Ryabinin wrote: >> In not-instrumented code KASAN replaces instrumented >> memset/memcpy/memmove with not-instrumented analogues >> __memset/__memcpy/__memove. >> However, on x86 the EFI stub is not linked with the kernel. >> It uses not-instrumented mem*() functions from >> arch/x86/boot/compressed/string.c >> So we don't replace them with __mem*() variants in EFI stub. >> >> On ARM64 the EFI stub is linked with the kernel, so we should >> replace mem*() functions with __mem*(), because the EFI stub >> runs before KASAN sets up early shadow. >> >> So let's move these #undef mem* into arch's asm/efi.h which is >> also included by the EFI stub. >> >> Signed-off-by: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx> >> --- >> arch/x86/include/asm/efi.h | 11 +++++++++++ >> drivers/firmware/efi/libstub/efistub.h | 4 ---- >> 2 files changed, 11 insertions(+), 4 deletions(-) >> >> diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h >> index 155162e..6862f11 100644 >> --- a/arch/x86/include/asm/efi.h >> +++ b/arch/x86/include/asm/efi.h >> @@ -25,6 +25,17 @@ >> #define EFI32_LOADER_SIGNATURE "EL32" >> #define EFI64_LOADER_SIGNATURE "EL64" >> >> +/* >> + * Sometimes we may redefine memset to __memset. >> + * The EFI stub doesn't have __memset() because it's not >> + * linked with the kernel. So we should use standard >> + * memset from arch/x86/boot/compressed/string.c >> + * The same applies to memcpy and memmove. >> + */ >> +#undef memcpy >> +#undef memset >> +#undef memmove >> + > > I think the key piece of information missing in this comment is that > it's redefined for KASAN, right? > Right. >> #ifdef CONFIG_X86_32 >> >> >> diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h >> index e334a01..6b6548f 100644 >> --- a/drivers/firmware/efi/libstub/efistub.h >> +++ b/drivers/firmware/efi/libstub/efistub.h >> @@ -5,10 +5,6 @@ >> /* error code which can't be mistaken for valid address */ >> #define EFI_ERROR (~0UL) >> >> -#undef memcpy >> -#undef memset >> -#undef memmove >> - >> void efi_char16_printk(efi_system_table_t *, efi_char16_t *); >> >> efi_status_t efi_open_volume(efi_system_table_t *sys_table_arg, void *__image, > > Does this patch have any negative consequences for arm64? Can we > safely remove these #undefs without breaking the arm64 EFI stub? > The whole point of this patch is to remove these #undefs on ARM64. Otherwise we end up calling instrumented memset, which will access to kasan shadow, before we set it up So on ARM64 we should use not-instumented __memset on ARM64, iow we need to keep #define memset __memset. > -- > Matt Fleming, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
