On Fri, Oct 09, 2015 at 01:18:09PM +0300, Andrey Ryabinin wrote: > 2015-10-09 12:48 GMT+03:00 Mark Rutland <mark.rutland@xxxxxxx>: > > On Fri, Oct 09, 2015 at 12:32:18PM +0300, Andrey Ryabinin wrote: > > [...] > > > >> I thought the EFI stub isolation patches create a copy of mem*() functions in the stub, > >> but they are just create aliases with __efistub_ prefix. > >> > >> We only need to create some more aliases for KASAN. > >> The following patch on top of the EFI stub isolation series works for me. > >> > >> > >> Signed-off-by: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx> > >> --- > >> arch/arm64/kernel/image.h | 6 ++++++ > >> 1 file changed, 6 insertions(+) > >> > >> diff --git a/arch/arm64/kernel/image.h b/arch/arm64/kernel/image.h > >> index e083af0..6eb8fee 100644 > >> --- a/arch/arm64/kernel/image.h > >> +++ b/arch/arm64/kernel/image.h > >> @@ -80,6 +80,12 @@ __efistub_strcmp = __pi_strcmp; > >> __efistub_strncmp = __pi_strncmp; > >> __efistub___flush_dcache_area = __pi___flush_dcache_area; > >> > >> +#ifdef CONFIG_KASAN > >> +__efistub___memcpy = __pi_memcpy; > >> +__efistub___memmove = __pi_memmove; > >> +__efistub___memset = __pi_memset; > >> +#endif > > > > Ard's v4 stub isolation series has these aliases [1], as the stub > > requires these aliases regardless of KASAN in order to link. > > Stub isolation series has __efistub_memcpy, not __efistub___memcpy > (two additional '_'). Ah, I see, sorry for my sloppy reading. > The thing is, KASAN provides own implementation of memcpy() which > checks memory before access. > The original 'memcpy()' becomes __memcpy(), so we could still use it. Ok. > In code that not instrumented by KASAN (like the EFI stub) we replace > KASAN's memcpy() with the original __mempcy(): > #define memcpy() __memcpy() I'm a little confused by this. Surely that doesn't override implicit calls generated by the compiler, leaving us with a mixture of calls to memcpy and __memcpy? That doesn't matter for the stub, as both __efistub_mem* and __efistub___mem* would point at __pe_mem*, but doesn't that matter for other users that shouldn't be instrumented? Is that not a problem, or do we inhibit/override that somehow? > So with CONFIG_KASAN=y the EFI stub uses __memcpy, thus we need to > create the __efistub___memcpy alias. Ok, that makes sense to me. Thanks, Mark. -- 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
