Messages in this thread Patch in this message | | | Subject | Re: [PATCH v14 2/4] kasan: allow architectures to provide an outline readiness check | From | Christophe Leroy <> | Date | Thu, 17 Jun 2021 08:59:30 +0200 |
| |
Le 17/06/2021 à 08:39, Daniel Axtens a écrit : > Allow architectures to define a kasan_arch_is_ready() hook that bails > out of any function that's about to touch the shadow unless the arch > says that it is ready for the memory to be accessed. This is fairly > uninvasive and should have a negligible performance penalty. > > This will only work in outline mode, so an arch must specify > ARCH_DISABLE_KASAN_INLINE if it requires this. > > Cc: Balbir Singh <bsingharora@gmail.com> > Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> > Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu> > Signed-off-by: Daniel Axtens <dja@axtens.net> > > -- > > Both previous RFCs for ppc64 - by 2 different people - have > needed this trick! See: > - https://lore.kernel.org/patchwork/patch/592820/ # ppc64 hash series > - https://patchwork.ozlabs.org/patch/795211/ # ppc radix series > > I haven't been able to exercise the arch hook error for !GENERIC as I > don't have a particularly modern aarch64 toolchain or a lot of experience > cross-compiling with clang. But it does fire for GENERIC + INLINE on x86. > --- > mm/kasan/common.c | 4 ++++ > mm/kasan/generic.c | 3 +++ > mm/kasan/kasan.h | 8 ++++++++ > mm/kasan/shadow.c | 8 ++++++++ > 4 files changed, 23 insertions(+) > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 8f450bc28045..b18abaf8c78e 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -449,6 +449,14 @@ static inline void kasan_poison_last_granule(const void *address, size_t size) { > > #endif /* CONFIG_KASAN_GENERIC */ > > +#ifndef kasan_arch_is_ready > +static inline bool kasan_arch_is_ready(void) { return true; } > +#else > +#if !defined(CONFIG_KASAN_GENERIC) || !defined(CONFIG_KASAN_OUTLINE) > +#error kasan_arch_is_ready only works in KASAN generic outline mode! > +#endif > +#endif
Would be cleaner and more readable as
+#ifndef kasan_arch_is_ready +static inline bool kasan_arch_is_ready(void) { return true; } +#elif !defined(CONFIG_KASAN_GENERIC) || !defined(CONFIG_KASAN_OUTLINE) +#error kasan_arch_is_ready only works in KASAN generic outline mode! +#endif
> + > /* > * Exported functions for interfaces called from assembly or from generated > * code. Declarations here to avoid warning about missing declarations. > diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c > index 082ee5b6d9a1..3c7f7efe6f68 100644 > --- a/mm/kasan/shadow.c > +++ b/mm/kasan/shadow.c > @@ -73,6 +73,10 @@ void kasan_poison(const void *addr, size_t size, u8 value, bool init) > { > void *shadow_start, *shadow_end; > > + /* Don't touch the shadow memory if arch isn't ready */ > + if (!kasan_arch_is_ready()) > + return; > + > /* > * Perform shadow offset calculation based on untagged address, as > * some of the callers (e.g. kasan_poison_object_data) pass tagged > @@ -99,6 +103,10 @@ EXPORT_SYMBOL(kasan_poison); > #ifdef CONFIG_KASAN_GENERIC > void kasan_poison_last_granule(const void *addr, size_t size) > { > + /* Don't touch the shadow memory if arch isn't ready */ > + if (!kasan_arch_is_ready()) > + return; > + > if (size & KASAN_GRANULE_MASK) { > u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size); > *shadow = size & KASAN_GRANULE_MASK; >
| |