Christophe Leroy <christophe.le...@c-s.fr> writes: > Le 23/05/2019 à 07:21, Daniel Axtens a écrit : >> Not all arches have a specific space carved out for modules - >> some, such as powerpc, just use regular vmalloc space. Therefore, >> globals in these modules cannot be backed by real shadow memory. > > Can you explain in more details the reason why ?
At this point, purely simplicity. As you discuss below, it's possible to do better. > > PPC32 also uses regular vmalloc space, and it has been possible to > manage globals on it, by simply implementing a module_alloc() function. > > See > https://elixir.bootlin.com/linux/v5.2-rc1/source/arch/powerpc/mm/kasan/kasan_init_32.c#L135 > > It is also possible to easily define a different area for modules, by > replacing the call to vmalloc_exec() by a call to __vmalloc_node_range() > as done by vmalloc_exec(), but with different bounds than > VMALLOC_START/VMALLOC_END > > See https://elixir.bootlin.com/linux/v5.2-rc1/source/mm/vmalloc.c#L2633 > > Today in PPC64 (unlike PPC32), there is already a split between VMALLOC > space and IOREMAP space. I'm sure it would be easy to split it once more > for modules. > OK, good to know, I'll look into one of those approaches for the next spin! Regards, Daniel > Christophe > >> >> In order to allow arches to perform this check, add a hook. >> >> Signed-off-by: Daniel Axtens <d...@axtens.net> >> --- >> include/linux/kasan.h | 5 +++++ >> mm/kasan/generic.c | 3 +++ >> 2 files changed, 8 insertions(+) >> >> diff --git a/include/linux/kasan.h b/include/linux/kasan.h >> index dfee2b42d799..4752749e4797 100644 >> --- a/include/linux/kasan.h >> +++ b/include/linux/kasan.h >> @@ -18,6 +18,11 @@ struct task_struct; >> static inline bool kasan_arch_is_ready(void) { return true; } >> #endif >> >> +#ifndef kasan_arch_can_register_global >> +static inline bool kasan_arch_can_register_global(const void * addr) >> { return true; } >> +#endif >> + >> + >> #ifndef ARCH_HAS_KASAN_EARLY_SHADOW >> extern unsigned char kasan_early_shadow_page[PAGE_SIZE]; >> extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE]; >> diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c >> index 0336f31bbae3..935b06f659a0 100644 >> --- a/mm/kasan/generic.c >> +++ b/mm/kasan/generic.c >> @@ -208,6 +208,9 @@ static void register_global(struct kasan_global *global) >> { >> size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE); >> >> + if (!kasan_arch_can_register_global(global->beg)) >> + return; >> + >> kasan_unpoison_shadow(global->beg, global->size); >> >> kasan_poison_shadow(global->beg + aligned_size, >>
