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    SubjectRe: [PATCH V2 05/10] kasan: Enable arch to hook into kasan callbacks.
    Date
    Andrey Ryabinin <ryabinin.a.a@gmail.com> writes:

    > 2015-08-26 11:26 GMT+03:00 Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>:
    >> We add enable/disable callbacks in this patch which architecture
    >> can implemement. We will use this in the later patches for architecture
    >> like ppc64, that cannot have early zero page kasan shadow region for the
    >> entire virtual address space. Such architectures also cannot use
    >> inline kasan support.
    >>
    >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    >> ---
    >> mm/kasan/kasan.c | 9 +++++++++
    >> mm/kasan/kasan.h | 15 +++++++++++++++
    >> 2 files changed, 24 insertions(+)
    >>
    >> diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
    >> index 7b28e9cdf1c7..e4d33afd0eaf 100644
    >> --- a/mm/kasan/kasan.c
    >> +++ b/mm/kasan/kasan.c
    >> @@ -43,6 +43,9 @@ static void kasan_poison_shadow(const void *address, size_t size, u8 value)
    >> {
    >> void *shadow_start, *shadow_end;
    >>
    >> + if (!kasan_enabled())
    >> + return;
    >> +
    >
    > By the time this function called we already should have shadow,
    > so it should be safe to remove this check.
    >

    I remember hitting that call before enabling kasan completely. Will
    check that again.

    >
    >> shadow_start = kasan_mem_to_shadow(address);
    >> shadow_end = kasan_mem_to_shadow(address + size);
    >>
    >> @@ -51,6 +54,9 @@ static void kasan_poison_shadow(const void *address, size_t size, u8 value)
    >>
    >> void kasan_unpoison_shadow(const void *address, size_t size)
    >> {
    >> + if (!kasan_enabled())
    >> + return;
    >> +
    >
    > Ditto.
    >
    >> kasan_poison_shadow(address, size, 0);
    >>
    >> if (size & KASAN_SHADOW_MASK) {
    >> @@ -238,6 +244,9 @@ static __always_inline void check_memory_region(unsigned long addr,
    >> {
    >> struct kasan_access_info info;
    >>
    >> + if (!kasan_enabled())
    >> + return;
    >> +
    >> if (unlikely(size == 0))
    >> return;
    >>
    >> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
    >> index a6b46cc94907..deb547d5a916 100644
    >> --- a/mm/kasan/kasan.h
    >> +++ b/mm/kasan/kasan.h
    >> @@ -68,6 +68,21 @@ static inline bool kasan_report_enabled(void)
    >> return !current->kasan_depth;
    >> }
    >>
    >> +#ifndef kasan_enabled
    >> +/*
    >> + * Some archs may want to disable kasan callbacks.
    >> + */
    >> +static inline bool kasan_enabled(void)
    >> +{
    >> + return true;
    >> +}
    >> +#define kasan_enabled kasan_enabled
    >
    > Why we need this define?


    That is to make sure that we don't endup with different definition of
    kasan_enabled due to header include errors. Once we select a
    particular definition of the overloaded function, it is always good to mark
    the function as defined, so that checks like #ifndef kasan_enabled will
    always fail.

    >
    >> +#else
    >> +#ifdef CONFIG_KASAN_INLINE
    >> +#error "Kasan inline support cannot work with KASAN arch hooks"
    >> +#endif
    >> +#endif
    >> +
    >> void kasan_report(unsigned long addr, size_t size,
    >> bool is_write, unsigned long ip);
    >>
    >> --
    >> 2.5.0
    >>

    -aneesh



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