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    Subject[PATCH v4 5/5] kasan: added functions for unpoisoning stack variables
    Date
    From: Alexander Potapenko <glider@google.com>

    As a code-size optimization, LLVM builds since r279383 may
    bulk-manipulate the shadow region when (un)poisoning large memory
    blocks. This requires new callbacks that simply do an uninstrumented
    memset().

    This fixes linking the Clang-built kernel when using KASAN.

    Signed-off-by: Alexander Potapenko <glider@google.com>
    [ghackmann@google.com: fix memset() parameters, and tweak
    commit message to describe new callbacks]
    Signed-off-by: Greg Hackmann <ghackmann@google.com>
    Signed-off-by: Paul Lawrence <paullawrence@google.com>
    ---
    mm/kasan/kasan.c | 15 +++++++++++++++
    1 file changed, 15 insertions(+)

    diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
    index d96b36088b2f..8aaee42fcfab 100644
    --- a/mm/kasan/kasan.c
    +++ b/mm/kasan/kasan.c
    @@ -770,6 +770,21 @@ void __asan_allocas_unpoison(const void *stack_top, const void *stack_bottom)
    }
    EXPORT_SYMBOL(__asan_allocas_unpoison);

    +/* Emitted by the compiler to [un]poison local variables. */
    +#define DEFINE_ASAN_SET_SHADOW(byte) \
    + void __asan_set_shadow_##byte(const void *addr, size_t size) \
    + { \
    + __memset((void *)addr, 0x##byte, size); \
    + } \
    + EXPORT_SYMBOL(__asan_set_shadow_##byte)
    +
    +DEFINE_ASAN_SET_SHADOW(00);
    +DEFINE_ASAN_SET_SHADOW(f1);
    +DEFINE_ASAN_SET_SHADOW(f2);
    +DEFINE_ASAN_SET_SHADOW(f3);
    +DEFINE_ASAN_SET_SHADOW(f5);
    +DEFINE_ASAN_SET_SHADOW(f8);
    +
    #ifdef CONFIG_MEMORY_HOTPLUG
    static int __meminit kasan_mem_notifier(struct notifier_block *nb,
    unsigned long action, void *data)
    --
    2.15.0.531.g2ccb3012c9-goog
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