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    Subject[PATCH v4 35/45] x86: kmsan: handle open-coded assembly in lib/iomem.c
    From
    KMSAN cannot intercept memory accesses within asm() statements.
    That's why we add kmsan_unpoison_memory() and kmsan_check_memory() to
    hint it how to handle memory copied from/to I/O memory.

    Signed-off-by: Alexander Potapenko <glider@google.com>
    ---
    Link: https://linux-review.googlesource.com/id/Icb16bf17269087e475debf07a7fe7d4bebc3df23
    ---
    arch/x86/lib/iomem.c | 5 +++++
    1 file changed, 5 insertions(+)

    diff --git a/arch/x86/lib/iomem.c b/arch/x86/lib/iomem.c
    index 3e2f33fc33de2..e0411a3774d49 100644
    --- a/arch/x86/lib/iomem.c
    +++ b/arch/x86/lib/iomem.c
    @@ -1,6 +1,7 @@
    #include <linux/string.h>
    #include <linux/module.h>
    #include <linux/io.h>
    +#include <linux/kmsan-checks.h>

    #define movs(type,to,from) \
    asm volatile("movs" type:"=&D" (to), "=&S" (from):"0" (to), "1" (from):"memory")
    @@ -37,6 +38,8 @@ static void string_memcpy_fromio(void *to, const volatile void __iomem *from, si
    n-=2;
    }
    rep_movs(to, (const void *)from, n);
    + /* KMSAN must treat values read from devices as initialized. */
    + kmsan_unpoison_memory(to, n);
    }

    static void string_memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
    @@ -44,6 +47,8 @@ static void string_memcpy_toio(volatile void __iomem *to, const void *from, size
    if (unlikely(!n))
    return;

    + /* Make sure uninitialized memory isn't copied to devices. */
    + kmsan_check_memory(from, n);
    /* Align any unaligned destination IO */
    if (unlikely(1 & (unsigned long)to)) {
    movs("b", to, from);
    --
    2.37.0.rc0.161.g10f37bed90-goog
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