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    Subject[PATCH v3 09/17] khwasan, arm64: enable top byte ignore for the kernel
    Date
    KHWASAN uses the Top Byte Ignore feature of arm64 CPUs to store a pointer
    tag in the top byte of each pointer. This commit enables the TCR_TBI1 bit,
    which enables Top Byte Ignore for the kernel, when KHWASAN is used.

    Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
    ---
    arch/arm64/include/asm/pgtable-hwdef.h | 1 +
    arch/arm64/mm/proc.S | 8 +++++++-
    2 files changed, 8 insertions(+), 1 deletion(-)

    diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
    index fd208eac9f2a..483aceedad76 100644
    --- a/arch/arm64/include/asm/pgtable-hwdef.h
    +++ b/arch/arm64/include/asm/pgtable-hwdef.h
    @@ -289,6 +289,7 @@
    #define TCR_A1 (UL(1) << 22)
    #define TCR_ASID16 (UL(1) << 36)
    #define TCR_TBI0 (UL(1) << 37)
    +#define TCR_TBI1 (UL(1) << 38)
    #define TCR_HA (UL(1) << 39)
    #define TCR_HD (UL(1) << 40)
    #define TCR_NFD1 (UL(1) << 54)
    diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
    index 5f9a73a4452c..f3dfcd74a285 100644
    --- a/arch/arm64/mm/proc.S
    +++ b/arch/arm64/mm/proc.S
    @@ -47,6 +47,12 @@
    /* PTWs cacheable, inner/outer WBWA */
    #define TCR_CACHE_FLAGS TCR_IRGN_WBWA | TCR_ORGN_WBWA

    +#ifdef CONFIG_KASAN_HW
    +#define TCR_KASAN_FLAGS TCR_TBI1
    +#else
    +#define TCR_KASAN_FLAGS 0
    +#endif
    +
    #define MAIR(attr, mt) ((attr) << ((mt) * 8))

    /*
    @@ -439,7 +445,7 @@ ENTRY(__cpu_setup)
    */
    ldr x10, =TCR_TxSZ(VA_BITS) | TCR_CACHE_FLAGS | TCR_SMP_FLAGS | \
    TCR_TG_FLAGS | TCR_KASLR_FLAGS | TCR_ASID16 | \
    - TCR_TBI0 | TCR_A1
    + TCR_TBI0 | TCR_A1 | TCR_KASAN_FLAGS
    tcr_set_idmap_t0sz x10, x9

    /*
    --
    2.18.0.rc1.244.gcf134e6275-goog
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