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    Subject[PATCH 5.16 0238/1039] arm64: mte: DC {GVA,GZVA} shouldnt be used when DCZID_EL0.DZP == 1
    Date
    From: Reiji Watanabe <reijiw@google.com>

    [ Upstream commit 685e2564daa1493053fcd7f1dbed38b35ee2f3cb ]

    Currently, mte_set_mem_tag_range() and mte_zero_clear_page_tags() use
    DC {GVA,GZVA} unconditionally. But, they should make sure that
    DCZID_EL0.DZP, which indicates whether or not use of those instructions
    is prohibited, is zero when using those instructions.
    Use ST{G,ZG,Z2G} instead when DCZID_EL0.DZP == 1.

    Fixes: 013bb59dbb7c ("arm64: mte: handle tags zeroing at page allocation time")
    Fixes: 3d0cca0b02ac ("kasan: speed up mte_set_mem_tag_range")
    Signed-off-by: Reiji Watanabe <reijiw@google.com>
    Link: https://lore.kernel.org/r/20211206004736.1520989-3-reijiw@google.com
    Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/arm64/include/asm/mte-kasan.h | 8 +++++---
    arch/arm64/lib/mte.S | 8 +++++++-
    2 files changed, 12 insertions(+), 4 deletions(-)

    diff --git a/arch/arm64/include/asm/mte-kasan.h b/arch/arm64/include/asm/mte-kasan.h
    index 478b9bcf69ad1..e4704a403237e 100644
    --- a/arch/arm64/include/asm/mte-kasan.h
    +++ b/arch/arm64/include/asm/mte-kasan.h
    @@ -84,10 +84,12 @@ static inline void __dc_gzva(u64 p)
    static inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag,
    bool init)
    {
    - u64 curr, mask, dczid_bs, end1, end2, end3;
    + u64 curr, mask, dczid, dczid_bs, dczid_dzp, end1, end2, end3;

    /* Read DC G(Z)VA block size from the system register. */
    - dczid_bs = 4ul << (read_cpuid(DCZID_EL0) & 0xf);
    + dczid = read_cpuid(DCZID_EL0);
    + dczid_bs = 4ul << (dczid & 0xf);
    + dczid_dzp = (dczid >> 4) & 1;

    curr = (u64)__tag_set(addr, tag);
    mask = dczid_bs - 1;
    @@ -106,7 +108,7 @@ static inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag,
    */
    #define SET_MEMTAG_RANGE(stg_post, dc_gva) \
    do { \
    - if (size >= 2 * dczid_bs) { \
    + if (!dczid_dzp && size >= 2 * dczid_bs) {\
    do { \
    curr = stg_post(curr); \
    } while (curr < end1); \
    diff --git a/arch/arm64/lib/mte.S b/arch/arm64/lib/mte.S
    index e83643b3995f4..f531dcb95174a 100644
    --- a/arch/arm64/lib/mte.S
    +++ b/arch/arm64/lib/mte.S
    @@ -43,17 +43,23 @@ SYM_FUNC_END(mte_clear_page_tags)
    * x0 - address to the beginning of the page
    */
    SYM_FUNC_START(mte_zero_clear_page_tags)
    + and x0, x0, #(1 << MTE_TAG_SHIFT) - 1 // clear the tag
    mrs x1, dczid_el0
    + tbnz x1, #4, 2f // Branch if DC GZVA is prohibited
    and w1, w1, #0xf
    mov x2, #4
    lsl x1, x2, x1
    - and x0, x0, #(1 << MTE_TAG_SHIFT) - 1 // clear the tag

    1: dc gzva, x0
    add x0, x0, x1
    tst x0, #(PAGE_SIZE - 1)
    b.ne 1b
    ret
    +
    +2: stz2g x0, [x0], #(MTE_GRANULE_SIZE * 2)
    + tst x0, #(PAGE_SIZE - 1)
    + b.ne 2b
    + ret
    SYM_FUNC_END(mte_zero_clear_page_tags)

    /*
    --
    2.34.1


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