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    Subject[PATCH -next v4 6/7] arm64: add {get, put}_user to machine check safe
    Date
    Add {get, put}_user() to machine check safe.

    If get/put fail due to hardware memory error, only the relevant processes
    are affected, so killing the user process and isolate the user page with
    hardware memory errors is a more reasonable choice than kernel panic.

    Add new extable type EX_TYPE_UACCESS_MC_ERR_ZERO which can be used for
    uaccess that can be recovered from hardware memory errors. The difference
    from EX_TYPE_UACCESS_MC is that this type also sets additional two target
    register which save error code and value needs to be set zero.

    Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
    ---
    arch/arm64/include/asm/asm-extable.h | 14 ++++++++++++++
    arch/arm64/include/asm/uaccess.h | 4 ++--
    arch/arm64/mm/extable.c | 4 ++++
    3 files changed, 20 insertions(+), 2 deletions(-)

    diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h
    index 75b2c00e9523..80410899a9ad 100644
    --- a/arch/arm64/include/asm/asm-extable.h
    +++ b/arch/arm64/include/asm/asm-extable.h
    @@ -13,6 +13,7 @@

    /* _MC indicates that can fixup from machine check errors */
    #define EX_TYPE_UACCESS_MC 5
    +#define EX_TYPE_UACCESS_MC_ERR_ZERO 6

    #ifdef __ASSEMBLY__

    @@ -78,6 +79,15 @@
    #define EX_DATA_REG(reg, gpr) \
    "((.L__gpr_num_" #gpr ") << " __stringify(EX_DATA_REG_##reg##_SHIFT) ")"

    +#define _ASM_EXTABLE_UACCESS_MC_ERR_ZERO(insn, fixup, err, zero) \
    + __DEFINE_ASM_GPR_NUMS \
    + __ASM_EXTABLE_RAW(#insn, #fixup, \
    + __stringify(EX_TYPE_UACCESS_MC_ERR_ZERO), \
    + "(" \
    + EX_DATA_REG(ERR, err) " | " \
    + EX_DATA_REG(ZERO, zero) \
    + ")")
    +
    #define _ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, err, zero) \
    __DEFINE_ASM_GPR_NUMS \
    __ASM_EXTABLE_RAW(#insn, #fixup, \
    @@ -90,6 +100,10 @@
    #define _ASM_EXTABLE_UACCESS_ERR(insn, fixup, err) \
    _ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, err, wzr)

    +
    +#define _ASM_EXTABLE_UACCESS_MC_ERR(insn, fixup, err) \
    + _ASM_EXTABLE_UACCESS_MC_ERR_ZERO(insn, fixup, err, wzr)
    +
    #define EX_DATA_REG_DATA_SHIFT 0
    #define EX_DATA_REG_DATA GENMASK(4, 0)
    #define EX_DATA_REG_ADDR_SHIFT 5
    diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
    index e8dce0cc5eaa..e41b47df48b0 100644
    --- a/arch/arm64/include/asm/uaccess.h
    +++ b/arch/arm64/include/asm/uaccess.h
    @@ -236,7 +236,7 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
    asm volatile( \
    "1: " load " " reg "1, [%2]\n" \
    "2:\n" \
    - _ASM_EXTABLE_UACCESS_ERR_ZERO(1b, 2b, %w0, %w1) \
    + _ASM_EXTABLE_UACCESS_MC_ERR_ZERO(1b, 2b, %w0, %w1) \
    : "+r" (err), "=&r" (x) \
    : "r" (addr))

    @@ -325,7 +325,7 @@ do { \
    asm volatile( \
    "1: " store " " reg "1, [%2]\n" \
    "2:\n" \
    - _ASM_EXTABLE_UACCESS_ERR(1b, 2b, %w0) \
    + _ASM_EXTABLE_UACCESS_MC_ERR(1b, 2b, %w0) \
    : "+r" (err) \
    : "r" (x), "r" (addr))

    diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c
    index 525876c3ebf4..1023ccdb2f89 100644
    --- a/arch/arm64/mm/extable.c
    +++ b/arch/arm64/mm/extable.c
    @@ -88,6 +88,7 @@ bool fixup_exception(struct pt_regs *regs)
    case EX_TYPE_BPF:
    return ex_handler_bpf(ex, regs);
    case EX_TYPE_UACCESS_ERR_ZERO:
    + case EX_TYPE_UACCESS_MC_ERR_ZERO:
    return ex_handler_uaccess_err_zero(ex, regs);
    case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
    return ex_handler_load_unaligned_zeropad(ex, regs);
    @@ -107,6 +108,9 @@ bool fixup_exception_mc(struct pt_regs *regs)
    switch (ex->type) {
    case EX_TYPE_UACCESS_MC:
    return ex_handler_uaccess_type(ex, regs, FIXUP_TYPE_MC);
    + case EX_TYPE_UACCESS_MC_ERR_ZERO:
    + return ex_handler_uaccess_err_zero(ex, regs);
    +
    }

    return false;
    --
    2.25.1
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