On Wed, Apr 06, 2022 at 09:13:09AM +0000, Tong Tiangen wrote:
> Add scenarios get_user to machine check safe. The processing of
> EX_TYPE_UACCESS_ERR_ZERO and EX_TYPE_UACCESS_ERR_ZERO_UCE_RECOVERY is same
> and both return -EFAULT.
Which uaccess cases do we expect to *not* be recoverable?
Naively I would assume that if we're going to treat a memory error on a uaccess
as fatal to userspace we should be able to do that for *any* uacesses.
The commit message should explain why we need the distinction between a
recoverable uaccess and a non-recoverable uaccess.
Thanks,
Mark.
>
> Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
> ---
> arch/arm64/include/asm/asm-extable.h | 14 +++++++++++++-
> arch/arm64/include/asm/uaccess.h | 2 +-
> arch/arm64/mm/extable.c | 1 +
> 3 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h
> index 74d1db74fd86..bfc2d224cbae 100644
> --- a/arch/arm64/include/asm/asm-extable.h
> +++ b/arch/arm64/include/asm/asm-extable.h
> @@ -10,8 +10,11 @@
>
> /* _MC indicates that can fixup from machine check errors */
> #define EX_TYPE_FIXUP_MC 5
> +#define EX_TYPE_UACCESS_ERR_ZERO_MC 6
>
> -#define IS_EX_TYPE_MC(type) (type == EX_TYPE_FIXUP_MC)
> +#define IS_EX_TYPE_MC(type) \
> + (type == EX_TYPE_FIXUP_MC || \
> + type == EX_TYPE_UACCESS_ERR_ZERO_MC)
>
> #ifdef __ASSEMBLY__
>
> @@ -77,6 +80,15 @@
> #define EX_DATA_REG(reg, gpr) \
> "((.L__gpr_num_" #gpr ") << " __stringify(EX_DATA_REG_##reg##_SHIFT) ")"
>
> +#define _ASM_EXTABLE_UACCESS_ERR_ZERO_MC(insn, fixup, err, zero) \
> + __DEFINE_ASM_GPR_NUMS \
> + __ASM_EXTABLE_RAW(#insn, #fixup, \
> + __stringify(EX_TYPE_UACCESS_ERR_ZERO_MC), \
> + "(" \
> + 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, \
> diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
> index e8dce0cc5eaa..24b662407fbd 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_ERR_ZERO_MC(1b, 2b, %w0, %w1) \
> : "+r" (err), "=&r" (x) \
> : "r" (addr))
>
> diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c
> index f1134c88e849..7c05f8d2bce0 100644
> --- a/arch/arm64/mm/extable.c
> +++ b/arch/arm64/mm/extable.c
> @@ -95,6 +95,7 @@ bool fixup_exception(struct pt_regs *regs, unsigned int esr)
> case EX_TYPE_BPF:
> return ex_handler_bpf(ex, regs);
> case EX_TYPE_UACCESS_ERR_ZERO:
> + case EX_TYPE_UACCESS_ERR_ZERO_MC:
> return ex_handler_uaccess_err_zero(ex, regs);
> case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
> return ex_handler_load_unaligned_zeropad(ex, regs);
> --
> 2.18.0.huawei.25
>
>
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