Re: [PATCH -next v5 2/8] arm64: extable: make uaaccess helper use extable type EX_TYPE_UACCESS_ERR_ZERO

Tong Tiangen
2022-06-18T03:27:45Z

在 2022/6/17 16:24, Mark Rutland 写道:
> On Sat, May 28, 2022 at 06:50:50AM +0000, Tong Tiangen wrote:
>> Currnetly, the extable type used by __arch_copy_from/to_user() is
>> EX_TYPE_FIXUP. In fact, It is more clearly to use meaningful
>> EX_TYPE_UACCESS_*.
>>
>> Suggested-by: Mark Rutland <mark.rutland@arm.com>
>> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
>> ---
>> arch/arm64/include/asm/asm-extable.h | 8 ++++++++
>> arch/arm64/include/asm/asm-uaccess.h | 12 ++++++------
>> 2 files changed, 14 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h
>> index 56ebe183e78b..9c94ac1f082c 100644
>> --- a/arch/arm64/include/asm/asm-extable.h
>> +++ b/arch/arm64/include/asm/asm-extable.h
>> @@ -28,6 +28,14 @@
>> __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0)
>> .endm
>>
>> +/*
>> + * Create an exception table entry for uaccess `insn`, which will branch to `fixup`
>> + * when an unhandled fault is taken.
>> + * ex->data = ~0 means both reg_err and reg_zero is set to wzr(x31).
>> + */
>> + .macro _asm_extable_uaccess, insn, fixup
>> + __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_UACCESS_ERR_ZERO, ~0)
>> + .endm
>
> I'm not too keen on using `~0` here, since that also sets other bits in the
> data field, and its somewhat opaque.
>
> How painful is it to generate the data fields as with the C version of this
> macro, so that we can pass in wzr explciitly for the two sub-fields?
>
> Other than that, this looks good to me.
>
> Thanks,
> Mark.

ok, will fix next version.

Thanks,
Tong.

>
>> /*
>> * Create an exception table entry for `insn` if `fixup` is provided. Otherwise
>> * do nothing.
>> diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h
>> index 0557af834e03..75b211c98dea 100644
>> --- a/arch/arm64/include/asm/asm-uaccess.h
>> +++ b/arch/arm64/include/asm/asm-uaccess.h
>> @@ -61,7 +61,7 @@ alternative_else_nop_endif
>>
>> #define USER(l, x...) \
>> 9999: x; \
>> - _asm_extable 9999b, l
>> + _asm_extable_uaccess 9999b, l
>>
>> /*
>> * Generate the assembly for LDTR/STTR with exception table entries.
>> @@ -73,8 +73,8 @@ alternative_else_nop_endif
>> 8889: ldtr \reg2, [\addr, #8];
>> add \addr, \addr, \post_inc;
>>
>> - _asm_extable 8888b,\l;
>> - _asm_extable 8889b,\l;
>> + _asm_extable_uaccess 8888b, \l;
>> + _asm_extable_uaccess 8889b, \l;
>> .endm
>>
>> .macro user_stp l, reg1, reg2, addr, post_inc
>> @@ -82,14 +82,14 @@ alternative_else_nop_endif
>> 8889: sttr \reg2, [\addr, #8];
>> add \addr, \addr, \post_inc;
>>
>> - _asm_extable 8888b,\l;
>> - _asm_extable 8889b,\l;
>> + _asm_extable_uaccess 8888b,\l;
>> + _asm_extable_uaccess 8889b,\l;
>> .endm
>>
>> .macro user_ldst l, inst, reg, addr, post_inc
>> 8888: \inst \reg, [\addr];
>> add \addr, \addr, \post_inc;
>>
>> - _asm_extable 8888b,\l;
>> + _asm_extable_uaccess 8888b, \l;
>> .endm
>> #endif
>> --
>> 2.25.1
>>
> .