[RFC PATCH -next V3 4/6] arm64: add copy_{to, from}_user to machine check safe

[Tong Tiangen]

在 2022/4/13 1:08, Robin Murphy 写道:
> On 12/04/2022 8:25 am, Tong Tiangen wrote:
> [...]
>> diff --git a/arch/arm64/include/asm/asm-uaccess.h 
>> b/arch/arm64/include/asm/asm-uaccess.h
>> index 0557af834e03..bb17f0829042 100644
>> --- a/arch/arm64/include/asm/asm-uaccess.h
>> +++ b/arch/arm64/include/asm/asm-uaccess.h
>> @@ -92,4 +92,20 @@ alternative_else_nop_endif
>>           _asm_extable    8888b,\l;
>>       .endm
>> +
>> +    .macro user_ldp_mc l, reg1, reg2, addr, post_inc
>> +8888:        ldtr    \reg1, [\addr];
>> +8889:        ldtr    \reg2, [\addr, #8];
>> +        add    \addr, \addr, \post_inc;
>> +
>> +        _asm_extable_uaccess_mc    8888b, \l;
>> +        _asm_extable_uaccess_mc    8889b, \l;
>> +    .endm
> 
> You're replacing the only user of this, so please just 
> s/_asm_extable/_asm_extable_uaccess_mc/ in the existing macro and save 
> the rest of the churn.
> 
> Furthermore, how come you're not similarly updating user_stp, given that 
> you *are* updating the other stores in copy_to_user?

I think all load/store instructions should be handled.

Generally speaking, the load operation will receive a sea when consuming 
a hardware memory error, and the store operation will not receive a sea 
when consuming a hardware error. Depends on chip behavior.

So add store class instructions to processed is no harm.

If there is any problem with my understanding, correct me.

Thanks,
Tong.

> 
>> +
>> +    .macro user_ldst_mc l, inst, reg, addr, post_inc
>> +8888:        \inst        \reg, [\addr];
>> +        add        \addr, \addr, \post_inc;
>> +
>> +        _asm_extable_uaccess_mc    8888b, \l;
>> +    .endm
>
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