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SubjectRe: [PATCH bpf] bpf, docs: Correct the example of BPF_XOR
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On 2022/11/30 02:54, David Vernet wrote:
> On Tue, Nov 29, 2022 at 09:45:58PM +0800, Zheng Yejian wrote:
>> Refer to description of BPF_XOR, dst_reg should be used but not src_reg
>> in the examples.
>>
>> Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
>> ---
>> Documentation/bpf/instruction-set.rst | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst
>> index 5d798437dad4..e672d5ec6cc7 100644
>> --- a/Documentation/bpf/instruction-set.rst
>> +++ b/Documentation/bpf/instruction-set.rst
>> @@ -122,11 +122,11 @@ BPF_END 0xd0 byte swap operations (see `Byte swap instructions`_ below)
>>
>> ``BPF_XOR | BPF_K | BPF_ALU`` means::
>>
>> - src_reg = (u32) src_reg ^ (u32) imm32
>> + dst_reg = (u32) dst_reg ^ (u32) imm32
>
> Shouldn't this be
>
> dst_reg = (u32) dst_reg ^ (u32) src_reg
>
> Same idea below for 64 bit

See Chapter 'Instruction classes', BPF_K means "use 32-bit immediate as
source operand", so it should be 'imm32' instead of 'src_reg'.

>
>>
>> ``BPF_XOR | BPF_K | BPF_ALU64`` means::
>>
>> - src_reg = src_reg ^ imm32
>> + dst_reg = dst_reg ^ imm32
>>
>>
>> Byte swap instructions
>> --
>> 2.25.1
>>
>

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