Messages in this thread | | | Date | Wed, 30 Nov 2022 09:17:11 +0800 | Subject | Re: [PATCH bpf] bpf, docs: Correct the example of BPF_XOR | From | Zheng Yejian <> |
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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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