Re: [PATCH] update the consistency issue in documentation

[David Vernet <void@manifault.com>]

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On Thu, Jan 04, 2024 at 03:09:32AM +0000, Aoyang Fang (SSE, 222010547) wrote:
> From fa9f3f47ddeb3e9a615c17aea57d2ecd53a7d201 Mon Sep 17 00:00:00 2001
> From: lincyawer <53161583+Lincyaw@users.noreply.github.com>
> Date: Thu, 4 Jan 2024 10:51:36 +0800
> Subject: [PATCH] The original documentation of BPF_JMP instructions is somehow
> misleading. The code part of instruction, e.g., BPF_JEQ's value is noted as
> 0x1, however, in `include/uapi/linux/bpf.h`, the value of BPF_JEQ is 0x10. At
> the same time, the description convention is inconsistent with the BPF_ALU,
> whose code are also 4bit, but the value of BPF_ADD is 0x00
> 
> Signed-off-by: lincyawer <53161583+Lincyaw@users.noreply.github.com>

Hi Aoyang,

Could you please resend this patch to the lists in plain text? The Linux
kernel mailing lists will drop html-encoded emails. Please see [0] for
more information. You can just use git send-email with a patch file as
follows:

$ git format-patch HEAD~ --subject-prefix='PATCH bpf-next' HEAD~
$ git send-email <patch> --to bpf@vger.kernel.org --cc bpf@ietf.org

[0]: https://docs.kernel.org/process/submitting-patches.html#no-mime-no-links-no-compression-no-attachments-just-plain-text

Please make sure that the Signed-off-by tag includes your name and real
email address as well.

Thanks,
David

> ---
> .../bpf/standardization/instruction-set.rst | 34 +++++++++----------
> 1 file changed, 17 insertions(+), 17 deletions(-)
> 
> diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst
> index 245b6defc..dee3b1fa8 100644
> --- a/Documentation/bpf/standardization/instruction-set.rst
> +++ b/Documentation/bpf/standardization/instruction-set.rst
> @@ -355,23 +355,23 @@ The 'code' field encodes the operation as below:
> ======== ===== === =========================================== =========================================
> code value src description notes
> ======== ===== === =========================================== =========================================
> -BPF_JA 0x0 0x0 PC += offset BPF_JMP class
> -BPF_JA 0x0 0x0 PC += imm BPF_JMP32 class
> -BPF_JEQ 0x1 any PC += offset if dst == src
> -BPF_JGT 0x2 any PC += offset if dst > src unsigned
> -BPF_JGE 0x3 any PC += offset if dst >= src unsigned
> -BPF_JSET 0x4 any PC += offset if dst & src
> -BPF_JNE 0x5 any PC += offset if dst != src
> -BPF_JSGT 0x6 any PC += offset if dst > src signed
> -BPF_JSGE 0x7 any PC += offset if dst >= src signed
> -BPF_CALL 0x8 0x0 call helper function by address see `Helper functions`_
> -BPF_CALL 0x8 0x1 call PC += imm see `Program-local functions`_
> -BPF_CALL 0x8 0x2 call helper function by BTF ID see `Helper functions`_
> -BPF_EXIT 0x9 0x0 return BPF_JMP only
> -BPF_JLT 0xa any PC += offset if dst < src unsigned
> -BPF_JLE 0xb any PC += offset if dst <= src unsigned
> -BPF_JSLT 0xc any PC += offset if dst < src signed
> -BPF_JSLE 0xd any PC += offset if dst <= src signed
> +BPF_JA 0x00 0x0 PC += offset BPF_JMP class
> +BPF_JA 0x00 0x0 PC += imm BPF_JMP32 class
> +BPF_JEQ 0x10 any PC += offset if dst == src
> +BPF_JGT 0x20 any PC += offset if dst > src unsigned
> +BPF_JGE 0x30 any PC += offset if dst >= src unsigned
> +BPF_JSET 0x40 any PC += offset if dst & src
> +BPF_JNE 0x50 any PC += offset if dst != src
> +BPF_JSGT 0x60 any PC += offset if dst > src signed
> +BPF_JSGE 0x70 any PC += offset if dst >= src signed
> +BPF_CALL 0x80 0x0 call helper function by address see `Helper functions`_
> +BPF_CALL 0x80 0x1 call PC += imm see `Program-local functions`_
> +BPF_CALL 0x80 0x2 call helper function by BTF ID see `Helper functions`_
> +BPF_EXIT 0x90 0x0 return BPF_JMP only
> +BPF_JLT 0xa0 any PC += offset if dst < src unsigned
> +BPF_JLE 0xb0 any PC += offset if dst <= src unsigned
> +BPF_JSLT 0xc0 any PC += offset if dst < src signed
> +BPF_JSLE 0xd0 any PC += offset if dst <= src signed
> ======== ===== === =========================================== =========================================
> The BPF program needs to store the return value into register R0 before doing a
> --
> 2.42.0
> 
> 

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