On 01/16/2018 12:31 PM, Jesper Dangaard Brouer wrote:
> Doc BPF ld/ldx size defines, as it help me understand the code in filter.c.
>
> Signed-off-by: Jesper Dangaard Brouer <bro...@redhat.com>
> ---
> 0 files changed
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 395d261948de..4729d9a002d4 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -17,7 +17,7 @@
> #define BPF_ALU64 0x07 /* alu mode in double word width */
>
> /* ld/ldx fields */
> -#define BPF_DW 0x18 /* double word */
> +#define BPF_DW 0x18 /* double word (64-bit) */
> #define BPF_XADD 0xc0 /* exclusive add */
>
> /* alu/jmp fields */
> diff --git a/include/uapi/linux/bpf_common.h b/include/uapi/linux/bpf_common.h
> index 18be90725ab0..ee97668bdadb 100644
> --- a/include/uapi/linux/bpf_common.h
> +++ b/include/uapi/linux/bpf_common.h
> @@ -15,9 +15,10 @@
>
> /* ld/ldx fields */
> #define BPF_SIZE(code) ((code) & 0x18)
> -#define BPF_W 0x00
> -#define BPF_H 0x08
> -#define BPF_B 0x10
> +#define BPF_W 0x00 /* 32-bit */
> +#define BPF_H 0x08 /* 16-bit */
> +#define BPF_B 0x10 /* 8-bit */
> +/* eBPF BPF_DW 0x18 64-bit */
Hmm, I don't really mind, but we do have it documented in:
Documentation/networking/filter.txt +942
Feels like if we put a comment only on BPF_{B,H,W}, then we
might also want to document all the others such as ALU ops,
etc.
> #define BPF_MODE(code) ((code) & 0xe0)
> #define BPF_IMM 0x00
> #define BPF_ABS 0x20
>
