From: Yonghong Song <yhs@fb.com>
To: Andrii Nakryiko <andriin@fb.com>, <bpf@vger.kernel.org>,
<netdev@vger.kernel.org>, <ast@fb.com>, <daniel@iogearbox.net>
Cc: <andrii.nakryiko@gmail.com>, <kernel-team@fb.com>
Subject: Re: [PATCH v2 bpf-next 1/3] bpf: switch BPF UAPI #define constants to enums
Date: Mon, 2 Mar 2020 08:22:11 -0800 [thread overview]
Message-ID: <b57cdf6d-0849-2d54-982e-352886f86201@fb.com> (raw)
In-Reply-To: <20200301062405.2850114-2-andriin@fb.com>
On 2/29/20 10:24 PM, Andrii Nakryiko wrote:
> Switch BPF UAPI constants, previously defined as #define macro, to anonymous
> enum values. This preserves constants values and behavior in expressions, but
> has added advantaged of being captured as part of DWARF and, subsequently, BTF
> type info. Which, in turn, greatly improves usefulness of generated vmlinux.h
> for BPF applications, as it will not require BPF users to copy/paste various
> flags and constants, which are frequently used with BPF helpers.
>
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> ---
> include/uapi/linux/bpf.h | 272 +++++++++++++++----------
> include/uapi/linux/bpf_common.h | 86 ++++----
> include/uapi/linux/btf.h | 60 +++---
> tools/include/uapi/linux/bpf.h | 274 ++++++++++++++++----------
> tools/include/uapi/linux/bpf_common.h | 86 ++++----
> tools/include/uapi/linux/btf.h | 60 +++---
> 6 files changed, 497 insertions(+), 341 deletions(-)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 8e98ced0963b..03e08f256bd1 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -14,34 +14,36 @@
> /* Extended instruction set based on top of classic BPF */
>
> /* instruction classes */
> -#define BPF_JMP32 0x06 /* jmp mode in word width */
> -#define BPF_ALU64 0x07 /* alu mode in double word width */
> +enum {
> + BPF_JMP32 = 0x06, /* jmp mode in word width */
> + BPF_ALU64 = 0x07, /* alu mode in double word width */
Not sure whether we have uapi backward compatibility or not.
One possibility is to add
#define BPF_ALU64 BPF_ALU64
this way, people uses macros will continue to work.
If this is an acceptable solution, we have a lot of constants
in net related headers and will benefit from this conversion for
kprobe/tracepoint of networking related functions.
>
> /* ld/ldx fields */
> -#define BPF_DW 0x18 /* double word (64-bit) */
> -#define BPF_XADD 0xc0 /* exclusive add */
> + BPF_DW = 0x18, /* double word (64-bit) */
> + BPF_XADD = 0xc0, /* exclusive add */
>
> /* alu/jmp fields */
> -#define BPF_MOV 0xb0 /* mov reg to reg */
> -#define BPF_ARSH 0xc0 /* sign extending arithmetic shift right */
> + BPF_MOV = 0xb0, /* mov reg to reg */
> + BPF_ARSH = 0xc0, /* sign extending arithmetic shift right */
>
> /* change endianness of a register */
> -#define BPF_END 0xd0 /* flags for endianness conversion: */
> -#define BPF_TO_LE 0x00 /* convert to little-endian */
> -#define BPF_TO_BE 0x08 /* convert to big-endian */
> -#define BPF_FROM_LE BPF_TO_LE
> -#define BPF_FROM_BE BPF_TO_BE
> + BPF_END = 0xd0, /* flags for endianness conversion: */
> + BPF_TO_LE = 0x00, /* convert to little-endian */
> + BPF_TO_BE = 0x08, /* convert to big-endian */
> + BPF_FROM_LE = BPF_TO_LE,
> + BPF_FROM_BE = BPF_TO_BE,
>
> /* jmp encodings */
> -#define BPF_JNE 0x50 /* jump != */
> -#define BPF_JLT 0xa0 /* LT is unsigned, '<' */
> -#define BPF_JLE 0xb0 /* LE is unsigned, '<=' */
> -#define BPF_JSGT 0x60 /* SGT is signed '>', GT in x86 */
> -#define BPF_JSGE 0x70 /* SGE is signed '>=', GE in x86 */
> -#define BPF_JSLT 0xc0 /* SLT is signed, '<' */
> -#define BPF_JSLE 0xd0 /* SLE is signed, '<=' */
> -#define BPF_CALL 0x80 /* function call */
> -#define BPF_EXIT 0x90 /* function return */
> + BPF_JNE = 0x50, /* jump != */
> + BPF_JLT = 0xa0, /* LT is unsigned, '<' */
> + BPF_JLE = 0xb0, /* LE is unsigned, '<=' */
> + BPF_JSGT = 0x60, /* SGT is signed '>', GT in x86 */
> + BPF_JSGE = 0x70, /* SGE is signed '>=', GE in x86 */
> + BPF_JSLT = 0xc0, /* SLT is signed, '<' */
> + BPF_JSLE = 0xd0, /* SLE is signed, '<=' */
> + BPF_CALL = 0x80, /* function call */
> + BPF_EXIT = 0x90, /* function return */
> +};
>
[...]
next prev parent reply other threads:[~2020-03-02 16:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-01 6:24 [PATCH v2 bpf-next 0/3] Convert BPF UAPI constants into enum values Andrii Nakryiko
2020-03-01 6:24 ` [PATCH v2 bpf-next 1/3] bpf: switch BPF UAPI #define constants to enums Andrii Nakryiko
2020-03-02 16:22 ` Yonghong Song [this message]
2020-03-02 18:25 ` Andrii Nakryiko
2020-03-02 18:33 ` Yonghong Song
2020-03-02 19:14 ` Andrii Nakryiko
2020-03-02 20:48 ` Daniel Borkmann
2020-03-02 22:37 ` Alexei Starovoitov
2020-03-02 23:14 ` Andrii Nakryiko
2020-03-01 6:24 ` [PATCH v2 bpf-next 2/3] libbpf: assume unsigned values for BTF_KIND_ENUM Andrii Nakryiko
2020-03-01 6:24 ` [PATCH v2 bpf-next 3/3] tools/runqslower: drop copy/pasted BPF_F_CURRENT_CPU definiton Andrii Nakryiko
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