On Mon, Mar 2, 2020 at 8:22 AM Yonghong Song <yhs@xxxxxx> wrote:
>
>
>
> 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@xxxxxx>
> > ---
> > 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.
This is going to be a really ugly solution, though. I wonder if it was
ever an expected behavior of UAPI constants to be able to do #ifdef on
them.
Do you know any existing application that relies on those constants
being #defines?
>
> 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 */
> > +};
> >
> [...]
