On Wed, May 7, 2025 at 10:17 AM Kumar Kartikeya Dwivedi
<memxor@xxxxxxxxx> wrote:
>
> Introduce a new macro that allows printing data similar to bpf_printk(),
> but to BPF streams. The first argument is the stream ID, the rest of the
> arguments are same as what one would pass to bpf_printk().
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> ---
> kernel/bpf/stream.c | 10 +++++++--
> tools/lib/bpf/bpf_helpers.h | 44 +++++++++++++++++++++++++++++++------
> 2 files changed, 45 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/bpf/stream.c b/kernel/bpf/stream.c
> index eaf0574866b1..d64975486ad1 100644
> --- a/kernel/bpf/stream.c
> +++ b/kernel/bpf/stream.c
> @@ -257,7 +257,12 @@ __bpf_kfunc int bpf_stream_vprintk(struct bpf_stream *stream, const char *fmt__s
> return ret;
> }
>
> -__bpf_kfunc struct bpf_stream *bpf_stream_get(enum bpf_stream_id stream_id, void *aux__ign)
> +/* Use int vs enum stream_id here, we use this kfunc in bpf_helpers.h, and
> + * keeping enum stream_id necessitates a complete definition of enum, but we
> + * can't copy it in the header as it may conflict with the definition in
> + * vmlinux.h.
> + */
> +__bpf_kfunc struct bpf_stream *bpf_stream_get(int stream_id, void *aux__ign)
> {
> struct bpf_prog_aux *aux = aux__ign;
>
> @@ -351,7 +356,8 @@ __bpf_kfunc struct bpf_stream_elem *bpf_stream_next_elem(struct bpf_stream *stre
> return elem;
> }
>
> -__bpf_kfunc struct bpf_stream *bpf_prog_stream_get(enum bpf_stream_id stream_id, u32 prog_id)
> +/* Use int vs enum bpf_stream_id for consistency with bpf_stream_get. */
> +__bpf_kfunc struct bpf_stream *bpf_prog_stream_get(int stream_id, u32 prog_id)
> {
> struct bpf_stream *stream;
> struct bpf_prog *prog;
> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
> index a50773d4616e..1a748c21e358 100644
> --- a/tools/lib/bpf/bpf_helpers.h
> +++ b/tools/lib/bpf/bpf_helpers.h
> @@ -314,17 +314,47 @@ enum libbpf_tristate {
> ___param, sizeof(___param)); \
> })
>
> +struct bpf_stream;
> +
> +extern struct bpf_stream *bpf_stream_get(int stream_id, void *aux__ign) __weak __ksym;
> +extern int bpf_stream_vprintk(struct bpf_stream *stream, const char *fmt__str, const void *args,
> + __u32 len__sz) __weak __ksym;
> +
> +#define __bpf_stream_vprintk(stream, fmt, args...) \
> +({ \
> + static const char ___fmt[] = fmt; \
> + unsigned long long ___param[___bpf_narg(args)]; \
> + \
> + _Pragma("GCC diagnostic push") \
> + _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \
> + ___bpf_fill(___param, args); \
> + _Pragma("GCC diagnostic pop") \
> + \
> + int ___id = stream; \
What's the point of ___id variable? Just use `stream` in
bpf_stream_get() directly?
> + struct bpf_stream *___sptr = bpf_stream_get(___id, NULL); \
> + if (___sptr) \
> + bpf_stream_vprintk(___sptr, ___fmt, ___param, sizeof(___param));\
> +})
> +
> /* Use __bpf_printk when bpf_printk call has 3 or fewer fmt args
> - * Otherwise use __bpf_vprintk
> + * Otherwise use __bpf_vprintk. Virtualize choices so stream printk
> + * can override it to bpf_stream_vprintk.
> */
> -#define ___bpf_pick_printk(...) \
> - ___bpf_nth(_, ##__VA_ARGS__, __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, \
> - __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, \
> - __bpf_vprintk, __bpf_vprintk, __bpf_printk /*3*/, __bpf_printk /*2*/,\
> - __bpf_printk /*1*/, __bpf_printk /*0*/)
> +#define ___bpf_pick_printk(choice, choice_3, ...) \
> + ___bpf_nth(_, ##__VA_ARGS__, choice, choice, choice, \
> + choice, choice, choice, choice, \
> + choice, choice, choice_3 /*3*/, choice_3 /*2*/, \
> + choice_3 /*1*/, choice_3 /*0*/)
>
> /* Helper macro to print out debug messages */
> -#define bpf_printk(fmt, args...) ___bpf_pick_printk(args)(fmt, ##args)
> +#define __bpf_trace_printk(fmt, args...) \
> + ___bpf_pick_printk(__bpf_vprintk, __bpf_printk, args)(fmt, ##args)
> +#define __bpf_stream_printk(stream, fmt, args...) \
> + ___bpf_pick_printk(__bpf_stream_vprintk, __bpf_stream_vprintk, args)(stream, fmt, ##args)
> +
> +#define bpf_stream_printk(stream, fmt, args...) __bpf_stream_printk(stream, fmt, ##args)
> +
> +#define bpf_printk(arg, args...) __bpf_trace_printk(arg, ##args)
>
> struct bpf_iter_num;
>
> --
> 2.47.1
>
