On Fri, Aug 20, 2021 at 7:59 PM Dave Marchevsky <davemarchevsky@xxxxxx> wrote:
>
> bpf_vprintk functions similarly to BPF_SEQ_PRINTF and BPF_SNPRINTF
> macros elsewhere in the file - it allows use of bpf_trace_vprintk
> without manual conversion of varargs to u64 array.
>
> Like the bpf_printk macro, bpf_vprintk is meant to be the main interface
> to the bpf_trace_vprintk helper and thus is uncapitalized.
>
> Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx>
> ---
> tools/lib/bpf/bpf_helpers.h | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
> index b9987c3efa3c..43c8115956c3 100644
> --- a/tools/lib/bpf/bpf_helpers.h
> +++ b/tools/lib/bpf/bpf_helpers.h
> @@ -224,4 +224,22 @@ enum libbpf_tristate {
> ___param, sizeof(___param)); \
> })
>
> +/*
> + * bpf_vprintk wraps the bpf_trace_printk helper with variadic arguments
> + * instead of an array of u64.
> + */
> +#define bpf_vprintk(fmt, args...) \
Given BPF_SNPRINTF and BPF_SEQ_PRINTF, should we call this one in
all-caps as well?
> +({ \
> + static const char ___fmt[] = fmt; \
> + unsigned long long ___param[___bpf_narg(args)]; \
I wonder how hard would it be to still use bpf_trace_printk() if the
number of input arguments is less than 3? That way you could use
BPF_PRINTF() everywhere, even on old kernels (you just need to
remember to use < 3 arguments). WDYT? It might be more challenging
than it seems, given it's hard to do conditionals inside #defines :(
> + \
> + _Pragma("GCC diagnostic push") \
> + _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \
> + ___bpf_fill(___param, args); \
> + _Pragma("GCC diagnostic pop") \
> + \
> + bpf_trace_vprintk(___fmt, sizeof(___fmt), \
> + ___param, sizeof(___param)); \
> +})
> +
> #endif
> --
> 2.30.2
>
