On Fri, Aug 27, 2021 at 10:20 PM Dave Marchevsky <davemarchevsky@xxxxxx> wrote:
>
> The __bpf_printk convenience macro was using a 'char' fmt string holder
> as it predates support for globals in libbpf. Move to more efficient
> 'static const char', but provide a fallback to the old way via
> BPF_NO_GLOBAL_DATA so users on old kernels can still use the macro.
>
> Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx>
> ---
> tools/lib/bpf/bpf_helpers.h | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
> index 5f087306cdfe..a1d5ec6f285c 100644
> --- a/tools/lib/bpf/bpf_helpers.h
> +++ b/tools/lib/bpf/bpf_helpers.h
> @@ -216,10 +216,16 @@ enum libbpf_tristate {
> ___param, sizeof(___param)); \
> })
>
> +#ifdef BPF_NO_GLOBAL_DATA
> +#define BPF_PRINTK_FMT_TYPE char
> +#else
> +#define BPF_PRINTK_FMT_TYPE static const char
> +#endif
> +
> /* Helper macro to print out debug messages */
> #define __bpf_printk(fmt, ...) \
> ({ \
> - char ____fmt[] = fmt; \
> + BPF_PRINTK_FMT_TYPE ____fmt[] = fmt; \
personal preferences, of course, but I'd leave char right there (I
think it makes it a bit more obvious what's going on right there), and
s/BPF_PRINTK_FMT_TYPE/BPF_PRINTK_FMT_MOD/ and have it as either "" or
"static const".
> bpf_trace_printk(____fmt, sizeof(____fmt), \
> ##__VA_ARGS__); \
> })
> --
> 2.30.2
>
