netdev - Re: [PATCH bpf-next v3 1/3] libbpf: move pr_*() functions to common header file

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Date:   Thu, 31 Jan 2019 11:35:22 -0800
From:   Y Song <ys114321@...il.com>
To:     Magnus Karlsson <magnus.karlsson@...el.com>
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        netdev <netdev@...r.kernel.org>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Björn Töpel <bjorn.topel@...il.com>,
        qi.z.zhang@...el.com, Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH bpf-next v3 1/3] libbpf: move pr_*() functions to common
 header file

On Tue, Jan 29, 2019 at 7:13 AM Magnus Karlsson
<magnus.karlsson@...el.com> wrote:
>
> Move the pr_*() functions in libbpf.c to a common header file called
> libbpf_internal.h. This so that the later libbpf AF_XDP helper library
> code in xsk.c can use these printing functions too.
>
> Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
> ---
>  tools/lib/bpf/libbpf.c          | 30 +-----------------------------
>  tools/lib/bpf/libbpf_internal.h | 41 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 42 insertions(+), 29 deletions(-)
>  create mode 100644 tools/lib/bpf/libbpf_internal.h
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 2ccde17..1d7fe26 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -39,6 +39,7 @@
>  #include <gelf.h>
>
>  #include "libbpf.h"
> +#include "libbpf_internal.h"
>  #include "bpf.h"
>  #include "btf.h"
>  #include "str_error.h"
> @@ -51,34 +52,6 @@
>  #define BPF_FS_MAGIC           0xcafe4a11
>  #endif
>
> -#define __printf(a, b) __attribute__((format(printf, a, b)))
> -
> -__printf(1, 2)
> -static int __base_pr(const char *format, ...)
> -{
> -       va_list args;
> -       int err;
> -
> -       va_start(args, format);
> -       err = vfprintf(stderr, format, args);
> -       va_end(args);
> -       return err;
> -}
> -
> -static __printf(1, 2) libbpf_print_fn_t __pr_warning = __base_pr;
> -static __printf(1, 2) libbpf_print_fn_t __pr_info = __base_pr;
> -static __printf(1, 2) libbpf_print_fn_t __pr_debug;
> -
> -#define __pr(func, fmt, ...)   \
> -do {                           \
> -       if ((func))             \
> -               (func)("libbpf: " fmt, ##__VA_ARGS__); \
> -} while (0)
> -
> -#define pr_warning(fmt, ...)   __pr(__pr_warning, fmt, ##__VA_ARGS__)
> -#define pr_info(fmt, ...)      __pr(__pr_info, fmt, ##__VA_ARGS__)
> -#define pr_debug(fmt, ...)     __pr(__pr_debug, fmt, ##__VA_ARGS__)
> -
>  void libbpf_set_print(libbpf_print_fn_t warn,
>                       libbpf_print_fn_t info,
>                       libbpf_print_fn_t debug)
> @@ -96,7 +69,6 @@ void libbpf_set_print(libbpf_print_fn_t warn,
>                 goto out;               \
>  } while(0)
>
> -
>  /* Copied from tools/perf/util/util.h */
>  #ifndef zfree
>  # define zfree(ptr) ({ free(*ptr); *ptr = NULL; })
> diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
> new file mode 100644
> index 0000000..951c078
> --- /dev/null
> +++ b/tools/lib/bpf/libbpf_internal.h
> @@ -0,0 +1,41 @@
> +/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
> +
> +/*
> + * Common internal libbpf functions and definitions.
> + *
> + * Copyright (C) 2013-2015 Alexei Starovoitov <ast@...nel.org>
> + * Copyright (C) 2015 Wang Nan <wangnan0@...wei.com>
> + * Copyright (C) 2015 Huawei Inc.
> + */
> +#ifndef __LIBBPF_LIBBPF_INTERNAL_H
> +#define __LIBBPF_LIBBPF_INTERNAL_H
> +
> +#define __printf(a, b) __attribute__((format(printf, a, b)))
> +
> +__printf(1, 2)
> +static int __base_pr(const char *format, ...)
> +{
> +       va_list args;
> +       int err;
> +
> +       va_start(args, format);
> +       err = vfprintf(stderr, format, args);
> +       va_end(args);
> +       return err;
> +}

Hmm. This will introduce this static function into every .c file.

Maybe we could define a global function in libbpf.c like
  libbpf_debug_pr(level, ...)
This function will be internal to the library and implemented in libbpf.c.
All files can call this function to print out the debug information
based on level?

> +
> +static __maybe_unused __printf(1, 2) libbpf_print_fn_t __pr_warning = __base_pr;
> +static __maybe_unused __printf(1, 2) libbpf_print_fn_t __pr_info = __base_pr;
> +static __maybe_unused __printf(1, 2) libbpf_print_fn_t __pr_debug;
> +
> +#define __pr(func, fmt, ...)   \
> +do {                           \
> +       if ((func))             \
> +               (func)("libbpf: " fmt, ##__VA_ARGS__); \
> +} while (0)
> +
> +#define pr_warning(fmt, ...)   __pr(__pr_warning, fmt, ##__VA_ARGS__)
> +#define pr_info(fmt, ...)      __pr(__pr_info, fmt, ##__VA_ARGS__)
> +#define pr_debug(fmt, ...)     __pr(__pr_debug, fmt, ##__VA_ARGS__)
> +
> +#endif /* __LIBBPF_LIBBPF_INTERNAL_H */
> --
> 2.7.4
>