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    SubjectRe: [RFC PATCH v10 20/50] bpf tools: Introduce accessors for struct bpf_program
    Em Wed, Jul 01, 2015 at 02:14:08AM +0000, Wang Nan escreveu:
    > This patch introduces accessors for user of libbpf to retrieve section
    > name and fd of a opened/loaded eBPF program. 'struct bpf_prog_handler'
    > is used for that purpose. Accessors of programs section name and file
    > descriptor are provided. Set/get private data are also impelmented.
    >
    > Signed-off-by: Wang Nan <wangnan0@huawei.com>
    > Acked-by: Alexei Starovoitov <ast@plumgrid.com>
    > ---
    > tools/lib/bpf/libbpf.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++
    > tools/lib/bpf/libbpf.h | 25 +++++++++++++++
    > 2 files changed, 107 insertions(+)
    >
    > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
    > index 33452f8..e4c5f07 100644
    > --- a/tools/lib/bpf/libbpf.c
    > +++ b/tools/lib/bpf/libbpf.c
    > @@ -98,6 +98,10 @@ struct bpf_program {
    > int nr_reloc;
    >
    > int fd;
    > +
    > + struct bpf_object *obj;
    > + void *priv;
    > + bpf_program_clear_priv_t clear_priv;
    > };
    >
    > struct bpf_object {
    > @@ -150,6 +154,12 @@ static void bpf_program__clear(struct bpf_program *prog)
    > if (!prog)
    > return;
    >
    > + if (prog->clear_priv)
    > + prog->clear_priv(prog, prog->priv);
    > +
    > + prog->priv = NULL;
    > + prog->clear_priv = NULL;
    > +
    > bpf_program__unload(prog);
    > zfree(&prog->section_name);
    > zfree(&prog->insns);
    > @@ -211,6 +221,7 @@ bpf_program__new(struct bpf_object *obj, void *data, size_t size,
    > prog->insns_cnt * sizeof(struct bpf_insn));
    > prog->idx = idx;
    > prog->fd = -1;
    > + prog->obj = obj;
    >
    > return prog;
    > out:
    > @@ -924,3 +935,74 @@ void bpf_object__close(struct bpf_object *obj)
    >
    > free(obj);
    > }
    > +
    > +struct bpf_program *
    > +bpf_program__next(struct bpf_program *prev, struct bpf_object *obj)
    > +{
    > + size_t idx;
    > +
    > + if (!obj->programs)
    > + return NULL;
    > + /* First handler */
    > + if (prev == NULL)
    > + return &obj->programs[0];
    > +
    > + if (prev->obj != obj) {
    > + pr_warning("error: program handler doesn't match object\n");
    > + return NULL;
    > + }
    > +
    > + idx = (prev - obj->programs) + 1;
    > + if (idx >= obj->nr_programs)
    > + return NULL;
    > + return &obj->programs[idx];
    > +}
    > +
    > +int bpf_program__set_private(struct bpf_program *prog,
    > + void *priv,
    > + bpf_program_clear_priv_t clear_priv)
    > +{
    > + if (prog->priv && prog->clear_priv)
    > + prog->clear_priv(prog, prog->priv);
    > +
    > + prog->priv = priv;
    > + prog->clear_priv = clear_priv;
    > + return 0;
    > +}
    > +
    > +int bpf_program__get_private(struct bpf_program *prog, void **ppriv)
    > +{
    > + *ppriv = prog->priv;
    > + return 0;
    > +}
    > +
    > +int bpf_program__get_title(struct bpf_program *prog,
    > + const char **ptitle, bool dup)
    > +{
    > + const char *title;
    > +
    > + if (!ptitle)
    > + return -EINVAL;
    > +
    > + title = prog->section_name;
    > + if (dup) {
    > + title = strdup(title);
    > + if (!title) {
    > + pr_warning("failed to strdup program title\n");
    > + *ptitle = NULL;
    > + return -ENOMEM;
    > + }
    > + }
    > +
    > + *ptitle = title;
    > + return 0;
    > +}
    > +
    > +int bpf_program__get_fd(struct bpf_program *prog, int *pfd)
    > +{
    > + if (!pfd)
    > + return -EINVAL;
    > +
    > + *pfd = prog->fd;
    > + return 0;

    Why not:

    int bpf_program__fd(struct bpf_program *prog)
    {
    return prog->fd;
    }

    Or plain ditch completely this function and go ahead and use:
    prog->fd;

    I see, you don't export the bpf_program struct definition, but
    then why not return it straight away?

    Ditto for bpf_program__get_title()

    - Arnaldo

    > +}
    > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
    > index 3e69600..9e0e102 100644
    > --- a/tools/lib/bpf/libbpf.h
    > +++ b/tools/lib/bpf/libbpf.h
    > @@ -9,6 +9,7 @@
    > #define __BPF_LIBBPF_H
    >
    > #include <stdio.h>
    > +#include <stdbool.h>
    >
    > /*
    > * In include/linux/compiler-gcc.h, __printf is defined. However
    > @@ -34,6 +35,30 @@ void bpf_object__close(struct bpf_object *object);
    > int bpf_object__load(struct bpf_object *obj);
    > int bpf_object__unload(struct bpf_object *obj);
    >
    > +/* Accessors of bpf_program. */
    > +struct bpf_program;
    > +struct bpf_program *bpf_program__next(struct bpf_program *prog,
    > + struct bpf_object *obj);
    > +
    > +#define bpf_object__for_each_program(pos, obj) \
    > + for ((pos) = bpf_program__next(NULL, (obj)); \
    > + (pos) != NULL; \
    > + (pos) = bpf_program__next((pos), (obj)))
    > +
    > +typedef void (*bpf_program_clear_priv_t)(struct bpf_program *,
    > + void *);
    > +
    > +int bpf_program__set_private(struct bpf_program *prog, void *priv,
    > + bpf_program_clear_priv_t clear_priv);
    > +
    > +int bpf_program__get_private(struct bpf_program *prog,
    > + void **ppriv);
    > +
    > +int bpf_program__get_title(struct bpf_program *prog,
    > + const char **ptitle, bool dup);
    > +
    > +int bpf_program__get_fd(struct bpf_program *prog, int *pfd);
    > +
    > /*
    > * We don't need __attribute__((packed)) now since it is
    > * unnecessary for 'bpf_map_def' because they are all aligned.
    > --
    > 1.8.3.4


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