On Fri, Oct 9, 2020 at 9:04 AM Daniel T. Lee <danieltimlee@xxxxxxxxx> wrote:
>
> From commit d7a18ea7e8b6 ("libbpf: Add generic bpf_program__attach()"),
> for some BPF programs, it is now possible to attach BPF programs
> with __attach() instead of explicitly calling __attach_<type>().
>
> This commit refactors the __attach_tracepoint() with libbpf's generic
> __attach() method. In addition, this refactors the logic of setting
> the map FD to simplify the code. Also, the missing removal of
> bpf_load.o in Makefile has been fixed.
>
> Signed-off-by: Daniel T. Lee <danieltimlee@xxxxxxxxx>
> ---
> samples/bpf/Makefile | 2 +-
> samples/bpf/xdp_redirect_cpu_user.c | 138 +++++++++++++---------------
> 2 files changed, 67 insertions(+), 73 deletions(-)
>
[...]
> #define NUM_TP 5
> +#define NUM_MAP 9
> struct bpf_link *tp_links[NUM_TP] = { 0 };
= {}
> +static int map_fds[NUM_MAP];
> static int tp_cnt = 0;
>
> /* Exit return codes */
[...]
> -static struct bpf_link * attach_tp(struct bpf_object *obj,
> - const char *tp_category,
> - const char* tp_name)
> +static int init_tracepoints(struct bpf_object *obj)
> {
> + char *tp_section = "tracepoint/";
> struct bpf_program *prog;
> - struct bpf_link *link;
> - char sec_name[PATH_MAX];
> - int len;
> + const char *section;
>
> - len = snprintf(sec_name, PATH_MAX, "tracepoint/%s/%s",
> - tp_category, tp_name);
> - if (len < 0)
> - exit(EXIT_FAIL);
> + bpf_object__for_each_program(prog, obj) {
> + section = bpf_program__section_name(prog);
> + if (strncmp(section, tp_section, strlen(tp_section)) != 0)
> + continue;
that's a convoluted and error-prone way (you can also use "tp/bla/bla"
for tracepoint programs, for example). Use
bpf_program__is_tracepoint() check.
>
> - prog = bpf_object__find_program_by_title(obj, sec_name);
> - if (!prog) {
> - fprintf(stderr, "ERR: finding progsec: %s\n", sec_name);
> - exit(EXIT_FAIL_BPF);
> + tp_links[tp_cnt] = bpf_program__attach(prog);
> + if (libbpf_get_error(tp_links[tp_cnt])) {
> + tp_links[tp_cnt] = NULL;
> + return -EINVAL;
> + }
> + tp_cnt++;
> }
>
[...]
