On Wed, Apr 20, 2022 at 02:56:53PM -0700, Andrii Nakryiko wrote:
SNIP
> > +#define DEBUGFS "/sys/kernel/debug/tracing/"
> > +
> > +static int get_syms(char ***symsp, size_t *cntp)
> > +{
> > + size_t cap = 0, cnt = 0, i;
> > + char *name, **syms = NULL;
> > + struct hashmap *map;
> > + char buf[256];
> > + FILE *f;
> > + int err;
> > +
> > + /*
> > + * The available_filter_functions contains many duplicates,
> > + * but other than that all symbols are usable in kprobe multi
> > + * interface.
> > + * Filtering out duplicates by using hashmap__add, which won't
> > + * add existing entry.
> > + */
> > + f = fopen(DEBUGFS "available_filter_functions", "r");
>
> nit: DEBUGFS "constant" just makes it harder to follow the code and
> doesn't add anything, please just use the full path here directly
there's another one DEBUGFS in trace_helpers.c,
we could put it in trace_helpers.h
>
> > + if (!f)
> > + return -EINVAL;
> > +
> > + map = hashmap__new(symbol_hash, symbol_equal, NULL);
> > + err = libbpf_get_error(map);
>
> hashmap__new() is an internal API, so please use IS_ERR() directly
> here. libbpf_get_error() should be used for public libbpf APIs, and
> preferably not in libbpf 1.0 mode
ok
>
> > + if (err)
> > + goto error;
> > +
> > + while (fgets(buf, sizeof(buf), f)) {
> > + /* skip modules */
> > + if (strchr(buf, '['))
> > + continue;
>
> [...]
>
> > + attach_delta = (attach_end_ns - attach_start_ns) / 1000000000.0;
> > + detach_delta = (detach_end_ns - detach_start_ns) / 1000000000.0;
> > +
> > + fprintf(stderr, "%s: found %lu functions\n", __func__, cnt);
> > + fprintf(stderr, "%s: attached in %7.3lfs\n", __func__, attach_delta);
> > + fprintf(stderr, "%s: detached in %7.3lfs\n", __func__, detach_delta);
>
>
> why stderr? just do printf() and let test_progs handle output
ok
>
>
> > +
> > +cleanup:
> > + kprobe_multi_empty__destroy(skel);
> > + if (syms) {
> > + for (i = 0; i < cnt; i++)
> > + free(syms[i]);
> > + free(syms);
> > + }
> > +}
> > +
> > void test_kprobe_multi_test(void)
> > {
> > if (!ASSERT_OK(load_kallsyms(), "load_kallsyms"))
> > @@ -320,4 +454,6 @@ void test_kprobe_multi_test(void)
> > test_attach_api_syms();
> > if (test__start_subtest("attach_api_fails"))
> > test_attach_api_fails();
> > + if (test__start_subtest("bench_attach"))
> > + test_bench_attach();
> > }
> > diff --git a/tools/testing/selftests/bpf/progs/kprobe_multi_empty.c b/tools/testing/selftests/bpf/progs/kprobe_multi_empty.c
> > new file mode 100644
> > index 000000000000..be9e3d891d46
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/kprobe_multi_empty.c
> > @@ -0,0 +1,12 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include <linux/bpf.h>
> > +#include <bpf/bpf_helpers.h>
> > +#include <bpf/bpf_tracing.h>
> > +
> > +char _license[] SEC("license") = "GPL";
> > +
> > +SEC("kprobe.multi/*")
>
> use SEC("kprobe.multi") to make it clear that we are attaching it "manually"?
yep, will do
thanks,
jirka
