On Sun, Jun 25, 2023 at 09:13:26AM +0800, Jackie Liu wrote: > From: Jackie Liu <liuyun01@xxxxxxxxxx> > > When using regular expression matching with "kprobe multi", it scans all > the functions under "/proc/kallsyms" that can be matched. However, not all > of them can be traced by kprobe.multi. If any one of the functions fails > to be traced, it will result in the failure of all functions. The best > approach is to filter out the functions that cannot be traced to ensure > proper tracking of the functions. > > Use available_filter_functions_addrs check first, if failed, fallback to > kallsyms. > > Here is the test eBPF program [1]. > [1] https://github.com/JackieLiu1/ketones/tree/master/src/funccount > > Suggested-by: Jiri Olsa <jolsa@xxxxxxxxxx> > Signed-off-by: Jackie Liu <liuyun01@xxxxxxxxxx> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx> thanks, jirka > --- > tools/lib/bpf/libbpf.c | 81 ++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 75 insertions(+), 6 deletions(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index a27f6e9ccce7..fca5d2e412c5 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -10107,6 +10107,12 @@ static const char *tracefs_uprobe_events(void) > return use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events"; > } > > +static const char *tracefs_available_filter_functions_addrs(void) > +{ > + return use_debugfs() ? DEBUGFS"/available_filter_functions_addrs" : > + TRACEFS"/available_filter_functions_addrs"; > +} > + > static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz, > const char *kfunc_name, size_t offset) > { > @@ -10422,9 +10428,8 @@ struct kprobe_multi_resolve { > size_t cnt; > }; > > -static int > -resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type, > - const char *sym_name, void *ctx) > +static int ftrace_resolve_kprobe_multi_cb(unsigned long long sym_addr, > + const char *sym_name, void *ctx) > { > struct kprobe_multi_resolve *res = ctx; > int err; > @@ -10441,6 +10446,63 @@ resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type, > return 0; > } > > +static int > +kallsyms_resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type, > + const char *sym_name, void *ctx) > +{ > + return ftrace_resolve_kprobe_multi_cb(sym_addr, sym_name, ctx); > +} > + > +typedef int (*available_kprobe_cb_t)(unsigned long long sym_addr, > + const char *sym_name, void *ctx); > + > +static int > +libbpf_available_kprobes_parse(available_kprobe_cb_t cb, void *ctx) > +{ > + unsigned long long sym_addr; > + char sym_name[256]; > + FILE *f; > + int ret, err = 0; > + const char *available_path = tracefs_available_filter_functions_addrs(); > + > + f = fopen(available_path, "r"); > + if (!f) { > + err = -errno; > + pr_warn("failed to open %s, fallback to /proc/kallsyms.\n", > + available_path); > + return err; > + } > + > + while (true) { > + ret = fscanf(f, "%llx %255s%*[^\n]\n", &sym_addr, sym_name); > + if (ret == EOF && feof(f)) > + break; > + if (ret != 2) { > + pr_warn("failed to read available kprobe entry: %d\n", > + ret); > + err = -EINVAL; > + break; > + } > + > + err = cb(sym_addr, sym_name, ctx); > + if (err) > + break; > + } > + > + fclose(f); > + return err; > +} > + > +static void kprobe_multi_resolve_reinit(struct kprobe_multi_resolve *res) > +{ > + free(res->addrs); > + > + /* reset to zero, when fallback */ > + res->cap = 0; > + res->cnt = 0; > + res->addrs = NULL; > +} > + > struct bpf_link * > bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog, > const char *pattern, > @@ -10477,9 +10539,16 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog, > return libbpf_err_ptr(-EINVAL); > > if (pattern) { > - err = libbpf_kallsyms_parse(resolve_kprobe_multi_cb, &res); > - if (err) > - goto error; > + err = libbpf_available_kprobes_parse(ftrace_resolve_kprobe_multi_cb, > + &res); > + if (err) { > + /* fallback to kallsyms */ > + kprobe_multi_resolve_reinit(&res); > + err = libbpf_kallsyms_parse(kallsyms_resolve_kprobe_multi_cb, > + &res); > + if (err) > + goto error; > + } > if (!res.cnt) { > err = -ENOENT; > goto error; > -- > 2.25.1 >
