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. > > Reported-by: kernel test robot <lkp@xxxxxxxxx> > Closes: https://lore.kernel.org/oe-kbuild-all/202307030355.TdXOHklM-lkp@xxxxxxxxx/ > Suggested-by: Jiri Olsa <jolsa@xxxxxxxxxx> > Suggested-by: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> > Signed-off-by: Jackie Liu <liuyun01@xxxxxxxxxx> > --- > v2->v3: fix 'fscanf' may overflow > > tools/lib/bpf/libbpf.c | 122 ++++++++++++++++++++++++++++++++++++----- > 1 file changed, 109 insertions(+), 13 deletions(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 214f828ece6b..232268215bb7 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -10224,6 +10224,12 @@ static const char *tracefs_uprobe_events(void) > return use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events"; > } > > +static const char *tracefs_available_filter_functions(void) > +{ > + return use_debugfs() ? DEBUGFS"/available_filter_functions" : > + TRACEFS"/available_filter_functions"; > +} > + > static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz, > const char *kfunc_name, size_t offset) > { > @@ -10539,23 +10545,113 @@ 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 qsort_compare_function(const void *a, const void *b) > { > - struct kprobe_multi_resolve *res = ctx; > - int err; > + return strcmp(*(const char **)a, *(const char **)b); > +} > > - if (!glob_match(sym_name, res->pattern)) > - return 0; > +static int bsearch_compare_function(const void *a, const void *b) > +{ > + return strcmp((const char *)a, *(const char **)b); > +} > > - err = libbpf_ensure_mem((void **) &res->addrs, &res->cap, sizeof(unsigned long), > - res->cnt + 1); > - if (err) > +static int libbpf_available_kallsyms_parse(struct kprobe_multi_resolve *res) > +{ > + char sym_name[500]; > + const char *available_functions_file = tracefs_available_filter_functions(); > + FILE *f; > + int err = 0, ret, i; > + struct function_info { > + const char **syms; > + size_t cap; > + size_t cnt; > + } infos = {}; > + > + f = fopen(available_functions_file, "r"); > + if (!f) { > + err = -errno; > + pr_warn("failed to open %s\n", available_functions_file); > return err; > + } > > - res->addrs[res->cnt++] = (unsigned long) sym_addr; > - return 0; > + while (true) { > + char *name; > + > + ret = fscanf(f, "%499s%*[^\n]\n", sym_name); > + if (ret == EOF && feof(f)) > + break; > + Looks like you fixed up the fclose() issues, sorry about the noise reading email backwards. bit of a nit... Its probably worth handling the case where ret == EOF and its not feof(f) that man page claims can happen on read error for example. Might never happen but would be good to distinguish from -EINVAL below? > + if (ret != 1) { > + pr_warn("failed to read available function file entry: %d\n", > + ret); > + err = -EINVAL; > + goto cleanup; > + } > + > + if (!glob_match(sym_name, res->pattern)) > + continue; > + > + err = libbpf_ensure_mem((void **)&infos.syms, &infos.cap, > + sizeof(void *), infos.cnt + 1); > + if (err) > + goto cleanup; > + > + name = strdup(sym_name); > + if (!name) { > + err = -errno; > + goto cleanup; > + } > + > + infos.syms[infos.cnt++] = name; > + } > + fclose(f); > + > + /* sort available functions */ > + qsort(infos.syms, infos.cnt, sizeof(void *), qsort_compare_function); > + > + f = fopen("/proc/kallsyms", "r"); > + if (!f) { > + err = -errno; > + pr_warn("failed to open /proc/kallsyms\n"); > + goto free_infos; > + } > + > + while (true) { > + unsigned long long sym_addr; > + > + ret = fscanf(f, "%llx %*c %499s%*[^\n]\n", &sym_addr, sym_name); > + if (ret == EOF && feof(f)) > + break; Same off chance we get ret == EOF and !feof(f)? > + > + if (ret != 2) { > + pr_warn("failed to read kallsyms entry: %d\n", ret); > + err = -EINVAL; > + break; > + } > + > + if (!glob_match(sym_name, res->pattern)) > + continue; > + > + if (!bsearch(&sym_name, infos.syms, infos.cnt, sizeof(void *), > + bsearch_compare_function)) > + continue; I'm wondering if we could get a debug print if the func was skipped? Its not always clear when running many kernels what is going to be skipped and where. > + > + err = libbpf_ensure_mem((void **)&res->addrs, &res->cap, > + sizeof(unsigned long), res->cnt + 1); > + if (err) > + break; > + > + res->addrs[res->cnt++] = (unsigned long) sym_addr; > + } > + > +cleanup: > + fclose(f); > +free_infos: > + for (i = 0; i < infos.cnt; i++) > + free((char *)infos.syms[i]); > + free(infos.syms); > + > + return err; > } > > struct bpf_link * > @@ -10594,7 +10690,7 @@ 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); > + err = libbpf_available_kallsyms_parse(&res); > if (err) > goto error; > if (!res.cnt) { > -- > 2.25.1 > >
