在 2023/7/3 20:59, Jiri Olsa 写道:
On Mon, Jul 03, 2023 at 09:36:17AM +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.
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 = {};
do you need to define new struct for this? there's just on infos
variable of that, you could use just:
const char **syms = NULL;
size_t cap = 0, cnt = 0;
+
+ 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;
+
+ 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);
should you check if you found anything (infos.cnt != 0) and return early
if there's nothing found
+
+ /* sort available functions */
+ qsort(infos.syms, infos.cnt, sizeof(void *), qsort_compare_function);
+
+ f = fopen("/proc/kallsyms", "r");
why not use libbpf_kallsyms_parse for kallsyms parsing? the call below
would be in its callback
This place cannot directly use libbpf_kallsyms_parse, because we need
info.syms, this value cannot be passed into the parameters of
libbpf_kallsyms_parse, and we cannot turn info.syms into a global
variable, which is unnecessary. The easiest way is to reimplement a A
copy of libbpf_kallsyms_parse.
Modifications to other parts will be carried along with the next
version.
--
Jackie
+ 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;
+
+ if (ret != 2) {
+ pr_warn("failed to read kallsyms entry: %d\n", ret);
+ err = -EINVAL;
+ break;
+ }
+
+ if (!glob_match(sym_name, res->pattern))
+ continue;
hm, we don't need to call glob_match again, we just want to check
if the kallsyms symbol is in infos.syms
+
+ if (!bsearch(&sym_name, infos.syms, infos.cnt, sizeof(void *),
+ bsearch_compare_function))
+ continue;
+
+ 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;
+ }
res->cnt is check outside for 0, so we should be find here
jirka
+
+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
