Commit a1a771bd authored by Ihor Solodrai's avatar Ihor Solodrai Committed by Alexei Starovoitov
Browse files

selftests/bpf: Refactor bpf_get_ksyms() trace helper 



ASAN reported a memory leak in bpf_get_ksyms(): it allocates a struct
ksyms internally and never frees it.

Move struct ksyms to trace_helpers.h and return it from the
bpf_get_ksyms(), giving ownership to the caller. Add filtered_syms and
filtered_cnt fields to the ksyms to hold the filtered array of
symbols, previously returned by bpf_get_ksyms().

Fixup the call sites: kprobe_multi_test and bench_trigger.

Signed-off-by: default avatarIhor Solodrai <ihor.solodrai@linux.dev>
Acked-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260223190736.649171-10-ihor.solodrai@linux.dev


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 45897ced

tools/testing/selftests/bpf/benchs/bench_trigger.c

+8 −6
Original line number Diff line number Diff line
@@ -230,8 +230,8 @@ static void trigger_fentry_setup(void) 
static void attach_ksyms_all(struct bpf_program *empty, bool kretprobe)

{

	LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);

	char **syms = NULL;

	size_t cnt = 0;

	struct bpf_link *link = NULL;

	struct ksyms *ksyms = NULL;



	/* Some recursive functions will be skipped in

	 * bpf_get_ksyms -> skip_entry, as they can introduce sufficient
@@ -241,16 +241,18 @@ static void attach_ksyms_all(struct bpf_program *empty, bool kretprobe) 
	 * So, don't run the kprobe-multi-all and kretprobe-multi-all on

	 * a debug kernel.

	 */

	if (bpf_get_ksyms(&syms, &cnt, true)) {

	if (bpf_get_ksyms(&ksyms, true)) {

		fprintf(stderr, "failed to get ksyms\n");

		exit(1);

	}



	opts.syms = (const char **) syms;

	opts.cnt = cnt;

	opts.syms = (const char **)ksyms->filtered_syms;

	opts.cnt = ksyms->filtered_cnt;

	opts.retprobe = kretprobe;

	/* attach empty to all the kernel functions except bpf_get_numa_node_id. */

	if (!bpf_program__attach_kprobe_multi_opts(empty, NULL, &opts)) {

	link = bpf_program__attach_kprobe_multi_opts(empty, NULL, &opts);

	free_kallsyms_local(ksyms);

	if (!link) {

		fprintf(stderr, "failed to attach bpf_program__attach_kprobe_multi_opts to all\n");

		exit(1);

	}

tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c

+5 −7
Original line number Diff line number Diff line
@@ -456,25 +456,23 @@ static void test_kprobe_multi_bench_attach(bool kernel) 
{

	LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);

	struct kprobe_multi_empty *skel = NULL;

	char **syms = NULL;

	size_t cnt = 0;

	struct ksyms *ksyms = NULL;



	if (!ASSERT_OK(bpf_get_ksyms(&syms, &cnt, kernel), "bpf_get_ksyms"))

	if (!ASSERT_OK(bpf_get_ksyms(&ksyms, kernel), "bpf_get_ksyms"))

		return;



	skel = kprobe_multi_empty__open_and_load();

	if (!ASSERT_OK_PTR(skel, "kprobe_multi_empty__open_and_load"))

		goto cleanup;



	opts.syms = (const char **) syms;

	opts.cnt = cnt;

	opts.syms = (const char **)ksyms->filtered_syms;

	opts.cnt = ksyms->filtered_cnt;



	do_bench_test(skel, &opts);



cleanup:

	kprobe_multi_empty__destroy(skel);

	if (syms)

		free(syms);

	free_kallsyms_local(ksyms);

}



static void test_kprobe_multi_bench_attach_addr(bool kernel)

tools/testing/selftests/bpf/trace_helpers.c

+12 −11
Original line number Diff line number Diff line
@@ -24,12 +24,6 @@ 
#define TRACEFS_PIPE	"/sys/kernel/tracing/trace_pipe"

#define DEBUGFS_PIPE	"/sys/kernel/debug/tracing/trace_pipe"



struct ksyms {

	struct ksym *syms;

	size_t sym_cap;

	size_t sym_cnt;

};



static struct ksyms *ksyms;

static pthread_mutex_t ksyms_mutex = PTHREAD_MUTEX_INITIALIZER;
@@ -54,6 +48,8 @@ void free_kallsyms_local(struct ksyms *ksyms) 
	if (!ksyms)

		return;



	free(ksyms->filtered_syms);



	if (!ksyms->syms) {

		free(ksyms);

		return;
@@ -610,7 +606,7 @@ static int search_kallsyms_compare(const void *p1, const struct ksym *p2) 
	return compare_name(p1, p2->name);

}



int bpf_get_ksyms(char ***symsp, size_t *cntp, bool kernel)

int bpf_get_ksyms(struct ksyms **ksymsp, bool kernel)

{

	size_t cap = 0, cnt = 0;

	char *name = NULL, *ksym_name, **syms = NULL;
@@ -637,8 +633,10 @@ int bpf_get_ksyms(char ***symsp, size_t *cntp, bool kernel) 
	else

		f = fopen("/sys/kernel/debug/tracing/available_filter_functions", "r");



	if (!f)

	if (!f) {

		free_kallsyms_local(ksyms);

		return -EINVAL;

	}



	map = hashmap__new(symbol_hash, symbol_equal, NULL);

	if (IS_ERR(map)) {
@@ -679,15 +677,18 @@ int bpf_get_ksyms(char ***symsp, size_t *cntp, bool kernel) 
		syms[cnt++] = ksym_name;

	}



	*symsp = syms;

	*cntp = cnt;

	ksyms->filtered_syms = syms;

	ksyms->filtered_cnt = cnt;

	*ksymsp = ksyms;



error:

	free(name);

	fclose(f);

	hashmap__free(map);

	if (err)

	if (err) {

		free(syms);

		free_kallsyms_local(ksyms);

	}

	return err;

}

tools/testing/selftests/bpf/trace_helpers.h

+9 −2
Original line number Diff line number Diff line
@@ -23,7 +23,14 @@ struct ksym { 
	long addr;

	char *name;

};

struct ksyms;



struct ksyms {

	struct ksym *syms;

	size_t sym_cap;

	size_t sym_cnt;

	char **filtered_syms;

	size_t filtered_cnt;

};



typedef int (*ksym_cmp_t)(const void *p1, const void *p2);

typedef int (*ksym_search_cmp_t)(const void *p1, const struct ksym *p2);
@@ -53,7 +60,7 @@ ssize_t get_rel_offset(uintptr_t addr); 


int read_build_id(const char *path, char *build_id, size_t size);



int bpf_get_ksyms(char ***symsp, size_t *cntp, bool kernel);

int bpf_get_ksyms(struct ksyms **ksymsp, bool kernel);

int bpf_get_addrs(unsigned long **addrsp, size_t *cntp, bool kernel);



#endif