Commit 20d1b54a authored by Song Liu's avatar Song Liu Committed by Andrii Nakryiko
Browse files

selftests/bpf: Guess function end for test_get_branch_snapshot 



Function in modules could appear in /proc/kallsyms in random order.

ffffffffa02608a0 t bpf_testmod_loop_test
ffffffffa02600c0 t __traceiter_bpf_testmod_test_writable_bare
ffffffffa0263b60 d __tracepoint_bpf_testmod_test_write_bare
ffffffffa02608c0 T bpf_testmod_test_read
ffffffffa0260d08 t __SCT__tp_func_bpf_testmod_test_writable_bare
ffffffffa0263300 d __SCK__tp_func_bpf_testmod_test_read
ffffffffa0260680 T bpf_testmod_test_write
ffffffffa0260860 t bpf_testmod_test_mod_kfunc

Therefore, we cannot reliably use kallsyms_find_next() to find the end of
a function. Replace it with a simple guess (start + 128). This is good
enough for this test.

Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211022234814.318457-1-songliubraving@fb.com
parent b4e87072

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

+4 −3
Original line number Diff line number Diff line
@@ -97,9 +97,10 @@ void serial_test_get_branch_snapshot(void) 
	if (!ASSERT_OK(err, "kallsyms_find"))

		goto cleanup;



	err = kallsyms_find_next("bpf_testmod_loop_test", &skel->bss->address_high);

	if (!ASSERT_OK(err, "kallsyms_find_next"))

		goto cleanup;

	/* Just a guess for the end of this function, as module functions

	 * in /proc/kallsyms could come in any order.

	 */

	skel->bss->address_high = skel->bss->address_low + 128;



	err = get_branch_snapshot__attach(skel);

	if (!ASSERT_OK(err, "get_branch_snapshot__attach"))

tools/testing/selftests/bpf/trace_helpers.c

+0 −36
Original line number Diff line number Diff line
@@ -118,42 +118,6 @@ int kallsyms_find(const char *sym, unsigned long long *addr) 
	return err;

}



/* find the address of the next symbol of the same type, this can be used

 * to determine the end of a function.

 */

int kallsyms_find_next(const char *sym, unsigned long long *addr)

{

	char type, found_type, name[500];

	unsigned long long value;

	bool found = false;

	int err = 0;

	FILE *f;



	f = fopen("/proc/kallsyms", "r");

	if (!f)

		return -EINVAL;



	while (fscanf(f, "%llx %c %499s%*[^\n]\n", &value, &type, name) > 0) {

		/* Different types of symbols in kernel modules are mixed

		 * in /proc/kallsyms. Only return the next matching type.

		 * Use tolower() for type so that 'T' matches 't'.

		 */

		if (found && found_type == tolower(type)) {

			*addr = value;

			goto out;

		}

		if (strcmp(name, sym) == 0) {

			found = true;

			found_type = tolower(type);

		}

	}

	err = -ENOENT;



out:

	fclose(f);

	return err;

}



void read_trace_pipe(void)

{

	int trace_fd;

tools/testing/selftests/bpf/trace_helpers.h

+0 −5
Original line number Diff line number Diff line
@@ -16,11 +16,6 @@ long ksym_get_addr(const char *name); 
/* open kallsyms and find addresses on the fly, faster than load + search. */

int kallsyms_find(const char *sym, unsigned long long *addr);



/* find the address of the next symbol, this can be used to determine the

 * end of a function

 */

int kallsyms_find_next(const char *sym, unsigned long long *addr);



void read_trace_pipe(void);



ssize_t get_uprobe_offset(const void *addr, ssize_t base);