| Message ID | 20211022234814.318457-1-songliubraving@fb.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf-next] selftests/bpf: guess function end for test_get_branch_snapshot | expand |
On Fri, Oct 22, 2021 at 4:48 PM Song Liu <songliubraving@fb.com> wrote: > > 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. It's so annoying that sizes of all those symbols are known and available in ELF, yet kallsyms don't expose them :( I've applied this "fix", but it makes me very sad. > > Signed-off-by: Song Liu <songliubraving@fb.com> > --- > .../bpf/prog_tests/get_branch_snapshot.c | 7 ++-- > tools/testing/selftests/bpf/trace_helpers.c | 36 ------------------- > tools/testing/selftests/bpf/trace_helpers.h | 5 --- > 3 files changed, 4 insertions(+), 44 deletions(-) > [...]
diff --git a/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c index d6d70a359aeb5..bc2b6e6d167d4 100644 --- a/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c +++ b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c @@ -91,9 +91,10 @@ 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")) diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c index 5100a169b72b1..7b7f918eda776 100644 --- a/tools/testing/selftests/bpf/trace_helpers.c +++ b/tools/testing/selftests/bpf/trace_helpers.c @@ -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; diff --git a/tools/testing/selftests/bpf/trace_helpers.h b/tools/testing/selftests/bpf/trace_helpers.h index bc8ed86105d94..d907b445524d5 100644 --- a/tools/testing/selftests/bpf/trace_helpers.h +++ b/tools/testing/selftests/bpf/trace_helpers.h @@ -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);
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: Song Liu <songliubraving@fb.com> --- .../bpf/prog_tests/get_branch_snapshot.c | 7 ++-- tools/testing/selftests/bpf/trace_helpers.c | 36 ------------------- tools/testing/selftests/bpf/trace_helpers.h | 5 --- 3 files changed, 4 insertions(+), 44 deletions(-)