[PATCH v3 1/2] selftests/bpf: ksym_search won't check symbols exists

[PATCH v3 1/2] selftests/bpf: ksym_search won't check symbols exists

[Daniel T. Lee]

Currently, ksym_search located at trace_helpers won't check symbols are
existing or not.

In ksym_search, when symbol is not found, it will return &syms[0](_stext).
But when the kernel symbols are not loaded, it will return NULL, which is
not a desired action.

This commit will add verification logic whether symbols are loaded prior
to the symbol search.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
---
 tools/testing/selftests/bpf/trace_helpers.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
index 4cdb63bf0521..9a9fc6c9b70b 100644
--- a/tools/testing/selftests/bpf/trace_helpers.c
+++ b/tools/testing/selftests/bpf/trace_helpers.c
@@ -52,6 +52,10 @@ struct ksym *ksym_search(long key)
 	int start = 0, end = sym_cnt;
 	int result;
 
+	/* kallsyms not loaded. return NULL */
+	if (sym_cnt <= 0)
+		return NULL;
+
 	while (start < end) {
 		size_t mid = start + (end - start) / 2;
 
-- 
2.17.1

[PATCH v3 2/2] samples, selftests/bpf: add NULL check for ksym_search

[Daniel T. Lee]

Since, ksym_search added with verification logic for symbols existence,
it could return NULL when the kernel symbols are not loaded.

This commit will add NULL check logic after ksym_search.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
---
Changes in v3:
    - Added NULL check for samples/spintest_user.c

Changes in v2:
    - Added NULL check for selftests/bpf/prog_tests/get_stack_raw_tp.c

 samples/bpf/offwaketime_user.c                            | 5 +++++
 samples/bpf/sampleip_user.c                               | 5 +++++
 samples/bpf/spintest_user.c                               | 7 ++++++-
 samples/bpf/trace_event_user.c                            | 5 +++++
 tools/testing/selftests/bpf/prog_tests/get_stack_raw_tp.c | 4 ++--
 5 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/samples/bpf/offwaketime_user.c b/samples/bpf/offwaketime_user.c
index f06063af9fcb..bb315ce1b866 100644
--- a/samples/bpf/offwaketime_user.c
+++ b/samples/bpf/offwaketime_user.c
@@ -28,6 +28,11 @@ static void print_ksym(__u64 addr)
 	if (!addr)
 		return;
 	sym = ksym_search(addr);
+	if (!sym) {
+		printf("ksym not found. Is kallsyms loaded?\n");
+		return;
+	}
+
 	if (PRINT_RAW_ADDR)
 		printf("%s/%llx;", sym->name, addr);
 	else
diff --git a/samples/bpf/sampleip_user.c b/samples/bpf/sampleip_user.c
index 216c7ecbbbe9..23b90a45c802 100644
--- a/samples/bpf/sampleip_user.c
+++ b/samples/bpf/sampleip_user.c
@@ -109,6 +109,11 @@ static void print_ip_map(int fd)
 	for (i = 0; i < max; i++) {
 		if (counts[i].ip > PAGE_OFFSET) {
 			sym = ksym_search(counts[i].ip);
+			if (!sym) {
+				printf("ksym not found. Is kallsyms loaded?\n");
+				continue;
+			}
+
 			printf("0x%-17llx %-32s %u\n", counts[i].ip, sym->name,
 			       counts[i].count);
 		} else {
diff --git a/samples/bpf/spintest_user.c b/samples/bpf/spintest_user.c
index 8d3e9cfa1909..2556af2d9b3e 100644
--- a/samples/bpf/spintest_user.c
+++ b/samples/bpf/spintest_user.c
@@ -37,8 +37,13 @@ int main(int ac, char **argv)
 			bpf_map_lookup_elem(map_fd[0], &next_key, &value);
 			assert(next_key == value);
 			sym = ksym_search(value);
-			printf(" %s", sym->name);
 			key = next_key;
+			if (!sym) {
+				printf("ksym not found. Is kallsyms loaded?\n");
+				continue;
+			}
+
+			printf(" %s", sym->name);
 		}
 		if (key)
 			printf("\n");
diff --git a/samples/bpf/trace_event_user.c b/samples/bpf/trace_event_user.c
index d08046ab81f0..d4178f60e075 100644
--- a/samples/bpf/trace_event_user.c
+++ b/samples/bpf/trace_event_user.c
@@ -34,6 +34,11 @@ static void print_ksym(__u64 addr)
 	if (!addr)
 		return;
 	sym = ksym_search(addr);
+	if (!sym) {
+		printf("ksym not found. Is kallsyms loaded?\n");
+		return;
+	}
+
 	printf("%s;", sym->name);
 	if (!strcmp(sym->name, "sys_read"))
 		sys_read_seen = true;
diff --git a/tools/testing/selftests/bpf/prog_tests/get_stack_raw_tp.c b/tools/testing/selftests/bpf/prog_tests/get_stack_raw_tp.c
index d7bb5beb1c57..c2a0a9d5591b 100644
--- a/tools/testing/selftests/bpf/prog_tests/get_stack_raw_tp.c
+++ b/tools/testing/selftests/bpf/prog_tests/get_stack_raw_tp.c
@@ -39,7 +39,7 @@ static int get_stack_print_output(void *data, int size)
 		} else {
 			for (i = 0; i < num_stack; i++) {
 				ks = ksym_search(raw_data[i]);
-				if (strcmp(ks->name, nonjit_func) == 0) {
+				if (ks && (strcmp(ks->name, nonjit_func) == 0)) {
 					found = true;
 					break;
 				}
@@ -56,7 +56,7 @@ static int get_stack_print_output(void *data, int size)
 		} else {
 			for (i = 0; i < num_stack; i++) {
 				ks = ksym_search(e->kern_stack[i]);
-				if (strcmp(ks->name, nonjit_func) == 0) {
+				if (ks && (strcmp(ks->name, nonjit_func) == 0)) {
 					good_kern_stack = true;
 					break;
 				}
-- 
2.17.1

Re: [PATCH v3 1/2] selftests/bpf: ksym_search won't check symbols exists

[Daniel Borkmann]

On 04/04/2019 12:17 AM, Daniel T. Lee wrote:
> Currently, ksym_search located at trace_helpers won't check symbols are
> existing or not.
> 
> In ksym_search, when symbol is not found, it will return &syms[0](_stext).
> But when the kernel symbols are not loaded, it will return NULL, which is
> not a desired action.
> 
> This commit will add verification logic whether symbols are loaded prior
> to the symbol search.
> 
> Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>

Applied, thanks.