[PATCHv3 bpf-next 7/9] selftests/bpf: Allow to use kfunc from testmod.ko in test_verifier

Jiri Olsa
2023-02-03T16:25:11Z

Currently the test_verifier allows test to specify kfunc symbol
and search for it in the kernel BTF.

Adding the possibility to search for kfunc also in bpf_testmod
module when it's not found in kernel BTF.

To find bpf_testmod btf we need to get back SYS_ADMIN cap.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/testing/selftests/bpf/test_verifier.c | 161 +++++++++++++++++---
1 file changed, 139 insertions(+), 22 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 14f11f2dfbce..0a570195be37 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -879,8 +879,140 @@ static int create_map_kptr(void)
return fd;
}

+static void set_root(bool set)
+{
+ __u64 caps;
+
+ if (set) {
+ if (cap_enable_effective(1ULL << CAP_SYS_ADMIN, &caps))
+ perror("cap_disable_effective(CAP_SYS_ADMIN)");
+ } else {
+ if (cap_disable_effective(1ULL << CAP_SYS_ADMIN, &caps))
+ perror("cap_disable_effective(CAP_SYS_ADMIN)");
+ }
+}
+
+static inline __u64 ptr_to_u64(const void *ptr)
+{
+ return (__u64) (unsigned long) ptr;
+}
+
+static struct btf *btf__load_testmod_btf(struct btf *vmlinux)
+{
+ struct bpf_btf_info info;
+ __u32 len = sizeof(info);
+ struct btf *btf = NULL;
+ char name[64];
+ __u32 id = 0;
+ int err, fd;
+
+ /* Iterate all loaded BTF objects and find bpf_testmod,
+ * we need SYS_ADMIN cap for that.
+ */
+ set_root(true);
+
+ while (true) {
+ err = bpf_btf_get_next_id(id, &id);
+ if (err) {
+ if (errno == ENOENT)
+ break;
+ perror("bpf_btf_get_next_id failed");
+ break;
+ }
+
+ fd = bpf_btf_get_fd_by_id(id);
+ if (fd < 0) {
+ if (errno == ENOENT)
+ continue;
+ perror("bpf_btf_get_fd_by_id failed");
+ break;
+ }
+
+ memset(&info, 0, sizeof(info));
+ info.name_len = sizeof(name);
+ info.name = ptr_to_u64(name);
+ len = sizeof(info);
+
+ err = bpf_obj_get_info_by_fd(fd, &info, &len);
+ if (err) {
+ close(fd);
+ perror("bpf_obj_get_info_by_fd failed");
+ break;
+ }
+
+ if (strcmp("bpf_testmod", name)) {
+ close(fd);
+ continue;
+ }
+
+ btf = btf__load_from_kernel_by_id_split(id, vmlinux);
+ if (!btf) {
+ close(fd);
+ break;
+ }
+
+ /* We need the fd to stay open so it can be used in fd_array.
+ * The final cleanup call to btf__free will free btf object
+ * and close the file descriptor.
+ */
+ btf__set_fd(btf, fd);
+ break;
+ }
+
+ set_root(false);
+ return btf;
+}
+
+static struct btf *testmod_btf;
+static struct btf *vmlinux_btf;
+
+static void kfuncs_cleanup(void)
+{
+ btf__free(testmod_btf);
+ btf__free(vmlinux_btf);
+}
+
+static void fixup_prog_kfuncs(struct bpf_insn *prog, int *fd_array,
+ struct kfunc_btf_id_pair *fixup_kfunc_btf_id)
+{
+ /* Patch in kfunc BTF IDs */
+ while (fixup_kfunc_btf_id->kfunc) {
+ int btf_id = 0;
+
+ /* try to find kfunc in kernel BTF */
+ vmlinux_btf = vmlinux_btf ?: btf__load_vmlinux_btf();
+ if (vmlinux_btf) {
+ btf_id = btf__find_by_name_kind(vmlinux_btf,
+ fixup_kfunc_btf_id->kfunc,
+ BTF_KIND_FUNC);
+ btf_id = btf_id < 0 ? 0 : btf_id;
+ }
+
+ /* kfunc not found in kernel BTF, try bpf_testmod BTF */
+ if (!btf_id) {
+ testmod_btf = testmod_btf ?: btf__load_testmod_btf(vmlinux_btf);
+ if (testmod_btf) {
+ btf_id = btf__find_by_name_kind(testmod_btf,
+ fixup_kfunc_btf_id->kfunc,
+ BTF_KIND_FUNC);
+ btf_id = btf_id < 0 ? 0 : btf_id;
+ if (btf_id) {
+ /* We put bpf_testmod module fd into fd_array
+ * and its index 1 into instruction 'off'.
+ */
+ *fd_array = btf__fd(testmod_btf);
+ prog[fixup_kfunc_btf_id->insn_idx].off = 1;
+ }
+ }
+ }
+
+ prog[fixup_kfunc_btf_id->insn_idx].imm = btf_id;
+ fixup_kfunc_btf_id++;
+ }
+}
+
static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
- struct bpf_insn *prog, int *map_fds)
+ struct bpf_insn *prog, int *map_fds, int *fd_array)
{
int *fixup_map_hash_8b = test->fixup_map_hash_8b;
int *fixup_map_hash_48b = test->fixup_map_hash_48b;
@@ -905,7 +1037,6 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
int *fixup_map_ringbuf = test->fixup_map_ringbuf;
int *fixup_map_timer = test->fixup_map_timer;
int *fixup_map_kptr = test->fixup_map_kptr;
- struct kfunc_btf_id_pair *fixup_kfunc_btf_id = test->fixup_kfunc_btf_id;

if (test->fill_helper) {
test->fill_insns = calloc(MAX_TEST_INSNS, sizeof(struct bpf_insn));
@@ -1106,25 +1237,7 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
} while (*fixup_map_kptr);
}

- /* Patch in kfunc BTF IDs */
- if (fixup_kfunc_btf_id->kfunc) {
- struct btf *btf;
- int btf_id;
-
- do {
- btf_id = 0;
- btf = btf__load_vmlinux_btf();
- if (btf) {
- btf_id = btf__find_by_name_kind(btf,
- fixup_kfunc_btf_id->kfunc,
- BTF_KIND_FUNC);
- btf_id = btf_id < 0 ? 0 : btf_id;
- }
- btf__free(btf);
- prog[fixup_kfunc_btf_id->insn_idx].imm = btf_id;
- fixup_kfunc_btf_id++;
- } while (fixup_kfunc_btf_id->kfunc);
- }
+ fixup_prog_kfuncs(prog, fd_array, test->fixup_kfunc_btf_id);
}

struct libcap {
@@ -1451,6 +1564,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
int run_errs, run_successes;
int map_fds[MAX_NR_MAPS];
const char *expected_err;
+ int fd_array[2] = { -1, -1 };
int saved_errno;
int fixup_skips;
__u32 pflags;
@@ -1464,7 +1578,7 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
if (!prog_type)
prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
fixup_skips = skips;
- do_test_fixup(test, prog_type, prog, map_fds);
+ do_test_fixup(test, prog_type, prog, map_fds, &fd_array[1]);
if (test->fill_insns) {
prog = test->fill_insns;
prog_len = test->prog_len;
@@ -1498,6 +1612,8 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
else
opts.log_level = DEFAULT_LIBBPF_LOG_LEVEL;
opts.prog_flags = pflags;
+ if (fd_array[1] != -1)
+ opts.fd_array = &fd_array[0];

if ((prog_type == BPF_PROG_TYPE_TRACING ||
prog_type == BPF_PROG_TYPE_LSM) && test->kfunc) {
@@ -1740,6 +1856,7 @@ static int do_test(bool unpriv, unsigned int from, unsigned int to)
}

unload_bpf_testmod(verbose);
+ kfuncs_cleanup();

printf("Summary: %d PASSED, %d SKIPPED, %d FAILED\n", passes,
skips, errors);
--
2.39.1