bpf: improve error message for unsupported helper

BPF verifier emits "unknown func" message when given BPF program type
does not support BPF helper. This message may be confusing for users, as
important context that helper is unknown only to current program type is
not provided.

This patch changes message to "program of this type cannot use helper "
and aligns dependent code in libbpf and tests. Any suggestions on
improving/changing this message are welcome.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Quentin Monnet <qmo@kernel.org>
Link: https://lore.kernel.org/r/20240325152210.377548-1-yatsenko@meta.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 17f26ba1a9e011606572f4308fbe523a6f85670d..edb650667f44d753e195628edcc82279d008b41b 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10201,8 +10201,8 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
        if (env->ops->get_func_proto)
                fn = env->ops->get_func_proto(func_id, env->prog);
        if (!fn) {
-               verbose(env, "unknown func %s#%d\n", func_id_name(func_id),
-                       func_id);
+               verbose(env, "program of this type cannot use helper %s#%d\n",
+                       func_id_name(func_id), func_id);
                return -EINVAL;
        }
 

diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c
index 708733b0ea061ec46c01797998bb45f7a0840e9c..c754a428c8c6e18542225998ad7c4f08039eb743 100644 (file)
--- a/tools/bpf/bpftool/feature.c
+++ b/tools/bpf/bpftool/feature.c
@@ -664,7 +664,8 @@ probe_helper_ifindex(enum bpf_func_id id, enum bpf_prog_type prog_type,
 
        probe_prog_load_ifindex(prog_type, insns, ARRAY_SIZE(insns), buf,
                                sizeof(buf), ifindex);
-       res = !grep(buf, "invalid func ") && !grep(buf, "unknown func ");
+       res = !grep(buf, "invalid func ") && !grep(buf, "unknown func ") &&
+               !grep(buf, "program of this type cannot use helper ");
 
        switch (get_vendor_id(ifindex)) {
        case 0x19ee: /* Netronome specific */

diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index 3021881224392a52b082e02fef18e93f8b698ec5..9dfbe7750f564ac2ad8b86a087ee708c88e97017 100644 (file)
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -448,7 +448,8 @@ int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_id helpe
        /* If BPF verifier doesn't recognize BPF helper ID (enum bpf_func_id)
         * at all, it will emit something like "invalid func unknown#181".
         * If BPF verifier recognizes BPF helper but it's not supported for
-        * given BPF program type, it will emit "unknown func bpf_sys_bpf#166".
+        * given BPF program type, it will emit "unknown func bpf_sys_bpf#166"
+        * or "program of this type cannot use helper bpf_sys_bpf#166".
         * In both cases, provided combination of BPF program type and BPF
         * helper is not supported by the kernel.
         * In all other cases, probe_prog_load() above will either succeed (e.g.,
@@ -457,7 +458,8 @@ int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_id helpe
         * that), or we'll get some more specific BPF verifier error about
         * some unsatisfied conditions.
         */
-       if (ret == 0 && (strstr(buf, "invalid func ") || strstr(buf, "unknown func ")))
+       if (ret == 0 && (strstr(buf, "invalid func ") || strstr(buf, "unknown func ") ||
+                        strstr(buf, "program of this type cannot use helper ")))
                return 0;
        return 1; /* assume supported */
 }

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
index 94cb22b014821d1f3830db85440b219ebbf9a74d..99dc60fe59d51b4d4dc3b8746f9fbaeb5a24cddc 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
@@ -304,7 +304,7 @@ static void test_rel_setsockopt(void)
        struct bpf_dctcp_release *rel_skel;
        libbpf_print_fn_t old_print_fn;
 
-       err_str = "unknown func bpf_setsockopt";
+       err_str = "program of this type cannot use helper bpf_setsockopt";
        found = false;
 
        old_print_fn = libbpf_set_print(libbpf_debug_print);

diff --git a/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c b/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c
index 0ede0ccd090c4266392d7d8b7d185f73cde3ff0d..059aa716e3d0badba8a62ff3c957ce0847e72001 100644 (file)
--- a/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c
+++ b/tools/testing/selftests/bpf/progs/verifier_helper_restricted.c
@@ -30,7 +30,7 @@ struct {
 
 SEC("kprobe")
 __description("bpf_ktime_get_coarse_ns is forbidden in BPF_PROG_TYPE_KPROBE")
-__failure __msg("unknown func bpf_ktime_get_coarse_ns")
+__failure __msg("program of this type cannot use helper bpf_ktime_get_coarse_ns")
 __naked void in_bpf_prog_type_kprobe_1(void)
 {
        asm volatile ("                                 \
@@ -44,7 +44,7 @@ __naked void in_bpf_prog_type_kprobe_1(void)
 
 SEC("tracepoint")
 __description("bpf_ktime_get_coarse_ns is forbidden in BPF_PROG_TYPE_TRACEPOINT")
-__failure __msg("unknown func bpf_ktime_get_coarse_ns")
+__failure __msg("program of this type cannot use helper bpf_ktime_get_coarse_ns")
 __naked void in_bpf_prog_type_tracepoint_1(void)
 {
        asm volatile ("                                 \
@@ -58,7 +58,7 @@ __naked void in_bpf_prog_type_tracepoint_1(void)
 
 SEC("perf_event")
 __description("bpf_ktime_get_coarse_ns is forbidden in BPF_PROG_TYPE_PERF_EVENT")
-__failure __msg("unknown func bpf_ktime_get_coarse_ns")
+__failure __msg("program of this type cannot use helper bpf_ktime_get_coarse_ns")
 __naked void bpf_prog_type_perf_event_1(void)
 {
        asm volatile ("                                 \
@@ -72,7 +72,7 @@ __naked void bpf_prog_type_perf_event_1(void)
 
 SEC("raw_tracepoint")
 __description("bpf_ktime_get_coarse_ns is forbidden in BPF_PROG_TYPE_RAW_TRACEPOINT")
-__failure __msg("unknown func bpf_ktime_get_coarse_ns")
+__failure __msg("program of this type cannot use helper bpf_ktime_get_coarse_ns")
 __naked void bpf_prog_type_raw_tracepoint_1(void)
 {
        asm volatile ("                                 \