selftests/bpf: Add testcases for tailcall hierarchy fixing

Add some test cases to confirm the tailcall hierarchy issue has been fixed.

On x64, the selftests result is:

cd tools/testing/selftests/bpf && ./test_progs -t tailcalls
327/18  tailcalls/tailcall_bpf2bpf_hierarchy_1:OK
327/19  tailcalls/tailcall_bpf2bpf_hierarchy_fentry:OK
327/20  tailcalls/tailcall_bpf2bpf_hierarchy_fexit:OK
327/21  tailcalls/tailcall_bpf2bpf_hierarchy_fentry_fexit:OK
327/22  tailcalls/tailcall_bpf2bpf_hierarchy_fentry_entry:OK
327/23  tailcalls/tailcall_bpf2bpf_hierarchy_2:OK
327/24  tailcalls/tailcall_bpf2bpf_hierarchy_3:OK
327     tailcalls:OK
Summary: 1/24 PASSED, 0 SKIPPED, 0 FAILED

On arm64, the selftests result is:

cd tools/testing/selftests/bpf && ./test_progs -t tailcalls
327/18  tailcalls/tailcall_bpf2bpf_hierarchy_1:OK
327/19  tailcalls/tailcall_bpf2bpf_hierarchy_fentry:OK
327/20  tailcalls/tailcall_bpf2bpf_hierarchy_fexit:OK
327/21  tailcalls/tailcall_bpf2bpf_hierarchy_fentry_fexit:OK
327/22  tailcalls/tailcall_bpf2bpf_hierarchy_fentry_entry:OK
327/23  tailcalls/tailcall_bpf2bpf_hierarchy_2:OK
327/24  tailcalls/tailcall_bpf2bpf_hierarchy_3:OK
327     tailcalls:OK
Summary: 1/24 PASSED, 0 SKIPPED, 0 FAILED

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>
Link: https://lore.kernel.org/r/20240714123902.32305-4-hffilwlqm@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/tailcalls.c b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
index 59993fc9c0d7e2b33d9ac6e4fa1caf434398cc04..e01fabb8cc415978e3d2a6e1930c83c07195fcc4 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/tailcalls.c
+++ b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
@@ -3,6 +3,8 @@
 #include <test_progs.h>
 #include <network_helpers.h>
 #include "tailcall_poke.skel.h"
+#include "tailcall_bpf2bpf_hierarchy2.skel.h"
+#include "tailcall_bpf2bpf_hierarchy3.skel.h"
 
 
 /* test_tailcall_1 checks basic functionality by patching multiple locations
@@ -1187,6 +1189,312 @@ out:
        tailcall_poke__destroy(call);
 }
 
+static void test_tailcall_hierarchy_count(const char *which, bool test_fentry,
+                                         bool test_fexit,
+                                         bool test_fentry_entry)
+{
+       int err, map_fd, prog_fd, main_data_fd, fentry_data_fd, fexit_data_fd, i, val;
+       struct bpf_object *obj = NULL, *fentry_obj = NULL, *fexit_obj = NULL;
+       struct bpf_link *fentry_link = NULL, *fexit_link = NULL;
+       struct bpf_program *prog, *fentry_prog;
+       struct bpf_map *prog_array, *data_map;
+       int fentry_prog_fd;
+       char buff[128] = {};
+
+       LIBBPF_OPTS(bpf_test_run_opts, topts,
+               .data_in = buff,
+               .data_size_in = sizeof(buff),
+               .repeat = 1,
+       );
+
+       err = bpf_prog_test_load(which, BPF_PROG_TYPE_SCHED_CLS, &obj,
+                                &prog_fd);
+       if (!ASSERT_OK(err, "load obj"))
+               return;
+
+       prog = bpf_object__find_program_by_name(obj, "entry");
+       if (!ASSERT_OK_PTR(prog, "find entry prog"))
+               goto out;
+
+       prog_fd = bpf_program__fd(prog);
+       if (!ASSERT_GE(prog_fd, 0, "prog_fd"))
+               goto out;
+
+       if (test_fentry_entry) {
+               fentry_obj = bpf_object__open_file("tailcall_bpf2bpf_hierarchy_fentry.bpf.o",
+                                                  NULL);
+               if (!ASSERT_OK_PTR(fentry_obj, "open fentry_obj file"))
+                       goto out;
+
+               fentry_prog = bpf_object__find_program_by_name(fentry_obj,
+                                                              "fentry");
+               if (!ASSERT_OK_PTR(prog, "find fentry prog"))
+                       goto out;
+
+               err = bpf_program__set_attach_target(fentry_prog, prog_fd,
+                                                    "entry");
+               if (!ASSERT_OK(err, "set_attach_target entry"))
+                       goto out;
+
+               err = bpf_object__load(fentry_obj);
+               if (!ASSERT_OK(err, "load fentry_obj"))
+                       goto out;
+
+               fentry_link = bpf_program__attach_trace(fentry_prog);
+               if (!ASSERT_OK_PTR(fentry_link, "attach_trace"))
+                       goto out;
+
+               fentry_prog_fd = bpf_program__fd(fentry_prog);
+               if (!ASSERT_GE(fentry_prog_fd, 0, "fentry_prog_fd"))
+                       goto out;
+
+               prog_array = bpf_object__find_map_by_name(fentry_obj, "jmp_table");
+               if (!ASSERT_OK_PTR(prog_array, "find jmp_table"))
+                       goto out;
+
+               map_fd = bpf_map__fd(prog_array);
+               if (!ASSERT_GE(map_fd, 0, "map_fd"))
+                       goto out;
+
+               i = 0;
+               err = bpf_map_update_elem(map_fd, &i, &fentry_prog_fd, BPF_ANY);
+               if (!ASSERT_OK(err, "update jmp_table"))
+                       goto out;
+
+               data_map = bpf_object__find_map_by_name(fentry_obj, ".bss");
+               if (!ASSERT_FALSE(!data_map || !bpf_map__is_internal(data_map),
+                                 "find data_map"))
+                       goto out;
+
+       } else {
+               prog_array = bpf_object__find_map_by_name(obj, "jmp_table");
+               if (!ASSERT_OK_PTR(prog_array, "find jmp_table"))
+                       goto out;
+
+               map_fd = bpf_map__fd(prog_array);
+               if (!ASSERT_GE(map_fd, 0, "map_fd"))
+                       goto out;
+
+               i = 0;
+               err = bpf_map_update_elem(map_fd, &i, &prog_fd, BPF_ANY);
+               if (!ASSERT_OK(err, "update jmp_table"))
+                       goto out;
+
+               data_map = bpf_object__find_map_by_name(obj, ".bss");
+               if (!ASSERT_FALSE(!data_map || !bpf_map__is_internal(data_map),
+                                 "find data_map"))
+                       goto out;
+       }
+
+       if (test_fentry) {
+               fentry_obj = bpf_object__open_file("tailcall_bpf2bpf_fentry.bpf.o",
+                                                  NULL);
+               if (!ASSERT_OK_PTR(fentry_obj, "open fentry_obj file"))
+                       goto out;
+
+               prog = bpf_object__find_program_by_name(fentry_obj, "fentry");
+               if (!ASSERT_OK_PTR(prog, "find fentry prog"))
+                       goto out;
+
+               err = bpf_program__set_attach_target(prog, prog_fd,
+                                                    "subprog_tail");
+               if (!ASSERT_OK(err, "set_attach_target subprog_tail"))
+                       goto out;
+
+               err = bpf_object__load(fentry_obj);
+               if (!ASSERT_OK(err, "load fentry_obj"))
+                       goto out;
+
+               fentry_link = bpf_program__attach_trace(prog);
+               if (!ASSERT_OK_PTR(fentry_link, "attach_trace"))
+                       goto out;
+       }
+
+       if (test_fexit) {
+               fexit_obj = bpf_object__open_file("tailcall_bpf2bpf_fexit.bpf.o",
+                                                 NULL);
+               if (!ASSERT_OK_PTR(fexit_obj, "open fexit_obj file"))
+                       goto out;
+
+               prog = bpf_object__find_program_by_name(fexit_obj, "fexit");
+               if (!ASSERT_OK_PTR(prog, "find fexit prog"))
+                       goto out;
+
+               err = bpf_program__set_attach_target(prog, prog_fd,
+                                                    "subprog_tail");
+               if (!ASSERT_OK(err, "set_attach_target subprog_tail"))
+                       goto out;
+
+               err = bpf_object__load(fexit_obj);
+               if (!ASSERT_OK(err, "load fexit_obj"))
+                       goto out;
+
+               fexit_link = bpf_program__attach_trace(prog);
+               if (!ASSERT_OK_PTR(fexit_link, "attach_trace"))
+                       goto out;
+       }
+
+       err = bpf_prog_test_run_opts(prog_fd, &topts);
+       ASSERT_OK(err, "tailcall");
+       ASSERT_EQ(topts.retval, 1, "tailcall retval");
+
+       main_data_fd = bpf_map__fd(data_map);
+       if (!ASSERT_GE(main_data_fd, 0, "main_data_fd"))
+               goto out;
+
+       i = 0;
+       err = bpf_map_lookup_elem(main_data_fd, &i, &val);
+       ASSERT_OK(err, "tailcall count");
+       ASSERT_EQ(val, 34, "tailcall count");
+
+       if (test_fentry) {
+               data_map = bpf_object__find_map_by_name(fentry_obj, ".bss");
+               if (!ASSERT_FALSE(!data_map || !bpf_map__is_internal(data_map),
+                                 "find tailcall_bpf2bpf_fentry.bss map"))
+                       goto out;
+
+               fentry_data_fd = bpf_map__fd(data_map);
+               if (!ASSERT_GE(fentry_data_fd, 0,
+                                 "find tailcall_bpf2bpf_fentry.bss map fd"))
+                       goto out;
+
+               i = 0;
+               err = bpf_map_lookup_elem(fentry_data_fd, &i, &val);
+               ASSERT_OK(err, "fentry count");
+               ASSERT_EQ(val, 68, "fentry count");
+       }
+
+       if (test_fexit) {
+               data_map = bpf_object__find_map_by_name(fexit_obj, ".bss");
+               if (!ASSERT_FALSE(!data_map || !bpf_map__is_internal(data_map),
+                                 "find tailcall_bpf2bpf_fexit.bss map"))
+                       goto out;
+
+               fexit_data_fd = bpf_map__fd(data_map);
+               if (!ASSERT_GE(fexit_data_fd, 0,
+                                 "find tailcall_bpf2bpf_fexit.bss map fd"))
+                       goto out;
+
+               i = 0;
+               err = bpf_map_lookup_elem(fexit_data_fd, &i, &val);
+               ASSERT_OK(err, "fexit count");
+               ASSERT_EQ(val, 68, "fexit count");
+       }
+
+       i = 0;
+       err = bpf_map_delete_elem(map_fd, &i);
+       if (!ASSERT_OK(err, "delete_elem from jmp_table"))
+               goto out;
+
+       err = bpf_prog_test_run_opts(prog_fd, &topts);
+       ASSERT_OK(err, "tailcall");
+       ASSERT_EQ(topts.retval, 1, "tailcall retval");
+
+       i = 0;
+       err = bpf_map_lookup_elem(main_data_fd, &i, &val);
+       ASSERT_OK(err, "tailcall count");
+       ASSERT_EQ(val, 35, "tailcall count");
+
+       if (test_fentry) {
+               i = 0;
+               err = bpf_map_lookup_elem(fentry_data_fd, &i, &val);
+               ASSERT_OK(err, "fentry count");
+               ASSERT_EQ(val, 70, "fentry count");
+       }
+
+       if (test_fexit) {
+               i = 0;
+               err = bpf_map_lookup_elem(fexit_data_fd, &i, &val);
+               ASSERT_OK(err, "fexit count");
+               ASSERT_EQ(val, 70, "fexit count");
+       }
+
+out:
+       bpf_link__destroy(fentry_link);
+       bpf_link__destroy(fexit_link);
+       bpf_object__close(fentry_obj);
+       bpf_object__close(fexit_obj);
+       bpf_object__close(obj);
+}
+
+/* test_tailcall_bpf2bpf_hierarchy_1 checks that the count value of the tail
+ * call limit enforcement matches with expectations when tailcalls are preceded
+ * with two bpf2bpf calls.
+ *
+ *         subprog --tailcall-> entry
+ * entry <
+ *         subprog --tailcall-> entry
+ */
+static void test_tailcall_bpf2bpf_hierarchy_1(void)
+{
+       test_tailcall_hierarchy_count("tailcall_bpf2bpf_hierarchy1.bpf.o",
+                                     false, false, false);
+}
+
+/* test_tailcall_bpf2bpf_hierarchy_fentry checks that the count value of the
+ * tail call limit enforcement matches with expectations when tailcalls are
+ * preceded with two bpf2bpf calls, and the two subprogs are traced by fentry.
+ */
+static void test_tailcall_bpf2bpf_hierarchy_fentry(void)
+{
+       test_tailcall_hierarchy_count("tailcall_bpf2bpf_hierarchy1.bpf.o",
+                                     true, false, false);
+}
+
+/* test_tailcall_bpf2bpf_hierarchy_fexit checks that the count value of the tail
+ * call limit enforcement matches with expectations when tailcalls are preceded
+ * with two bpf2bpf calls, and the two subprogs are traced by fexit.
+ */
+static void test_tailcall_bpf2bpf_hierarchy_fexit(void)
+{
+       test_tailcall_hierarchy_count("tailcall_bpf2bpf_hierarchy1.bpf.o",
+                                     false, true, false);
+}
+
+/* test_tailcall_bpf2bpf_hierarchy_fentry_fexit checks that the count value of
+ * the tail call limit enforcement matches with expectations when tailcalls are
+ * preceded with two bpf2bpf calls, and the two subprogs are traced by both
+ * fentry and fexit.
+ */
+static void test_tailcall_bpf2bpf_hierarchy_fentry_fexit(void)
+{
+       test_tailcall_hierarchy_count("tailcall_bpf2bpf_hierarchy1.bpf.o",
+                                     true, true, false);
+}
+
+/* test_tailcall_bpf2bpf_hierarchy_fentry_entry checks that the count value of
+ * the tail call limit enforcement matches with expectations when tailcalls are
+ * preceded with two bpf2bpf calls in fentry.
+ */
+static void test_tailcall_bpf2bpf_hierarchy_fentry_entry(void)
+{
+       test_tailcall_hierarchy_count("tc_dummy.bpf.o", false, false, true);
+}
+
+/* test_tailcall_bpf2bpf_hierarchy_2 checks that the count value of the tail
+ * call limit enforcement matches with expectations:
+ *
+ *         subprog_tail0 --tailcall-> classifier_0 -> subprog_tail0
+ * entry <
+ *         subprog_tail1 --tailcall-> classifier_1 -> subprog_tail1
+ */
+static void test_tailcall_bpf2bpf_hierarchy_2(void)
+{
+       RUN_TESTS(tailcall_bpf2bpf_hierarchy2);
+}
+
+/* test_tailcall_bpf2bpf_hierarchy_3 checks that the count value of the tail
+ * call limit enforcement matches with expectations:
+ *
+ *                                   subprog with jmp_table0 to classifier_0
+ * entry --tailcall-> classifier_0 <
+ *                                   subprog with jmp_table1 to classifier_0
+ */
+static void test_tailcall_bpf2bpf_hierarchy_3(void)
+{
+       RUN_TESTS(tailcall_bpf2bpf_hierarchy3);
+}
+
 void test_tailcalls(void)
 {
        if (test__start_subtest("tailcall_1"))
@@ -1223,4 +1531,16 @@ void test_tailcalls(void)
                test_tailcall_bpf2bpf_fentry_entry();
        if (test__start_subtest("tailcall_poke"))
                test_tailcall_poke();
+       if (test__start_subtest("tailcall_bpf2bpf_hierarchy_1"))
+               test_tailcall_bpf2bpf_hierarchy_1();
+       if (test__start_subtest("tailcall_bpf2bpf_hierarchy_fentry"))
+               test_tailcall_bpf2bpf_hierarchy_fentry();
+       if (test__start_subtest("tailcall_bpf2bpf_hierarchy_fexit"))
+               test_tailcall_bpf2bpf_hierarchy_fexit();
+       if (test__start_subtest("tailcall_bpf2bpf_hierarchy_fentry_fexit"))
+               test_tailcall_bpf2bpf_hierarchy_fentry_fexit();
+       if (test__start_subtest("tailcall_bpf2bpf_hierarchy_fentry_entry"))
+               test_tailcall_bpf2bpf_hierarchy_fentry_entry();
+       test_tailcall_bpf2bpf_hierarchy_2();
+       test_tailcall_bpf2bpf_hierarchy_3();
 }

diff --git a/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy1.c b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy1.c
new file mode 100644 (file)
index 0000000..327ca39
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy1.c
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_legacy.h"
+
+struct {
+       __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+       __uint(max_entries, 1);
+       __uint(key_size, sizeof(__u32));
+       __uint(value_size, sizeof(__u32));
+} jmp_table SEC(".maps");
+
+int count = 0;
+
+static __noinline
+int subprog_tail(struct __sk_buff *skb)
+{
+       bpf_tail_call_static(skb, &jmp_table, 0);
+       return 0;
+}
+
+SEC("tc")
+int entry(struct __sk_buff *skb)
+{
+       int ret = 1;
+
+       count++;
+       subprog_tail(skb);
+       subprog_tail(skb);
+
+       return ret;
+}
+
+char __license[] SEC("license") = "GPL";

diff --git a/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy2.c b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy2.c
new file mode 100644 (file)
index 0000000..37604b0
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy2.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+int classifier_0(struct __sk_buff *skb);
+int classifier_1(struct __sk_buff *skb);
+
+struct {
+       __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+       __uint(max_entries, 2);
+       __uint(key_size, sizeof(__u32));
+       __array(values, void (void));
+} jmp_table SEC(".maps") = {
+       .values = {
+               [0] = (void *) &classifier_0,
+               [1] = (void *) &classifier_1,
+       },
+};
+
+int count0 = 0;
+int count1 = 0;
+
+static __noinline
+int subprog_tail0(struct __sk_buff *skb)
+{
+       bpf_tail_call_static(skb, &jmp_table, 0);
+       return 0;
+}
+
+__auxiliary
+SEC("tc")
+int classifier_0(struct __sk_buff *skb)
+{
+       count0++;
+       subprog_tail0(skb);
+       return 0;
+}
+
+static __noinline
+int subprog_tail1(struct __sk_buff *skb)
+{
+       bpf_tail_call_static(skb, &jmp_table, 1);
+       return 0;
+}
+
+__auxiliary
+SEC("tc")
+int classifier_1(struct __sk_buff *skb)
+{
+       count1++;
+       subprog_tail1(skb);
+       return 0;
+}
+
+__success
+__retval(33)
+SEC("tc")
+int tailcall_bpf2bpf_hierarchy_2(struct __sk_buff *skb)
+{
+       volatile int ret = 0;
+
+       subprog_tail0(skb);
+       subprog_tail1(skb);
+
+       asm volatile (""::"r+"(ret));
+       return (count1 << 16) | count0;
+}
+
+char __license[] SEC("license") = "GPL";

diff --git a/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy3.c b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy3.c
new file mode 100644 (file)
index 0000000..0cdbb78
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy3.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+int classifier_0(struct __sk_buff *skb);
+
+struct {
+       __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+       __uint(max_entries, 1);
+       __uint(key_size, sizeof(__u32));
+       __array(values, void (void));
+} jmp_table0 SEC(".maps") = {
+       .values = {
+               [0] = (void *) &classifier_0,
+       },
+};
+
+struct {
+       __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+       __uint(max_entries, 1);
+       __uint(key_size, sizeof(__u32));
+       __array(values, void (void));
+} jmp_table1 SEC(".maps") = {
+       .values = {
+               [0] = (void *) &classifier_0,
+       },
+};
+
+int count = 0;
+
+static __noinline
+int subprog_tail(struct __sk_buff *skb, void *jmp_table)
+{
+       bpf_tail_call_static(skb, jmp_table, 0);
+       return 0;
+}
+
+__auxiliary
+SEC("tc")
+int classifier_0(struct __sk_buff *skb)
+{
+       count++;
+       subprog_tail(skb, &jmp_table0);
+       subprog_tail(skb, &jmp_table1);
+       return count;
+}
+
+__success
+__retval(33)
+SEC("tc")
+int tailcall_bpf2bpf_hierarchy_3(struct __sk_buff *skb)
+{
+       volatile int ret = 0;
+
+       bpf_tail_call_static(skb, &jmp_table0, 0);
+
+       asm volatile (""::"r+"(ret));
+       return ret;
+}
+
+char __license[] SEC("license") = "GPL";

diff --git a/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy_fentry.c b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy_fentry.c
new file mode 100644 (file)
index 0000000..c87f9ca
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy_fentry.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Leon Hwang */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+struct {
+       __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+       __uint(max_entries, 1);
+       __uint(key_size, sizeof(__u32));
+       __uint(value_size, sizeof(__u32));
+} jmp_table SEC(".maps");
+
+int count = 0;
+
+static __noinline
+int subprog_tail(void *ctx)
+{
+       bpf_tail_call_static(ctx, &jmp_table, 0);
+       return 0;
+}
+
+SEC("fentry/dummy")
+int BPF_PROG(fentry, struct sk_buff *skb)
+{
+       count++;
+       subprog_tail(ctx);
+       subprog_tail(ctx);
+
+       return 0;
+}
+
+
+char _license[] SEC("license") = "GPL";

diff --git a/tools/testing/selftests/bpf/progs/tc_dummy.c b/tools/testing/selftests/bpf/progs/tc_dummy.c
new file mode 100644 (file)
index 0000000..69a3d0d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/tc_dummy.c
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_legacy.h"
+
+SEC("tc")
+int entry(struct __sk_buff *skb)
+{
+       return 1;
+}
+
+char __license[] SEC("license") = "GPL";