Thanks for expanding tests. On Tue, Jan 21, 2025 at 01:07 PM +08, Jiayuan Chen wrote: > Add test cases for bpf + strparser and separated them from > sockmap_basic, as strparser has more encapsulation and parsing > capabilities compared to sockmap. > > Signed-off-by: Jiayuan Chen <mrpre@xxxxxxx> > --- > .../selftests/bpf/prog_tests/sockmap_basic.c | 53 -- > .../selftests/bpf/prog_tests/sockmap_strp.c | 452 ++++++++++++++++++ > .../selftests/bpf/progs/test_sockmap_strp.c | 53 ++ > 3 files changed, 505 insertions(+), 53 deletions(-) > create mode 100644 tools/testing/selftests/bpf/prog_tests/sockmap_strp.c > create mode 100644 tools/testing/selftests/bpf/progs/test_sockmap_strp.c > > diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c > index 0c51b7288978..f8953455db29 100644 > --- a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c > +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c > @@ -531,57 +531,6 @@ static void test_sockmap_skb_verdict_shutdown(void) > test_sockmap_pass_prog__destroy(skel); > } > > -static void test_sockmap_stream_pass(void) > -{ > - int zero = 0, sent, recvd; > - int verdict, parser; > - int err, map; > - int c = -1, p = -1; > - struct test_sockmap_pass_prog *pass = NULL; > - char snd[256] = "0123456789"; > - char rcv[256] = "0"; > - > - pass = test_sockmap_pass_prog__open_and_load(); > - verdict = bpf_program__fd(pass->progs.prog_skb_verdict); > - parser = bpf_program__fd(pass->progs.prog_skb_parser); > - map = bpf_map__fd(pass->maps.sock_map_rx); > - > - err = bpf_prog_attach(parser, map, BPF_SK_SKB_STREAM_PARSER, 0); > - if (!ASSERT_OK(err, "bpf_prog_attach stream parser")) > - goto out; > - > - err = bpf_prog_attach(verdict, map, BPF_SK_SKB_STREAM_VERDICT, 0); > - if (!ASSERT_OK(err, "bpf_prog_attach stream verdict")) > - goto out; > - > - err = create_pair(AF_INET, SOCK_STREAM, &c, &p); > - if (err) > - goto out; > - > - /* sk_data_ready of 'p' will be replaced by strparser handler */ > - err = bpf_map_update_elem(map, &zero, &p, BPF_NOEXIST); > - if (!ASSERT_OK(err, "bpf_map_update_elem(p)")) > - goto out_close; > - > - /* > - * as 'prog_skb_parser' return the original skb len and > - * 'prog_skb_verdict' return SK_PASS, the kernel will just > - * pass it through to original socket 'p' > - */ > - sent = xsend(c, snd, sizeof(snd), 0); > - ASSERT_EQ(sent, sizeof(snd), "xsend(c)"); > - > - recvd = recv_timeout(p, rcv, sizeof(rcv), SOCK_NONBLOCK, > - IO_TIMEOUT_SEC); > - ASSERT_EQ(recvd, sizeof(rcv), "recv_timeout(p)"); > - > -out_close: > - close(c); > - close(p); > - > -out: > - test_sockmap_pass_prog__destroy(pass); > -} > > static void test_sockmap_skb_verdict_fionread(bool pass_prog) > { > @@ -1101,8 +1050,6 @@ void test_sockmap_basic(void) > test_sockmap_progs_query(BPF_SK_SKB_VERDICT); > if (test__start_subtest("sockmap skb_verdict shutdown")) > test_sockmap_skb_verdict_shutdown(); > - if (test__start_subtest("sockmap stream parser and verdict pass")) > - test_sockmap_stream_pass(); > if (test__start_subtest("sockmap skb_verdict fionread")) > test_sockmap_skb_verdict_fionread(true); > if (test__start_subtest("sockmap skb_verdict fionread on drop")) > diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_strp.c b/tools/testing/selftests/bpf/prog_tests/sockmap_strp.c > new file mode 100644 > index 000000000000..01ed1fca1d9c > --- /dev/null > +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_strp.c > @@ -0,0 +1,452 @@ > +// SPDX-License-Identifier: GPL-2.0 > +#include <error.h> > +#include <netinet/tcp.h> > +#include <test_progs.h> > +#include "sockmap_helpers.h" > +#include "test_skmsg_load_helpers.skel.h" > +#include "test_sockmap_strp.skel.h" Nit: add new line to separate cpp defines visually > +#define STRP_PKT_HEAD_LEN 4 > +#define STRP_PKT_BODY_LEN 6 > +#define STRP_PKT_FULL_LEN (STRP_PKT_HEAD_LEN + STRP_PKT_BODY_LEN) Nit: add new line to constants visually > +static const char packet[STRP_PKT_FULL_LEN] = "head+body\0"; > +static const int test_packet_num = 100; > + > +/* current implementation of tcp_bpf_recvmsg_parser() invoke Nit: grammar, "invoke*s*" > + * data_ready with sk held if skb exist in sk_receive_queue. Nit: grammar, "exist*s*" > + * Then for data_ready implementation of strparser, it will > + * delay the read operation if sk was held and EAGAIN is returned. > + */ > +static int sockmap_strp_consume_pre_data(int p) > +{ > + int recvd; > + bool retried = false; > + char rcv[10]; > + > +retry: > + errno = 0; > + recvd = recv_timeout(p, rcv, sizeof(rcv), 0, 1); > + if (recvd < 0 && errno == EAGAIN && retried == false) { > + /* On the first call, EAGAIN will certainly be returned. > + * Waiting 1 second is pretty enough wait workqueue finish. Nit: style, "Wait for workqueue to finish." > + */ > + sleep(1); > + retried = true; > + goto retry; > + } > + > + if (!ASSERT_EQ(recvd, STRP_PKT_FULL_LEN, "recv_timeout(pre-data)") || Meaningful error message like "recv error or truncated data" would be better. ASSERT_EQ / CHECK macros print the function name, so "(pre-data)" tag is redundant. > + !ASSERT_OK(memcmp(packet, rcv, STRP_PKT_FULL_LEN), > + "memcmp pre-data")) Suggested error message: "data mismatch". > + return -1; > + return 0; > +} > + > +static struct test_sockmap_strp *sockmap_strp_init(int *out_map, bool pass, > + bool need_parser) > +{ > + struct test_sockmap_strp *strp = NULL; > + int verdict, parser; > + int err; > + > + strp = test_sockmap_strp__open_and_load(); > + *out_map = bpf_map__fd(strp->maps.sock_map); > + > + if (need_parser) > + parser = bpf_program__fd(strp->progs.prog_skb_parser_partial); > + else > + parser = bpf_program__fd(strp->progs.prog_skb_parser); > + > + if (pass) > + verdict = bpf_program__fd(strp->progs.prog_skb_verdict_pass); > + else > + verdict = bpf_program__fd(strp->progs.prog_skb_verdict); > + > + err = bpf_prog_attach(parser, *out_map, BPF_SK_SKB_STREAM_PARSER, 0); > + if (!ASSERT_OK(err, "bpf_prog_attach stream parser")) > + goto err; > + > + err = bpf_prog_attach(verdict, *out_map, BPF_SK_SKB_STREAM_VERDICT, 0); > + if (!ASSERT_OK(err, "bpf_prog_attach stream verdict")) > + goto err; > + > + return strp; > +err: > + test_sockmap_strp__destroy(strp); > + return NULL; > +} > + > +/* Dispatch packets to different socket by packet size: > + * > + * ------ ------ > + * | pkt4 || pkt1 |... > remote socket > + * ------ ------ / ------ ------ > + * | pkt8 | pkt7 |... > + * ------ ------ \ ------ ------ > + * | pkt3 || pkt2 |... > local socket > + * ------ ------ > + */ > +static void test_sockmap_strp_dispatch_pkt(int family, int sotype) > +{ > + int i, j, zero = 0, one = 1, recvd; > + int err, map; > + int c0 = -1, p0 = -1, c1 = -1, p1 = -1; > + struct test_sockmap_strp *strp = NULL; > + int test_cnt = 6; > + char rcv[10]; > + struct { > + char data[7]; > + int data_len; > + int send_cnt; > + int *receiver; > + } send_dir[2] = { > + /* data expected to deliver to local */ > + {"llllll", 6, 0, &p0}, > + /* data expected to deliver to remote */ > + {"rrrrr", 5, 0, &c1} > + }; > + > + strp = sockmap_strp_init(&map, false, false); > + if (!ASSERT_TRUE(strp, "sockmap_strp_init")) > + return; > + > + err = create_socket_pairs(family, sotype, &c0, &c1, &p0, &p1); > + if (!ASSERT_OK(err, "create_socket_pairs()")) > + goto out; > + > + err = bpf_map_update_elem(map, &zero, &p0, BPF_NOEXIST); > + if (!ASSERT_OK(err, "bpf_map_update_elem(p0)")) > + goto out_close; > + > + err = bpf_map_update_elem(map, &one, &p1, BPF_NOEXIST); > + if (!ASSERT_OK(err, "bpf_map_update_elem(p1)")) > + goto out_close; > + > + err = setsockopt(c1, IPPROTO_TCP, TCP_NODELAY, &zero, sizeof(zero)); > + if (!ASSERT_OK(err, "setsockopt(TCP_NODELAY)")) > + goto out_close; > + > + /* deliver data with data size greater than 5 to local */ > + strp->data->verdict_max_size = 5; > + > + for (i = 0; i < test_cnt; i++) { > + int d = i % 2; > + > + xsend(c0, send_dir[d].data, send_dir[d].data_len, 0); > + send_dir[d].send_cnt++; > + } > + > + for (i = 0; i < 2; i++) { > + for (j = 0; j < send_dir[i].send_cnt; j++) { > + int expected = send_dir[i].data_len; > + > + recvd = recv_timeout(*send_dir[i].receiver, rcv, > + expected, MSG_DONTWAIT, > + IO_TIMEOUT_SEC); > + if (!ASSERT_EQ(recvd, expected, "recv_timeout()")) > + goto out_close; > + if (!ASSERT_OK(memcmp(send_dir[i].data, rcv, recvd), > + "memcmp(rcv)")) > + goto out_close; > + } > + } > +out_close: > + close(c0); > + close(c1); > + close(p0); > + close(p1); > +out: > + test_sockmap_strp__destroy(strp); > +} > + > +/* We have multiple packets in one skb > + * ------------ ------------ ------------ > + * | packet1 | packet2 | ... > + * ------------ ------------ ------------ > + */ > +static void test_sockmap_strp_multiple_pkt(int family, int sotype) > +{ > + int i, zero = 0; > + int sent, recvd, total; > + int err, map; > + int c = -1, p = -1; > + struct test_sockmap_strp *strp = NULL; > + char *snd = NULL, *rcv = NULL; > + > + strp = sockmap_strp_init(&map, true, true); > + if (!ASSERT_TRUE(strp, "sockmap_strp_init")) > + return; > + > + err = create_pair(family, sotype, &c, &p); > + if (err) > + goto out; > + > + err = bpf_map_update_elem(map, &zero, &p, BPF_NOEXIST); > + if (!ASSERT_OK(err, "bpf_map_update_elem(zero, p)")) > + goto out_close; > + > + /* construct multiple packets in one buffer */ > + total = test_packet_num * STRP_PKT_FULL_LEN; > + snd = malloc(total); > + rcv = malloc(total + 1); > + if (!ASSERT_TRUE(snd, "malloc(snd)") || > + !ASSERT_TRUE(rcv, "malloc(rcv)")) > + goto out_close; > + > + for (i = 0; i < test_packet_num; i++) { > + memcpy(snd + i * STRP_PKT_FULL_LEN, > + packet, STRP_PKT_FULL_LEN); > + } > + > + sent = xsend(c, snd, total, 0); > + if (!ASSERT_EQ(sent, total, "xsend(c)")) > + goto out_close; > + > + /* try to recv one more byte to avoid truncation check */ > + recvd = recv_timeout(p, rcv, total + 1, MSG_DONTWAIT, IO_TIMEOUT_SEC); > + if (!ASSERT_EQ(recvd, total, "recv(rcv)")) > + goto out_close; > + > + /* we sent TCP segment with multiple encapsulation > + * then check whether packets are handled correctly > + */ > + if (!ASSERT_OK(memcmp(snd, rcv, total), "memcmp(snd, rcv)")) > + goto out_close; > + > +out_close: > + close(c); > + close(p); > + if (snd) > + free(snd); > + if (rcv) > + free(rcv); > +out: > + test_sockmap_strp__destroy(strp); > +} > + > +/* Test strparser with partial read */ > +static void test_sockmap_strp_partial_read(int family, int sotype) > +{ > + int zero = 0, recvd, off; > + int err, map; > + int c = -1, p = -1; > + struct test_sockmap_strp *strp = NULL; > + char rcv[STRP_PKT_FULL_LEN + 1] = "0"; > + > + strp = sockmap_strp_init(&map, true, true); > + if (!ASSERT_TRUE(strp, "sockmap_strp_init")) > + return; > + > + err = create_pair(family, sotype, &c, &p); > + if (err) > + goto out; > + > + /* sk_data_ready of 'p' will be replaced by strparser handler */ > + err = bpf_map_update_elem(map, &zero, &p, BPF_NOEXIST); > + if (!ASSERT_OK(err, "bpf_map_update_elem(zero, p)")) > + goto out_close; > + > + /* 1.1 send partial head, 1 byte header left*/ Nit: missing space before comment-close tag, "left */". > + off = STRP_PKT_HEAD_LEN - 1; > + xsend(c, packet, off, 0); > + recvd = recv_timeout(p, rcv, sizeof(rcv), MSG_DONTWAIT, 1); > + if (!ASSERT_EQ(-1, recvd, "insufficient head, should no data recvd")) "partial head sent, expected no data" > + goto out_close; > + > + /* 1.2 send remaining head and body */ > + xsend(c, packet + off, STRP_PKT_FULL_LEN - off, 0); > + recvd = recv_timeout(p, rcv, sizeof(rcv), MSG_DONTWAIT, IO_TIMEOUT_SEC); > + if (!ASSERT_EQ(recvd, STRP_PKT_FULL_LEN, "should full data recvd")) "expected full data" > + goto out_close; > + > + /* 2.1 send partial head, 1 byte header left */ > + off = STRP_PKT_HEAD_LEN - 1; > + xsend(c, packet, off, 0); > + > + /* 2.2 send remaining head and partial body, 1 byte body left */ > + xsend(c, packet + off, STRP_PKT_FULL_LEN - off - 1, 0); > + off = STRP_PKT_FULL_LEN - 1; > + recvd = recv_timeout(p, rcv, sizeof(rcv), MSG_DONTWAIT, 1); > + if (!ASSERT_EQ(-1, recvd, "insufficient body, should no data read")) "partial body sent, expected no data" > + goto out_close; > + > + /* 2.3 send remaining body */ > + xsend(c, packet + off, STRP_PKT_FULL_LEN - off, 0); > + recvd = recv_timeout(p, rcv, sizeof(rcv), MSG_DONTWAIT, IO_TIMEOUT_SEC); > + if (!ASSERT_EQ(recvd, STRP_PKT_FULL_LEN, "should full data recvd")) "expected full data" > + goto out_close; > + > +out_close: > + close(c); > + close(p); > + > +out: > + test_sockmap_strp__destroy(strp); > +} > + > +/* Test simple socket read/write with strparser + FIONREAD */ > +static void test_sockmap_strp_pass(int family, int sotype, bool fionread) > +{ > + int zero = 0, pkt_size = STRP_PKT_FULL_LEN, sent, recvd, avail; > + int err, map; > + int c = -1, p = -1; > + int test_cnt = 10, i; > + struct test_sockmap_strp *strp = NULL; > + char rcv[STRP_PKT_FULL_LEN + 1] = "0"; > + > + strp = sockmap_strp_init(&map, true, true); > + if (!ASSERT_TRUE(strp, "sockmap_strp_init")) > + return; > + > + err = create_pair(family, sotype, &c, &p); > + if (err) > + goto out; > + > + /* inject some data before bpf process, it should be read > + * correctly because we check sk_receive_queue in > + * tcp_bpf_recvmsg_parser() > + */ > + sent = xsend(c, packet, pkt_size, 0); > + if (!ASSERT_EQ(sent, pkt_size, "xsend(pre-data)")) > + goto out_close; > + > + /* sk_data_ready of 'p' will be replaced by strparser handler */ > + err = bpf_map_update_elem(map, &zero, &p, BPF_NOEXIST); > + if (!ASSERT_OK(err, "bpf_map_update_elem(p)")) > + goto out_close; > + > + /* consume previous data we injected */ > + if (sockmap_strp_consume_pre_data(p)) > + goto out_close; > + > + /* Previously, we encountered issues such as deadlocks and > + * sequence errors that resulted in the inability to read > + * continuously. Therefore, we perform multiple iterations > + * of testing here. > + */ > + for (i = 0; i < test_cnt; i++) { > + sent = xsend(c, packet, pkt_size, 0); > + if (!ASSERT_EQ(sent, pkt_size, "xsend(c)")) > + goto out_close; > + > + recvd = recv_timeout(p, rcv, sizeof(rcv), MSG_DONTWAIT, > + IO_TIMEOUT_SEC); > + if (!ASSERT_EQ(recvd, pkt_size, "recv_timeout(p)") || > + !ASSERT_OK(memcmp(packet, rcv, pkt_size), > + "memcmp")) > + goto out_close; > + } > + > + if (fionread) { > + sent = xsend(c, packet, pkt_size, 0); > + if (!ASSERT_EQ(sent, pkt_size, "second xsend(c)")) > + goto out_close; > + > + err = ioctl(p, FIONREAD, &avail); > + if (!ASSERT_OK(err, "ioctl(FIONREAD) error") || > + !ASSERT_EQ(avail, pkt_size, "ioctl(FIONREAD)")) > + goto out_close; > + > + recvd = recv_timeout(p, rcv, sizeof(rcv), MSG_DONTWAIT, > + IO_TIMEOUT_SEC); > + if (!ASSERT_EQ(recvd, pkt_size, "second recv_timeout(p)") || > + !ASSERT_OK(memcmp(packet, rcv, pkt_size), > + "second memcmp")) > + goto out_close; > + } > + > +out_close: > + close(c); > + close(p); > + > +out: > + test_sockmap_strp__destroy(strp); > +} > + > +/* Test strparser with verdict mode */ > +static void test_sockmap_strp_verdict(int family, int sotype) > +{ > + int zero = 0, one = 1, sent, recvd, off; > + int err, map; > + int c0 = -1, p0 = -1, c1 = -1, p1 = -1; > + struct test_sockmap_strp *strp = NULL; > + char rcv[STRP_PKT_FULL_LEN + 1] = "0"; > + > + strp = sockmap_strp_init(&map, false, true); > + if (!ASSERT_TRUE(strp, "sockmap_strp_init")) > + return; > + > + /* We simulate a reverse proxy server. > + * When p0 receives data from c0, we forward it to c1. > + * From c1's perspective, it will consider this data > + * as being sent by p1. > + */ > + err = create_socket_pairs(family, sotype, &c0, &c1, &p0, &p1); > + if (!ASSERT_OK(err, "create_socket_pairs()")) > + goto out; > + > + err = bpf_map_update_elem(map, &zero, &p0, BPF_NOEXIST); > + if (!ASSERT_OK(err, "bpf_map_update_elem(p0)")) > + goto out_close; > + > + err = bpf_map_update_elem(map, &one, &p1, BPF_NOEXIST); > + if (!ASSERT_OK(err, "bpf_map_update_elem(c1)")) > + goto out_close; > + > + sent = xsend(c0, packet, STRP_PKT_FULL_LEN, 0); > + if (!ASSERT_EQ(sent, STRP_PKT_FULL_LEN, "xsend(c0)")) > + goto out_close; > + > + recvd = recv_timeout(c1, rcv, sizeof(rcv), MSG_DONTWAIT, > + IO_TIMEOUT_SEC); > + if (!ASSERT_EQ(recvd, STRP_PKT_FULL_LEN, "recv_timeout(p1)") || > + !ASSERT_OK(memcmp(packet, rcv, STRP_PKT_FULL_LEN), > + "received data does not match the sent data")) > + goto out_close; > + > + /* send again to ensure the stream is functioning correctly. */ > + sent = xsend(c0, packet, STRP_PKT_FULL_LEN, 0); > + if (!ASSERT_EQ(sent, STRP_PKT_FULL_LEN, "second xsend(c0)")) > + goto out_close; > + > + /* partial read */ > + off = STRP_PKT_FULL_LEN / 2; > + recvd = recv_timeout(c1, rcv, off, MSG_DONTWAIT, > + IO_TIMEOUT_SEC); > + recvd += recv_timeout(c1, rcv + off, sizeof(rcv) - off, MSG_DONTWAIT, > + IO_TIMEOUT_SEC); > + > + if (!ASSERT_EQ(recvd, STRP_PKT_FULL_LEN, "partial recv_timeout(c1)") || > + !ASSERT_OK(memcmp(packet, rcv, STRP_PKT_FULL_LEN), > + "partial received data does not match the sent data")) > + goto out_close; > + > +out_close: > + close(c0); > + close(c1); > + close(p0); > + close(p1); > +out: > + test_sockmap_strp__destroy(strp); > +} > + > +void test_sockmap_strp(void) > +{ > + if (test__start_subtest("sockmap strp tcp pass")) > + test_sockmap_strp_pass(AF_INET, SOCK_STREAM, false); > + if (test__start_subtest("sockmap strp tcp v6 pass")) > + test_sockmap_strp_pass(AF_INET6, SOCK_STREAM, false); > + if (test__start_subtest("sockmap strp tcp pass fionread")) > + test_sockmap_strp_pass(AF_INET, SOCK_STREAM, true); > + if (test__start_subtest("sockmap strp tcp v6 pass fionread")) > + test_sockmap_strp_pass(AF_INET6, SOCK_STREAM, true); > + if (test__start_subtest("sockmap strp tcp verdict")) > + test_sockmap_strp_verdict(AF_INET, SOCK_STREAM); > + if (test__start_subtest("sockmap strp tcp v6 verdict")) > + test_sockmap_strp_verdict(AF_INET6, SOCK_STREAM); > + if (test__start_subtest("sockmap strp tcp partial read")) > + test_sockmap_strp_partial_read(AF_INET, SOCK_STREAM); > + if (test__start_subtest("sockmap strp tcp multiple packets")) > + test_sockmap_strp_multiple_pkt(AF_INET, SOCK_STREAM); > + if (test__start_subtest("sockmap strp tcp dispatch")) > + test_sockmap_strp_dispatch_pkt(AF_INET, SOCK_STREAM); > +} > diff --git a/tools/testing/selftests/bpf/progs/test_sockmap_strp.c b/tools/testing/selftests/bpf/progs/test_sockmap_strp.c > new file mode 100644 > index 000000000000..dde3d5bec515 > --- /dev/null > +++ b/tools/testing/selftests/bpf/progs/test_sockmap_strp.c > @@ -0,0 +1,53 @@ > +// SPDX-License-Identifier: GPL-2.0 > +#include <linux/bpf.h> > +#include <bpf/bpf_helpers.h> > +#include <bpf/bpf_endian.h> > +int verdict_max_size = 10000; > +struct { > + __uint(type, BPF_MAP_TYPE_SOCKMAP); > + __uint(max_entries, 20); > + __type(key, int); > + __type(value, int); > +} sock_map SEC(".maps"); > + > +SEC("sk_skb/stream_verdict") > +int prog_skb_verdict(struct __sk_buff *skb) > +{ > + __u32 one = 1; > + > + if (skb->len > verdict_max_size) > + return SK_PASS; > + > + return bpf_sk_redirect_map(skb, &sock_map, one, 0); > +} > + > +SEC("sk_skb/stream_verdict") > +int prog_skb_verdict_pass(struct __sk_buff *skb) > +{ > + return SK_PASS; > +} > + > +SEC("sk_skb/stream_parser") > +int prog_skb_parser(struct __sk_buff *skb) > +{ > + return skb->len; > +} > + > +SEC("sk_skb/stream_parser") > +int prog_skb_parser_partial(struct __sk_buff *skb) > +{ > + /* agreement with the test program on a 4-byte size header > + * and 6-byte body. > + */ > + if (skb->len < 4) { > + /* need more header to determine full length */ > + return 0; > + } > + /* return full length decoded from header. > + * the return value may be larger than skb->len which > + * means framework must wait body coming. > + */ > + return 10; > +} > + > +char _license[] SEC("license") = "GPL";