Add a test case for the tracepoint of xdp attaching failure by bpf tracepoint when attach XDP to a device with invalid flags option.

The bpf tracepoint retrieves error message from the tracepoint, and then put the error message to a perf buffer. The testing code receives error message from perf buffer, and then ASSERT "Invalid XDP flags for BPF link attachment".

Signed-off-by: Leon Hwang hffilwlqm@gmail.com --- .../selftests/bpf/prog_tests/xdp_attach.c | 65 +++++++++++++++++++ .../bpf/progs/test_xdp_attach_fail.c | 54 +++++++++++++++ 2 files changed, 119 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_attach_fail.c

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_attach.c index fa3cac5488f5d..8c1cde74e9cd6 100644 --- a/tools/testing/selftests/bpf/prog_tests/xdp_attach.c +++ b/tools/testing/selftests/bpf/prog_tests/xdp_attach.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include <test_progs.h> +#include "test_xdp_attach_fail.skel.h"

#define IFINDEX_LO 1 #define XDP_FLAGS_REPLACE (1U << 4) @@ -85,10 +86,74 @@ static void test_xdp_attach(const char *file) bpf_object__close(obj1); }

+#define ERRMSG_LEN 64 + +struct xdp_errmsg { + char msg[ERRMSG_LEN]; +}; + +static void on_xdp_errmsg(void *ctx, int cpu, void *data, __u32 size) +{ + struct xdp_errmsg *ctx_errmg = ctx, *tp_errmsg = data; + + memcpy(&ctx_errmg->msg, &tp_errmsg->msg, ERRMSG_LEN); +} + +static const char tgt_errmsg[] = "Invalid XDP flags for BPF link attachment"; + +static void test_xdp_attach_fail(const char *file) +{ + int err, fd_xdp; + struct bpf_object *obj = NULL; + struct test_xdp_attach_fail *skel = NULL; + struct perf_buffer *pb = NULL; + struct xdp_errmsg errmsg = {}; + + LIBBPF_OPTS(bpf_link_create_opts, opts); + + skel = test_xdp_attach_fail__open_and_load(); + if (!ASSERT_OK_PTR(skel, "test_xdp_attach_fail__open_and_load")) + goto out_close; + + err = test_xdp_attach_fail__attach(skel); + if (!ASSERT_EQ(err, 0, "test_xdp_attach_fail__attach")) + goto out_close; + + /* set up perf buffer */ + pb = perf_buffer__new(bpf_map__fd(skel->maps.xdp_errmsg_pb), 1, + on_xdp_errmsg, NULL, &errmsg, NULL); + if (!ASSERT_OK_PTR(pb, "perf_buffer__new")) + goto out_close; + + err = bpf_prog_test_load(file, BPF_PROG_TYPE_XDP, &obj, &fd_xdp); + if (!ASSERT_EQ(err, 0, "bpf_prog_test_load")) + goto out_close; + + opts.flags = 0xFF; // invalid flags to fail to attach XDP prog + err = bpf_link_create(fd_xdp, IFINDEX_LO, BPF_XDP, &opts); + if (!ASSERT_EQ(err, -EINVAL, "bpf_link_create")) + goto out_close; + + /* read perf buffer */ + err = perf_buffer__poll(pb, 100); + if (!ASSERT_GT(err, -1, "perf_buffer__poll")) + goto out_close; + + ASSERT_STRNEQ((const char *) errmsg.msg, tgt_errmsg, + 42 /* strlen(tgt_errmsg) */, "check error message"); + +out_close: + perf_buffer__free(pb); + bpf_object__close(obj); + test_xdp_attach_fail__destroy(skel); +} + void serial_test_xdp_attach(void) { if (test__start_subtest("xdp_attach")) test_xdp_attach("./test_xdp.bpf.o"); if (test__start_subtest("xdp_attach_dynptr")) test_xdp_attach("./test_xdp_dynptr.bpf.o"); + if (test__start_subtest("xdp_attach_failed")) + test_xdp_attach_fail("./xdp_dummy.bpf.o"); } diff --git a/tools/testing/selftests/bpf/progs/test_xdp_attach_fail.c b/tools/testing/selftests/bpf/progs/test_xdp_attach_fail.c new file mode 100644 index 0000000000000..d7149bbd95f75 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_xdp_attach_fail.c @@ -0,0 +1,54 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright Leon Hwang */ + +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> + +#define ERRMSG_LEN 64 + +struct xdp_errmsg { + char msg[ERRMSG_LEN]; +}; + +struct { + __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY); + __type(key, int); + __type(value, int); +} xdp_errmsg_pb SEC(".maps"); + +struct xdp_attach_error_ctx { + unsigned long unused; + + /* + * bpf does not support tracepoint __data_loc directly. + * + * Actually, this field is a 32 bit integer whose value encodes + * information on where to find the actual data. The first 2 bytes is + * the size of the data. The last 2 bytes is the offset from the start + * of the tracepoint struct where the data begins. + * -- https://github.com/iovisor/bpftrace/pull/1542 + */ + __u32 msg; // __data_loc char[] msg; +}; + +/* + * Catch the error message at the tracepoint. + */ + +SEC("tp/xdp/bpf_xdp_link_attach_failed") +int tp__xdp__bpf_xdp_link_attach_failed(struct xdp_attach_error_ctx *ctx) +{ + struct xdp_errmsg errmsg; + char *msg = (void *)(__u64) ((void *) ctx + (__u16) ctx->msg); + + bpf_probe_read_kernel_str(&errmsg.msg, ERRMSG_LEN, msg); + bpf_perf_event_output(ctx, &xdp_errmsg_pb, BPF_F_CURRENT_CPU, &errmsg, + ERRMSG_LEN); + return 0; +} + +/* + * Reuse the XDP program in xdp_dummy.c. + */ + +char LICENSE[] SEC("license") = "GPL";