[PATCH bpf-next 3/6] bpf: Retire tracepoint bpf_xdp_link_attach_failed

[Leon Hwang]

In the previous patch, it has a proper way to back-propagate the
underlying driver error message to user space via the BPF syscall common
attributes.

The tracepoint bpf_xdp_link_attach_failed seems redundant to report the
error message. And, the tracepoint doesn't report the ifindex alongside
the error message [1].

So, retire the tracepoint bpf_xdp_link_attach_failed and its selftest.

According to the tracepoint change discussion [2], please revert this
patch if users complain about the disappeared tracepoint
bpf_xdp_link_attach_failed in the future.

Links:
[1] https://lore.kernel.org/bpf/CAFk-A4mE9Jweo2hfX7y_85xbPyt0FqpMT1EvqX1OcYZ=LTLgRA@xxxxxxxxxxxxxx/
[2] https://lore.kernel.org/linux-mm/CY8PR11MB7134346A3E4BB28ECA28D6E989132@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/

Signed-off-by: Leon Hwang <leon.hwang@xxxxxxxxx>
---
 include/trace/events/xdp.h                    | 17 -----
 net/core/dev.c                                |  1 -
 .../selftests/bpf/prog_tests/xdp_attach.c     | 65 -------------------
 .../bpf/progs/test_xdp_attach_fail.c          | 54 ---------------
 4 files changed, 137 deletions(-)
 delete mode 100644 tools/testing/selftests/bpf/progs/test_xdp_attach_fail.c

diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h
index 18c0ac514fcb..f1d4d0702884 100644
--- a/include/trace/events/xdp.h
+++ b/include/trace/events/xdp.h
@@ -362,23 +362,6 @@ TRACE_EVENT(mem_connect,
 	)
 );
 
-TRACE_EVENT(bpf_xdp_link_attach_failed,
-
-	TP_PROTO(const char *msg),
-
-	TP_ARGS(msg),
-
-	TP_STRUCT__entry(
-		__string(msg, msg)
-	),
-
-	TP_fast_assign(
-		__assign_str(msg);
-	),
-
-	TP_printk("errmsg=%s", __get_str(msg))
-);
-
 #endif /* _TRACE_XDP_H */
 
 #include <trace/define_trace.h>
diff --git a/net/core/dev.c b/net/core/dev.c
index fdc1de21f358..266b510abd53 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10816,7 +10816,6 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog,
 		link->dev = NULL;
 		bpf_link_cleanup(&link_primer);
 		bpf_log(log, extack._msg);
-		trace_bpf_xdp_link_attach_failed(extack._msg);
 		goto out_put_dev;
 	}
 
diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_attach.c
index e6bcb6051402..fa3cac5488f5 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_attach.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_attach.c
@@ -1,6 +1,5 @@
 // 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)
@@ -86,74 +85,10 @@ 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)
-{
-	struct test_xdp_attach_fail *skel = NULL;
-	struct xdp_errmsg errmsg = {};
-	struct perf_buffer *pb = NULL;
-	struct bpf_object *obj = NULL;
-	int err, fd_xdp;
-
-	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
deleted file mode 100644
index 2ff1b596e87e..000000000000
--- a/tools/testing/selftests/bpf/progs/test_xdp_attach_fail.c
+++ /dev/null
@@ -1,54 +0,0 @@
-// 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)
-{
-	char *msg = (void *)(__u64) ((void *) ctx + (__u16) ctx->msg);
-	struct xdp_errmsg errmsg = {};
-
-	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";
-- 
2.55.0