Commit 87dc2bb3 authored by Alexei Starovoitov's avatar Alexei Starovoitov
Browse files

Merge branch 'bpf-xdp-add-tracepoint-to-xdp-attaching-failure' 

Leon Hwang says:

====================
bpf, xdp: Add tracepoint to xdp attaching failure

This series introduces a new tracepoint in bpf_xdp_link_attach(). By
this tracepoint, error message will be captured when error happens in
dev_xdp_attach(), e.g. invalid attaching flags.

v4 -> v5:
* Initialise the extack variable.
* Fix code style issue of variable declaration lines.

v3 -> v4:
* Fix selftest-crashed issue.
====================

Link: https://lore.kernel.org/r/20230801142621.7925-1-hffilwlqm@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parents 416c6d01 7fedbf32

include/trace/events/xdp.h

+17 −0
Original line number Diff line number Diff line
@@ -404,6 +404,23 @@ TRACE_EVENT(mem_return_failed, 
	)

);



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, msg);

	),



	TP_printk("errmsg=%s", __get_str(msg))

);



#endif /* _TRACE_XDP_H */



#include <trace/define_trace.h>

net/core/dev.c

+4 −1
Original line number Diff line number Diff line
@@ -133,6 +133,7 @@ 
#include <trace/events/net.h>

#include <trace/events/skb.h>

#include <trace/events/qdisc.h>

#include <trace/events/xdp.h>

#include <linux/inetdevice.h>

#include <linux/cpu_rmap.h>

#include <linux/static_key.h>
@@ -9470,6 +9471,7 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) 
{

	struct net *net = current->nsproxy->net_ns;

	struct bpf_link_primer link_primer;

	struct netlink_ext_ack extack = {};

	struct bpf_xdp_link *link;

	struct net_device *dev;

	int err, fd;
@@ -9497,12 +9499,13 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) 
		goto unlock;

	}



	err = dev_xdp_attach_link(dev, NULL, link);

	err = dev_xdp_attach_link(dev, &extack, link);

	rtnl_unlock();



	if (err) {

		link->dev = NULL;

		bpf_link_cleanup(&link_primer);

		trace_bpf_xdp_link_attach_failed(extack._msg);

		goto out_put_dev;

	}

tools/testing/selftests/bpf/prog_tests/xdp_attach.c

+65 −0
Original line number Diff line number Diff line 
// 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)

{

	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");

}

tools/testing/selftests/bpf/progs/test_xdp_attach_fail.c

0 → 100644
+54 −0
Original line number Diff line number Diff line 
// 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";