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Date:   Mon, 14 Sep 2020 18:13:29 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Alexei Starovoitov <ast@...nel.org>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>,
        KP Singh <kpsingh@...omium.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH bpf-next v4 6/8] libbpf: add support for freplace attachment
 in bpf_link_create

From: Toke Høiland-Jørgensen <toke@...hat.com>

This adds support for supplying a target btf ID for the bpf_link_create()
operation, and adds a new bpf_program__attach_freplace() high-level API for
attaching freplace functions with a target.

Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
 tools/lib/bpf/bpf.c      |    1 +
 tools/lib/bpf/bpf.h      |    3 ++-
 tools/lib/bpf/libbpf.c   |   24 ++++++++++++++++++------
 tools/lib/bpf/libbpf.h   |    3 +++
 tools/lib/bpf/libbpf.map |    1 +
 5 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 82b983ff6569..e928456c0dd6 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -599,6 +599,7 @@ int bpf_link_create(int prog_fd, int target_fd,
 	attr.link_create.iter_info =
 		ptr_to_u64(OPTS_GET(opts, iter_info, (void *)0));
 	attr.link_create.iter_info_len = OPTS_GET(opts, iter_info_len, 0);
+	attr.link_create.target_btf_id = OPTS_GET(opts, target_btf_id, 0);
 
 	return sys_bpf(BPF_LINK_CREATE, &attr, sizeof(attr));
 }
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 015d13f25fcc..f8dbf666b62b 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -174,8 +174,9 @@ struct bpf_link_create_opts {
 	__u32 flags;
 	union bpf_iter_link_info *iter_info;
 	__u32 iter_info_len;
+	__u32 target_btf_id;
 };
-#define bpf_link_create_opts__last_field iter_info_len
+#define bpf_link_create_opts__last_field target_btf_id
 
 LIBBPF_API int bpf_link_create(int prog_fd, int target_fd,
 			       enum bpf_attach_type attach_type,
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 550950eb1860..165131c73f40 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9322,12 +9322,14 @@ static struct bpf_link *attach_iter(const struct bpf_sec_def *sec,
 
 static struct bpf_link *
 bpf_program__attach_fd(struct bpf_program *prog, int target_fd,
-		       const char *target_name)
+		       int target_btf_id, const char *target_name)
 {
 	enum bpf_attach_type attach_type;
 	char errmsg[STRERR_BUFSIZE];
 	struct bpf_link *link;
 	int prog_fd, link_fd;
+	DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts,
+			    .target_btf_id = target_btf_id);
 
 	prog_fd = bpf_program__fd(prog);
 	if (prog_fd < 0) {
@@ -9340,8 +9342,12 @@ bpf_program__attach_fd(struct bpf_program *prog, int target_fd,
 		return ERR_PTR(-ENOMEM);
 	link->detach = &bpf_link__detach_fd;
 
-	attach_type = bpf_program__get_expected_attach_type(prog);
-	link_fd = bpf_link_create(prog_fd, target_fd, attach_type, NULL);
+	if (bpf_program__get_type(prog) == BPF_PROG_TYPE_EXT)
+		attach_type = BPF_TRACE_FREPLACE;
+	else
+		attach_type = bpf_program__get_expected_attach_type(prog);
+
+	link_fd = bpf_link_create(prog_fd, target_fd, attach_type, &opts);
 	if (link_fd < 0) {
 		link_fd = -errno;
 		free(link);
@@ -9357,19 +9363,25 @@ bpf_program__attach_fd(struct bpf_program *prog, int target_fd,
 struct bpf_link *
 bpf_program__attach_cgroup(struct bpf_program *prog, int cgroup_fd)
 {
-	return bpf_program__attach_fd(prog, cgroup_fd, "cgroup");
+	return bpf_program__attach_fd(prog, cgroup_fd, 0, "cgroup");
 }
 
 struct bpf_link *
 bpf_program__attach_netns(struct bpf_program *prog, int netns_fd)
 {
-	return bpf_program__attach_fd(prog, netns_fd, "netns");
+	return bpf_program__attach_fd(prog, netns_fd, 0, "netns");
 }
 
 struct bpf_link *bpf_program__attach_xdp(struct bpf_program *prog, int ifindex)
 {
 	/* target_fd/target_ifindex use the same field in LINK_CREATE */
-	return bpf_program__attach_fd(prog, ifindex, "xdp");
+	return bpf_program__attach_fd(prog, ifindex, 0, "xdp");
+}
+
+struct bpf_link *bpf_program__attach_freplace(struct bpf_program *prog,
+					      int target_fd, int target_btf_id)
+{
+	return bpf_program__attach_fd(prog, target_fd, target_btf_id, "freplace");
 }
 
 struct bpf_link *
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index a750f67a23f6..ce5add9b9203 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -261,6 +261,9 @@ LIBBPF_API struct bpf_link *
 bpf_program__attach_netns(struct bpf_program *prog, int netns_fd);
 LIBBPF_API struct bpf_link *
 bpf_program__attach_xdp(struct bpf_program *prog, int ifindex);
+LIBBPF_API struct bpf_link *
+bpf_program__attach_freplace(struct bpf_program *prog,
+			     int target_fd, int target_btf_id);
 
 struct bpf_map;
 
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 92ceb48a5ca2..3cc2c42f435d 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -302,6 +302,7 @@ LIBBPF_0.1.0 {
 
 LIBBPF_0.2.0 {
 	global:
+		bpf_program__attach_freplace;
 		bpf_program__section_name;
 		perf_buffer__buffer_cnt;
 		perf_buffer__buffer_fd;

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