Merge branch 'bpftool: Add autoattach for bpf prog load|loadall'

Wang Yufen says:

====================

This patchset add "autoattach" optional for "bpftool prog load(_all)" to support
one-step load-attach-pin_link.

v8 -> v9: fix link leak, and change pathname_concat(specify not just buffer
	  pointer, but also it's size)
v7 -> v8: for the programs not supporting autoattach, fall back to reguler pinning
	  instead of skipping
v6 -> v7: add info msg print and update doc for the skip program
v5 -> v6: skip the programs not supporting auto-attach,
	  and change optional name from "auto_attach" to "autoattach"
v4 -> v5: some formatting nits of doc
v3 -> v4: rename functions, update doc, bash and do_help()
v2 -> v3: switch to extend prog load command instead of extend perf
v2: https://patchwork.kernel.org/project/netdevbpf/patch/20220824033837.458197-1-weiyongjun1@huawei.com/
v1: https://patchwork.kernel.org/project/netdevbpf/patch/20220816151725.153343-1-weiyongjun1@huawei.com/
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/bpf/bpftool/Documentation/bpftool-prog.rst

@@ -31,7 +31,7 @@ PROG COMMANDS
 |	**bpftool** **prog dump xlated** *PROG* [{**file** *FILE* | **opcodes** | **visual** | **linum**}]
 |	**bpftool** **prog dump jited**  *PROG* [{**file** *FILE* | **opcodes** | **linum**}]
 |	**bpftool** **prog pin** *PROG* *FILE*
-|	**bpftool** **prog** { **load** | **loadall** } *OBJ* *PATH* [**type** *TYPE*] [**map** {**idx** *IDX* | **name** *NAME*} *MAP*] [**dev** *NAME*] [**pinmaps** *MAP_DIR*]
+|	**bpftool** **prog** { **load** | **loadall** } *OBJ* *PATH* [**type** *TYPE*] [**map** {**idx** *IDX* | **name** *NAME*} *MAP*] [**dev** *NAME*] [**pinmaps** *MAP_DIR*] [**autoattach**]
 |	**bpftool** **prog attach** *PROG* *ATTACH_TYPE* [*MAP*]
 |	**bpftool** **prog detach** *PROG* *ATTACH_TYPE* [*MAP*]
 |	**bpftool** **prog tracelog**
@@ -131,7 +131,7 @@ DESCRIPTION
 		  contain a dot character ('.'), which is reserved for future
 		  extensions of *bpffs*.
 
-	**bpftool prog { load | loadall }** *OBJ* *PATH* [**type** *TYPE*] [**map** {**idx** *IDX* | **name** *NAME*} *MAP*] [**dev** *NAME*] [**pinmaps** *MAP_DIR*]
+	**bpftool prog { load | loadall }** *OBJ* *PATH* [**type** *TYPE*] [**map** {**idx** *IDX* | **name** *NAME*} *MAP*] [**dev** *NAME*] [**pinmaps** *MAP_DIR*] [**autoattach**]
 		  Load bpf program(s) from binary *OBJ* and pin as *PATH*.
 		  **bpftool prog load** pins only the first program from the
 		  *OBJ* as *PATH*. **bpftool prog loadall** pins all programs
@@ -150,6 +150,17 @@ DESCRIPTION
 		  Optional **pinmaps** argument can be provided to pin all
 		  maps under *MAP_DIR* directory.
 
+		  If **autoattach** is specified program will be attached
+		  before pin. In that case, only the link (representing the
+		  program attached to its hook) is pinned, not the program as
+		  such, so the path won't show in **bpftool prog show -f**,
+		  only show in **bpftool link show -f**. Also, this only works
+		  when bpftool (libbpf) is able to infer all necessary
+		  information from the object file, in particular, it's not
+		  supported for all program types. If a program does not
+		  support autoattach, bpftool falls back to regular pinning
+		  for that program instead.
+
 		  Note: *PATH* must be located in *bpffs* mount. It must not
 		  contain a dot character ('.'), which is reserved for future
 		  extensions of *bpffs*.

tools/bpf/bpftool/bash-completion/bpftool

@@ -505,6 +505,7 @@ _bpftool()
                             _bpftool_once_attr 'type'
                             _bpftool_once_attr 'dev'
                             _bpftool_once_attr 'pinmaps'
+                            _bpftool_once_attr 'autoattach'
                             return 0
                             ;;
                     esac

tools/bpf/bpftool/prog.c

@@ -1453,6 +1453,67 @@ get_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
 	return ret;
 }
 
+static int
+auto_attach_program(struct bpf_program *prog, const char *path)
+{
+	struct bpf_link *link;
+	int err;
+
+	link = bpf_program__attach(prog);
+	if (!link) {
+		p_info("Program %s does not support autoattach, falling back to pinning",
+		       bpf_program__name(prog));
+		return bpf_obj_pin(bpf_program__fd(prog), path);
+	}
+
+	err = bpf_link__pin(link, path);
+	bpf_link__destroy(link);
+	return err;
+}
+
+static int pathname_concat(char *buf, size_t buf_sz, const char *path, const char *name)
+{
+	int len;
+
+	len = snprintf(buf, buf_sz, "%s/%s", path, name);
+	if (len < 0)
+		return -EINVAL;
+	if ((size_t)len >= buf_sz)
+		return -ENAMETOOLONG;
+
+	return 0;
+}
+
+static int
+auto_attach_programs(struct bpf_object *obj, const char *path)
+{
+	struct bpf_program *prog;
+	char buf[PATH_MAX];
+	int err;
+
+	bpf_object__for_each_program(prog, obj) {
+		err = pathname_concat(buf, sizeof(buf), path, bpf_program__name(prog));
+		if (err)
+			goto err_unpin_programs;
+
+		err = auto_attach_program(prog, buf);
+		if (err)
+			goto err_unpin_programs;
+	}
+
+	return 0;
+
+err_unpin_programs:
+	while ((prog = bpf_object__prev_program(obj, prog))) {
+		if (pathname_concat(buf, sizeof(buf), path, bpf_program__name(prog)))
+			continue;
+
+		bpf_program__unpin(prog, buf);
+	}
+
+	return err;
+}
+
 static int load_with_options(int argc, char **argv, bool first_prog_only)
 {
 	enum bpf_prog_type common_prog_type = BPF_PROG_TYPE_UNSPEC;
@@ -1464,6 +1525,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
 	struct bpf_program *prog = NULL, *pos;
 	unsigned int old_map_fds = 0;
 	const char *pinmaps = NULL;
+	bool auto_attach = false;
 	struct bpf_object *obj;
 	struct bpf_map *map;
 	const char *pinfile;
@@ -1583,6 +1645,9 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
 				goto err_free_reuse_maps;
 
 			pinmaps = GET_ARG();
+		} else if (is_prefix(*argv, "autoattach")) {
+			auto_attach = true;
+			NEXT_ARG();
 		} else {
 			p_err("expected no more arguments, 'type', 'map' or 'dev', got: '%s'?",
 			      *argv);
@@ -1692,14 +1757,20 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
 			goto err_close_obj;
 		}
 
-		err = bpf_obj_pin(bpf_program__fd(prog), pinfile);
+		if (auto_attach)
+			err = auto_attach_program(prog, pinfile);
+		else
+			err = bpf_obj_pin(bpf_program__fd(prog), pinfile);
 		if (err) {
 			p_err("failed to pin program %s",
 			      bpf_program__section_name(prog));
 			goto err_close_obj;
 		}
 	} else {
-		err = bpf_object__pin_programs(obj, pinfile);
+		if (auto_attach)
+			err = auto_attach_programs(obj, pinfile);
+		else
+			err = bpf_object__pin_programs(obj, pinfile);
 		if (err) {
 			p_err("failed to pin all programs");
 			goto err_close_obj;
@@ -2338,6 +2409,7 @@ static int do_help(int argc, char **argv)
 		"                         [type TYPE] [dev NAME] \\\n"
 		"                         [map { idx IDX | name NAME } MAP]\\\n"
 		"                         [pinmaps MAP_DIR]\n"
+		"                         [autoattach]\n"
 		"       %1$s %2$s attach PROG ATTACH_TYPE [MAP]\n"
 		"       %1$s %2$s detach PROG ATTACH_TYPE [MAP]\n"
 		"       %1$s %2$s run PROG \\\n"