bpftool: Update doc (add autoattach to prog load)

Add autoattach optional to prog load|loadall for supporting
one-step load-attach-pin_link.

Signed-off-by: Wang Yufen <wangyufen@huawei.com>
Link: https://lore.kernel.org/r/1665736275-28143-3-git-send-email-wangyufen@huawei.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: wangyufen316

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*.