[PATCH bpf-next 1/3] tools: bpftool: document restriction on '.' in names to pin in bpffs

[Quentin Monnet <quentin.monnet@netronome.com>]

Names used to pin eBPF programs and maps under the eBPF virtual file
system cannot contain a dot character, which is reserved for future
extensions of this file system.

Document this in bpftool man pages to avoid users getting confused if
pinning fails because of a dot.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
---
 tools/bpf/bpftool/Documentation/bpftool-map.rst  | 4 +++-
 tools/bpf/bpftool/Documentation/bpftool-prog.rst | 8 ++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/tools/bpf/bpftool/Documentation/bpftool-map.rst b/tools/bpf/bpftool/Documentation/bpftool-map.rst
index 3497f2d80328..f55a2daed59b 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-map.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-map.rst
@@ -86,7 +86,9 @@ DESCRIPTION
 	**bpftool map pin**     *MAP*  *FILE*
 		  Pin map *MAP* as *FILE*.
 
-		  Note: *FILE* must be located in *bpffs* mount.
+		  Note: *FILE* must be located in *bpffs* mount. It must not
+		  contain a dot character ('.'), which is reserved for future
+		  extensions of *bpffs*.
 
 	**bpftool** **map event_pipe** *MAP* [**cpu** *N* **index** *M*]
 		  Read events from a BPF_MAP_TYPE_PERF_EVENT_ARRAY map.
diff --git a/tools/bpf/bpftool/Documentation/bpftool-prog.rst b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
index 12c803003ab2..ac4e904b10fb 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-prog.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
@@ -75,7 +75,9 @@ DESCRIPTION
 	**bpftool prog pin** *PROG* *FILE*
 		  Pin program *PROG* as *FILE*.
 
-		  Note: *FILE* must be located in *bpffs* mount.
+		  Note: *FILE* must be located in *bpffs* mount. It must not
+		  contain a dot character ('.'), which is reserved for future
+		  extensions of *bpffs*.
 
 	**bpftool prog load** *OBJ* *FILE* [**type** *TYPE*] [**map** {**idx** *IDX* | **name** *NAME*} *MAP*] [**dev** *NAME*]
 		  Load bpf program from binary *OBJ* and pin as *FILE*.
@@ -91,7 +93,9 @@ DESCRIPTION
 		  If **dev** *NAME* is specified program will be loaded onto
 		  given networking device (offload).
 
-		  Note: *FILE* must be located in *bpffs* mount.
+		  Note: *FILE* must be located in *bpffs* mount. It must not
+		  contain a dot character ('.'), which is reserved for future
+		  extensions of *bpffs*.
 
         **bpftool prog attach** *PROG* *ATTACH_TYPE* *MAP*
                   Attach bpf program *PROG* (with type specified by *ATTACH_TYPE*)
-- 
2.7.4