tools: bpftool: update documentation for --json and --pretty usage

Update the documentation to provide help about JSON output generation,
and add an example in bpftool-prog manual page.

Also reintroduce an example that was left aside when the tool was moved
from GitHub to the kernel sources, in order to show how to mount the
bpffs file system (to pin programs) inside the bpftool-prog manual page.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -10,6 +10,16 @@ tool for inspection and simple manipulation of eBPF progs
 SYNOPSIS
 ========
 
+	**bpftool** [*OPTIONS*] **prog** *COMMAND*
+
+	*OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] }
+
+	*COMMANDS* :=
+	{ **show** | **dump xlated** | **dump jited** | **pin** | **help** }
+
+MAP COMMANDS
+=============
+
 |	**bpftool** **prog show** [*PROG*]
 |	**bpftool** **prog dump xlated** *PROG* [{**file** *FILE* | **opcodes**}]
 |	**bpftool** **prog dump jited**  *PROG* [{**file** *FILE* | **opcodes**}]
@@ -58,6 +68,13 @@ OPTIONS
 	-v, --version
 		  Print version number (similar to **bpftool version**).
 
+	-j, --json
+		  Generate JSON output. For commands that cannot produce JSON, this
+		  option has no effect.
+
+	-p, --pretty
+		  Generate human-readable JSON output. Implies **-j**.
+
 EXAMPLES
 ========
 **# bpftool prog show**
@@ -67,13 +84,33 @@ EXAMPLES
 	loaded_at Sep 29/20:11  uid 0
 	xlated 528B  jited 370B  memlock 4096B  map_ids 10
 
+**# bpftool --json --pretty prog show**
+
+::
+
+    {
+        "programs": [{
+                "id": 10,
+                "type": "xdp",
+                "tag": "005a3d2123620c8b",
+                "loaded_at": "Sep 29/20:11",
+                "uid": 0,
+                "bytes_xlated": 528,
+                "jited": true,
+                "bytes_jited": 370,
+                "bytes_memlock": 4096,
+                "map_ids": [10
+                ]
+            }
+        ]
+    }
+
 |
 | **# bpftool prog dump xlated id 10 file /tmp/t**
 | **# ls -l /tmp/t**
 |   -rw------- 1 root root 560 Jul 22 01:42 /tmp/t
 
-|
-| **# bpftool prog dum jited pinned /sys/fs/bpf/prog**
+**# bpftool prog dum jited tag 005a3d2123620c8b**
 
 ::
 
@@ -83,6 +120,26 @@ EXAMPLES
     sub    $0x28,%rbp
     mov    %rbx,0x0(%rbp)
 
+|
+| **# mount -t bpf none /sys/fs/bpf/**
+| **# bpftool prog pin id 10 /sys/fs/bpf/prog**
+| **# ls -l /sys/fs/bpf/**
+|   -rw------- 1 root root 0 Jul 22 01:43 prog
+
+**# bpftool prog dum jited pinned /sys/fs/bpf/prog opcodes**
+
+::
+
+    push   %rbp
+    55
+    mov    %rsp,%rbp
+    48 89 e5
+    sub    $0x228,%rsp
+    48 81 ec 28 02 00 00
+    sub    $0x28,%rbp
+    48 83 ed 28
+    mov    %rbx,0x0(%rbp)
+    48 89 5d 00
 
 
 SEE ALSO