tools: bpftool: show that opcodes or file FILE should be exclusive

For the `bpftool prog dump { jited | xlated } ...` command, adding
`opcodes` keyword (to request opcodes to be printed) will have no effect
if `file FILE` (to write binary output to FILE) is provided.

The manual page and the help message to be displayed in the terminal
should reflect that, and indicate that these options should be mutually
exclusive.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@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

@@ -11,8 +11,8 @@ SYNOPSIS
 ========
 
 |	**bpftool** prog show [*PROG*]
-|	**bpftool** prog dump xlated *PROG* [file *FILE*] [opcodes]
-|	**bpftool** prog dump jited  *PROG* [file *FILE*] [opcodes]
+|	**bpftool** prog dump xlated *PROG* [{file *FILE* | opcodes }]
+|	**bpftool** prog dump jited  *PROG* [{file *FILE* | opcodes }]
 |	**bpftool** prog pin *PROG* *FILE*
 |	**bpftool** prog help
 |
@@ -28,14 +28,14 @@ DESCRIPTION
 		  Output will start with program ID followed by program type and
 		  zero or more named attributes (depending on kernel version).
 
-	**bpftool prog dump xlated** *PROG* [**file** *FILE*] [**opcodes**]
+	**bpftool prog dump xlated** *PROG* [{ **file** *FILE* | **opcodes** }]
 		  Dump eBPF instructions of the program from the kernel.
 		  If *FILE* is specified image will be written to a file,
 		  otherwise it will be disassembled and printed to stdout.
 
 		  **opcodes** controls if raw opcodes will be printed.
 
-	**bpftool prog dump jited**  *PROG* [**file** *FILE*] [**opcodes**]
+	**bpftool prog dump jited**  *PROG* [{ **file** *FILE* | **opcodes** }]
 		  Dump jited image (host machine code) of the program.
 		  If *FILE* is specified image will be written to a file,
 		  otherwise it will be disassembled and printed to stdout.

tools/bpf/bpftool/prog.c

@@ -469,8 +469,8 @@ static int do_help(int argc, char **argv)
 {
 	fprintf(stderr,
 		"Usage: %s %s show [PROG]\n"
-		"       %s %s dump xlated PROG [file FILE] [opcodes]\n"
-		"       %s %s dump jited  PROG [file FILE] [opcodes]\n"
+		"       %s %s dump xlated PROG [{ file FILE | opcodes }]\n"
+		"       %s %s dump jited  PROG [{ file FILE | opcodes }]\n"
 		"       %s %s pin   PROG FILE\n"
 		"       %s %s help\n"
 		"\n"