tools: bpftool: Automate generation for "SEE ALSO" sections in man pages

The "SEE ALSO" sections of bpftool's manual pages refer to bpf(2),
bpf-helpers(7), then all existing bpftool man pages (save the current
one).

This leads to nearly-identical lists being duplicated in all manual
pages. Ideally, when a new page is created, all lists should be updated
accordingly, but this has led to omissions and inconsistencies multiple
times in the past.

Let's take it out of the RST files and generate the "SEE ALSO" sections
automatically in the Makefile when generating the man pages. The lists
are not really useful in the RST anyway because all other pages are
available in the same directory.

v3:
- Fix conflict with a previous patchset that introduced RST2MAN_OPTS
  variable passed to rst2man.

v2:
- Use "echo -n" instead of "printf" in Makefile, to avoid any risk of
  passing a format string directly to the command.

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200910203935.25304-1-quentin@isovalent.com

tools/bpf/bpftool/Documentation/Makefile

@@ -30,11 +30,21 @@ man8: $(DOC_MAN8)
 RST2MAN_DEP := $(shell command -v rst2man 2>/dev/null)
 RST2MAN_OPTS += --verbose
 
+list_pages = $(sort $(basename $(filter-out $(1),$(MAN8_RST))))
+see_also = $(subst " ",, \
+	"\n" \
+	"SEE ALSO\n" \
+	"========\n" \
+	"\t**bpf**\ (2),\n" \
+	"\t**bpf-helpers**\\ (7)" \
+	$(foreach page,$(call list_pages,$(1)),",\n\t**$(page)**\\ (8)") \
+	"\n")
+
 $(OUTPUT)%.8: %.rst
 ifndef RST2MAN_DEP
 	$(error "rst2man not found, but required to generate man pages")
 endif
-	$(QUIET_GEN)rst2man $(RST2MAN_OPTS) $< > $@
+	$(QUIET_GEN)( cat $< ; echo -n $(call see_also,$<) ) | rst2man $(RST2MAN_OPTS) > $@
 
 clean: helpers-clean
 	$(call QUIET_CLEAN, Documentation)

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

@@ -217,20 +217,3 @@ All the standard ways to specify map or program are supported:
 **# bpftool btf dump prog tag b88e0a09b1d9759d**
 
 **# bpftool btf dump prog pinned /sys/fs/bpf/prog_name**
-
-SEE ALSO
-========
-	**bpf**\ (2),
-	**bpf-helpers**\ (7),
-	**bpftool**\ (8),
-	**bpftool-btf**\ (8),
-	**bpftool-cgroup**\ (8),
-	**bpftool-feature**\ (8),
-	**bpftool-gen**\ (8),
-	**bpftool-iter**\ (8),
-	**bpftool-link**\ (8),
-	**bpftool-map**\ (8),
-	**bpftool-net**\ (8),
-	**bpftool-perf**\ (8),
-	**bpftool-prog**\ (8),
-	**bpftool-struct_ops**\ (8)

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

@@ -143,19 +143,3 @@ EXAMPLES
 ::
 
     ID       AttachType      AttachFlags     Name
-
-SEE ALSO
-========
-	**bpf**\ (2),
-	**bpf-helpers**\ (7),
-	**bpftool**\ (8),
-	**bpftool-btf**\ (8),
-	**bpftool-feature**\ (8),
-	**bpftool-gen**\ (8),
-	**bpftool-iter**\ (8),
-	**bpftool-link**\ (8),
-	**bpftool-map**\ (8),
-	**bpftool-net**\ (8),
-	**bpftool-perf**\ (8),
-	**bpftool-prog**\ (8),
-	**bpftool-struct_ops**\ (8)

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

@@ -72,19 +72,3 @@ DESCRIPTION
 OPTIONS
 =======
 	.. include:: common_options.rst
-
-SEE ALSO
-========
-	**bpf**\ (2),
-	**bpf-helpers**\ (7),
-	**bpftool**\ (8),
-	**bpftool-btf**\ (8),
-	**bpftool-cgroup**\ (8),
-	**bpftool-gen**\ (8),
-	**bpftool-iter**\ (8),
-	**bpftool-link**\ (8),
-	**bpftool-map**\ (8),
-	**bpftool-net**\ (8),
-	**bpftool-perf**\ (8),
-	**bpftool-prog**\ (8),
-	**bpftool-struct_ops**\ (8)

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

@@ -279,19 +279,3 @@ and global variables.
   my_static_var: 7
 
 This is a stripped-out version of skeleton generated for above example code.
-
-SEE ALSO
-========
-	**bpf**\ (2),
-	**bpf-helpers**\ (7),
-	**bpftool**\ (8),
-	**bpftool-btf**\ (8),
-	**bpftool-cgroup**\ (8),
-	**bpftool-feature**\ (8),
-	**bpftool-iter**\ (8),
-	**bpftool-link**\ (8),
-	**bpftool-map**\ (8),
-	**bpftool-net**\ (8),
-	**bpftool-perf**\ (8),
-	**bpftool-prog**\ (8),
-	**bpftool-struct_ops**\ (8)

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

@@ -68,19 +68,3 @@ EXAMPLES
 
    Create a file-based bpf iterator from bpf_iter_hashmap.o and map with
    id 20, and pin it to /sys/fs/bpf/my_hashmap
-
-SEE ALSO
-========
-	**bpf**\ (2),
-	**bpf-helpers**\ (7),
-	**bpftool**\ (8),
-	**bpftool-btf**\ (8),
-	**bpftool-cgroup**\ (8),
-	**bpftool-feature**\ (8),
-	**bpftool-gen**\ (8),
-	**bpftool-link**\ (8),
-	**bpftool-map**\ (8),
-	**bpftool-net**\ (8),
-	**bpftool-perf**\ (8),
-	**bpftool-prog**\ (8),
-	**bpftool-struct_ops**\ (8)

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

@@ -106,20 +106,3 @@ EXAMPLES
 ::
 
     -rw------- 1 root root 0 Apr 23 21:39 link
-
-
-SEE ALSO
-========
-	**bpf**\ (2),
-	**bpf-helpers**\ (7),
-	**bpftool**\ (8),
-	**bpftool-btf**\ (8),
-	**bpftool-cgroup**\ (8),
-	**bpftool-feature**\ (8),
-	**bpftool-gen**\ (8),
-	**bpftool-iter**\ (8),
-	**bpftool-map**\ (8),
-	**bpftool-net**\ (8),
-	**bpftool-perf**\ (8),
-	**bpftool-prog**\ (8),
-	**bpftool-struct_ops**\ (8)

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

@@ -270,19 +270,3 @@ would be lost as soon as bpftool exits).
 
   key: 00 00 00 00  value: 22 02 00 00
   Found 1 element
-
-SEE ALSO
-========
-	**bpf**\ (2),
-	**bpf-helpers**\ (7),
-	**bpftool**\ (8),
-	**bpftool-btf**\ (8),
-	**bpftool-cgroup**\ (8),
-	**bpftool-feature**\ (8),
-	**bpftool-gen**\ (8),
-	**bpftool-iter**\ (8),
-	**bpftool-link**\ (8),
-	**bpftool-net**\ (8),
-	**bpftool-perf**\ (8),
-	**bpftool-prog**\ (8),
-	**bpftool-struct_ops**\ (8)

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

@@ -172,20 +172,3 @@ EXAMPLES
 ::
 
       xdp:
-
-
-SEE ALSO
-========
-	**bpf**\ (2),
-	**bpf-helpers**\ (7),
-	**bpftool**\ (8),
-	**bpftool-btf**\ (8),
-	**bpftool-cgroup**\ (8),
-	**bpftool-feature**\ (8),
-	**bpftool-gen**\ (8),
-	**bpftool-iter**\ (8),
-	**bpftool-link**\ (8),
-	**bpftool-map**\ (8),
-	**bpftool-perf**\ (8),
-	**bpftool-prog**\ (8),
-	**bpftool-struct_ops**\ (8)

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

@@ -63,20 +63,3 @@ EXAMPLES
      {"pid":21765,"fd":5,"prog_id":7,"fd_type":"kretprobe","func":"__x64_sys_nanosleep","offset":0}, \
      {"pid":21767,"fd":5,"prog_id":8,"fd_type":"tracepoint","tracepoint":"sys_enter_nanosleep"}, \
      {"pid":21800,"fd":5,"prog_id":9,"fd_type":"uprobe","filename":"/home/yhs/a.out","offset":1159}]
-
-
-SEE ALSO
-========
-	**bpf**\ (2),
-	**bpf-helpers**\ (7),
-	**bpftool**\ (8),
-	**bpftool-btf**\ (8),
-	**bpftool-cgroup**\ (8),
-	**bpftool-feature**\ (8),
-	**bpftool-gen**\ (8),
-	**bpftool-iter**\ (8),
-	**bpftool-link**\ (8),
-	**bpftool-map**\ (8),
-	**bpftool-net**\ (8),
-	**bpftool-prog**\ (8),
-	**bpftool-struct_ops**\ (8)

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

@@ -326,19 +326,3 @@ EXAMPLES
       40176203 cycles                                                 (83.05%)
       42518139 instructions    #   1.06 insns per cycle               (83.39%)
            123 llc_misses      #   2.89 LLC misses per million insns  (83.15%)
-
-SEE ALSO
-========
-	**bpf**\ (2),
-	**bpf-helpers**\ (7),
-	**bpftool**\ (8),
-	**bpftool-btf**\ (8),
-	**bpftool-cgroup**\ (8),
-	**bpftool-feature**\ (8),
-	**bpftool-gen**\ (8),
-	**bpftool-iter**\ (8),
-	**bpftool-link**\ (8),
-	**bpftool-map**\ (8),
-	**bpftool-net**\ (8),
-	**bpftool-perf**\ (8),
-	**bpftool-struct_ops**\ (8)

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

@@ -82,20 +82,3 @@ EXAMPLES
 ::
 
    Registered tcp_congestion_ops cubic id 110
-
-
-SEE ALSO
-========
-	**bpf**\ (2),
-	**bpf-helpers**\ (7),
-	**bpftool**\ (8),
-	**bpftool-btf**\ (8),
-	**bpftool-cgroup**\ (8),
-	**bpftool-feature**\ (8),
-	**bpftool-gen**\ (8),
-	**bpftool-iter**\ (8),
-	**bpftool-link**\ (8),
-	**bpftool-map**\ (8),
-	**bpftool-net**\ (8),
-	**bpftool-perf**\ (8),
-	**bpftool-prog**\ (8)

tools/bpf/bpftool/Documentation/bpftool.rst

@@ -54,19 +54,3 @@ OPTIONS
 	-n, --nomount
 		  Do not automatically attempt to mount any virtual file system
 		  (such as tracefs or BPF virtual file system) when necessary.
-
-SEE ALSO
-========
-	**bpf**\ (2),
-	**bpf-helpers**\ (7),
-	**bpftool-btf**\ (8),
-	**bpftool-cgroup**\ (8),
-	**bpftool-feature**\ (8),
-	**bpftool-gen**\ (8),
-	**bpftool-iter**\ (8),
-	**bpftool-link**\ (8),
-	**bpftool-map**\ (8),
-	**bpftool-net**\ (8),
-	**bpftool-perf**\ (8),
-	**bpftool-prog**\ (8),
-	**bpftool-struct_ops**\ (8)