scripts/check-sysctl-docs

#!/usr/bin/env -S gawk -f
# SPDX-License-Identifier: GPL-2.0

# Script to check sysctl documentation against source files
#
# Copyright (c) 2020 Stephen Kitt

# Example invocation:
#	scripts/check-sysctl-docs -vtable="kernel" \
#		Documentation/admin-guide/sysctl/kernel.rst \
#		$(git grep -l register_sysctl)
#
# Specify -vdebug=1 to see debugging information

BEGIN {
	if (!table) {
	print "Please specify the table to look for using the table variable" > "/dev/stderr"
	exit 1
	}

	# Documentation title skiplist
	skiplist[0] = "^Documentation for"
	skiplist[1] = "Network core options$"
	skiplist[2] = "POSIX message queues filesystem$"
	skiplist[3] = "Configuration options"
	skiplist[4] = ". /proc/sys/fs"
	skiplist[5] = "^Introduction$"
	skiplist[6] = "^seccomp$"
	skiplist[7] = "^pty$"
	skiplist[8] = "^firmware_config$"
	skiplist[9] = "^random$"
}

# The following globals are used:
# documented: maps documented entries (each key is an entry)
# entries: maps ctl_table names and procnames to counts (so
#          enumerating the subkeys for a given ctl_table lists its
#          procnames)
# curtable: the name of the current ctl_table struct
# curentry: the name of the current proc entry (procname when parsing
#           a ctl_table, constructed path when parsing a ctl_path)


# Remove punctuation from the given value
function trimpunct(value) {
	while (value ~ /^["&]/) {
		value = substr(value, 2)
	}
	while (value ~ /[]["&,}]$/) {
		value = substr(value, 1, length(value) - 1)
	}
	return value
}

# Print the information for the given entry
function printentry(entry) {
	seen[entry]++
	printf "* %s from %s", entry, file[entry]
	if (documented[entry]) {
		printf " (documented)"
	}
	print ""
}


# Stage 1: build the list of documented entries
FNR == NR && /^=+$/ {
	for (i in skiplist) {
		if (prevline ~ skiplist[i]) {
			next
		}
	}

	# The previous line is a section title, parse it
	$0 = prevline
	if (debug) print "Parsing " $0
	inbrackets = 0
	for (i = 1; i <= NF; i++) {
		if (length($i) == 0) {
			continue
		}
		if (!inbrackets && substr($i, 1, 1) == "(") {
			inbrackets = 1
		}
		if (!inbrackets) {
			token = trimpunct($i)
			if (length(token) > 0 && token != "and") {
				if (debug) print trimpunct($i)
					documented[trimpunct($i)]++
			}
		}
		if (inbrackets && substr($i, length($i), 1) == ")") {
			inbrackets = 0
		}
	}
}

FNR == NR {
	prevline = $0
	next
}


# Stage 2: process each file and find all sysctl tables
BEGINFILE {
	delete entries
	curtable = ""
	curentry = ""
	delete vars
	if (debug) print "Processing file " FILENAME
}

/^static( const)? struct ctl_table/ {
	match($0, /static( const)? struct ctl_table ([^][]+)/, tables)
	curtable = tables[2]
	if (debug) print "Processing table " curtable
}

/^};$/ {
	curtable = ""
	curentry = ""
	delete vars
}

curtable && /\.procname[\t ]*=[\t ]*".+"/ {
	match($0, /.procname[\t ]*=[\t ]*"([^"]+)"/, names)
	curentry = names[1]
	if (debug) print "Adding entry " curentry " to table " curtable
	entries[curtable][curentry]++
	file[curentry] = FILENAME
}

curtable && /UCOUNT_ENTRY.*/ {
	match($0, /UCOUNT_ENTRY\("([^"]+)"\)/, names)
	curentry = names[1]
	if (debug) print "Adding entry " curentry " to table " curtable
	entries[curtable][curentry]++
	file[curentry] = FILENAME
}

/register_sysctl.*/ {
	match($0, /register_sysctl(|_init|_sz)\("([^"]+)" *, *([^,)]+)/, tables)
	if (debug) print "Registering table " tables[3] " at " tables[2]
	if (tables[2] == table) {
		for (entry in entries[tables[3]]) {
			printentry(entry)
		}
	}
}

/kmemdup.*/ {
	match($0, /([^ \t]+) *= *kmemdup\(([^,]+) *,/, names)
	if (debug) print "Found variable " names[1] " for table " names[2]
	if (names[2] in entries) {
		vars[names[1]] = names[2]
	}
}

/__register_sysctl_table.*/ {
	match($0, /__register_sysctl_table\([^,]+, *"([^"]+)" *, *([^,]+)/, tables)
	if (debug) print "Registering variable table " tables[2] " at " tables[1]
	if (tables[1] == table && tables[2] in vars) {
		for (entry in entries[vars[tables[2]]]) {
			printentry(entry)
		}
	}
}

END {
	for (entry in documented) {
		if (!seen[entry])
			print "No implementation for " entry
	}
}