[PATCH v5 3/4] scripts: add verifier script for builtin module range data

[Kris Van Hees]

The modules.builtin.ranges offset range data for builtin modules is
generated at compile time based on the list of built-in modules and
the vmlinux.map and vmlinux.o.map linker maps.  This data can be used
to determine whether a symbol at a particular address belongs to
module code that was configured to be compiled into the kernel proper
as a built-in module (rather than as a standalone module).

This patch adds a script that uses the generated modules.builtin.ranges
data to annotate the symbols in the System.map with module names if
their address falls within a range that belongs to one or mre built-in
modules.

It then processes the vmlinux.map (and if needed, vmlinux.o.map) to
verify the annotation:

  - For each top-level section:
     - For each object in the section:
        - Determine whether the object is part of a built-in module
          (using modules.builtin and the .*.cmd file used to compile
           the object as suggested in [0])
        - For each symbol in that object, verify that the built-in
          module association (or lack thereof) matches the annotation
          given to the symbol.

Signed-off-by: Kris Van Hees <kris.van.hees@xxxxxxxxxx>
Reviewed-by: Nick Alcock <nick.alcock@xxxxxxxxxx>
Reviewed-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---

Notes:
    Changes since v4:
     - New patch in the series

 scripts/verify_builtin_ranges.awk | 348 ++++++++++++++++++++++++++++++
 1 file changed, 348 insertions(+)
 create mode 100755 scripts/verify_builtin_ranges.awk

diff --git a/scripts/verify_builtin_ranges.awk b/scripts/verify_builtin_ranges.awk
new file mode 100755
index 000000000000..a2475a38ba50
--- /dev/null
+++ b/scripts/verify_builtin_ranges.awk
@@ -0,0 +1,348 @@
+#!/usr/bin/gawk -f
+# SPDX-License-Identifier: GPL-2.0
+# verify_builtin_ranges.awk: Verify address range data for builtin modules
+# Written by Kris Van Hees <kris.van.hees@xxxxxxxxxx>
+#
+# Usage: verify_builtin_ranges.awk modules.builtin.ranges System.map \
+#				   modules.builtin vmlinux.map vmlinux.o.map
+#
+
+# Return the module name(s) (if any) associated with the given object.
+#
+# If we have seen this object before, return information from the cache.
+# Otherwise, retrieve it from the corresponding .cmd file.
+#
+function get_module_info(fn, mod, obj, mfn, s) {
+	if (fn in omod)
+		return omod[fn];
+
+	if (match(fn, /\/[^/]+$/) == 0)
+		return "";
+
+	obj = fn;
+	mod = "";
+	mfn = "";
+	fn = substr(fn, 1, RSTART) "." substr(fn, RSTART + 1) ".cmd";
+	if (getline s <fn == 1) {
+		if (match(s, /DKBUILD_MODFILE=['"]+[^'"]+/) > 0) {
+			mfn = substr(s, RSTART + 16, RLENGTH - 16);
+			gsub(/['"]/, "", mfn);
+
+			mod = mfn;
+			gsub(/([^/ ]*\/)+/, "", mod);
+			gsub(/-/, "_", mod);
+		}
+	}
+	close(fn);
+
+	# A single module (common case) also reflects objects that are not part
+	# of a module.  Some of those objects have names that are also a module
+	# name (e.g. core).  We check the associated module file name, and if
+	# they do not match, the object is not part of a module.
+	if (mod !~ / /) {
+		if (!(mod in mods))
+			return "";
+		if (mods[mod] != mfn)
+			return "";
+	}
+
+	# At this point, mod is a single (valid) module name, or a list of
+	# module names (that do not need validation).
+	omod[obj] = mod;
+	close(fn);
+
+	return mod;
+}
+
+# Return a representative integer value for a given hexadecimal address.
+#
+# Since all kernel addresses fall within the same memory region, we can safely
+# strip off the first 6 hex digits before performing the hex-to-dec conversion,
+# thereby avoiding integer overflows.
+#
+function addr2val(val) {
+	sub(/^0x/, "", val);
+	if (length(val) == 16)
+		val = substr(val, 5);
+	return strtonum("0x" val);
+}
+
+# (1) Load the built-in module address range data.
+#
+ARGIND == 1 {
+	ranges[FNR] = $0;
+	rcnt++;
+	next;
+}
+
+# (2) Annotate System.map symbols with module names.
+#
+ARGIND == 2 {
+	addr = addr2val($1);
+	name = $3;
+
+	while (addr >= mod_eaddr) {
+		if (sect_symb) {
+			if (sect_symb != name)
+				next;
+
+			sect_base = addr - sect_off;
+			if (dbg)
+				printf "[%s] BASE (%s) %016x - %016x = %016x\n", sect_name, sect_symb, addr, sect_off, sect_base >"/dev/stderr";
+			sect_symb = 0;
+		}
+
+		if (++ridx > rcnt)
+			break;
+
+		$0 = ranges[ridx];
+		sub(/-/, " ");
+		if ($4 != "=") {
+			sub(/-/, " ");
+			mod_saddr = strtonum("0x" $2) + sect_base;
+			mod_eaddr = strtonum("0x" $3) + sect_base;
+			$1 = $2 = $3 = "";
+			sub(/^ +/, "");
+			mod_name = $0;
+
+			if (dbg)
+				printf "[%s] %s from %016x to %016x\n", sect_name, mod_name, mod_saddr, mod_eaddr >"/dev/stderr";
+		} else {
+			sect_name = $1;
+			sect_off = strtonum("0x" $2);
+			sect_symb = $5;
+		}
+	}
+
+	idx = addr"-"name;
+	if (addr >= mod_saddr && addr < mod_eaddr)
+		sym2mod[idx] = mod_name;
+
+	next;
+}
+
+# Once we are done annotating the System.map, we no longer need the ranges data.
+#
+FNR == 1 && ARGIND == 3 {
+	delete ranges;
+}
+
+# (3) Build a lookup map of built-in module names.
+#
+# Lines from modules.builtin will be like:
+#	kernel/crypto/lzo-rle.ko
+# and we derive the built-in module name from this as "lzo_rle" and associate
+# it with object name "crypto/lzo-rle".
+#
+ARGIND == 3 {
+	sub(/kernel\//, "");			# strip off "kernel/" prefix
+	sub(/\.ko$/, "");			# strip off .ko suffix
+
+	mod = $1;
+	sub(/([^/]*\/)+/, "", mod);		# mod = basename($1)
+	gsub(/-/, "_", mod);			# Convert - to _
+
+	mods[mod] = $1;
+	next;
+}
+
+# (4) Get a list of symbols (per object).
+#
+# Symbols by object are read from vmlinux.map, with fallback to vmlinux.o.map
+# if vmlinux is found to have inked in vmlinux.o.
+#
+
+# If we were able to get the data we need from vmlinux.map, there is no need to
+# process vmlinux.o.map.
+#
+FNR == 1 && ARGIND == 5 && total > 0 {
+	if (dbg)
+		printf "Note: %s is not needed.\n", FILENAME >"/dev/stderr";
+	exit;
+}
+
+# First determine whether we are dealing with a GNU ld or LLVM lld linker map.
+#
+ARGIND >= 4 && FNR == 1 && NF == 7 && $1 == "VMA" && $7 == "Symbol" {
+	map_is_lld = 1;
+	next;
+}
+
+# (LLD) Convert a section record fronm lld format to ld format.
+#
+ARGIND >= 4 && map_is_lld && NF == 5 && /[0-9] [^ ]/ {
+	$0 = $5 " 0x"$1 " 0x"$3 " load address 0x"$2;
+}
+
+# (LLD) Convert an object record from lld format to ld format.
+#
+ARGIND >= 4 && map_is_lld && NF == 5 && $5 ~ /:\(\./ {
+	gsub(/\)/, "");
+	sub(/:\(/, " ");
+	sub(/ vmlinux\.a\(/, " ");
+	$0 = " "$6 " 0x"$1 " 0x"$3 " " $5;
+}
+
+# (LLD) Convert a symbol record from lld format to ld format.
+#
+ARGIND >= 4 && map_is_lld && NF == 5 && $5 ~ /^[A-Za-z_][A-Za-z0-9_]*$/ {
+	$0 = "  0x" $1 " " $5;
+}
+
+# (LLD) We do not need any other ldd linker map records.
+#
+ARGIND >= 4 && map_is_lld && /^[0-9a-f]{16} / {
+	next;
+}
+
+# Handle section records with long section names (spilling onto a 2nd line).
+#
+ARGIND >= 4 && !map_is_lld && NF == 1 && /^[^ ]/ {
+	s = $0;
+	getline;
+	$0 = s " " $0;
+}
+
+# Next section - previous one is done.
+#
+ARGIND >= 4 && /^[^ ]/ {
+	sect = 0;
+}
+
+# Get the (top level) section name.
+#
+ARGIND >= 4 && /^[^ ]/ && $2 ~ /^0x/ && $3 ~ /^0x/ {
+	# Empty section or per-CPU section - ignore.
+	if (NF < 3 || $1 ~ /\.percpu/) {
+		sect = 0;
+		next;
+	}
+
+	sect = $1;
+
+	next;
+}
+
+# If we are not currently in a section we care about, ignore records.
+#
+!sect {
+	next;
+}
+
+# Handle object records with long section names (spilling onto a 2nd line).
+#
+ARGIND >= 4 && /^ [^ \*]/ && NF == 1 {
+	# If the section name is long, the remainder of the entry is found on
+	# the next line.
+	s = $0;
+	getline;
+	$0 = s " " $0;
+}
+
+# If the object is vmlinux.o, we need to consult vmlinux.o.map for per-object
+# symbol information
+#
+ARGIND == 4 && /^ [^ ]/ && NF == 4 {
+	idx = sect":"$1;
+	if (!(idx in sect_addend)) {
+		sect_addend[idx] = addr2val($2);
+		if (dbg)
+			printf "ADDEND %s = %016x\n", idx, sect_addend[idx] >"/dev/stderr";
+	}
+	if ($4 == "vmlinux.o") {
+		need_o_map = 1;
+		next;
+	}
+}
+
+# If data from vmlinux.o.map is needed, we only process section and object
+# records from vmlinux.map to determine which section we need to pay attention
+# to in vmlinux.o.map.  So skip everything else from vmlinux.map.
+#
+ARGIND == 4 && need_o_map {
+	next;
+}
+
+# Get module information for the current object.
+#
+ARGIND >= 4 && /^ [^ ]/ && NF == 4 {
+	msect = $1;
+	mod_name = get_module_info($4);
+	mod_eaddr = addr2val($2) + addr2val($3);
+
+	next;
+}
+
+# Process a symbol record.
+#
+# Evaluate the module information obtained from vmlinux.map (or vmlinux.o.map)
+# as follows:
+#  - For all symbols in a given object:
+#     - If the symbol is annotated with the same module name(s) that the object
+#       belongs to, count it as a match.
+#     - Otherwise:
+#        - If the symbol is known to have duplicates of which at least one is
+#          in a built-in module, disregard it.
+#        - If the symbol us not annotated with any module name(s) AND the
+#          object belongs to built-in modules, count it as missing.
+#        - Otherwise, count it as a mismatch.
+#
+ARGIND >= 4 && /^ / && NF == 2 && $1 ~ /^0x/ {
+	idx = sect":"msect;
+	if (!(idx in sect_addend))
+		next;
+
+	addr = addr2val($1);
+
+	# Handle the rare but annoying case where a 0-size symbol is placed at
+	# the byte *after* the module range.  Based on vmlinux.map it will be
+	# considered part of the current object, but it falls just beyond the
+	# module address range.  Unfortunately, its address could be at the
+	# start of another built-in module, so the only safe thing to do is to
+	# ignore it.
+	if (mod_name && addr == mod_eaddr)
+		next;
+
+	# If we are processing vmlinux.o.map, we need to apply the base address
+	# of the section to the relative address on the record.
+	#
+	if (ARGIND == 5)
+		addr += sect_addend[idx];
+
+	idx = addr"-"$2;
+	mod = "";
+	if (idx in sym2mod) {
+		mod = sym2mod[idx];
+		if (sym2mod[idx] == mod_name) {
+			mod_matches++;
+			matches++;
+		} else if (mod_name == "") {
+			print $2 " in " sym2mod[idx] " (should NOT be)";
+			mismatches++;
+		} else {
+			print $2 " in " sym2mod[idx] " (should be " mod_name ")";
+			mismatches++;
+		}
+	} else if (mod_name != "") {
+		print $2 " should be in " mod_name;
+		missing++;
+	} else
+		matches++;
+
+	total++;
+
+	next;
+}
+
+# Issue the comparison report.
+#
+END {
+	if (total == 0)
+		total = 1;
+
+	printf "Verification of %s:\n", ARGV[1];
+	printf "  Correct matches:  %6d (%d%% of total)\n", matches, 100 * matches / total;
+	printf "    Module matches: %6d (%d%% of matches)\n", mod_matches, 100 * mod_matches / matches;
+	printf "  Mismatches:       %6d (%d%% of total)\n", mismatches, 100 * mismatches / total;
+	printf "  Missing:          %6d (%d%% of total)\n", missing, 100 * missing / total;
+}
-- 
2.45.1