[PATCH 3/3] tests: Add a test for the accounting of flexible arrays

[Arnaldo Carvalho de Melo <acme@kernel.org>]

From: Arnaldo Carvalho de Melo <acme@redhat.com>

  acme@x1:~/git/pahole$ tests/flexible_arrays.sh
  Flexible arrays accounting: Ok
  acme@x1:~/git/pahole$ VERBOSE=1 tests/flexible_arrays.sh
  Flexible arrays accounting: end: mem_cgroup: 2 2
  middle: mem_cgroup: 3 3
  end: pglist_data: 2 2
  middle: pglist_data: 0 0
  end: zone: 3 3
  middle: zone: 0 0
  end: cgroup: 1 1
  middle: cgroup: 0 0
  end: cgroup_root: 1 1
  middle: cgroup_root: 1 1
  end: page_counter: 2 2
  middle: page_counter: 0 0
  end: cpu_hw_events: 1 1
  middle: cpu_hw_events: 0 0
  end: crypto_shash: 1 1
  middle: crypto_shash: 0 0
  end: crypto_aead: 1 1
  middle: crypto_aead: 0 0
  end: crypto_ahash: 1 1
  middle: crypto_ahash: 0 0
  end: crypto_skcipher: 1 1
  middle: crypto_skcipher: 0 0
  end: crypto_sync_skcipher: 0 0
  middle: crypto_sync_skcipher: 1 1
  <SNIP>
  end: bpf_ctx_convert: 2 2
  middle: bpf_ctx_convert: 0 0
  Ok
  acme@x1:~/git/pahole$

Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tests/flexible_arrays.sh | 77 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100755 tests/flexible_arrays.sh

diff --git a/tests/flexible_arrays.sh b/tests/flexible_arrays.sh
new file mode 100755
index 0000000000000000..7c21253a7e08c9d3
--- /dev/null
+++ b/tests/flexible_arrays.sh
@@ -0,0 +1,77 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Match flexible array member info with the per struct final stats.
+#
+# Arnaldo Carvalho de Melo <acme@redhat.com> (C) 2024-
+
+vmlinux=${vmlinux:-$1}
+
+if [ -z "$vmlinux" ] ; then
+	vmlinux=$(pahole --running_kernel_vmlinux)
+fi
+
+if [ ! -f "$vmlinux" ] ; then
+	echo "$vmlinux file not available, please specify another"
+	exit 2
+fi
+
+pretty=$(mktemp /tmp/flexible_arrays.data.sh.XXXXXX.c)
+
+echo -n "Flexible arrays accounting: "
+
+for struct in $(pahole -F btf --sizes --with_embedded_flexible_array $vmlinux | cut -f1) ; do
+	pahole $struct > $pretty
+
+	# We need to check for just one tab before the comment as when expanding unnamed
+	# structs with members with flexible arrays inside another struct we would mess
+	# up the accounting, see 'pahole fanotify_fid_event' for instance, circa October 2024:
+	# $ pahole fanotify_fid_event
+	# struct fanotify_fid_event {
+	#	struct fanotify_event      fae;                  /*     0    48 */
+	#	__kernel_fsid_t            fsid;                 /*    48     8 */
+	#	struct {
+	#		struct fanotify_fh object_fh;            /*    56     4 */
+	#		/* XXX last struct has a flexible array */
+	#		unsigned char      _inline_fh_buf[12];   /*    60    12 */
+	#	};                                               /*    56    16 */
+
+	#	/* XXX last struct has embedded flexible array(s) */
+	#	/* size: 72, cachelines: 2, members: 3 */
+	#	/* flexible array members: middle: 1 */
+	#	/* last cacheline: 8 bytes */
+	# }
+
+	nr_flexible_arrays=$(grep $'^\t/\* XXX last struct has a flexible array' $pretty | wc -l)
+	nr_embedded_flexible_arrays=$(grep $'^\t/\* XXX last struct.*embedded flexible array' $pretty | wc -l)
+	stat_nr_flexible_arrays=$(grep "flexible array members:.*end:" $pretty | sed -r 's/.*end: *([[:digit:]]+).*/\1/g')
+	[ -z "$stat_nr_flexible_arrays" ] && stat_nr_flexible_arrays=0
+	stat_nr_embedded_flexible_arrays=$(grep "flexible array members:.*middle:" $pretty | sed -r 's/.*middle: *([[:digit:]]+).*/\1/g')
+	[ -z "$stat_nr_embedded_flexible_arrays" ] && stat_nr_embedded_flexible_arrays=0
+	test -n "$VERBOSE" && echo "end: $struct: $nr_flexible_arrays $stat_nr_flexible_arrays"
+	test -n "$VERBOSE" && echo "middle: $struct: $nr_embedded_flexible_arrays $stat_nr_embedded_flexible_arrays"
+
+	if [ "$nr_embedded_flexible_arrays" != "$stat_nr_embedded_flexible_arrays" ] ; then
+		test -n "$VERBOSE" && printf "struct %s: The number of embedded flexible arrays (%s) doesn't match the number of members marked as such (%s)\n" \
+			"$struct" "$stat_nr_embedded_flexible_arrays" "$nr_embedded_flexible_arrays"
+		test -n "$VERBOSE" && pahole $struct
+		FAILED=1
+	fi
+
+	if [ "$nr_flexible_arrays" != "$stat_nr_flexible_arrays" ] ; then
+		test -n "$VERBOSE" && printf "struct %s: The number of flexible arrays (%s) doesn't match the number of members marked as such (%s)\n" \
+			"$struct" "$stat_nr_flexible_arrays" "$nr_flexible_arrays"
+		test -n "$VERBOSE" && pahole $struct
+		FAILED=1
+	fi
+
+	rm -f $pretty
+done
+
+if [ -n "$FAILED" ] ; then
+	echo "FAILED"
+	exit 1
+fi
+
+echo "Ok"
+exit 0
-- 
2.46.0