[PATCH 12/12] tests: Add a BTF reproducible generation test

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

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

  $ time tests/reproducible_build.sh vmlinux
  Parallel reproducible DWARF Loading/Serial BTF encoding: Ok

  real  1m13.844s
  user  3m3.601s
  sys   0m9.049s
  $

If the number of threads started by pahole is different than what was
requests via its -j command line option, it will fail as well as if the
output of 'bpftool btf dump' differs from the BTF encoded totally
serially to one of the detached BTF encoded using reproducible DWARF
loading/BTF encoding.

Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Kui-Feng Lee <kuifeng@fb.com>
Cc: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tests/reproducible_build.sh | 56 +++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100755 tests/reproducible_build.sh

diff --git a/tests/reproducible_build.sh b/tests/reproducible_build.sh
new file mode 100755
index 0000000000000000..9c72d548c2a21136
--- /dev/null
+++ b/tests/reproducible_build.sh
@@ -0,0 +1,56 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Test if BTF generated serially matches reproducible parallel DWARF loading + serial BTF encoding
+# Arnaldo Carvalho de Melo <acme@redhat.com> (C) 2024-
+
+vmlinux=$1
+outdir=$(mktemp -d /tmp/reproducible_build.sh.XXXXXX)
+
+echo -n "Parallel reproducible DWARF Loading/Serial BTF encoding: "
+
+test -n "$VERBOSE" && printf "\nserial encoding...\n"
+
+pahole --btf_encode_detached=$outdir/vmlinux.btf.serial $vmlinux
+bpftool btf dump file $outdir/vmlinux.btf.serial > $outdir/bpftool.output.vmlinux.btf.serial
+
+nr_proc=$(getconf _NPROCESSORS_ONLN)
+
+for threads in $(seq $nr_proc) ; do
+	test -n "$VERBOSE" && echo $threads threads encoding
+	pahole -j$threads --reproducible_build --btf_encode_detached=$outdir/vmlinux.btf.parallel.reproducible $vmlinux &
+	pahole=$!
+	# HACK: Wait a bit for pahole to start its threads
+	sleep 0.3s
+	# PID part to remove ps output headers
+	nr_threads_started=$(ps -L -C pahole | grep -v PID | wc -l)
+
+	if [ $threads -gt 1 ] ; then
+		((nr_threads_started -= 1))
+	fi
+
+	if [ $threads != $nr_threads_started ] ; then
+		echo "ERROR: pahole asked to start $threads encoding threads, started $nr_threads_started"
+		exit 1;
+	fi
+
+	# ps -L -C pahole | grep -v PID | nl
+	test -n "$VERBOSE" && echo $nr_threads_started threads started
+	wait $pahole
+	rm -f $outdir/bpftool.output.vmlinux.btf.parallel.reproducible
+	bpftool btf dump file $outdir/vmlinux.btf.parallel.reproducible > $outdir/bpftool.output.vmlinux.btf.parallel.reproducible
+	test -n "$VERBOSE" && echo "diff from serial encoding:"
+	diff -u $outdir/bpftool.output.vmlinux.btf.serial $outdir/bpftool.output.vmlinux.btf.parallel.reproducible > $outdir/diff
+	if [ -s $outdir/diff ] ; then
+		echo "ERROR: BTF generated from DWARF in parallel is different from the one generated in serial!"
+		exit 1
+	fi
+	test -n "$VERBOSE" && echo -----------------------------
+done
+
+rm $outdir/*
+rmdir $outdir
+
+echo "Ok"
+
+exit 0
-- 
2.44.0