torture: Add kvm-tranform.sh script for qemu-cmd files

This commit adds a script that transforms qemu-cmd files to allow them
and the corresponding kernels to be run in contexts other than the one
that they were created for, including on systems other than the one that
they were built on.  For example, this allows the build products from a
--buildonly run to be transformed to allow distributed rcutorture testing.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/bin/kvm-transform.sh

+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Transform a qemu-cmd file to allow reuse.
+#
+# Usage: kvm-transform.sh bzImage console.log < qemu-cmd-in > qemu-cmd-out
+#
+#	bzImage: Kernel and initrd from the same prior kvm.sh run.
+#	console.log: File into which to place console output.
+#
+# The original qemu-cmd file is provided on standard input.
+# The transformed qemu-cmd file is on standard output.
+# The transformation assumes that the qemu command is confined to a
+# single line.  It also assumes no whitespace in filenames.
+#
+# Copyright (C) 2020 Facebook, Inc.
+#
+# Authors: Paul E. McKenney <paulmck@kernel.org>
+
+image="$1"
+if test -z "$image"
+then
+	echo Need kernel image file.
+	exit 1
+fi
+consolelog="$2"
+if test -z "$consolelog"
+then
+	echo "Need console log file name."
+	exit 1
+fi
+
+awk -v image="$image" -v consolelog="$consolelog" '
+{
+	line = "";
+	for (i = 1; i <= NF; i++) {
+		if (line == "")
+			line = $i;
+		else
+			line = line " " $i;
+		if ($i == "-serial") {
+			i++;
+			line = line " file:" consolelog;
+		}
+		if ($i == "-kernel") {
+			i++;
+			line = line " " image;
+		}
+	}
+	print line;
+}'