[PATCH RFC 2/5] rcutorture: Add a stress-ng build script

["Joel Fernandes (Google)" <joel@joelfernandes.org>]

This script automates the building of stress-ng and can be run from
any directory. It also support cross-compilation. The output is placed
into the initrd directory.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 .../selftests/rcutorture/bin/mkstress-ng.sh   | 86 +++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100755 tools/testing/selftests/rcutorture/bin/mkstress-ng.sh

diff --git a/tools/testing/selftests/rcutorture/bin/mkstress-ng.sh b/tools/testing/selftests/rcutorture/bin/mkstress-ng.sh
new file mode 100755
index 000000000000..e5a19cca6923
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/bin/mkstress-ng.sh
@@ -0,0 +1,86 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Clone and build the stress-ng tool, placing the binary in the
+# initrd directory. Ensure binary is up-to-date.
+#
+# Usage: ./bin/mkstress-ng.sh (run from any where).
+#
+# Copyright (C) Google LLC, 2024
+# Author: Joel Fernandes (Google) <joel@joelfernandes.org>
+
+# Get the directory where the script is located
+SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"
+
+REPO_URL="https://github.com/ColinIanKing/stress-ng.git"
+SRC_DIR="${SCRIPT_DIR}/../res/stress-ng"
+INITRD_DIR="${SCRIPT_DIR}/../initrd"
+BIN_NAME="stress-ng"
+export COMPILER="${CROSS_COMPILE}gcc"
+
+is_statically_linked() {
+    if file "$1" | grep -q "statically linked"; then
+        return 0
+    else
+        return 1
+    fi
+}
+
+needs_build() {
+    if [ ! -f "$INITRD_DIR/$BIN_NAME" ]; then
+        return 0
+    fi
+    if [ "$(find "$SRC_DIR" -newer "$INITRD_DIR/$BIN_NAME")" ]; then
+        return 0
+    fi
+    if ! is_statically_linked "$INITRD_DIR/$BIN_NAME"; then
+        return 0
+    fi
+    return 1
+}
+
+if [ ! -d "$INITRD_DIR" ]; then
+    echo "Error: INITRD_DIR ($INITRD_DIR) does not exist"
+    exit 1
+fi
+
+if ! which "$COMPILER" &> /dev/null; then
+    echo "Error: Compiler $COMPILER not found."
+    exit 1
+fi
+
+if [ ! -d "$SRC_DIR" ]; then
+    echo "Cloning stress-ng repository..."
+    if ! git clone "$REPO_URL" "$SRC_DIR"; then
+        echo "Failed to clone stress-ng repository."
+        rm -rf "$SRC_DIR"
+        exit 1
+    fi
+else
+    echo "Updating stress-ng repository..."
+    cd "$SRC_DIR" || exit 1
+    git pull || { echo "Failed to update stress-ng repository"; exit 1; }
+    cd - > /dev/null || exit 1
+fi
+
+# Build stress-ng binary if needed
+if needs_build; then
+    echo "Building stress-ng binary..."
+    cd "$SRC_DIR" || exit 1
+    STATIC=1 make -j 8 || { echo "stress-ng build failed"; exit 1; }
+    cd - > /dev/null || exit 1
+
+    # Verify the stress-ng binary is static
+    if ! is_statically_linked "$SRC_DIR/$BIN_NAME"; then
+        echo "Error: The stress-ng binary is not statically linked."
+        exit 1
+    fi
+
+    echo "Copying stress-ng binary to initrd directory..."
+    cp "$SRC_DIR/$BIN_NAME" "$INITRD_DIR" || { echo "Failed to copy stress-ng binary"; exit 1; }
+else
+    echo "stress-ng binary is up-to-date, no build needed."
+fi
+
+echo "stress-ng build process completed successfully."
+exit 0
\ No newline at end of file
-- 
2.34.1