linux-kernel - [PATCH] scripts: Add script to extract built-in firmware blobs

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Message-ID: <20250120190436.127578-1-gpiccoli@igalia.com>
Date: Mon, 20 Jan 2025 16:04:26 -0300
From: "Guilherme G. Piccoli" <gpiccoli@...lia.com>
To: linux-kernel@...r.kernel.org
Cc: mcgrof@...nel.org,
	russ.weight@...ux.dev,
	dakr@...nel.org,
	gregkh@...uxfoundation.org,
	rafael@...nel.org,
	masahiroy@...nel.org,
	akpm@...ux-foundation.org,
	nathan@...nel.org,
	nicolas@...sle.eu,
	kernel-dev@...lia.com,
	kernel@...ccoli.net,
	"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
	Thadeu Lima de Souza Cascardo <cascardo@...lia.com>
Subject: [PATCH] scripts: Add script to extract built-in firmware blobs

Through the options CONFIG_EXTRA_FIRMWARE{_DIR} one is able to build
a kernel including firmware blobs in a built-in fashion. This is
usually the case of built-in drivers that require some blobs in
order to work properly, for example, like in non-initrd based systems.

Add hereby a script to extract these blobs from a non-stripped vmlinux,
similar to the idea of "extract-ikconfig". The firmware loader interface
saves such built-in blobs as rodata entries, having a field for the FW
name as "_fw_<module_name>_<firmware_name>_bin"; the tool extracts files
named "<module_name>_<firmware_name>" for each rodata firmware entry
detected. It makes use of awk, bash, dd and readelf, pretty standard
tooling for Linux development.

Suggested-and-reviewed-by: Thadeu Lima de Souza Cascardo <cascardo@...lia.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@...lia.com>
---
 scripts/extract-fwblobs | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100755 scripts/extract-fwblobs

diff --git a/scripts/extract-fwblobs b/scripts/extract-fwblobs
new file mode 100755
index 000000000000..15e836e47368
--- /dev/null
+++ b/scripts/extract-fwblobs
@@ -0,0 +1,31 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# -----------------------------------------------------------------------------
+# Extracts the vmlinux built-in firmware blobs - requires a non-stripped image
+# -----------------------------------------------------------------------------
+
+if [ -z "$1" ]; then
+	echo "Must provide a non-stripped vmlinux as argument"
+	exit 1
+fi
+
+read -r RD_ADDR_HEX RD_OFF_HEX <<< "$( readelf -SW "$1" |\
+grep -w rodata | awk '{print "0x"$5" 0x"$6}' )"
+
+FW_SYMS="$(readelf -sW "$1" |\
+awk -n '/fw_end/ { end=$2 ; print name " 0x" start " 0x" end; } { start=$2; name=$8; }')"
+
+while IFS= read -r entry; do
+	read -r FW_NAME FW_ADDR_ST_HEX FW_ADDR_END_HEX <<< "$entry"
+
+	# Notice kernel prepends _fw_ and appends _bin to the FW name
+	# in rodata; hence we hereby filter that out.
+	FW_NAME=${FW_NAME:4:-4}
+
+	FW_OFFSET="$(printf "%d" $((FW_ADDR_ST_HEX - RD_ADDR_HEX + RD_OFF_HEX)))"
+	FW_SIZE="$(printf "%d" $((FW_ADDR_END_HEX - FW_ADDR_ST_HEX)))"
+
+	dd if="$1" of="./${FW_NAME}" bs="${FW_SIZE}" count=1 iflag=skip_bytes skip="${FW_OFFSET}"
+done <<< "${FW_SYMS}"
+
-- 
2.47.1