locking/atomics: Check atomic headers with sha1sum

We currently check the atomic headers at build-time to ensure they
haven't been modified directly, and these checks require regenerating
the headers in full. As this takes a few seconds, even when
parallelized, this is too slow to run for every kernel build.

Instead, we can generate a hash of each header as we generate them,
which we can cheaply check at build time (~0.16s for all headers).

This patch does so, updating headers with their hashes using the new
gen-atomics.sh script. As some users apparently build the kernel wihout
coreutils, lacking sha1sum, the checks are skipped in this case.
Presumably, most developers have a working coreutils installation.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: anders.roxell@linaro.org
Cc: linux-kernel@vger.kernel.rg
Cc: naresh.kamboju@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 40 insertions, 6 deletions

diff --git a/scripts/atomic/check-atomics.sh b/scripts/atomic/check-atomics.sh
index c30101cddf2d..cfa0c2f71c84 100755
--- a/scripts/atomic/check-atomics.sh
+++ b/scripts/atomic/check-atomics.sh
@@ -7,13 +7,27 @@ ATOMICDIR=$(dirname $0)
 ATOMICTBL=${ATOMICDIR}/atomics.tbl
 LINUXDIR=${ATOMICDIR}/../..
 
+echo '' | sha1sum - > /dev/null 2>&1
+if [ $? -ne 0 ]; then
+	printf "sha1sum not available, skipping atomic header checks.\n"
+	exit 0
+fi
+
 cat <<EOF |
-gen-atomic-instrumented.sh      asm-generic/atomic-instrumented.h
-gen-atomic-long.sh              asm-generic/atomic-long.h
-gen-atomic-fallback.sh          linux/atomic-fallback.h
+asm-generic/atomic-instrumented.h
+asm-generic/atomic-long.h
+linux/atomic-fallback.h
 EOF
-while read script header; do
-	if ! (${ATOMICDIR}/${script} ${ATOMICTBL} | diff - ${LINUXDIR}/include/${header} > /dev/null); then
-		printf "warning: include/${header} is out-of-date.\n"
+while read header; do
+	OLDSUM="$(tail -n 1 ${LINUXDIR}/include/${header})"
+	OLDSUM="${OLDSUM#// }"
+
+	NEWSUM="$(head -n -1 ${LINUXDIR}/include/${header} | sha1sum)"
+	NEWSUM="${NEWSUM%% *}"
+
+	if [ "${OLDSUM}" != "${NEWSUM}" ]; then
+		printf "warning: generated include/${header} has been modified.\n"
 	fi
 done
+
+exit 0
diff --git a/scripts/atomic/gen-atomics.sh b/scripts/atomic/gen-atomics.sh
new file mode 100644
index 000000000000..27400b0cd732
--- /dev/null
+++ b/scripts/atomic/gen-atomics.sh
@@ -0,0 +1,20 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Generate atomic headers
+
+ATOMICDIR=$(dirname $0)
+ATOMICTBL=${ATOMICDIR}/atomics.tbl
+LINUXDIR=${ATOMICDIR}/../..
+
+cat <<EOF |
+gen-atomic-instrumented.sh      asm-generic/atomic-instrumented.h
+gen-atomic-long.sh              asm-generic/atomic-long.h
+gen-atomic-fallback.sh          linux/atomic-fallback.h
+EOF
+while read script header; do
+	${ATOMICDIR}/${script} ${ATOMICTBL} > ${LINUXDIR}/include/${header}
+	HASH="$(sha1sum ${LINUXDIR}/include/${header})"
+	HASH="${HASH%% *}"
+	printf "// %s\n" "${HASH}" >> ${LINUXDIR}/include/${header}
+done