[PATCH 2/2] kbuild: move GCOV flags to scripts/Makefile.gcov

[Konstantin Khorenko]

 * split the CFLAGS_GCOV block out of the top-level Makefile into
   scripts/Makefile.gcov
 * include it via include-$(CONFIG_GCOV_KERNEL) like neighbour
   KASAN/KCOV/UBSAN makefiles do
 * keep the include before scripts/Makefile.gcc-plugins: the try-run
   must not get -fplugin= options, plugins do not exist on clean builds

CFLAGS_GCOV is no longer defined when CONFIG_GCOV_KERNEL is off:
 * its user in scripts/Makefile.lib is guarded by the CONFIG_GCOV_KERNEL
 * in i915/xe header an empty value is harmless

The try-run compiler invocations also stop running on builds without
GCOV.

Suggested-by: Peter Oberparleiter <oberpar@xxxxxxxxxxxxx>
Signed-off-by: Konstantin Khorenko <khorenko@xxxxxxxxxxxxx>
---
 MAINTAINERS           |  1 +
 Makefile              | 22 +---------------------
 scripts/Makefile.gcov | 21 +++++++++++++++++++++
 3 files changed, 23 insertions(+), 21 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 360977678f707..fabf33758351f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10897,6 +10897,7 @@ M:	Peter Oberparleiter <oberpar@xxxxxxxxxxxxx>
 S:	Maintained
 F:	Documentation/dev-tools/gcov.rst
 F:	kernel/gcov/
+F:	scripts/Makefile.gcov
 
 GDB KERNEL DEBUGGING HELPER SCRIPTS
 M:	Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
diff --git a/Makefile b/Makefile
index 3b69b973f7598..f3ea94ceb1cec 100644
--- a/Makefile
+++ b/Makefile
@@ -1176,27 +1176,6 @@ endif
 # Ensure compilers do not transform certain loops into calls to wcslen()
 KBUILD_CFLAGS += -fno-builtin-wcslen
 
-CFLAGS_GCOV	:= -fprofile-arcs -ftest-coverage
-ifdef CONFIG_CC_IS_GCC
-CFLAGS_GCOV	+= -fno-tree-loop-im
-# Use atomic counter updates to avoid concurrent-access crashes in GCOV.
-# Only enable if -fprofile-update=prefer-atomic does not introduce new
-# undefined symbols (e.g. libatomic calls that the kernel cannot link).
-CFLAGS_GCOV	+= $(call try-run,\
-	echo 'long long x; void f(void){x++;}' | \
-	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -w $(CFLAGS_GCOV) \
-	-x c - -c -o "$$TMP.base" && \
-	echo 'long long x; void f(void){x++;}' | \
-	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -w $(CFLAGS_GCOV) \
-	-fprofile-update=prefer-atomic \
-	-x c - -c -o "$$TMP" && \
-	$(NM) "$$TMP.base" | grep ' U ' > "$$TMP.ubase" || true ; \
-	$(NM) "$$TMP" | grep ' U ' > "$$TMP.utest" || true ; \
-	cmp -s "$$TMP.ubase" "$$TMP.utest",\
-	-fprofile-update=prefer-atomic)
-endif
-export CFLAGS_GCOV
-
 # change __FILE__ to the relative path to the source directory
 ifdef building_out_of_srctree
 KBUILD_CPPFLAGS += -fmacro-prefix-map=$(srcroot)/=
@@ -1214,6 +1193,7 @@ include-$(CONFIG_KCSAN)		+= scripts/Makefile.kcsan
 include-$(CONFIG_KMSAN)		+= scripts/Makefile.kmsan
 include-$(CONFIG_UBSAN)		+= scripts/Makefile.ubsan
 include-$(CONFIG_KCOV)		+= scripts/Makefile.kcov
+include-$(CONFIG_GCOV_KERNEL)	+= scripts/Makefile.gcov
 include-$(CONFIG_RANDSTRUCT)	+= scripts/Makefile.randstruct
 include-$(CONFIG_KSTACK_ERASE)	+= scripts/Makefile.kstack_erase
 include-$(CONFIG_AUTOFDO_CLANG)	+= scripts/Makefile.autofdo
diff --git a/scripts/Makefile.gcov b/scripts/Makefile.gcov
new file mode 100644
index 0000000000000..16c5b876440c2
--- /dev/null
+++ b/scripts/Makefile.gcov
@@ -0,0 +1,21 @@
+# SPDX-License-Identifier: GPL-2.0-only
+CFLAGS_GCOV	:= -fprofile-arcs -ftest-coverage
+ifdef CONFIG_CC_IS_GCC
+CFLAGS_GCOV	+= -fno-tree-loop-im
+# Use atomic counter updates to avoid concurrent-access crashes in GCOV.
+# Only enable if -fprofile-update=prefer-atomic does not introduce new
+# undefined symbols (e.g. libatomic calls that the kernel cannot link).
+CFLAGS_GCOV	+= $(call try-run,\
+	echo 'long long x; void f(void){x++;}' | \
+	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -w $(CFLAGS_GCOV) \
+	-x c - -c -o "$$TMP.base" && \
+	echo 'long long x; void f(void){x++;}' | \
+	$(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -w $(CFLAGS_GCOV) \
+	-fprofile-update=prefer-atomic \
+	-x c - -c -o "$$TMP" && \
+	$(NM) "$$TMP.base" | grep ' U ' > "$$TMP.ubase" || true ; \
+	$(NM) "$$TMP" | grep ' U ' > "$$TMP.utest" || true ; \
+	cmp -s "$$TMP.ubase" "$$TMP.utest",\
+	-fprofile-update=prefer-atomic)
+endif
+export CFLAGS_GCOV

-- 
2.43.0