kbuild: Allow arch Makefiles to override {cpp,ld,c}flags

Since commit a1c48bb1 (Makefile: Fix unrecognized cross-compiler command
line options), the arch Makefile is included earlier by the main
Makefile, preventing the arc architecture to set its -O3 compiler
option. Since there might be more use cases for an arch Makefile to
fine-tune the options, add support for ARCH_CPPFLAGS, ARCH_AFLAGS and
ARCH_CFLAGS variables that are appended to the respective kbuild
variables. The user still has the final say via the KCPPFLAGS, KAFLAGS
and KCFLAGS variables.

Reported-by: Vineet Gupta <Vineet.Gupta1@synopsys.com>
Cc: stable@vger.kernel.org # 3.16+
Signed-off-by: Michal Marek <mmarek@suse.com>

diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index e63b446d973cd716097adb60295577fe558f3f96..13f888a02a3de5cb7ecfdb2ed03eb1d721601de9 100644 (file)
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -952,6 +952,14 @@ When kbuild executes, the following steps are followed (roughly):
        $(KBUILD_ARFLAGS) set by the top level Makefile to "D" (deterministic
        mode) if this option is supported by $(AR).
 
+    ARCH_CPPFLAGS, ARCH_AFLAGS, ARCH_CFLAGS   Overrides the kbuild defaults
+
+       These variables are appended to the KBUILD_CPPFLAGS,
+       KBUILD_AFLAGS, and KBUILD_CFLAGS, respectively, after the
+       top-level Makefile has set any other flags. This provides a
+       means for an architecture to override the defaults.
+
+
 --- 6.2 Add prerequisites to archheaders:
 
        The archheaders: rule is used to generate header files that

diff --git a/Makefile b/Makefile
index 13270c0a93363f079ccc3a112bfa7d7d80c7f429..8c31fbc90589451d3d2ff8fd3b1535f15ed64c54 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -780,10 +780,11 @@ endif
 include scripts/Makefile.kasan
 include scripts/Makefile.extrawarn
 
-# Add user supplied CPPFLAGS, AFLAGS and CFLAGS as the last assignments
-KBUILD_CPPFLAGS += $(KCPPFLAGS)
-KBUILD_AFLAGS += $(KAFLAGS)
-KBUILD_CFLAGS += $(KCFLAGS)
+# Add any arch overrides and user supplied CPPFLAGS, AFLAGS and CFLAGS as the
+# last assignments
+KBUILD_CPPFLAGS += $(ARCH_CPPFLAGS) $(KCPPFLAGS)
+KBUILD_AFLAGS   += $(ARCH_AFLAGS)   $(KAFLAGS)
+KBUILD_CFLAGS   += $(ARCH_CFLAGS)   $(KCFLAGS)
 
 # Use --build-id when available.
 LDFLAGS_BUILD_ID = $(patsubst -Wl$(comma)%,%,\