[PATCH v4 27/30] selftests/bpf: Append extra cflags

[Leo Yan]

Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

urandom_read is built with clang.  Introduce URANDOM_READ_CFLAGS to copy
the compiler flags without appending EXTRA_CFLAGS, which may contain
incompatible options with clang.

Signed-off-by: Leo Yan <leo.yan@xxxxxxx>
---
 tools/testing/selftests/bpf/Makefile | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 72a9ba41f95ebb825d25799c07ba3f0311243e45..27112f08c9a5b6cabc41902207d00897070b41b4 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -71,6 +71,12 @@ ifneq ($(LLVM),)
 CFLAGS += -Wno-unused-command-line-argument
 endif
 
+# urandom_read is built with clang. Copy $(CFLAGS) before EXTRA_CFLAGS are
+# appended so that it does not inherit potentially incompatible options.
+URANDOM_READ_CFLAGS := $(CFLAGS)
+
+CFLAGS += $(EXTRA_CFLAGS)
+
 # Check whether bpf cpu=v4 is supported or not by clang
 ifneq ($(shell $(CLANG) --target=bpf -mcpu=help 2>&1 | grep 'v4'),)
 CLANG_CPUV4 := 1
@@ -255,7 +261,7 @@ endif
 $(OUTPUT)/liburandom_read.so: urandom_read_lib1.c urandom_read_lib2.c liburandom_read.map
 	$(call msg,LIB,,$@)
 	$(Q)$(CLANG) $(CLANG_TARGET_ARCH) \
-		     $(filter-out -static,$(CFLAGS) $(LDFLAGS)) \
+		     $(filter-out -static,$(URANDOM_READ_CFLAGS) $(LDFLAGS)) \
 		     $(filter %.c,$^) $(filter-out -static,$(LDLIBS)) \
 		     -Wno-unused-command-line-argument \
 		     -fuse-ld=$(LLD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \
@@ -265,7 +271,7 @@ $(OUTPUT)/liburandom_read.so: urandom_read_lib1.c urandom_read_lib2.c liburandom
 $(OUTPUT)/urandom_read: urandom_read.c urandom_read_aux.c $(OUTPUT)/liburandom_read.so
 	$(call msg,BINARY,,$@)
 	$(Q)$(CLANG) $(CLANG_TARGET_ARCH) \
-		     $(filter-out -static,$(CFLAGS) $(LDFLAGS)) $(filter %.c,$^) \
+		     $(filter-out -static,$(URANDOM_READ_CFLAGS) $(LDFLAGS)) $(filter %.c,$^) \
 		     -Wno-unused-command-line-argument \
 		     -lurandom_read $(filter-out -static,$(LDLIBS)) -L$(OUTPUT) \
 		     -fuse-ld=$(LLD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \

-- 
2.34.1