There exist compiler flags supported by GCC but not supported by Clang
(e.g. -specs=...). Currently, these cannot be passed to BPF selftests
builds, even when building with GCC, as some binaries (urandom_read and
liburandom_read.so) are always built with Clang and the unsupported
flags make the compilation fail (as -Werror is turned on).
Add new Makefile variable CLANG_FILTEROUT_FLAGS which can be used by
users to specify which flags (from the user-provided CFLAGS or LDFLAGS)
should be filtered out for Clang invocations.
This allows to do things like:
$ CFLAGS="-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1" \
CLANG_FILTEROUT_FLAGS="-specs=%" \
make -C tools/testing/selftests/bpf
Without this patch, the compilation would fail with:
[...]
clang: error: argument unused during compilation: '-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1' [-Werror,-Wunused-command-line-argument]
make: *** [Makefile:273: /bpf-next/tools/testing/selftests/bpf/liburandom_read.so] Error 1
[...]
Signed-off-by: Viktor Malik <vmalik@xxxxxxxxxx>
---
tools/testing/selftests/bpf/Makefile | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index d81583b2aef9..89662fe0470a 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -31,6 +31,11 @@ SAN_LDFLAGS ?= $(SAN_CFLAGS)
RELEASE ?=
OPT_FLAGS ?= $(if $(RELEASE),-O2,-O0)
+# Some flags supported by GCC are not supported by Clang.
+# This variable allows users to specify such flags so that they can use custom
+# CFLAGS and binaries built with Clang do not fail to build.
+CLANG_FILTEROUT_FLAGS ?=
+
LIBELF_CFLAGS := $(shell $(PKG_CONFIG) libelf --cflags 2>/dev/null)
LIBELF_LIBS := $(shell $(PKG_CONFIG) libelf --libs 2>/dev/null || echo -lelf)
@@ -271,7 +276,7 @@ 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 $(CLANG_FILTEROUT_FLAGS),$(CFLAGS) $(LDFLAGS)) \
$(filter %.c,$^) $(filter-out -static,$(LDLIBS)) \
-fuse-ld=$(LLD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \
-Wl,--version-script=liburandom_read.map \
@@ -280,7 +285,7 @@ $(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 $(CLANG_FILTEROUT_FLAGS),$(CFLAGS) $(LDFLAGS)) $(filter %.c,$^) \
-lurandom_read $(filter-out -static,$(LDLIBS)) -L$(OUTPUT) \
-fuse-ld=$(LLD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \
-Wl,-rpath=. -o $@
--
2.47.0
