selftests/bpf: Enable cross-building with clang

Cross building using clang requires passing the "-target" flag rather
than using the CROSS_COMPILE prefix. Makefile.include transforms
CROSS_COMPILE into CLANG_CROSS_FLAGS. Clear CROSS_COMPILE for bpftool
and the host libbpf, and use the clang flags for urandom_read and bench.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20211216163842.829836-7-jean-philippe@linaro.org

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 43f6f31..42ffc24 100644 (file)
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -170,7 +170,7 @@ $(OUTPUT)/%:%.c
 
 $(OUTPUT)/urandom_read: urandom_read.c
        $(call msg,BINARY,,$@)
-       $(Q)$(CC) $(LDFLAGS) $< $(LDLIBS) -Wl,--build-id=sha1 -o $@
+       $(Q)$(CC) $(CFLAGS) $(LDFLAGS) $< $(LDLIBS) -Wl,--build-id=sha1 -o $@
 
 $(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(wildcard bpf_testmod/Makefile bpf_testmod/*.[ch])
        $(call msg,MOD,,$@)
@@ -217,7 +217,7 @@ BPFTOOL ?= $(DEFAULT_BPFTOOL)
 $(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)    \
                    $(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/bpftool
        $(Q)$(MAKE) $(submake_extras)  -C $(BPFTOOLDIR)                        \
-                   CC=$(HOSTCC) LD=$(HOSTLD)                                  \
+                   ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD)             \
                    EXTRA_CFLAGS='-g -O0'                                      \
                    OUTPUT=$(HOST_BUILD_DIR)/bpftool/                          \
                    LIBBPF_OUTPUT=$(HOST_BUILD_DIR)/libbpf/                    \
@@ -248,7 +248,7 @@ $(HOST_BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile)                    \
                $(APIDIR)/linux/bpf.h                                          \
                | $(HOST_BUILD_DIR)/libbpf
        $(Q)$(MAKE) $(submake_extras) -C $(BPFDIR)                             \
-                   EXTRA_CFLAGS='-g -O0'                                      \
+                   EXTRA_CFLAGS='-g -O0' ARCH= CROSS_COMPILE=                 \
                    OUTPUT=$(HOST_BUILD_DIR)/libbpf/ CC=$(HOSTCC) LD=$(HOSTLD) \
                    DESTDIR=$(HOST_SCRATCH_DIR)/ prefix= all install_headers
 endif
@@ -551,7 +551,7 @@ $(OUTPUT)/bench: $(OUTPUT)/bench.o \
                 $(OUTPUT)/bench_bpf_loop.o \
                 $(OUTPUT)/bench_strncmp.o
        $(call msg,BINARY,,$@)
-       $(Q)$(CC) $(LDFLAGS) $(filter %.a %.o,$^) $(LDLIBS) -o $@
+       $(Q)$(CC) $(CFLAGS) $(LDFLAGS) $(filter %.a %.o,$^) $(LDLIBS) -o $@
 
 EXTRA_CLEAN := $(TEST_CUSTOM_PROGS) $(SCRATCH_DIR) $(HOST_SCRATCH_DIR) \
        prog_tests/tests.h map_tests/tests.h verifier/tests.h           \