selftests/bpf: Allow building with extra flags

In order to specify extra compilation or linking flags to BPF selftests,
it is possible to set EXTRA_CFLAGS and EXTRA_LDFLAGS from the command
line. The problem is that they are not propagated to sub-make calls
(runqslower, bpftool, libbpf) and in the better case are not applied, in
the worse case cause the entire build fail.

Propagate EXTRA_CFLAGS and EXTRA_LDFLAGS to the sub-makes.

This, for instance, allows to build selftests as PIE with

    $ make EXTRA_CFLAGS='-fPIE' EXTRA_LDFLAGS='-pie'

Without this change, the command would fail because libbpf.a would not
be built with -fPIE and other PIE binaries would not link against it.

The only problem is that we have to explicitly provide empty
EXTRA_CFLAGS='' and EXTRA_LDFLAGS='' to the builds of kernel modules as
we don't want to build modules with flags used for userspace (the above
example would fail as kernel doesn't support PIE).

Signed-off-by: Viktor Malik <vmalik@redhat.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index d5aaa67..edef5df 100644 (file)
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -297,25 +297,33 @@ $(OUTPUT)/sign-file: ../../../../scripts/sign-file.c
 $(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(RESOLVE_BTFIDS) $(wildcard bpf_testmod/Makefile bpf_testmod/*.[ch])
        $(call msg,MOD,,$@)
        $(Q)$(RM) bpf_testmod/bpf_testmod.ko # force re-compilation
-       $(Q)$(MAKE) $(submake_extras) RESOLVE_BTFIDS=$(RESOLVE_BTFIDS) -C bpf_testmod
+       $(Q)$(MAKE) $(submake_extras) -C bpf_testmod \
+               RESOLVE_BTFIDS=$(RESOLVE_BTFIDS)     \
+               EXTRA_CFLAGS='' EXTRA_LDFLAGS=''
        $(Q)cp bpf_testmod/bpf_testmod.ko $@
 
 $(OUTPUT)/bpf_test_no_cfi.ko: $(VMLINUX_BTF) $(RESOLVE_BTFIDS) $(wildcard bpf_test_no_cfi/Makefile bpf_test_no_cfi/*.[ch])
        $(call msg,MOD,,$@)
        $(Q)$(RM) bpf_test_no_cfi/bpf_test_no_cfi.ko # force re-compilation
-       $(Q)$(MAKE) $(submake_extras) RESOLVE_BTFIDS=$(RESOLVE_BTFIDS) -C bpf_test_no_cfi
+       $(Q)$(MAKE) $(submake_extras) -C bpf_test_no_cfi \
+               RESOLVE_BTFIDS=$(RESOLVE_BTFIDS)         \
+               EXTRA_CFLAGS='' EXTRA_LDFLAGS=''
        $(Q)cp bpf_test_no_cfi/bpf_test_no_cfi.ko $@
 
 $(OUTPUT)/bpf_test_modorder_x.ko: $(VMLINUX_BTF) $(RESOLVE_BTFIDS) $(wildcard bpf_test_modorder_x/Makefile bpf_test_modorder_x/*.[ch])
        $(call msg,MOD,,$@)
        $(Q)$(RM) bpf_test_modorder_x/bpf_test_modorder_x.ko # force re-compilation
-       $(Q)$(MAKE) $(submake_extras) RESOLVE_BTFIDS=$(RESOLVE_BTFIDS) -C bpf_test_modorder_x
+       $(Q)$(MAKE) $(submake_extras) -C bpf_test_modorder_x \
+               RESOLVE_BTFIDS=$(RESOLVE_BTFIDS)             \
+               EXTRA_CFLAGS='' EXTRA_LDFLAGS=''
        $(Q)cp bpf_test_modorder_x/bpf_test_modorder_x.ko $@
 
 $(OUTPUT)/bpf_test_modorder_y.ko: $(VMLINUX_BTF) $(RESOLVE_BTFIDS) $(wildcard bpf_test_modorder_y/Makefile bpf_test_modorder_y/*.[ch])
        $(call msg,MOD,,$@)
        $(Q)$(RM) bpf_test_modorder_y/bpf_test_modorder_y.ko # force re-compilation
-       $(Q)$(MAKE) $(submake_extras) RESOLVE_BTFIDS=$(RESOLVE_BTFIDS) -C bpf_test_modorder_y
+       $(Q)$(MAKE) $(submake_extras) -C bpf_test_modorder_y \
+               RESOLVE_BTFIDS=$(RESOLVE_BTFIDS)             \
+               EXTRA_CFLAGS='' EXTRA_LDFLAGS=''
        $(Q)cp bpf_test_modorder_y/bpf_test_modorder_y.ko $@
 
 
@@ -335,8 +343,8 @@ $(OUTPUT)/runqslower: $(BPFOBJ) | $(DEFAULT_BPFTOOL) $(RUNQSLOWER_OUTPUT)
                    BPFTOOL_OUTPUT=$(HOST_BUILD_DIR)/bpftool/                  \
                    BPFOBJ_OUTPUT=$(BUILD_DIR)/libbpf/                         \
                    BPFOBJ=$(BPFOBJ) BPF_INCLUDE=$(INCLUDE_DIR)                \
-                   EXTRA_CFLAGS='-g $(OPT_FLAGS) $(SAN_CFLAGS)'               \
-                   EXTRA_LDFLAGS='$(SAN_LDFLAGS)' &&                          \
+                   EXTRA_CFLAGS='-g $(OPT_FLAGS) $(SAN_CFLAGS) $(EXTRA_CFLAGS)' \
+                   EXTRA_LDFLAGS='$(SAN_LDFLAGS) $(EXTRA_LDFLAGS)' &&         \
                    cp $(RUNQSLOWER_OUTPUT)runqslower $@
 
 TEST_GEN_PROGS_EXTENDED += $(TRUNNER_BPFTOOL)
@@ -369,7 +377,8 @@ $(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)    \
                    $(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/bpftool
        $(Q)$(MAKE) $(submake_extras)  -C $(BPFTOOLDIR)                        \
                    ARCH= CROSS_COMPILE= CC="$(HOSTCC)" LD="$(HOSTLD)"         \
-                   EXTRA_CFLAGS='-g $(OPT_FLAGS)'                             \
+                   EXTRA_CFLAGS='-g $(OPT_FLAGS) $(EXTRA_CFLAGS)'             \
+                   EXTRA_LDFLAGS='$(EXTRA_LDFLAGS)'                           \
                    OUTPUT=$(HOST_BUILD_DIR)/bpftool/                          \
                    LIBBPF_OUTPUT=$(HOST_BUILD_DIR)/libbpf/                    \
                    LIBBPF_DESTDIR=$(HOST_SCRATCH_DIR)/                        \
@@ -380,7 +389,8 @@ $(CROSS_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)   \
                    $(BPFOBJ) | $(BUILD_DIR)/bpftool
        $(Q)$(MAKE) $(submake_extras)  -C $(BPFTOOLDIR)                         \
                    ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE)                 \
-                   EXTRA_CFLAGS='-g $(OPT_FLAGS)'                              \
+                   EXTRA_CFLAGS='-g $(OPT_FLAGS) $(EXTRA_CFLAGS)'              \
+                   EXTRA_LDFLAGS='$(EXTRA_LDFLAGS)'                            \
                    OUTPUT=$(BUILD_DIR)/bpftool/                                \
                    LIBBPF_OUTPUT=$(BUILD_DIR)/libbpf/                          \
                    LIBBPF_DESTDIR=$(SCRATCH_DIR)/                              \
@@ -403,8 +413,8 @@ $(BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile)                 \
           $(APIDIR)/linux/bpf.h                                               \
           | $(BUILD_DIR)/libbpf
        $(Q)$(MAKE) $(submake_extras) -C $(BPFDIR) OUTPUT=$(BUILD_DIR)/libbpf/ \
-                   EXTRA_CFLAGS='-g $(OPT_FLAGS) $(SAN_CFLAGS)'               \
-                   EXTRA_LDFLAGS='$(SAN_LDFLAGS)'                             \
+                   EXTRA_CFLAGS='-g $(OPT_FLAGS) $(SAN_CFLAGS) $(EXTRA_CFLAGS)' \
+                   EXTRA_LDFLAGS='$(SAN_LDFLAGS) $(EXTRA_LDFLAGS)'            \
                    DESTDIR=$(SCRATCH_DIR) prefix= all install_headers
 
 ifneq ($(BPFOBJ),$(HOST_BPFOBJ))
@@ -412,7 +422,9 @@ $(HOST_BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile)                    \
                $(APIDIR)/linux/bpf.h                                          \
                | $(HOST_BUILD_DIR)/libbpf
        $(Q)$(MAKE) $(submake_extras) -C $(BPFDIR)                             \
-                   EXTRA_CFLAGS='-g $(OPT_FLAGS)' ARCH= CROSS_COMPILE=        \
+                   ARCH= CROSS_COMPILE=                                       \
+                   EXTRA_CFLAGS='-g $(OPT_FLAGS) $(EXTRA_CFLAGS)'             \
+                   EXTRA_LDFLAGS='$(EXTRA_LDFLAGS)'                           \
                    OUTPUT=$(HOST_BUILD_DIR)/libbpf/                           \
                    CC="$(HOSTCC)" LD="$(HOSTLD)"                              \
                    DESTDIR=$(HOST_SCRATCH_DIR)/ prefix= all install_headers