selftests/bpf: Cross-compile bpftool

When the BPF selftests are cross-compiled, only the a host version of
bpftool is built. This version of bpftool is used on the host-side to
generate various intermediates, e.g., skeletons.

The test runners are also using bpftool, so the Makefile will symlink
bpftool from the selftest/bpf root, where the test runners will look
the tool:

  | $(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/bootstrap/bpftool \
  |    $(OUTPUT)/$(if $2,$2/)bpftool

There are two problems for cross-compilation builds:

 1. There is no native (cross-compilation target) of bpftool
 2. The bootstrap/bpftool is never cross-compiled (by design)

Make sure that a native/cross-compiled version of bpftool is built,
and if CROSS_COMPILE is set, symlink the native/non-bootstrap version.

Acked-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20230214161253.183458-1-bjorn@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index f7771592a920291ddd921928dad95edaa937c14c..521933bc15fea9caaa14318428ddc1316b462b23 100644 (file)
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -156,8 +156,9 @@ $(notdir $(TEST_GEN_PROGS)                                          \
         $(TEST_CUSTOM_PROGS)): %: $(OUTPUT)/% ;
 
 # sort removes libbpf duplicates when not cross-building
-MAKE_DIRS := $(sort $(BUILD_DIR)/libbpf $(HOST_BUILD_DIR)/libbpf              \
-              $(HOST_BUILD_DIR)/bpftool $(HOST_BUILD_DIR)/resolve_btfids      \
+MAKE_DIRS := $(sort $(BUILD_DIR)/libbpf $(HOST_BUILD_DIR)/libbpf       \
+              $(BUILD_DIR)/bpftool $(HOST_BUILD_DIR)/bpftool           \
+              $(HOST_BUILD_DIR)/resolve_btfids                         \
               $(RUNQSLOWER_OUTPUT) $(INCLUDE_DIR))
 $(MAKE_DIRS):
        $(call msg,MKDIR,,$@)
@@ -207,6 +208,14 @@ $(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(wildcard bpf_testmod/Makefile bpf_tes
        $(Q)cp bpf_testmod/bpf_testmod.ko $@
 
 DEFAULT_BPFTOOL := $(HOST_SCRATCH_DIR)/sbin/bpftool
+ifneq ($(CROSS_COMPILE),)
+CROSS_BPFTOOL := $(SCRATCH_DIR)/sbin/bpftool
+TRUNNER_BPFTOOL := $(CROSS_BPFTOOL)
+USE_BOOTSTRAP := ""
+else
+TRUNNER_BPFTOOL := $(DEFAULT_BPFTOOL)
+USE_BOOTSTRAP := "bootstrap/"
+endif
 
 $(OUTPUT)/runqslower: $(BPFOBJ) | $(DEFAULT_BPFTOOL) $(RUNQSLOWER_OUTPUT)
        $(Q)$(MAKE) $(submake_extras) -C $(TOOLSDIR)/bpf/runqslower            \
@@ -218,7 +227,7 @@ $(OUTPUT)/runqslower: $(BPFOBJ) | $(DEFAULT_BPFTOOL) $(RUNQSLOWER_OUTPUT)
                    EXTRA_LDFLAGS='$(SAN_LDFLAGS)' &&                          \
                    cp $(RUNQSLOWER_OUTPUT)runqslower $@
 
-TEST_GEN_PROGS_EXTENDED += $(DEFAULT_BPFTOOL)
+TEST_GEN_PROGS_EXTENDED += $(TRUNNER_BPFTOOL)
 
 $(TEST_GEN_PROGS) $(TEST_GEN_PROGS_EXTENDED): $(BPFOBJ)
 
@@ -256,6 +265,18 @@ $(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)    \
                    LIBBPF_DESTDIR=$(HOST_SCRATCH_DIR)/                        \
                    prefix= DESTDIR=$(HOST_SCRATCH_DIR)/ install-bin
 
+ifneq ($(CROSS_COMPILE),)
+$(CROSS_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)      \
+                   $(BPFOBJ) | $(BUILD_DIR)/bpftool
+       $(Q)$(MAKE) $(submake_extras)  -C $(BPFTOOLDIR)                         \
+                   ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE)                 \
+                   EXTRA_CFLAGS='-g -O0'                                       \
+                   OUTPUT=$(BUILD_DIR)/bpftool/                                \
+                   LIBBPF_OUTPUT=$(BUILD_DIR)/libbpf/                          \
+                   LIBBPF_DESTDIR=$(SCRATCH_DIR)/                              \
+                   prefix= DESTDIR=$(SCRATCH_DIR)/ install-bin
+endif
+
 all: docs
 
 docs:
@@ -521,11 +542,12 @@ endif
 $(OUTPUT)/$(TRUNNER_BINARY): $(TRUNNER_TEST_OBJS)                      \
                             $(TRUNNER_EXTRA_OBJS) $$(BPFOBJ)           \
                             $(RESOLVE_BTFIDS)                          \
+                            $(TRUNNER_BPFTOOL)                         \
                             | $(TRUNNER_BINARY)-extras
        $$(call msg,BINARY,,$$@)
        $(Q)$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) -o $$@
        $(Q)$(RESOLVE_BTFIDS) --btf $(TRUNNER_OUTPUT)/btf_data.bpf.o $$@
-       $(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/bootstrap/bpftool \
+       $(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/$(USE_BOOTSTRAP)bpftool \
                   $(OUTPUT)/$(if $2,$2/)bpftool
 
 endef