[PATCH 04/11] selftests: hornet: handle cross compilation and test skipping

[Blaise Boscaccy <bboscaccy@linux.microsoft.com>]

There were a few spots in the hornet selftest makefile where some host
resources were assumed to be used. Additionally add proper skip
detection for scenarios where the autogenerated signing keys don't
exist.

Signed-off-by: Blaise Boscaccy <bboscaccy@linux.microsoft.com>
---
 tools/testing/selftests/hornet/Makefile | 114 ++++++++++++++++++------
 1 file changed, 89 insertions(+), 25 deletions(-)

diff --git a/tools/testing/selftests/hornet/Makefile b/tools/testing/selftests/hornet/Makefile
index 316364f95f28c..460adab35e238 100644
--- a/tools/testing/selftests/hornet/Makefile
+++ b/tools/testing/selftests/hornet/Makefile
@@ -5,59 +5,123 @@ include ../../../scripts/Makefile.include
 
 CLANG ?= clang
 CFLAGS := -g -O2 -Wall
+TOOLSDIR := $(abspath ../../..)
 BPFTOOL ?= $(TOOLSDIR)/bpf/bpftool/bpftool
 SCRIPTSDIR := $(abspath ../../../../scripts/hornet)
-TOOLSDIR := $(abspath ../../..)
 LIBDIR := $(TOOLSDIR)/lib
 BPFDIR := $(LIBDIR)/bpf
 TOOLSINCDIR := $(TOOLSDIR)/include
 APIDIR := $(TOOLSINCDIR)/uapi
 CERTDIR := $(abspath ../../../../certs)
-PKG_CONFIG ?= $(CROSS_COMPILE)pkg-config
+HOSTPKG_CONFIG ?= pkg-config
+
+SIGNING_KEY  := $(CERTDIR)/signing_key.pem
+SIGNING_CERT := $(CERTDIR)/signing_key.x509
+
+VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux)				\
+		     $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)	\
+		     ../../../../vmlinux				\
+		     /sys/kernel/btf/vmlinux				\
+		     /boot/vmlinux-$(shell uname -r)
+VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
+
+# The hornet selftest needs the kernel module signing key/cert (generated when
+# the kernel is built with CONFIG_MODULE_SIG=y), a bpftool binary, and a
+# vmlinux with BTF for trivial.bpf.o. If any of those are missing (cross-build
+# without artifacts, container CI, CONFIG_MODULE_SIG disabled, etc.) skip the
+# targets rather than failing the global selftests build.
+hornet_skip_reason :=
+ifeq ($(wildcard $(SIGNING_KEY)),)
+hornet_skip_reason := module signing key not found at $(SIGNING_KEY) (build the kernel with CONFIG_MODULE_SIG=y first)
+else ifeq ($(wildcard $(SIGNING_CERT)),)
+hornet_skip_reason := module signing cert not found at $(SIGNING_CERT)
+else ifeq ($(wildcard $(BPFTOOL)),)
+hornet_skip_reason := bpftool not found at $(BPFTOOL) (build it under tools/bpf/bpftool first)
+else ifeq ($(VMLINUX_BTF),)
+hornet_skip_reason := no vmlinux with BTF found; tried $(VMLINUX_BTF_PATHS) (build the kernel with CONFIG_DEBUG_INFO_BTF=y or set VMLINUX_BTF=)
+endif
+
+ifneq ($(hornet_skip_reason),)
+$(warning Skipping hornet selftests: $(hornet_skip_reason))
+TEST_GEN_PROGS :=
+TEST_GEN_FILES :=
+
+include ../lib.mk
+
+else
 
 TEST_GEN_PROGS := loader
 TEST_GEN_FILES := vmlinux.h loader.h trivial.bpf.o map.bin sig.bin insn.bin signed_loader.h
-$(TEST_GEN_PROGS): LDLIBS += -lbpf
-$(TEST_GEN_PROGS): $(TEST_GEN_FILES)
 
 include ../lib.mk
 
-BPF_CFLAGS := -target bpf \
-	-D__TARGET_ARCH_$(ARCH) \
-	-I/usr/include/$(shell uname -m)-linux-gnu \
+define get_sys_includes
+$(shell $(1) $(2) -v -E - </dev/null 2>&1 \
+	| sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }') \
+$(shell $(1) $(2) -dM -E - </dev/null | grep '__riscv_xlen ' | awk '{printf("-D__riscv_xlen=%d -D__BITS_PER_LONG=%d", $$3, $$3)}') \
+$(shell $(1) $(2) -dM -E - </dev/null | grep '__loongarch_grlen ' | awk '{printf("-D__BITS_PER_LONG=%d", $$3)}') \
+$(shell $(1) $(2) -dM -E - </dev/null | grep -E 'MIPS(EL|EB)|_MIPS_SZ(PTR|LONG) |_MIPS_SIM |_ABI(O32|N32|64) ' | awk '{printf("-D%s=%s ", $$2, $$3)}')
+endef
+
+ifneq ($(CROSS_COMPILE),)
+CLANG_TARGET_ARCH = --target=$(notdir $(CROSS_COMPILE:%-=%))
+endif
+CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))
+
+IS_LITTLE_ENDIAN := $(shell $(CC) -dM -E - </dev/null | \
+			grep 'define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__')
+BPF_TARGET_ENDIAN := $(if $(IS_LITTLE_ENDIAN),--target=bpfel,--target=bpfeb)
+
+BPF_CFLAGS := $(BPF_TARGET_ENDIAN) \
+	-D__TARGET_ARCH_$(SRCARCH) \
+	$(CLANG_SYS_INCLUDES) \
 	$(KHDR_INCLUDES)
 
-vmlinux.h:
-	$(BPFTOOL) btf dump file /sys/kernel/btf/vmlinux format c > vmlinux.h
+$(OUTPUT)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
+	$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
 
-trivial.bpf.o: trivial.bpf.c vmlinux.h
-	$(CLANG) $(CFLAGS) $(BPF_CFLAGS) -c $< -o $@
+$(OUTPUT)/trivial.bpf.o: trivial.bpf.c $(OUTPUT)/vmlinux.h
+	$(CLANG) $(CFLAGS) $(BPF_CFLAGS) -I$(OUTPUT) -c $< -o $@
 
-loader.h: trivial.bpf.o
-	$(BPFTOOL) gen skeleton -S -k $(CERTDIR)/signing_key.pem -i $(CERTDIR)/signing_key.x509 \
+$(OUTPUT)/loader.h: $(OUTPUT)/trivial.bpf.o
+	$(BPFTOOL) gen skeleton -S -k $(SIGNING_KEY) -i $(SIGNING_CERT) \
 		-L $< name trivial > $@
 
-insn.bin: loader.h
+$(OUTPUT)/insn.bin: $(OUTPUT)/loader.h
 	$(SCRIPTSDIR)/extract-insn.sh $< > $@
 
-map.bin: loader.h
+$(OUTPUT)/map.bin: $(OUTPUT)/loader.h
 	$(SCRIPTSDIR)/extract-map.sh $< > $@
 
 $(OUTPUT)/gen_sig: ../../../../scripts/hornet/gen_sig.c
 	$(call msg,GEN_SIG,,$@)
-	$(Q)$(CC) $(shell $(PKG_CONFIG) --cflags libcrypto 2> /dev/null) \
+	$(Q)$(HOSTCC) $(shell $(HOSTPKG_CONFIG) --cflags libcrypto 2> /dev/null) \
 		  $< -o $@ \
-		  $(shell $(PKG_CONFIG) --libs libcrypto 2> /dev/null || echo -lcrypto)
+		  $(shell $(HOSTPKG_CONFIG) --libs libcrypto 2> /dev/null || echo -lcrypto)
+
+$(OUTPUT)/sig.bin: $(OUTPUT)/insn.bin $(OUTPUT)/map.bin $(OUTPUT)/gen_sig
+	$(OUTPUT)/gen_sig --key $(SIGNING_KEY) --cert $(SIGNING_CERT) \
+		--data $(OUTPUT)/insn.bin --add $(OUTPUT)/map.bin --out $@
+
+$(OUTPUT)/signed_loader.h: $(OUTPUT)/sig.bin $(OUTPUT)/loader.h
+	$(SCRIPTSDIR)/write-sig.sh $(OUTPUT)/loader.h $(OUTPUT)/sig.bin > $@
+
+BPFOBJ := $(OUTPUT)/libbpf/libbpf.a
+
+$(OUTPUT)/libbpf:
+	$(Q)mkdir -p $@
 
-sig.bin: insn.bin map.bin $(OUTPUT)/gen_sig
-	$(OUTPUT)/gen_sig --key $(CERTDIR)/signing_key.pem --cert $(CERTDIR)/signing_key.x509 \
-		--data insn.bin --add map.bin --out sig.bin
+$(BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile) \
+	   $(APIDIR)/linux/bpf.h | $(OUTPUT)/libbpf
+	$(Q)$(MAKE) -C $(BPFDIR) OUTPUT=$(OUTPUT)/libbpf/ \
+		    DESTDIR=$(OUTPUT) prefix= \
+		    $(BPFOBJ) install_headers
 
-signed_loader.h: sig.bin
-	$(SCRIPTSDIR)/write-sig.sh loader.h sig.bin > $@
+$(OUTPUT)/loader: loader.c $(OUTPUT)/signed_loader.h $(BPFOBJ)
+	$(CC) $(CFLAGS) -I$(LIBDIR) -I$(APIDIR) -I$(OUTPUT) \
+		$< $(BPFOBJ) -o $@ -lelf -lz
 
-loader: loader.c signed_loader.h
-	$(CC) $(CFLAGS) -I$(LIBDIR) -I$(APIDIR) $< -o $@ -lbpf
 
+EXTRA_CLEAN = $(OUTPUT)/gen_sig $(OUTPUT)/libbpf
 
-EXTRA_CLEAN = $(OUTPUT)/gen_sig
+endif
-- 
2.53.0