selftests: sched_ext: Add sched_ext as proper selftest target

The sched_ext selftests is missing proper cross-compilation support, a
proper target entry, and out-of-tree build support.

When building the kselftest suite, e.g.:

  make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu-  \
    TARGETS=sched_ext SKIP_TARGETS="" O=/output/foo \
    -C tools/testing/selftests install

or:

  make ARCH=arm64 LLVM=1 TARGETS=sched_ext SKIP_TARGETS="" \
    O=/output/foo -C tools/testing/selftests install

The expectation is that the sched_ext is included, cross-built, the
correct toolchain is picked up, and placed into /output/foo.

In contrast to the BPF selftests, the sched_ext suite does not use
bpftool at test run-time, so it is sufficient to build bpftool for the
build host only.

Add ARCH, CROSS_COMPILE, OUTPUT, and TARGETS support to the sched_ext
selftest. Also, remove some variables that were unused by the
Makefile.
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: David Vernet <void@manifault.com>
Tested-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

tools/testing/selftests/Makefile

@@ -88,6 +88,7 @@ TARGETS += rlimits
 TARGETS += rseq
 TARGETS += rtc
 TARGETS += rust
+TARGETS += sched_ext
 TARGETS += seccomp
 TARGETS += sgx
 TARGETS += sigaltstack
@@ -129,10 +130,10 @@ ifeq ($(filter net/lib,$(TARGETS)),)
 endif
 endif
 
-# User can optionally provide a TARGETS skiplist.  By default we skip
-# BPF since it has cutting edge build time dependencies which require
-# more effort to install.
-SKIP_TARGETS ?= bpf
+# User can optionally provide a TARGETS skiplist. By default we skip
+# targets using BPF since it has cutting edge build time dependencies
+# which require more effort to install.
+SKIP_TARGETS ?= bpf sched_ext
 ifneq ($(SKIP_TARGETS),)
 	TMP := $(filter-out $(SKIP_TARGETS), $(TARGETS))
 	override TARGETS := $(TMP)

tools/testing/selftests/sched_ext/Makefile

@@ -3,23 +3,12 @@
 include ../../../build/Build.include
 include ../../../scripts/Makefile.arch
 include ../../../scripts/Makefile.include
-include ../lib.mk
 
-ifneq ($(LLVM),)
-ifneq ($(filter %/,$(LLVM)),)
-LLVM_PREFIX := $(LLVM)
-else ifneq ($(filter -%,$(LLVM)),)
-LLVM_SUFFIX := $(LLVM)
-endif
-
-CC := $(LLVM_PREFIX)clang$(LLVM_SUFFIX) $(CLANG_FLAGS) -fintegrated-as
-else
-CC := gcc
-endif # LLVM
+TEST_GEN_PROGS := runner
 
-ifneq ($(CROSS_COMPILE),)
-$(error CROSS_COMPILE not supported for scx selftests)
-endif # CROSS_COMPILE
+# override lib.mk's default rules
+OVERRIDE_TARGETS := 1
+include ../lib.mk
 
 CURDIR := $(abspath .)
 REPOROOT := $(abspath ../../../..)
@@ -34,18 +23,23 @@ GENHDR := $(GENDIR)/autoconf.h
 SCXTOOLSDIR := $(TOOLSDIR)/sched_ext
 SCXTOOLSINCDIR := $(TOOLSDIR)/sched_ext/include
 
-OUTPUT_DIR := $(CURDIR)/build
+OUTPUT_DIR := $(OUTPUT)/build
 OBJ_DIR := $(OUTPUT_DIR)/obj
 INCLUDE_DIR := $(OUTPUT_DIR)/include
 BPFOBJ_DIR := $(OBJ_DIR)/libbpf
 SCXOBJ_DIR := $(OBJ_DIR)/sched_ext
 BPFOBJ := $(BPFOBJ_DIR)/libbpf.a
 LIBBPF_OUTPUT := $(OBJ_DIR)/libbpf/libbpf.a
-DEFAULT_BPFTOOL := $(OUTPUT_DIR)/sbin/bpftool
-HOST_BUILD_DIR := $(OBJ_DIR)
-HOST_OUTPUT_DIR := $(OUTPUT_DIR)
 
-VMLINUX_BTF_PATHS ?= ../../../../vmlinux					\
+DEFAULT_BPFTOOL := $(OUTPUT_DIR)/host/sbin/bpftool
+HOST_OBJ_DIR := $(OBJ_DIR)/host/bpftool
+HOST_LIBBPF_OUTPUT := $(OBJ_DIR)/host/libbpf/
+HOST_LIBBPF_DESTDIR := $(OUTPUT_DIR)/host/
+HOST_DESTDIR := $(OUTPUT_DIR)/host/
+
+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))))
@@ -80,17 +74,23 @@ IS_LITTLE_ENDIAN = $(shell $(CC) -dM -E - </dev/null |				\
 # Use '-idirafter': Don't interfere with include mechanics except where the
 # build would have failed anyways.
 define get_sys_includes
-$(shell $(1) -v -E - </dev/null 2>&1 \
+$(shell $(1) $(2) -v -E - </dev/null 2>&1 \
 	| sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }') \
-$(shell $(1) -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 '__riscv_xlen ' | awk '{printf("-D__riscv_xlen=%d -D__BITS_PER_LONG=%d", $$3, $$3)}')
 endef
 
+ifneq ($(CROSS_COMPILE),)
+CLANG_TARGET_ARCH = --target=$(notdir $(CROSS_COMPILE:%-=%))
+endif
+
+CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))
+
 BPF_CFLAGS = -g -D__TARGET_ARCH_$(SRCARCH)					\
 	     $(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian)		\
 	     -I$(CURDIR)/include -I$(CURDIR)/include/bpf-compat			\
 	     -I$(INCLUDE_DIR) -I$(APIDIR) -I$(SCXTOOLSINCDIR)			\
 	     -I$(REPOROOT)/include						\
-	     $(call get_sys_includes,$(CLANG))					\
+	     $(CLANG_SYS_INCLUDES) 						\
 	     -Wall -Wno-compare-distinct-pointer-types				\
 	     -Wno-incompatible-function-pointer-types				\
 	     -O2 -mcpu=v3
@@ -98,7 +98,7 @@ BPF_CFLAGS = -g -D__TARGET_ARCH_$(SRCARCH)					\
 # sort removes libbpf duplicates when not cross-building
 MAKE_DIRS := $(sort $(OBJ_DIR)/libbpf $(OBJ_DIR)/libbpf				\
 	       $(OBJ_DIR)/bpftool $(OBJ_DIR)/resolve_btfids			\
-	       $(INCLUDE_DIR) $(SCXOBJ_DIR))
+	       $(HOST_OBJ_DIR) $(INCLUDE_DIR) $(SCXOBJ_DIR))
 
 $(MAKE_DIRS):
 	$(call msg,MKDIR,,$@)
@@ -108,18 +108,19 @@ $(BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile)			\
 	   $(APIDIR)/linux/bpf.h						\
 	   | $(OBJ_DIR)/libbpf
 	$(Q)$(MAKE) $(submake_extras) -C $(BPFDIR) OUTPUT=$(OBJ_DIR)/libbpf/	\
+		    ARCH=$(ARCH) CC="$(CC)" CROSS_COMPILE=$(CROSS_COMPILE)	\
 		    EXTRA_CFLAGS='-g -O0 -fPIC'					\
 		    DESTDIR=$(OUTPUT_DIR) prefix= all install_headers
 
 $(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)	\
-		    $(LIBBPF_OUTPUT) | $(OBJ_DIR)/bpftool
+		    $(LIBBPF_OUTPUT) | $(HOST_OBJ_DIR)
 	$(Q)$(MAKE) $(submake_extras)  -C $(BPFTOOLDIR)				\
 		    ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD)		\
 		    EXTRA_CFLAGS='-g -O0'					\
-		    OUTPUT=$(OBJ_DIR)/bpftool/					\
-		    LIBBPF_OUTPUT=$(OBJ_DIR)/libbpf/				\
-		    LIBBPF_DESTDIR=$(OUTPUT_DIR)/				\
-		    prefix= DESTDIR=$(OUTPUT_DIR)/ install-bin
+		    OUTPUT=$(HOST_OBJ_DIR)/					\
+		    LIBBPF_OUTPUT=$(HOST_LIBBPF_OUTPUT)				\
+		    LIBBPF_DESTDIR=$(HOST_LIBBPF_DESTDIR)			\
+		    prefix= DESTDIR=$(HOST_DESTDIR) install-bin
 
 $(INCLUDE_DIR)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL) | $(INCLUDE_DIR)
 ifeq ($(VMLINUX_H),)
@@ -150,9 +151,7 @@ $(INCLUDE_DIR)/%.bpf.skel.h: $(SCXOBJ_DIR)/%.bpf.o $(INCLUDE_DIR)/vmlinux.h $(BP
 
 override define CLEAN
 	rm -rf $(OUTPUT_DIR)
-	rm -f *.o *.bpf.o *.bpf.skel.h *.bpf.subskel.h
 	rm -f $(TEST_GEN_PROGS)
-	rm -f runner
 endef
 
 # Every testcase takes all of the BPF progs are dependencies by default. This
@@ -196,21 +195,15 @@ $(SCXOBJ_DIR)/runner.o: runner.c | $(SCXOBJ_DIR)
 # function doesn't support using implicit rules otherwise.
 $(testcase-targets): $(SCXOBJ_DIR)/%.o: %.c $(SCXOBJ_DIR)/runner.o $(all_test_bpfprogs) | $(SCXOBJ_DIR)
 	$(eval test=$(patsubst %.o,%.c,$(notdir $@)))
-	$(CC) $(CFLAGS) -c $< -o $@ $(SCXOBJ_DIR)/runner.o
+	$(CC) $(CFLAGS) -c $< -o $@
 
 $(SCXOBJ_DIR)/util.o: util.c | $(SCXOBJ_DIR)
 	$(CC) $(CFLAGS) -c $< -o $@
 
-runner: $(SCXOBJ_DIR)/runner.o $(SCXOBJ_DIR)/util.o $(BPFOBJ) $(testcase-targets)
+$(OUTPUT)/runner: $(SCXOBJ_DIR)/runner.o $(SCXOBJ_DIR)/util.o $(BPFOBJ) $(testcase-targets)
 	@echo "$(testcase-targets)"
 	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
 
-TEST_GEN_PROGS := runner
-
-all: runner
-
-.PHONY: all clean help
-
 .DEFAULT_GOAL := all
 
 .DELETE_ON_ERROR: