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Kaitao Chengkawasaki
Kaitao Cheng
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kawasaki
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tools/ufq_iosched: add BPF example scheduler and build scaffolding
Add ufq_iosched as a simple example for the UFQ block I/O scheduler, In the ufq_simple example, we implement the eBPF struct_ops hooks the kernel exposes so we can exercise and validate the behavior and stability of the kernel UFQ scheduling framework. The Makefile and directory layout are modeled after sched_ext. This mirrors the sched_ext examples pattern so developers can experiment with user-defined queueing policies on top of IOSCHED_UFQ. Signed-off-by: Kaitao Cheng <[email protected]>
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‎tools/ufq_iosched/.gitignore‎

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tools/
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build/

‎tools/ufq_iosched/Makefile‎

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# SPDX-License-Identifier: GPL-2.0
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# Copyright (c) 2026 KylinSoft Corporation.
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# Copyright (c) 2026 Kaitao Cheng <[email protected]>
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include ../build/Build.include
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include ../scripts/Makefile.arch
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include ../scripts/Makefile.include
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all: all_targets
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ifneq ($(LLVM),)
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ifneq ($(filter %/,$(LLVM)),)
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LLVM_PREFIX := $(LLVM)
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else ifneq ($(filter -%,$(LLVM)),)
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LLVM_SUFFIX := $(LLVM)
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endif
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CLANG_TARGET_FLAGS_arm := arm-linux-gnueabi
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CLANG_TARGET_FLAGS_arm64 := aarch64-linux-gnu
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CLANG_TARGET_FLAGS_hexagon := hexagon-linux-musl
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CLANG_TARGET_FLAGS_m68k := m68k-linux-gnu
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CLANG_TARGET_FLAGS_mips := mipsel-linux-gnu
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CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu
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CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu
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CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu
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CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu
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CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(ARCH))
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ifeq ($(CROSS_COMPILE),)
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ifeq ($(CLANG_TARGET_FLAGS),)
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$(error Specify CROSS_COMPILE or add '--target=' option to lib.mk)
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else
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CLANG_FLAGS += --target=$(CLANG_TARGET_FLAGS)
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endif # CLANG_TARGET_FLAGS
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else
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CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%))
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endif # CROSS_COMPILE
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CC := $(LLVM_PREFIX)clang$(LLVM_SUFFIX) $(CLANG_FLAGS) -fintegrated-as
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else
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CC := $(CROSS_COMPILE)gcc
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endif # LLVM
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CURDIR := $(abspath .)
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TOOLSDIR := $(abspath ..)
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LIBDIR := $(TOOLSDIR)/lib
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BPFDIR := $(LIBDIR)/bpf
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TOOLSINCDIR := $(TOOLSDIR)/include
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BPFTOOLDIR := $(TOOLSDIR)/bpf/bpftool
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APIDIR := $(TOOLSINCDIR)/uapi
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GENDIR := $(abspath ../../include/generated)
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GENHDR := $(GENDIR)/autoconf.h
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ifeq ($(O),)
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OUTPUT_DIR := $(CURDIR)/build
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else
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OUTPUT_DIR := $(O)/build
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endif # O
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OBJ_DIR := $(OUTPUT_DIR)/obj
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INCLUDE_DIR := $(OUTPUT_DIR)/include
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BPFOBJ_DIR := $(OBJ_DIR)/libbpf
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UFQOBJ_DIR := $(OBJ_DIR)/ufq_iosched
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BINDIR := $(OUTPUT_DIR)/bin
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BPFOBJ := $(BPFOBJ_DIR)/libbpf.a
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ifneq ($(CROSS_COMPILE),)
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HOST_BUILD_DIR := $(OBJ_DIR)/host/obj
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HOST_OUTPUT_DIR := $(OBJ_DIR)/host
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HOST_INCLUDE_DIR := $(HOST_OUTPUT_DIR)/include
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else
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HOST_BUILD_DIR := $(OBJ_DIR)
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HOST_OUTPUT_DIR := $(OUTPUT_DIR)
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HOST_INCLUDE_DIR := $(INCLUDE_DIR)
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endif
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HOST_BPFOBJ := $(HOST_BUILD_DIR)/libbpf/libbpf.a
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RESOLVE_BTFIDS := $(HOST_BUILD_DIR)/resolve_btfids/resolve_btfids
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DEFAULT_BPFTOOL := $(HOST_OUTPUT_DIR)/sbin/bpftool
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VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux) \
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$(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux) \
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../../vmlinux \
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/sys/kernel/btf/vmlinux \
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/boot/vmlinux-$(shell uname -r)
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VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
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ifeq ($(VMLINUX_BTF),)
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$(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)")
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endif
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BPFTOOL ?= $(DEFAULT_BPFTOOL)
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ifneq ($(wildcard $(GENHDR)),)
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GENFLAGS := -DHAVE_GENHDR
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endif
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CFLAGS += -g -O2 -rdynamic -pthread -Wall -Werror $(GENFLAGS) \
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-I$(INCLUDE_DIR) -I$(GENDIR) -I$(LIBDIR) \
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-I$(TOOLSINCDIR) -I$(APIDIR) -I$(CURDIR)/include
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# Silence some warnings when compiled with clang
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ifneq ($(LLVM),)
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CFLAGS += -Wno-unused-command-line-argument
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endif
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LDFLAGS += -lelf -lz -lpthread
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IS_LITTLE_ENDIAN = $(shell $(CC) -dM -E - </dev/null | \
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grep 'define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__')
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# Get Clang's default includes on this system, as opposed to those seen by
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# '-target bpf'. This fixes "missing" files on some architectures/distros,
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# such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
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#
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# Use '-idirafter': Don't interfere with include mechanics except where the
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# build would have failed anyways.
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define get_sys_includes
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$(shell $(1) -v -E - </dev/null 2>&1 \
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| sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }') \
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$(shell $(1) -dM -E - </dev/null | grep '__riscv_xlen ' | awk '{printf("-D__riscv_xlen=%d -D__BITS_PER_LONG=%d", $$3, $$3)}')
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endef
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BPF_CFLAGS = -g -D__TARGET_ARCH_$(SRCARCH) \
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$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian) \
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-I$(CURDIR)/include -I$(CURDIR)/include/bpf-compat \
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-I$(INCLUDE_DIR) -I$(APIDIR) \
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-I../../include \
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$(call get_sys_includes,$(CLANG)) \
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-Wall -Wno-compare-distinct-pointer-types \
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-Wno-microsoft-anon-tag \
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-fms-extensions \
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-O2 -mcpu=v3
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# sort removes libbpf duplicates when not cross-building
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MAKE_DIRS := $(sort $(OBJ_DIR)/libbpf $(HOST_BUILD_DIR)/libbpf \
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$(HOST_BUILD_DIR)/bpftool $(HOST_BUILD_DIR)/resolve_btfids \
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$(INCLUDE_DIR) $(UFQOBJ_DIR) $(BINDIR))
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$(MAKE_DIRS):
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$(call msg,MKDIR,,$@)
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$(Q)mkdir -p $@
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ifneq ($(CROSS_COMPILE),)
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$(BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile) \
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$(APIDIR)/linux/bpf.h \
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| $(OBJ_DIR)/libbpf
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$(Q)$(MAKE) $(submake_extras) CROSS_COMPILE=$(CROSS_COMPILE) \
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-C $(BPFDIR) OUTPUT=$(OBJ_DIR)/libbpf/ \
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EXTRA_CFLAGS='-g -O0 -fPIC' \
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LDFLAGS="$(LDFLAGS)" \
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DESTDIR=$(OUTPUT_DIR) prefix= all install_headers
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endif
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$(HOST_BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile) \
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$(APIDIR)/linux/bpf.h \
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| $(HOST_BUILD_DIR)/libbpf
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$(Q)$(MAKE) $(submake_extras) -C $(BPFDIR) \
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OUTPUT=$(HOST_BUILD_DIR)/libbpf/ \
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ARCH= CROSS_COMPILE= CC="$(HOSTCC)" LD=$(HOSTLD) \
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EXTRA_CFLAGS='-g -O0 -fPIC' \
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DESTDIR=$(HOST_OUTPUT_DIR) prefix= all install_headers
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$(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) \
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$(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/bpftool
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$(Q)$(MAKE) $(submake_extras) -C $(BPFTOOLDIR) \
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ARCH= CROSS_COMPILE= CC="$(HOSTCC)" LD=$(HOSTLD) \
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EXTRA_CFLAGS='-g -O0' \
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OUTPUT=$(HOST_BUILD_DIR)/bpftool/ \
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LIBBPF_OUTPUT=$(HOST_BUILD_DIR)/libbpf/ \
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LIBBPF_DESTDIR=$(HOST_OUTPUT_DIR)/ \
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prefix= DESTDIR=$(HOST_OUTPUT_DIR)/ install-bin
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$(INCLUDE_DIR)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL) | $(INCLUDE_DIR)
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ifeq ($(VMLINUX_H),)
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$(call msg,GEN,,$@)
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$(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
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else
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$(call msg,CP,,$@)
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$(Q)cp "$(VMLINUX_H)" $@
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endif
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$(UFQOBJ_DIR)/%.bpf.o: %.bpf.c $(INCLUDE_DIR)/vmlinux.h include/ufq/*.h \
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| $(BPFOBJ) $(UFQOBJ_DIR)
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$(call msg,CLNG-BPF,,$(notdir $@))
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$(Q)$(CLANG) $(BPF_CFLAGS) -target bpf -c $< -o $@
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$(INCLUDE_DIR)/%.bpf.skel.h: $(UFQOBJ_DIR)/%.bpf.o $(INCLUDE_DIR)/vmlinux.h $(BPFTOOL)
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$(eval sched=$(notdir $@))
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$(call msg,GEN-SKEL,,$(sched))
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$(Q)$(BPFTOOL) gen object $(<:.o=.linked1.o) $<
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$(Q)$(BPFTOOL) gen object $(<:.o=.linked2.o) $(<:.o=.linked1.o)
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$(Q)$(BPFTOOL) gen object $(<:.o=.linked3.o) $(<:.o=.linked2.o)
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$(Q)diff $(<:.o=.linked2.o) $(<:.o=.linked3.o)
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$(Q)$(BPFTOOL) gen skeleton $(<:.o=.linked3.o) name $(subst .bpf.skel.h,,$(sched)) > $@
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$(Q)$(BPFTOOL) gen subskeleton $(<:.o=.linked3.o) name $(subst .bpf.skel.h,,$(sched)) > $(@:.skel.h=.subskel.h)
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UFQ_COMMON_DEPS := include/ufq/common.h include/ufq/simple_stat.h | $(BINDIR)
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c-sched-targets = ufq_simple
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$(addprefix $(BINDIR)/,$(c-sched-targets)): \
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$(BINDIR)/%: \
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$(filter-out %.bpf.c,%.c) \
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$(INCLUDE_DIR)/%.bpf.skel.h \
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$(UFQ_COMMON_DEPS)
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$(eval sched=$(notdir $@))
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$(CC) $(CFLAGS) -c $(sched).c -o $(UFQOBJ_DIR)/$(sched).o
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$(CC) -o $@ $(UFQOBJ_DIR)/$(sched).o $(BPFOBJ) $(LDFLAGS)
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$(c-sched-targets): %: $(BINDIR)/%
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install: all
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$(Q)mkdir -p $(DESTDIR)/usr/local/bin/
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$(Q)cp $(BINDIR)/* $(DESTDIR)/usr/local/bin/
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clean:
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rm -rf $(OUTPUT_DIR) $(HOST_OUTPUT_DIR)
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rm -f *.o *.bpf.o *.bpf.skel.h *.bpf.subskel.h
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rm -f $(c-sched-targets)
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help:
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@echo 'Building targets'
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@echo '================'
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@echo ''
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@echo ' all - Compile all schedulers'
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@echo ''
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@echo 'Alternatively, you may compile individual schedulers:'
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@echo ''
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@printf ' %s\n' $(c-sched-targets)
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@echo ''
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@echo 'For any scheduler build target, you may specify an alternative'
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@echo 'build output path with the O= environment variable. For example:'
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@echo ''
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@echo ' O=/tmp/ufq_iosched make all'
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@echo ''
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@echo 'will compile all schedulers, and emit the build artifacts to'
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@echo '/tmp/ufq_iosched/build.'
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@echo ''
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@echo ''
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@echo 'Installing targets'
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@echo '=================='
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@echo ''
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@echo ' install - Compile and install all schedulers to /usr/bin.'
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@echo ' You may specify the DESTDIR= environment variable'
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@echo ' to indicate a prefix for /usr/bin. For example:'
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@echo ''
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@echo ' DESTDIR=/tmp/ufq_iosched make install'
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@echo ''
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@echo ' will build the schedulers in CWD/build, and'
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@echo ' install the schedulers to /tmp/ufq_iosched/usr/bin.'
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@echo ''
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@echo ''
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@echo 'Cleaning targets'
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@echo '================'
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@echo ''
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@echo ' clean - Remove all generated files'
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all_targets: $(c-sched-targets)
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.PHONY: all all_targets $(c-sched-targets) clean help
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# delete failed targets
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.DELETE_ON_ERROR:
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# keep intermediate (.bpf.skel.h, .bpf.o, etc) targets
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.SECONDARY:

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