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    #
    # Kbuild for top-level directory of the kernel
    # This file takes care of the following:
    # 1) Generate bounds.h
    # 2) Generate timeconst.h
    # 3) Generate asm-offsets.h (may need bounds.h and timeconst.h)
    # 4) Check for missing system calls
    # 5) Generate constants.py (may need bounds.h)
    
    # Default sed regexp - multiline due to syntax constraints
    define sed-y
    	"/^->/{s:->#\(.*\):/* \1 */:; \
    	s:^->\([^ ]*\) [\$$#]*\([-0-9]*\) \(.*\):#define \1 \2 /* \3 */:; \
    	s:^->\([^ ]*\) [\$$#]*\([^ ]*\) \(.*\):#define \1 \2 /* \3 */:; \
    	s:->::; p;}"
    endef
    
    # Use filechk to avoid rebuilds when a header changes, but the resulting file
    # does not
    define filechk_offsets
    	(set -e; \
    	 echo "#ifndef $2"; \
    	 echo "#define $2"; \
    	 echo "/*"; \
    	 echo " * DO NOT MODIFY."; \
    	 echo " *"; \
    	 echo " * This file was generated by Kbuild"; \
    	 echo " */"; \
    	 echo ""; \
    	 sed -ne $(sed-y); \
    	 echo ""; \
    	 echo "#endif" )
    endef
    
    #####
    # 1) Generate bounds.h
    
    bounds-file := include/generated/bounds.h
    
    always  := $(bounds-file)
    targets := kernel/bounds.s
    
    # We use internal kbuild rules to avoid the "is up to date" message from make
    kernel/bounds.s: kernel/bounds.c FORCE
    	$(Q)mkdir -p $(dir $@)
    	$(call if_changed_dep,cc_s_c)
    
    $(obj)/$(bounds-file): kernel/bounds.s FORCE
    	$(call filechk,offsets,__LINUX_BOUNDS_H__)
    
    #####
    # 2) Generate timeconst.h
    
    timeconst-file := include/generated/timeconst.h
    
    targets += $(timeconst-file)
    
    quiet_cmd_gentimeconst = GEN     $@
    define cmd_gentimeconst
    	(echo $(CONFIG_HZ) | bc -q $< ) > $@
    endef
    define filechk_gentimeconst
    	(echo $(CONFIG_HZ) | bc -q $< )
    endef
    
    $(obj)/$(timeconst-file): kernel/time/timeconst.bc FORCE
    	$(call filechk,gentimeconst)
    
    #####
    # 3) Generate asm-offsets.h
    #
    
    offsets-file := include/generated/asm-offsets.h
    
    always  += $(offsets-file)
    targets += arch/$(SRCARCH)/kernel/asm-offsets.s
    
    # We use internal kbuild rules to avoid the "is up to date" message from make
    arch/$(SRCARCH)/kernel/asm-offsets.s: arch/$(SRCARCH)/kernel/asm-offsets.c \
                                          $(obj)/$(timeconst-file) $(obj)/$(bounds-file) FORCE
    	$(Q)mkdir -p $(dir $@)
    	$(call if_changed_dep,cc_s_c)
    
    $(obj)/$(offsets-file): arch/$(SRCARCH)/kernel/asm-offsets.s FORCE
    	$(call filechk,offsets,__ASM_OFFSETS_H__)
    
    #####
    # 4) Check for missing system calls
    #
    
    always += missing-syscalls
    targets += missing-syscalls
    
    quiet_cmd_syscalls = CALL    $<
          cmd_syscalls = $(CONFIG_SHELL) $< $(CC) $(c_flags) $(missing_syscalls_flags)
    
    missing-syscalls: scripts/checksyscalls.sh $(offsets-file) FORCE
    	$(call cmd,syscalls)
    
    #####
    # 5) Generate constants for Python GDB integration
    #
    
    extra-$(CONFIG_GDB_SCRIPTS) += build_constants_py
    
    build_constants_py: $(obj)/$(timeconst-file) $(obj)/$(bounds-file)
    	@$(MAKE) $(build)=scripts/gdb/linux $@
    
    # Keep these three files during make clean
    no-clean-files := $(bounds-file) $(offsets-file) $(timeconst-file)