@@ -1065,8 +1065,7 @@ When kbuild executes, the following steps are followed (roughly):
- The values of the above variables are expanded in arch/$(SRCARCH)/Makefile.
5) All object files are then linked and the resulting file vmlinux is
located at the root of the obj tree.
- The very first objects linked are listed in head-y, assigned by
- arch/$(SRCARCH)/Makefile.
+ The very first objects linked are listed in scripts/head-object-list.txt.
6) Finally, the architecture-specific part does any required post processing
and builds the final bootimage.
- This includes building boot records
@@ -1214,6 +1213,9 @@ When kbuild executes, the following steps are followed (roughly):
All object files for vmlinux. They are linked to vmlinux in the same
order as listed in KBUILD_VMLINUX_OBJS.
+ The objects listed in scripts/head-object-list.txt are exceptions;
+ they are placed before the other objects.
+
KBUILD_VMLINUX_LIBS
All .a "lib" files for vmlinux. KBUILD_VMLINUX_OBJS and
@@ -1257,8 +1259,7 @@ When kbuild executes, the following steps are followed (roughly):
machinery is all architecture-independent.
- head-y, core-y, libs-y, drivers-y
- $(head-y) lists objects to be linked first in vmlinux.
+ core-y, libs-y, drivers-y
$(libs-y) lists directories where a lib.a archive can be located.
@@ -1159,10 +1159,10 @@ quiet_cmd_ar_vmlinux.a = AR $@
cmd_ar_vmlinux.a = \
rm -f $@; \
$(AR) cDPrST $@ $(KBUILD_VMLINUX_OBJS); \
- $(AR) mPi $$($(AR) t $@| head -n1) $@ $(head-y)
+ $(AR) mPi $$($(AR) t $@| head -n1) $@ $$($(AR) t $@ | grep -F --file=$(srctree)/scripts/head-object-list.txt)
targets += vmlinux.a
-vmlinux.a: $(KBUILD_VMLINUX_OBJS) FORCE
+vmlinux.a: $(KBUILD_VMLINUX_OBJS) scripts/head-object-list.txt FORCE
$(call if_changed,ar_vmlinux.a)
targets += vmlinux.o
@@ -36,8 +36,6 @@ cflags-y += $(cpuflags-y)
# BWX is most important, but we don't really want any emulation ever.
KBUILD_CFLAGS += $(cflags-y) -Wa,-mev6
-head-y := arch/alpha/kernel/head.o
-
libs-y += arch/alpha/lib/
# export what is needed by arch/alpha/boot/Makefile
@@ -82,8 +82,6 @@ KBUILD_CFLAGS += $(cflags-y)
KBUILD_AFLAGS += $(KBUILD_CFLAGS)
KBUILD_LDFLAGS += $(ldflags-y)
-head-y := arch/arc/kernel/head.o
-
# w/o this dtb won't embed into kernel binary
core-y += arch/arc/boot/dts/
@@ -134,9 +134,6 @@ KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_ISA) $(arch-y) $(tune-y) -include asm/uni
CHECKFLAGS += -D__arm__
-#Default value
-head-y := arch/arm/kernel/head$(MMUEXT).o
-
# Text offset. This list is sorted numerically by address in order to
# provide a means to avoid/resolve conflicts in multi-arch kernels.
# Note: the 32kB below this value is reserved for use by the kernel
@@ -133,9 +133,6 @@ ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_REGS),y)
CC_FLAGS_FTRACE := -fpatchable-function-entry=2
endif
-# Default value
-head-y := arch/arm64/kernel/head.o
-
ifeq ($(CONFIG_KASAN_SW_TAGS), y)
KASAN_SHADOW_SCALE_SHIFT := 4
else ifeq ($(CONFIG_KASAN_GENERIC), y)
@@ -59,8 +59,6 @@ LDFLAGS += -EL
KBUILD_AFLAGS += $(KBUILD_CFLAGS)
-head-y := arch/csky/kernel/head.o
-
core-y += arch/csky/$(CSKYABI)/
libs-y += arch/csky/lib/ \
@@ -32,5 +32,3 @@ KBUILD_LDFLAGS += $(ldflags-y)
TIR_NAME := r19
KBUILD_CFLAGS += -ffixed-$(TIR_NAME) -DTHREADINFO_REG=$(TIR_NAME) -D__linux__
KBUILD_AFLAGS += -DTHREADINFO_REG=$(TIR_NAME)
-
-head-y := arch/hexagon/kernel/head.o
@@ -44,7 +44,6 @@ quiet_cmd_objcopy = OBJCOPY $@
cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@
KBUILD_CFLAGS += $(cflags-y)
-head-y := arch/ia64/kernel/head.o
libs-y += arch/ia64/lib/
@@ -72,8 +72,6 @@ CHECKFLAGS += $(shell $(CC) $(KBUILD_CFLAGS) -dM -E -x c /dev/null | \
sed -e "s/^\#define /-D'/" -e "s/ /'='/" -e "s/$$/'/" -e 's/\$$/&&/g')
endif
-head-y := arch/loongarch/kernel/head.o
-
libs-y += arch/loongarch/lib/
ifeq ($(KBUILD_EXTMOD),)
@@ -86,15 +86,6 @@ ifdef CONFIG_KGDB
KBUILD_CFLAGS := $(subst -fomit-frame-pointer,,$(KBUILD_CFLAGS)) -g
endif
-#
-# Select the assembler head startup code. Order is important. The default
-# head code is first, processor specific selections can override it after.
-#
-head-y := arch/m68k/kernel/head.o
-head-$(CONFIG_SUN3) := arch/m68k/kernel/sun3-head.o
-head-$(CONFIG_M68000) := arch/m68k/68000/head.o
-head-$(CONFIG_COLDFIRE) := arch/m68k/coldfire/head.o
-
libs-y += arch/m68k/lib/
@@ -48,7 +48,6 @@ CPUFLAGS-1 += $(call cc-option,-mcpu=v$(CPU_VER))
# r31 holds current when in kernel mode
KBUILD_CFLAGS += -ffixed-r31 $(CPUFLAGS-y) $(CPUFLAGS-1) $(CPUFLAGS-2)
-head-y := arch/microblaze/kernel/head.o
libs-y += arch/microblaze/lib/
boot := arch/microblaze/boot
@@ -324,8 +324,6 @@ endif
OBJCOPYFLAGS += --remove-section=.reginfo
-head-y := arch/mips/kernel/head.o
-
libs-y += arch/mips/lib/
libs-$(CONFIG_MIPS_FP_SUPPORT) += arch/mips/math-emu/
@@ -37,7 +37,6 @@ KBUILD_CFLAGS += -DUTS_SYSNAME=\"$(UTS_SYSNAME)\"
KBUILD_CFLAGS += -fno-builtin
KBUILD_CFLAGS += -G 0
-head-y := arch/nios2/kernel/head.o
libs-y += arch/nios2/lib/ $(LIBGCC)
INSTALL_PATH ?= /tftpboot
@@ -55,8 +55,6 @@ ifeq ($(CONFIG_OPENRISC_HAVE_INST_SEXT),y)
KBUILD_CFLAGS += $(call cc-option,-msext)
endif
-head-y := arch/openrisc/kernel/head.o
-
libs-y += $(LIBGCC)
PHONY += vmlinux.bin
@@ -113,8 +113,6 @@ cflags-$(CONFIG_PA7100LC) += -march=1.1 -mschedule=7100LC
cflags-$(CONFIG_PA7300LC) += -march=1.1 -mschedule=7300
cflags-$(CONFIG_PA8X00) += -march=2.0 -mschedule=8000
-head-y := arch/parisc/kernel/head.o
-
KBUILD_CFLAGS += $(cflags-y)
LIBGCC := $(shell $(CC) -print-libgcc-file-name)
export LIBGCC
@@ -220,18 +220,6 @@ KBUILD_CFLAGS += $(cpu-as-y)
KBUILD_AFLAGS += $(aflags-y)
KBUILD_CFLAGS += $(cflags-y)
-head-$(CONFIG_PPC64) := arch/powerpc/kernel/head_64.o
-head-$(CONFIG_PPC_BOOK3S_32) := arch/powerpc/kernel/head_book3s_32.o
-head-$(CONFIG_PPC_8xx) := arch/powerpc/kernel/head_8xx.o
-head-$(CONFIG_40x) := arch/powerpc/kernel/head_40x.o
-head-$(CONFIG_44x) := arch/powerpc/kernel/head_44x.o
-head-$(CONFIG_FSL_BOOKE) := arch/powerpc/kernel/head_fsl_booke.o
-
-head-$(CONFIG_PPC64) += arch/powerpc/kernel/entry_64.o
-head-$(CONFIG_PPC_FPU) += arch/powerpc/kernel/fpu.o
-head-$(CONFIG_ALTIVEC) += arch/powerpc/kernel/vector.o
-head-$(CONFIG_PPC_OF_BOOT_TRAMPOLINE) += arch/powerpc/kernel/prom_init.o
-
# Default to zImage, override when needed
all: zImage
@@ -110,8 +110,6 @@ else
KBUILD_IMAGE := $(boot)/Image.gz
endif
-head-y := arch/riscv/kernel/head.o
-
libs-y += arch/riscv/lib/
libs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
@@ -119,8 +119,6 @@ export KBUILD_CFLAGS_DECOMPRESSOR
OBJCOPYFLAGS := -O binary
-head-y := arch/s390/kernel/head64.o
-
libs-y += arch/s390/lib/
drivers-y += drivers/s390/
@@ -114,8 +114,6 @@ endif
export ld-bfd
-head-y := arch/sh/kernel/head_32.o
-
# Mach groups
machdir-$(CONFIG_SOLUTION_ENGINE) += mach-se
machdir-$(CONFIG_SH_HP6XX) += mach-hp6xx
@@ -56,8 +56,6 @@ endif
endif
-head-y := arch/sparc/kernel/head_$(BITS).o
-
libs-y += arch/sparc/prom/
libs-y += arch/sparc/lib/
@@ -234,11 +234,6 @@ archheaders:
###
# Kernel objects
-head-y := arch/x86/kernel/head_$(BITS).o
-head-y += arch/x86/kernel/head$(BITS).o
-head-y += arch/x86/kernel/ebda.o
-head-y += arch/x86/kernel/platform-quirks.o
-
libs-y += arch/x86/lib/
# drivers-y are linked after core-y
@@ -55,8 +55,6 @@ KBUILD_CPPFLAGS += $(patsubst %,-I$(srctree)/%include,$(vardirs) $(plfdirs))
KBUILD_DEFCONFIG := iss_defconfig
-head-y := arch/xtensa/kernel/head.o
-
libs-y += arch/xtensa/lib/
boot := arch/xtensa/boot
new file mode 100644
@@ -0,0 +1,53 @@
+# Head objects
+#
+# The objects listed here are placed at the head of vmlinux. A typical use-case
+# is an object that contains the entry point. This is kept for compatibility
+# with head-y, Kbuild used to support.
+#
+# A counter approach is to control the section placement in the linker script.
+# The code marked as __HEAD goes into the ".head.text" section, which is placed
+# before the normal ".text" section.
+#
+# If you can achieve the correct code ordering by linker script, please delete
+# the entry from this file.
+#
+arch/alpha/kernel/head.o
+arch/arc/kernel/head.o
+arch/arm/kernel/head-nommu.o
+arch/arm/kernel/head.o
+arch/arm64/kernel/head.o
+arch/csky/kernel/head.o
+arch/hexagon/kernel/head.o
+arch/ia64/kernel/head.o
+arch/loongarch/kernel/head.o
+arch/m68k/68000/head.o
+arch/m68k/coldfire/head.o
+arch/m68k/kernel/head.o
+arch/m68k/kernel/sun3-head.o
+arch/microblaze/kernel/head.o
+arch/mips/kernel/head.o
+arch/nios2/kernel/head.o
+arch/openrisc/kernel/head.o
+arch/parisc/kernel/head.o
+arch/powerpc/kernel/head_40x.o
+arch/powerpc/kernel/head_44x.o
+arch/powerpc/kernel/head_64.o
+arch/powerpc/kernel/head_8xx.o
+arch/powerpc/kernel/head_book3s_32.o
+arch/powerpc/kernel/head_fsl_booke.o
+arch/powerpc/kernel/entry_64.o
+arch/powerpc/kernel/fpu.o
+arch/powerpc/kernel/vector.o
+arch/powerpc/kernel/prom_init.o
+arch/riscv/kernel/head.o
+arch/s390/kernel/head64.o
+arch/sh/kernel/head_32.o
+arch/sparc/kernel/head_32.o
+arch/sparc/kernel/head_64.o
+arch/x86/kernel/head_32.o
+arch/x86/kernel/head_64.o
+arch/x86/kernel/head32.o
+arch/x86/kernel/head64.o
+arch/x86/kernel/ebda.o
+arch/x86/kernel/platform-quirks.o
+arch/xtensa/kernel/head.o
Kbuild puts the objects listed in head-y at the head of vmlinux. Conventionally, we do this for head*.S, which contains the kernel entry point. A counter approach is to control the section order in the linker script. Actually, the code marked as __HEAD goes into the ".head.text" section, which is placed before the normal ".text" section. I do not know if both of them are needed. head-y is not mandatory. If you can achieve the proper code placement by the linker script only, it would be cleaner. I collected the current head-y objects into head-object-list.txt. It is a whitelist. My hope is it will be reduced in the long run. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> --- Documentation/kbuild/makefiles.rst | 9 ++--- Makefile | 4 +-- arch/alpha/Makefile | 2 -- arch/arc/Makefile | 2 -- arch/arm/Makefile | 3 -- arch/arm64/Makefile | 3 -- arch/csky/Makefile | 2 -- arch/hexagon/Makefile | 2 -- arch/ia64/Makefile | 1 - arch/loongarch/Makefile | 2 -- arch/m68k/Makefile | 9 ----- arch/microblaze/Makefile | 1 - arch/mips/Makefile | 2 -- arch/nios2/Makefile | 1 - arch/openrisc/Makefile | 2 -- arch/parisc/Makefile | 2 -- arch/powerpc/Makefile | 12 ------- arch/riscv/Makefile | 2 -- arch/s390/Makefile | 2 -- arch/sh/Makefile | 2 -- arch/sparc/Makefile | 2 -- arch/x86/Makefile | 5 --- arch/xtensa/Makefile | 2 -- scripts/head-object-list.txt | 53 ++++++++++++++++++++++++++++++ 24 files changed, 60 insertions(+), 67 deletions(-) create mode 100644 scripts/head-object-list.txt