kbuild: remove head-y syntax

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 by 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. From the build system perspective, 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.

Masahiro Yamada committed 4 years ago

Commit ce697cc1 parent 321648424 files · +60 −67Browse files

Unified · Split

24 files

Documentation/kbuild/makefiles.rst +5 −4
Makefile +2 −2
arch/alpha/Makefile +0 −2
arch/arc/Makefile +0 −2
arch/arm/Makefile +0 −3
arch/arm64/Makefile +0 −3
arch/csky/Makefile +0 −2
arch/hexagon/Makefile +0 −2
arch/ia64/Makefile +0 −1
arch/loongarch/Makefile +0 −2
arch/m68k/Makefile +0 −9
arch/microblaze/Makefile +0 −1
arch/mips/Makefile +0 −2
arch/nios2/Makefile +0 −1
arch/openrisc/Makefile +0 −2
arch/parisc/Makefile +0 −2
arch/powerpc/Makefile +0 −12
arch/riscv/Makefile +0 −2
arch/s390/Makefile +0 −2
arch/sh/Makefile +0 −2
arch/sparc/Makefile +0 −2
arch/x86/Makefile +0 −5
arch/xtensa/Makefile +0 −2
scripts/head-object-list.txt +53 −0

Documentation/kbuild/makefiles.rst+5−4

@@ -1070,8 +1070,7 @@ When kbuild executes, the following steps are followed (roughly): · 1069 unmodified lines
1070	1070	- The values of the above variables are expanded in arch/$(SRCARCH)/Makefile.
1071	1071	5) All object files are then linked and the resulting file vmlinux is
1072	1072	located at the root of the obj tree.
1073		− The very first objects linked are listed in head-y, assigned by
1074		− arch/$(SRCARCH)/Makefile.
	1073	+ The very first objects linked are listed in scripts/head-object-list.txt.
1075	1074	6) Finally, the architecture-specific part does any required post processing
1076	1075	and builds the final bootimage.
1077	1076	- This includes building boot records
@@ -1219,6 +1218,9 @@ When kbuild executes, the following steps are followed (roughly): · 141 unmodified lines
1219	1218	All object files for vmlinux. They are linked to vmlinux in the same
1220	1219	order as listed in KBUILD_VMLINUX_OBJS.
1221	1220
	1221	+ The objects listed in scripts/head-object-list.txt are exceptions;
	1222	+ they are placed before the other objects.
	1223	+
1222	1224	KBUILD_VMLINUX_LIBS
1223	1225
1224	1226	All .a "lib" files for vmlinux. KBUILD_VMLINUX_OBJS and
@@ -1262,8 +1264,7 @@ When kbuild executes, the following steps are followed (roughly): · 37 unmodified lines
1262	1264	machinery is all architecture-independent.
1263	1265
1264	1266
1265		− head-y, core-y, libs-y, drivers-y
1266		− $(head-y) lists objects to be linked first in vmlinux.
	1267	+ core-y, libs-y, drivers-y
1267	1268
1268	1269	$(libs-y) lists directories where a lib.a archive can be located.
1269	1270

Makefile+2−2

@@ -1147,10 +1147,10 @@ quiet_cmd_ar_vmlinux.a = AR $@ · 1146 unmodified lines
1147	1147	cmd_ar_vmlinux.a = \
1148	1148	rm -f $@; \
1149	1149	$(AR) cDPrST $@ $(KBUILD_VMLINUX_OBJS); \
1150		− $(AR) mPiT $$($(AR) t $@ \| head -n1) $@ $(head-y)
	1150	+ $(AR) mPiT $$($(AR) t $@ \| head -n1) $@ $$($(AR) t $@ \| grep -F --file=$(srctree)/scripts/head-object-list.txt)
1151	1151
1152	1152	targets += vmlinux.a
1153		−vmlinux.a: $(KBUILD_VMLINUX_OBJS) autoksyms_recursive FORCE
	1153	+vmlinux.a: $(KBUILD_VMLINUX_OBJS) scripts/head-object-list.txt autoksyms_recursive FORCE
1154	1154	$(call if_changed,ar_vmlinux.a)
1155	1155
1156	1156	vmlinux.o: vmlinux.a $(KBUILD_VMLINUX_LIBS) FORCE

arch/alpha/Makefile+0−2

@@ -36,8 +36,6 @@ cflags-y += $(cpuflags-y) · 35 unmodified lines
36	36	# BWX is most important, but we don't really want any emulation ever.
37	37	KBUILD_CFLAGS += $(cflags-y) -Wa,-mev6
38	38
39		−head-y := arch/alpha/kernel/head.o
40		−
41	39	libs-y += arch/alpha/lib/
42	40
43	41	# export what is needed by arch/alpha/boot/Makefile

arch/arc/Makefile+0−2

@@ -82,8 +82,6 @@ KBUILD_CFLAGS += $(cflags-y) · 81 unmodified lines
82	82	KBUILD_AFLAGS += $(KBUILD_CFLAGS)
83	83	KBUILD_LDFLAGS += $(ldflags-y)
84	84
85		−head-y := arch/arc/kernel/head.o
86		−
87	85	# w/o this dtb won't embed into kernel binary
88	86	core-y += arch/arc/boot/dts/
89	87

arch/arm/Makefile+0−3

@@ -134,9 +134,6 @@ KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_ISA) $(arch-y) $(tune-y) -include asm/uni · 133 unmodified lines
134	134
135	135	CHECKFLAGS += -D__arm__
136	136
137		−#Default value
138		−head-y := arch/arm/kernel/head$(MMUEXT).o
139		−
140	137	# Text offset. This list is sorted numerically by address in order to
141	138	# provide a means to avoid/resolve conflicts in multi-arch kernels.
142	139	# Note: the 32kB below this value is reserved for use by the kernel

arch/arm64/Makefile+0−3

@@ -133,9 +133,6 @@ ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_REGS),y) · 132 unmodified lines
133	133	CC_FLAGS_FTRACE := -fpatchable-function-entry=2
134	134	endif
135	135
136		−# Default value
137		−head-y := arch/arm64/kernel/head.o
138		−
139	136	ifeq ($(CONFIG_KASAN_SW_TAGS), y)
140	137	KASAN_SHADOW_SCALE_SHIFT := 4
141	138	else ifeq ($(CONFIG_KASAN_GENERIC), y)

arch/csky/Makefile+0−2

@@ -59,8 +59,6 @@ LDFLAGS += -EL · 58 unmodified lines
59	59
60	60	KBUILD_AFLAGS += $(KBUILD_CFLAGS)
61	61
62		−head-y := arch/csky/kernel/head.o
63		−
64	62	core-y += arch/csky/$(CSKYABI)/
65	63
66	64	libs-y += arch/csky/lib/ \

arch/hexagon/Makefile+0−2

@@ -32,5 +32,3 @@ KBUILD_LDFLAGS += $(ldflags-y) · 31 unmodified lines
32	32	TIR_NAME := r19
33	33	KBUILD_CFLAGS += -ffixed-$(TIR_NAME) -DTHREADINFO_REG=$(TIR_NAME) -D__linux__
34	34	KBUILD_AFLAGS += -DTHREADINFO_REG=$(TIR_NAME)
35		−
36		−head-y := arch/hexagon/kernel/head.o

arch/ia64/Makefile+0−1

@@ -44,7 +44,6 @@ quiet_cmd_objcopy = OBJCOPY $@ · 43 unmodified lines
44	44	cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@
45	45
46	46	KBUILD_CFLAGS += $(cflags-y)
47		−head-y := arch/ia64/kernel/head.o
48	47
49	48	libs-y += arch/ia64/lib/
50	49

arch/loongarch/Makefile+0−2

@@ -72,8 +72,6 @@ CHECKFLAGS += $(shell $(CC) $(KBUILD_CFLAGS) -dM -E -x c /dev/null \| \ · 71 unmodified lines
72	72	sed -e "s/^\#define /-D'/" -e "s/ /'='/" -e "s/$$/'/" -e 's/\$$/&&/g')
73	73	endif
74	74
75		−head-y := arch/loongarch/kernel/head.o
76		−
77	75	libs-y += arch/loongarch/lib/
78	76
79	77	ifeq ($(KBUILD_EXTMOD),)

arch/m68k/Makefile+0−9

@@ -86,15 +86,6 @@ ifdef CONFIG_KGDB · 85 unmodified lines
86	86	KBUILD_CFLAGS := $(subst -fomit-frame-pointer,,$(KBUILD_CFLAGS)) -g
87	87	endif
88	88
89		−#
90		−# Select the assembler head startup code. Order is important. The default
91		−# head code is first, processor specific selections can override it after.
92		−#
93		−head-y := arch/m68k/kernel/head.o
94		−head-$(CONFIG_SUN3) := arch/m68k/kernel/sun3-head.o
95		−head-$(CONFIG_M68000) := arch/m68k/68000/head.o
96		−head-$(CONFIG_COLDFIRE) := arch/m68k/coldfire/head.o
97		−
98	89	libs-y += arch/m68k/lib/
99	90
100	91

arch/microblaze/Makefile+0−1

@@ -48,7 +48,6 @@ CPUFLAGS-1 += $(call cc-option,-mcpu=v$(CPU_VER)) · 47 unmodified lines
48	48	# r31 holds current when in kernel mode
49	49	KBUILD_CFLAGS += -ffixed-r31 $(CPUFLAGS-y) $(CPUFLAGS-1) $(CPUFLAGS-2)
50	50
51		−head-y := arch/microblaze/kernel/head.o
52	51	libs-y += arch/microblaze/lib/
53	52
54	53	boot := arch/microblaze/boot

arch/mips/Makefile+0−2

@@ -324,8 +324,6 @@ endif · 323 unmodified lines
324	324
325	325	OBJCOPYFLAGS += --remove-section=.reginfo
326	326
327		−head-y := arch/mips/kernel/head.o
328		−
329	327	libs-y += arch/mips/lib/
330	328	libs-$(CONFIG_MIPS_FP_SUPPORT) += arch/mips/math-emu/
331	329

arch/nios2/Makefile+0−1

@@ -37,7 +37,6 @@ KBUILD_CFLAGS += -DUTS_SYSNAME=\"$(UTS_SYSNAME)\" · 36 unmodified lines
37	37	KBUILD_CFLAGS += -fno-builtin
38	38	KBUILD_CFLAGS += -G 0
39	39
40		−head-y := arch/nios2/kernel/head.o
41	40	libs-y += arch/nios2/lib/ $(LIBGCC)
42	41
43	42	INSTALL_PATH ?= /tftpboot

arch/openrisc/Makefile+0−2

@@ -55,8 +55,6 @@ ifeq ($(CONFIG_OPENRISC_HAVE_INST_SEXT),y) · 54 unmodified lines
55	55	KBUILD_CFLAGS += $(call cc-option,-msext)
56	56	endif
57	57
58		−head-y := arch/openrisc/kernel/head.o
59		−
60	58	libs-y += $(LIBGCC)
61	59
62	60	PHONY += vmlinux.bin

arch/parisc/Makefile+0−2

@@ -113,8 +113,6 @@ cflags-$(CONFIG_PA7100LC) += -march=1.1 -mschedule=7100LC · 112 unmodified lines
113	113	cflags-$(CONFIG_PA7300LC) += -march=1.1 -mschedule=7300
114	114	cflags-$(CONFIG_PA8X00) += -march=2.0 -mschedule=8000
115	115
116		−head-y := arch/parisc/kernel/head.o
117		−
118	116	KBUILD_CFLAGS += $(cflags-y)
119	117	LIBGCC := $(shell $(CC) -print-libgcc-file-name)
120	118	export LIBGCC

arch/powerpc/Makefile+0−12

@@ -226,18 +226,6 @@ KBUILD_CFLAGS += $(cpu-as-y) · 225 unmodified lines
226	226	KBUILD_AFLAGS += $(aflags-y)
227	227	KBUILD_CFLAGS += $(cflags-y)
228	228
229		−head-$(CONFIG_PPC64) := arch/powerpc/kernel/head_64.o
230		−head-$(CONFIG_PPC_BOOK3S_32) := arch/powerpc/kernel/head_book3s_32.o
231		−head-$(CONFIG_PPC_8xx) := arch/powerpc/kernel/head_8xx.o
232		−head-$(CONFIG_40x) := arch/powerpc/kernel/head_40x.o
233		−head-$(CONFIG_44x) := arch/powerpc/kernel/head_44x.o
234		−head-$(CONFIG_FSL_BOOKE) := arch/powerpc/kernel/head_fsl_booke.o
235		−
236		−head-$(CONFIG_PPC64) += arch/powerpc/kernel/entry_64.o
237		−head-$(CONFIG_PPC_FPU) += arch/powerpc/kernel/fpu.o
238		−head-$(CONFIG_ALTIVEC) += arch/powerpc/kernel/vector.o
239		−head-$(CONFIG_PPC_OF_BOOT_TRAMPOLINE) += arch/powerpc/kernel/prom_init.o
240		−
241	229	# Default to zImage, override when needed
242	230	all: zImage
243	231

arch/riscv/Makefile+0−2

@@ -110,8 +110,6 @@ else · 109 unmodified lines
110	110	KBUILD_IMAGE := $(boot)/Image.gz
111	111	endif
112	112
113		−head-y := arch/riscv/kernel/head.o
114		−
115	113	libs-y += arch/riscv/lib/
116	114	libs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
117	115

arch/s390/Makefile+0−2

@@ -119,8 +119,6 @@ export KBUILD_CFLAGS_DECOMPRESSOR · 118 unmodified lines
119	119
120	120	OBJCOPYFLAGS := -O binary
121	121
122		−head-y := arch/s390/kernel/head64.o
123		−
124	122	libs-y += arch/s390/lib/
125	123	drivers-y += drivers/s390/
126	124

arch/sh/Makefile+0−2

@@ -114,8 +114,6 @@ endif · 113 unmodified lines
114	114
115	115	export ld-bfd
116	116
117		−head-y := arch/sh/kernel/head_32.o
118		−
119	117	# Mach groups
120	118	machdir-$(CONFIG_SOLUTION_ENGINE) += mach-se
121	119	machdir-$(CONFIG_SH_HP6XX) += mach-hp6xx

arch/sparc/Makefile+0−2

@@ -56,8 +56,6 @@ endif · 55 unmodified lines
56	56
57	57	endif
58	58
59		−head-y := arch/sparc/kernel/head_$(BITS).o
60		−
61	59	libs-y += arch/sparc/prom/
62	60	libs-y += arch/sparc/lib/
63	61

arch/x86/Makefile+0−5

@@ -234,11 +234,6 @@ archheaders: · 233 unmodified lines
234	234	###
235	235	# Kernel objects
236	236
237		−head-y := arch/x86/kernel/head_$(BITS).o
238		−head-y += arch/x86/kernel/head$(BITS).o
239		−head-y += arch/x86/kernel/ebda.o
240		−head-y += arch/x86/kernel/platform-quirks.o
241		−
242	237	libs-y += arch/x86/lib/
243	238
244	239	# drivers-y are linked after core-y

arch/xtensa/Makefile+0−2

@@ -55,8 +55,6 @@ KBUILD_CPPFLAGS += $(patsubst %,-I$(srctree)/%include,$(vardirs) $(plfdirs)) · 54 unmodified lines
55	55
56	56	KBUILD_DEFCONFIG := iss_defconfig
57	57
58		−head-y := arch/xtensa/kernel/head.o
59		−
60	58	libs-y += arch/xtensa/lib/
61	59
62	60	boot := arch/xtensa/boot

scripts/head-object-list.txt+53−0

@@ -0,0 +1,53 @@
	1	+# Head objects
	2	+#
	3	+# The objects listed here are placed at the head of vmlinux. A typical use-case
	4	+# is an object that contains the entry point. This is kept for compatibility
	5	+# with head-y, which Kbuild used to support.
	6	+#
	7	+# A counter approach is to control the section placement by the linker script.
	8	+# The code marked as __HEAD goes into the ".head.text" section, which is placed
	9	+# before the normal ".text" section.
	10	+#
	11	+# If you can achieve the correct code ordering by linker script, please delete
	12	+# the entry from this file.
	13	+#
	14	+arch/alpha/kernel/head.o
	15	+arch/arc/kernel/head.o
	16	+arch/arm/kernel/head-nommu.o
	17	+arch/arm/kernel/head.o
	18	+arch/arm64/kernel/head.o
	19	+arch/csky/kernel/head.o
	20	+arch/hexagon/kernel/head.o
	21	+arch/ia64/kernel/head.o
	22	+arch/loongarch/kernel/head.o
	23	+arch/m68k/68000/head.o
	24	+arch/m68k/coldfire/head.o
	25	+arch/m68k/kernel/head.o
	26	+arch/m68k/kernel/sun3-head.o
	27	+arch/microblaze/kernel/head.o
	28	+arch/mips/kernel/head.o
	29	+arch/nios2/kernel/head.o
	30	+arch/openrisc/kernel/head.o
	31	+arch/parisc/kernel/head.o
	32	+arch/powerpc/kernel/head_40x.o
	33	+arch/powerpc/kernel/head_44x.o
	34	+arch/powerpc/kernel/head_64.o
	35	+arch/powerpc/kernel/head_8xx.o
	36	+arch/powerpc/kernel/head_book3s_32.o
	37	+arch/powerpc/kernel/head_fsl_booke.o
	38	+arch/powerpc/kernel/entry_64.o
	39	+arch/powerpc/kernel/fpu.o
	40	+arch/powerpc/kernel/vector.o
	41	+arch/powerpc/kernel/prom_init.o
	42	+arch/riscv/kernel/head.o
	43	+arch/s390/kernel/head64.o
	44	+arch/sh/kernel/head_32.o
	45	+arch/sparc/kernel/head_32.o
	46	+arch/sparc/kernel/head_64.o
	47	+arch/x86/kernel/head_32.o
	48	+arch/x86/kernel/head_64.o
	49	+arch/x86/kernel/head32.o
	50	+arch/x86/kernel/head64.o
	51	+arch/x86/kernel/ebda.o
	52	+arch/x86/kernel/platform-quirks.o
	53	+arch/xtensa/kernel/head.o