[PATCH 3/4] kbuild: separate out vmlinux.lds generation

From: Masahiro Yamada
Date: Thu Feb 25 2021 - 11:05:15 EST

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This is a preparation for the CONFIG_TRIM_UNUSED_KSYMS improvement.

In the new implementation of CONFIG_TRIM_UNUSED_KSYMS (next commit),
unused export symbols are trimmed at the link stage. Kbuild needs to
build the entire tree to know which symbols are needed by modules for
symbol resolution.

The list of needed symbols shall be generated after the directory
traverse, and included from vmlinux.lds.S and module.lds.S.

The build rule of module.lds.S is already separated as modules_prepare.

The build of vmlinux.lds must be delayed because such a list is not yet
available when Kbuild is visiting arch/$(SRCARCH)/kernel/Makefile.

Separate the build rule of vmlinux.lds, and invokes it from the top
Makefile.

I guarded the $(warning ) in scripts/Makefile.build, otherwise a false-
positive warning would be displayed for example when building ARCH=ia64
with CONFIG_IA64_PALINFO=m. Ideally, vmlinux.lds.S could be moved to a
different directory, but I am just doing less-invasive changes for now.

Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
---

Makefile | 8 ++++++--
arch/alpha/kernel/Makefile | 3 ++-
arch/arc/kernel/Makefile | 3 ++-
arch/arm/kernel/Makefile | 3 ++-
arch/arm64/kernel/Makefile | 3 ++-
arch/csky/kernel/Makefile | 3 ++-
arch/h8300/kernel/Makefile | 2 +-
arch/hexagon/kernel/Makefile | 3 ++-
arch/ia64/kernel/Makefile | 3 ++-
arch/m68k/kernel/Makefile | 2 +-
arch/microblaze/kernel/Makefile | 3 ++-
arch/mips/kernel/Makefile | 3 ++-
arch/nds32/kernel/Makefile | 3 ++-
arch/nios2/kernel/Makefile | 2 +-
arch/openrisc/kernel/Makefile | 3 ++-
arch/parisc/kernel/Makefile | 3 ++-
arch/powerpc/kernel/Makefile | 2 +-
arch/riscv/kernel/Makefile | 2 +-
arch/s390/kernel/Makefile | 3 ++-
arch/sh/kernel/Makefile | 3 ++-
arch/sparc/kernel/Makefile | 2 +-
arch/um/kernel/Makefile | 2 +-
arch/x86/kernel/Makefile | 2 +-
arch/xtensa/kernel/Makefile | 3 ++-
scripts/Makefile.build | 2 ++
25 files changed, 46 insertions(+), 25 deletions(-)

diff --git a/Makefile b/Makefile
index b18dbc634690..34393fd72fe1 100644
--- a/Makefile
+++ b/Makefile
@@ -1184,6 +1184,9 @@ quiet_cmd_autoksyms_h = GEN $@
$(autoksyms_h):
$(call cmd,autoksyms_h)

+$(KBUILD_LDS): prepare FORCE
+ $(Q)$(MAKE) $(build)=$(patsubst %/,%,$(dir $@)) $@
+
ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)

# Final link of vmlinux with optional arch pass after final link
@@ -1191,14 +1194,15 @@ cmd_link-vmlinux = \
$(CONFIG_SHELL) $< "$(LD)" "$(KBUILD_LDFLAGS)" "$(LDFLAGS_vmlinux)"; \
$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)

-vmlinux: scripts/link-vmlinux.sh autoksyms_recursive $(vmlinux-deps) FORCE
+vmlinux: scripts/link-vmlinux.sh autoksyms_recursive $(KBUILD_LDS) \
+ $(KBUILD_VMLINUX_OBJS) $(KBUILD_VMLINUX_LIBS) FORCE
+$(call if_changed,link-vmlinux)

targets := vmlinux

# The actual objects are generated when descending,
# make sure no implicit rule kicks in
-$(sort $(vmlinux-deps) $(subdir-modorder)): descend ;
+$(sort $(KBUILD_VMLINUX_OBJS) $(KBUILD_VMLINUX_LIBS) $(subdir-modorder)): descend ;

filechk_kernel.release = \
echo "$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion $(srctree))"
diff --git a/arch/alpha/kernel/Makefile b/arch/alpha/kernel/Makefile
index 5a74581bf0ee..6e2baaebdee3 100644
--- a/arch/alpha/kernel/Makefile
+++ b/arch/alpha/kernel/Makefile
@@ -3,7 +3,8 @@
# Makefile for the linux kernel.
#

-extra-y := head.o vmlinux.lds
+extra-y := head.o
+targets += vmlinux.lds
asflags-y := $(KBUILD_CFLAGS)
ccflags-y := -Wno-sign-compare

diff --git a/arch/arc/kernel/Makefile b/arch/arc/kernel/Makefile
index 8c4fc4b54c14..0a06c018f0cd 100644
--- a/arch/arc/kernel/Makefile
+++ b/arch/arc/kernel/Makefile
@@ -31,4 +31,5 @@ else
obj-y += ctx_sw_asm.o
endif

-extra-y := vmlinux.lds head.o
+targets += vmlinux.lds
+extra-y := head.o
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index ae295a3bcfef..7483916c034d 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -106,4 +106,5 @@ endif

obj-$(CONFIG_HAVE_ARM_SMCCC) += smccc-call.o

-extra-y := $(head-y) vmlinux.lds
+extra-y := $(head-y)
+targets += vmlinux.lds
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index ed65576ce710..32e530c22cba 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -64,7 +64,8 @@ obj-$(CONFIG_COMPAT_VDSO) += vdso32-wrap.o

obj-y += probes/
head-y := head.o
-extra-y += $(head-y) vmlinux.lds
+extra-y += $(head-y)
+targets += vmlinux.lds

ifeq ($(CONFIG_DEBUG_EFI),y)
AFLAGS_head.o += -DVMLINUX_PATH="\"$(realpath $(objtree)/vmlinux)\""
diff --git a/arch/csky/kernel/Makefile b/arch/csky/kernel/Makefile
index 37f37c0e934a..2ebc393b57f4 100644
--- a/arch/csky/kernel/Makefile
+++ b/arch/csky/kernel/Makefile
@@ -1,5 +1,6 @@
# SPDX-License-Identifier: GPL-2.0-only
-extra-y := head.o vmlinux.lds
+extra-y := head.o
+targets += vmlinux.lds

obj-y += entry.o atomic.o signal.o traps.o irq.o time.o vdso.o
obj-y += power.o syscall.o syscall_table.o setup.o
diff --git a/arch/h8300/kernel/Makefile b/arch/h8300/kernel/Makefile
index 307aa51576dd..7ef912ee576f 100644
--- a/arch/h8300/kernel/Makefile
+++ b/arch/h8300/kernel/Makefile
@@ -3,7 +3,7 @@
# Makefile for the linux kernel.
#

-extra-y := vmlinux.lds
+targets += vmlinux.lds

obj-y := process.o traps.o ptrace.o \
signal.o setup.o syscalls.o \
diff --git a/arch/hexagon/kernel/Makefile b/arch/hexagon/kernel/Makefile
index fae3dce32fde..9765301d2672 100644
--- a/arch/hexagon/kernel/Makefile
+++ b/arch/hexagon/kernel/Makefile
@@ -1,5 +1,6 @@
# SPDX-License-Identifier: GPL-2.0
-extra-y := head.o vmlinux.lds
+extra-y := head.o
+targets += vmlinux.lds

obj-$(CONFIG_SMP) += smp.o

diff --git a/arch/ia64/kernel/Makefile b/arch/ia64/kernel/Makefile
index c89bd5f8cbf8..d430230b21af 100644
--- a/arch/ia64/kernel/Makefile
+++ b/arch/ia64/kernel/Makefile
@@ -7,7 +7,8 @@ ifdef CONFIG_DYNAMIC_FTRACE
CFLAGS_REMOVE_ftrace.o = -pg
endif

-extra-y := head.o vmlinux.lds
+extra-y := head.o
+targets += vmlinux.lds

obj-y := entry.o efi.o efi_stub.o gate-data.o fsys.o ia64_ksyms.o irq.o irq_ia64.o \
irq_lsapic.o ivt.o pal.o patch.o process.o ptrace.o sal.o \
diff --git a/arch/m68k/kernel/Makefile b/arch/m68k/kernel/Makefile
index dbac7f8743fc..b054f4198e63 100644
--- a/arch/m68k/kernel/Makefile
+++ b/arch/m68k/kernel/Makefile
@@ -12,7 +12,7 @@ extra-$(CONFIG_HP300) := head.o
extra-$(CONFIG_Q40) := head.o
extra-$(CONFIG_SUN3X) := head.o
extra-$(CONFIG_SUN3) := sun3-head.o
-extra-y += vmlinux.lds
+targets += vmlinux.lds

obj-y := entry.o irq.o module.o process.o ptrace.o
obj-y += setup.o signal.o sys_m68k.o syscalltable.o time.o traps.o
diff --git a/arch/microblaze/kernel/Makefile b/arch/microblaze/kernel/Makefile
index 15a20eb814ce..cdf98cbfcce9 100644
--- a/arch/microblaze/kernel/Makefile
+++ b/arch/microblaze/kernel/Makefile
@@ -12,7 +12,8 @@ CFLAGS_REMOVE_ftrace.o = -pg
CFLAGS_REMOVE_process.o = -pg
endif

-extra-y := head.o vmlinux.lds
+extra-y := head.o
+targets += vmlinux.lds

obj-y += dma.o exceptions.o \
hw_exception_handler.o irq.o \
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index b4a57f1de772..f2e82faa06c4 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -3,7 +3,8 @@
# Makefile for the Linux/MIPS kernel.
#

-extra-y := head.o vmlinux.lds
+extra-y := head.o
+targets += vmlinux.lds

obj-y += branch.o cmpxchg.o elf.o entry.o genex.o idle.o irq.o \
process.o prom.o ptrace.o reset.o setup.o signal.o \
diff --git a/arch/nds32/kernel/Makefile b/arch/nds32/kernel/Makefile
index 394df3f6442c..ec061f18f00f 100644
--- a/arch/nds32/kernel/Makefile
+++ b/arch/nds32/kernel/Makefile
@@ -19,7 +19,8 @@ obj-$(CONFIG_OF) += devtree.o
obj-$(CONFIG_CACHE_L2) += atl2c.o
obj-$(CONFIG_PERF_EVENTS) += perf_event_cpu.o
obj-$(CONFIG_PM) += pm.o sleep.o
-extra-y := head.o vmlinux.lds
+extra-y := head.o
+targets += vmlinux.lds

CFLAGS_fpu.o += -mext-fpu-sp -mext-fpu-dp

diff --git a/arch/nios2/kernel/Makefile b/arch/nios2/kernel/Makefile
index 0b645e1e3158..1ec4be68462e 100644
--- a/arch/nios2/kernel/Makefile
+++ b/arch/nios2/kernel/Makefile
@@ -4,7 +4,7 @@
#

extra-y += head.o
-extra-y += vmlinux.lds
+targets += vmlinux.lds

obj-y += cpuinfo.o
obj-y += entry.o
diff --git a/arch/openrisc/kernel/Makefile b/arch/openrisc/kernel/Makefile
index 2d172e79f58d..6be5c65ea3e9 100644
--- a/arch/openrisc/kernel/Makefile
+++ b/arch/openrisc/kernel/Makefile
@@ -3,7 +3,8 @@
# Makefile for the linux kernel.
#

-extra-y := head.o vmlinux.lds
+extra-y := head.o
+targets += vmlinux.lds

obj-y := setup.o or32_ksyms.o process.o dma.o \
traps.o time.o irq.o entry.o ptrace.o signal.o \
diff --git a/arch/parisc/kernel/Makefile b/arch/parisc/kernel/Makefile
index 068d90950d93..31e5109251aa 100644
--- a/arch/parisc/kernel/Makefile
+++ b/arch/parisc/kernel/Makefile
@@ -3,7 +3,8 @@
# Makefile for arch/parisc/kernel
#

-extra-y := head.o vmlinux.lds
+extra-y := head.o
+targets += vmlinux.lds

obj-y := cache.o pacache.o setup.o pdt.o traps.o time.o irq.o \
pa7300lc.o syscall.o entry.o sys_parisc.o firmware.o \
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 6084fa499aa3..c7576957f05a 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -101,7 +101,7 @@ extra-$(CONFIG_40x) := head_40x.o
extra-$(CONFIG_44x) := head_44x.o
extra-$(CONFIG_FSL_BOOKE) := head_fsl_booke.o
extra-$(CONFIG_PPC_8xx) := head_8xx.o
-extra-y += vmlinux.lds
+targets += vmlinux.lds

obj-$(CONFIG_RELOCATABLE) += reloc_$(BITS).o

diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index f6caf4d9ca15..fcebdb13bcda 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -9,7 +9,7 @@ CFLAGS_REMOVE_patch.o = -pg
endif

extra-y += head.o
-extra-y += vmlinux.lds
+targets += vmlinux.lds

obj-y += soc.o
obj-y += cpu.o
diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile
index c97818a382f3..15d3ee771f22 100644
--- a/arch/s390/kernel/Makefile
+++ b/arch/s390/kernel/Makefile
@@ -42,7 +42,8 @@ obj-y += entry.o reipl.o relocate_kernel.o kdebugfs.o alternative.o
obj-y += nospec-branch.o ipl_vmparm.o machine_kexec_reloc.o unwind_bc.o
obj-y += smp.o

-extra-y += head64.o vmlinux.lds
+extra-y += head64.o
+targets += vmlinux.lds

obj-$(CONFIG_SYSFS) += nospec-sysfs.o
CFLAGS_REMOVE_nospec-branch.o += $(CC_FLAGS_EXPOLINE)
diff --git a/arch/sh/kernel/Makefile b/arch/sh/kernel/Makefile
index aa0fbc9202b1..e8384889f5f0 100644
--- a/arch/sh/kernel/Makefile
+++ b/arch/sh/kernel/Makefile
@@ -3,7 +3,8 @@
# Makefile for the Linux/SuperH kernel.
#

-extra-y := head_32.o vmlinux.lds
+extra-y := head_32.o
+targets += vmlinux.lds

ifdef CONFIG_FUNCTION_TRACER
# Do not profile debug and lowlevel utilities
diff --git a/arch/sparc/kernel/Makefile b/arch/sparc/kernel/Makefile
index d3a0e072ebe8..685669edb9f8 100644
--- a/arch/sparc/kernel/Makefile
+++ b/arch/sparc/kernel/Makefile
@@ -12,7 +12,7 @@ extra-y := head_$(BITS).o
# Undefine sparc when processing vmlinux.lds - it is used
# And teach CPP we are doing $(BITS) builds (for this case)
CPPFLAGS_vmlinux.lds := -Usparc -m$(BITS)
-extra-y += vmlinux.lds
+targets += vmlinux.lds

ifdef CONFIG_FUNCTION_TRACER
# Do not profile debug and lowlevel utilities
diff --git a/arch/um/kernel/Makefile b/arch/um/kernel/Makefile
index 5aa882011e04..76eea4cc00f0 100644
--- a/arch/um/kernel/Makefile
+++ b/arch/um/kernel/Makefile
@@ -12,7 +12,7 @@ CPPFLAGS_vmlinux.lds := -DSTART=$(LDS_START) \
-DELF_ARCH=$(LDS_ELF_ARCH) \
-DELF_FORMAT=$(LDS_ELF_FORMAT) \
$(LDS_EXTRA)
-extra-y := vmlinux.lds
+targets += vmlinux.lds

obj-y = config.o exec.o exitcode.o irq.o ksyms.o mem.o \
physmem.o process.o ptrace.o reboot.o sigio.o \
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 2ddf08351f0b..7d6fce044f97 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -7,7 +7,7 @@ extra-y := head_$(BITS).o
extra-y += head$(BITS).o
extra-y += ebda.o
extra-y += platform-quirks.o
-extra-y += vmlinux.lds
+targets += vmlinux.lds

CPPFLAGS_vmlinux.lds += -U$(UTS_MACHINE)

diff --git a/arch/xtensa/kernel/Makefile b/arch/xtensa/kernel/Makefile
index d4082c6a121b..79be7bfdf989 100644
--- a/arch/xtensa/kernel/Makefile
+++ b/arch/xtensa/kernel/Makefile
@@ -3,7 +3,8 @@
# Makefile for the Linux/Xtensa kernel.
#

-extra-y := head.o vmlinux.lds
+extra-y := head.o
+targets += vmlinux.lds

obj-y := align.o coprocessor.o entry.o irq.o platform.o process.o \
ptrace.o setup.o signal.o stacktrace.o syscall.o time.o traps.o \
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 3f6bf0ea7c0e..fd573e5ca0b9 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -63,12 +63,14 @@ ifndef obj
$(warning kbuild: Makefile.build is included improperly)
endif

+ifeq ($(filter-out %.mod, $(MAKECMDGOALS)),)
ifeq ($(need-modorder),)
ifneq ($(obj-m),)
$(warning $(patsubst %.o,'%.ko',$(obj-m)) will not be built even though obj-m is specified.)
$(warning You cannot use subdir-y/m to visit a module Makefile. Use obj-y/m instead.)
endif
endif
+endif

# ===========================================================================

--
2.27.0

Next message: Masahiro Yamada: "[PATCH 4/4] kbuild: re-implement CONFIG_TRIM_UNUSED_KSYMS to make it work in one-pass"
Previous message: Masahiro Yamada: "[PATCH 0/4] kbuild: build speed improvment of CONFIG_TRIM_UNUSED_KSYMS"
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Next in thread: Masahiro Yamada: "[PATCH 4/4] kbuild: re-implement CONFIG_TRIM_UNUSED_KSYMS to make it work in one-pass"
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