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Date: Fri, 2 Jun 2017 22:54:54 +1000
From: Nicholas Piggin <npiggin@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Nicholas Piggin <npiggin@...il.com>
Subject: [PATCH] kbuild: switch to thin archives
Switch from incremental build to thin archives for packaging built-in.o.
binutils version must be bumped to 2.20. Proposed patch for 4.13.
Signed-off-by: Nicholas Piggin <npiggin@...il.com>
---
Documentation/process/changes.rst | 9 ++++-----
Makefile | 3 +++
arch/Kconfig | 6 ------
arch/powerpc/Kconfig | 8 --------
scripts/Makefile.build | 27 ++++++-------------------
scripts/link-vmlinux.sh | 42 +++++++++------------------------------
6 files changed, 22 insertions(+), 73 deletions(-)
diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
index e25d63f8c0da..56fd0687bd4a 100644
--- a/Documentation/process/changes.rst
+++ b/Documentation/process/changes.rst
@@ -31,7 +31,7 @@ you probably needn't concern yourself with isdn4k-utils.
====================== =============== ========================================
GNU C 3.2 gcc --version
GNU make 3.81 make --version
-binutils 2.12 ld -v
+binutils 2.20 ld -v
util-linux 2.10o fdformat --version
module-init-tools 0.9.10 depmod -V
e2fsprogs 1.41.4 e2fsck -V
@@ -75,10 +75,9 @@ You will need GNU make 3.81 or later to build the kernel.
Binutils
--------
-Linux on IA-32 has recently switched from using ``as86`` to using ``gas`` for
-assembling the 16-bit boot code, removing the need for ``as86`` to compile
-your kernel. This change does, however, mean that you need a recent
-release of binutils.
+The build system has recently switched to using thin archives (`ar T`) rather
+than incremental linking (`ld -r`) for built-in.o intermediate steps. This
+requires binutils 2.20 or newer.
Perl
----
diff --git a/Makefile b/Makefile
index 470bd4d9513a..58658d7a04a0 100644
--- a/Makefile
+++ b/Makefile
@@ -818,6 +818,9 @@ KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
# use the deterministic mode of AR if available
KBUILD_ARFLAGS := $(call ar-option,D)
+# Use thin archives.
+KBUILD_ARFLAGS :=$(KBUILD_ARFLAGS)T
+
include scripts/Makefile.kasan
include scripts/Makefile.extrawarn
include scripts/Makefile.ubsan
diff --git a/arch/Kconfig b/arch/Kconfig
index 6c00e5b00f8b..0a306916968a 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -510,12 +510,6 @@ config CC_STACKPROTECTOR_STRONG
endchoice
-config THIN_ARCHIVES
- bool
- help
- Select this if the architecture wants to use thin archives
- instead of ld -r to create the built-in.o files.
-
config LD_DEAD_CODE_DATA_ELIMINATION
bool
help
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index f7c8f9972f61..80d882a78426 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -472,14 +472,6 @@ config MPROFILE_KERNEL
depends on PPC64 && CPU_LITTLE_ENDIAN
def_bool !DISABLE_MPROFILE_KERNEL
-config USE_THIN_ARCHIVES
- bool "Build the kernel using thin archives"
- default n
- select THIN_ARCHIVES
- help
- Build the kernel using thin archives.
- If you're unsure say N.
-
config IOMMU_HELPER
def_bool PPC64
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 733e044fff8b..6cc07d09fce3 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -436,15 +436,9 @@ $(sort $(subdir-obj-y)): $(subdir-ym) ;
#
ifdef builtin-target
-ifdef CONFIG_THIN_ARCHIVES
- cmd_make_builtin = rm -f $@; $(AR) rcST$(KBUILD_ARFLAGS)
- cmd_make_empty_builtin = rm -f $@; $(AR) rcST$(KBUILD_ARFLAGS)
- quiet_cmd_link_o_target = AR $@
-else
- cmd_make_builtin = $(LD) $(ld_flags) -r -o
- cmd_make_empty_builtin = rm -f $@; $(AR) rcs$(KBUILD_ARFLAGS)
- quiet_cmd_link_o_target = LD $@
-endif
+cmd_make_builtin = rm -f $@; $(AR) rcS$(KBUILD_ARFLAGS)
+cmd_make_empty_builtin = rm -f $@; $(AR) rcS$(KBUILD_ARFLAGS)
+quiet_cmd_link_o_target = AR $@
# If the list of objects to link is empty, just create an empty built-in.o
cmd_link_o_target = $(if $(strip $(obj-y)),\
@@ -477,11 +471,7 @@ $(modorder-target): $(subdir-ym) FORCE
ifdef lib-target
quiet_cmd_link_l_target = AR $@
-ifdef CONFIG_THIN_ARCHIVES
- cmd_link_l_target = rm -f $@; $(AR) rcsT$(KBUILD_ARFLAGS) $@ $(lib-y)
-else
- cmd_link_l_target = rm -f $@; $(AR) rcs$(KBUILD_ARFLAGS) $@ $(lib-y)
-endif
+cmd_link_l_target = rm -f $@; $(AR) rcs$(KBUILD_ARFLAGS) $@ $(lib-y)
$(lib-target): $(lib-y) FORCE
$(call if_changed,link_l_target)
@@ -529,13 +519,8 @@ $($(subst $(obj)/,,$(@:.o=-m)))), $^)
cmd_link_multi-link = $(LD) $(ld_flags) -r -o $@ $(link_multi_deps) $(cmd_secanalysis)
-ifdef CONFIG_THIN_ARCHIVES
- quiet_cmd_link_multi-y = AR $@
- cmd_link_multi-y = rm -f $@; $(AR) rcST$(KBUILD_ARFLAGS) $@ $(link_multi_deps)
-else
- quiet_cmd_link_multi-y = LD $@
- cmd_link_multi-y = $(cmd_link_multi-link)
-endif
+quiet_cmd_link_multi-y = AR $@
+cmd_link_multi-y = rm -f $@; $(AR) rcS$(KBUILD_ARFLAGS) $@ $(link_multi_deps)
quiet_cmd_link_multi-m = LD [M] $@
cmd_link_multi-m = $(cmd_link_multi-link)
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index c80291319cb2..ac0d3b2faa09 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -47,13 +47,11 @@ info()
#
archive_builtin()
{
- if [ -n "${CONFIG_THIN_ARCHIVES}" ]; then
- info AR built-in.o
- rm -f built-in.o;
- ${AR} rcsT${KBUILD_ARFLAGS} built-in.o \
- ${KBUILD_VMLINUX_INIT} \
- ${KBUILD_VMLINUX_MAIN}
- fi
+ info AR built-in.o
+ rm -f built-in.o;
+ ${AR} rcs${KBUILD_ARFLAGS} built-in.o \
+ ${KBUILD_VMLINUX_INIT} \
+ ${KBUILD_VMLINUX_MAIN}
}
# Link of vmlinux.o used for section mismatch analysis
@@ -62,14 +60,8 @@ modpost_link()
{
local objects
- if [ -n "${CONFIG_THIN_ARCHIVES}" ]; then
- objects="--whole-archive built-in.o"
- else
- objects="${KBUILD_VMLINUX_INIT} \
- --start-group \
- ${KBUILD_VMLINUX_MAIN} \
- --end-group"
- fi
+ objects="--whole-archive built-in.o"
+
${LD} ${LDFLAGS} -r -o ${1} ${objects}
}
@@ -82,28 +74,12 @@ vmlinux_link()
local objects
if [ "${SRCARCH}" != "um" ]; then
- if [ -n "${CONFIG_THIN_ARCHIVES}" ]; then
- objects="--whole-archive built-in.o ${1}"
- else
- objects="${KBUILD_VMLINUX_INIT} \
- --start-group \
- ${KBUILD_VMLINUX_MAIN} \
- --end-group \
- ${1}"
- fi
+ objects="--whole-archive built-in.o ${1}"
${LD} ${LDFLAGS} ${LDFLAGS_vmlinux} -o ${2} \
-T ${lds} ${objects}
else
- if [ -n "${CONFIG_THIN_ARCHIVES}" ]; then
- objects="-Wl,--whole-archive built-in.o ${1}"
- else
- objects="${KBUILD_VMLINUX_INIT} \
- -Wl,--start-group \
- ${KBUILD_VMLINUX_MAIN} \
- -Wl,--end-group \
- ${1}"
- fi
+ objects="-Wl,--whole-archive built-in.o ${1}"
${CC} ${CFLAGS_vmlinux} -o ${2} \
-Wl,-T,${lds} \
--
2.11.0
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