Commit 3a166fc2 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Masahiro Yamada
Browse files

kbuild: handle libs-y archives separately from built-in.o archives 



The thin archives build currently puts all lib.a and built-in.o
files together and links them with --whole-archive.

This works because thin archives can recursively refer to thin
archives. However some architectures include libgcc.a, which may
not be a thin archive, or it may not be constructed with the "P"
option, in which case its contents do not get linked correctly.

So don't pull .a libs into the root built-in.o archive. These
libs should already have symbol tables and indexes built, so they
can be direct linker inputs. Move them out of the --whole-archive
option, which restore the conditional linking behaviour of lib.a
to thin archives builds.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
parent 9a6cfca4

Documentation/kbuild/kbuild.txt

+6 −2
Original line number Diff line number Diff line
@@ -236,5 +236,9 @@ Files specified with KBUILD_VMLINUX_INIT are linked first. 
KBUILD_VMLINUX_MAIN

--------------------------------------------------

All object files for the main part of vmlinux.

KBUILD_VMLINUX_INIT and KBUILD_VMLINUX_MAIN together specify

all the object files used to link vmlinux.
 


KBUILD_VMLINUX_LIBS

--------------------------------------------------

All .a "lib" files for vmlinux.

KBUILD_VMLINUX_INIT, KBUILD_VMLINUX_MAIN, and KBUILD_VMLINUX_LIBS together

specify all the object files used to link vmlinux.

Makefile

+4 −4
Original line number Diff line number Diff line
@@ -952,19 +952,19 @@ core-y := $(patsubst %/, %/built-in.o, $(core-y)) 
drivers-y	:= $(patsubst %/, %/built-in.o, $(drivers-y))

net-y		:= $(patsubst %/, %/built-in.o, $(net-y))

libs-y1		:= $(patsubst %/, %/lib.a, $(libs-y))

libs-y2		:= $(patsubst %/, %/built-in.o, $(libs-y))

libs-y		:= $(libs-y1) $(libs-y2)

libs-y2		:= $(filter-out %.a, $(patsubst %/, %/built-in.o, $(libs-y)))

virt-y		:= $(patsubst %/, %/built-in.o, $(virt-y))



# Externally visible symbols (used by link-vmlinux.sh)

export KBUILD_VMLINUX_INIT := $(head-y) $(init-y)

export KBUILD_VMLINUX_MAIN := $(core-y) $(libs-y) $(drivers-y) $(net-y) $(virt-y)

export KBUILD_VMLINUX_MAIN := $(core-y) $(libs-y2) $(drivers-y) $(net-y) $(virt-y)

export KBUILD_VMLINUX_LIBS := $(libs-y1)

export KBUILD_LDS          := arch/$(SRCARCH)/kernel/vmlinux.lds

export LDFLAGS_vmlinux

# used by scripts/pacmage/Makefile

export KBUILD_ALLDIRS := $(sort $(filter-out arch/%,$(vmlinux-alldirs)) arch Documentation include samples scripts tools)



vmlinux-deps := $(KBUILD_LDS) $(KBUILD_VMLINUX_INIT) $(KBUILD_VMLINUX_MAIN)

vmlinux-deps := $(KBUILD_LDS) $(KBUILD_VMLINUX_INIT) $(KBUILD_VMLINUX_MAIN) $(KBUILD_VMLINUX_LIBS)



# Include targets which we want to execute sequentially if the rest of the

# kernel build went well. If CONFIG_TRIM_UNUSED_KSYMS is set, this might be

scripts/link-vmlinux.sh

+36 −9
Original line number Diff line number Diff line
@@ -3,9 +3,12 @@ 
# link vmlinux

#

# vmlinux is linked from the objects selected by $(KBUILD_VMLINUX_INIT) and

# $(KBUILD_VMLINUX_MAIN). Most are built-in.o files from top-level directories

# in the kernel tree, others are specified in arch/$(ARCH)/Makefile.

# Ordering when linking is important, and $(KBUILD_VMLINUX_INIT) must be first.

# $(KBUILD_VMLINUX_MAIN) and $(KBUILD_VMLINUX_LIBS). Most are built-in.o files

# from top-level directories in the kernel tree, others are specified in

# arch/$(ARCH)/Makefile. Ordering when linking is important, and

# $(KBUILD_VMLINUX_INIT) must be first. $(KBUILD_VMLINUX_LIBS) are archives

# which are linked conditionally (not within --whole-archive), and do not

# require symbol indexes added.

#

# vmlinux

#   ^
@@ -16,6 +19,9 @@ 
#   +--< $(KBUILD_VMLINUX_MAIN)

#   |    +--< drivers/built-in.o mm/built-in.o + more

#   |

#   +--< $(KBUILD_VMLINUX_LIBS)

#   |    +--< lib/lib.a + more

#   |

#   +-< ${kallsymso} (see description in KALLSYMS section)

#

# vmlinux version (uname -v) cannot be updated during normal
@@ -37,9 +43,10 @@ info() 
	fi

}



# Thin archive build here makes a final archive with

# symbol table and indexes from vmlinux objects, which can be

# used as input to linker.

# Thin archive build here makes a final archive with symbol table and indexes

# from vmlinux objects INIT and MAIN, which can be used as input to linker.

# KBUILD_VMLINUX_LIBS archives should already have symbol table and indexes

# added.

#

# Traditional incremental style of link does not require this step

#
@@ -63,11 +70,17 @@ modpost_link() 
	local objects



	if [ -n "${CONFIG_THIN_ARCHIVES}" ]; then

		objects="--whole-archive built-in.o --no-whole-archive"

		objects="--whole-archive				\

			built-in.o					\

			--no-whole-archive				\

			--start-group					\

			${KBUILD_VMLINUX_LIBS}				\

			--end-group"

	else

		objects="${KBUILD_VMLINUX_INIT}				\

			--start-group					\

			${KBUILD_VMLINUX_MAIN}				\

			${KBUILD_VMLINUX_LIBS}				\

			--end-group"

	fi

	${LD} ${LDFLAGS} -r -o ${1} ${objects}
@@ -83,11 +96,18 @@ vmlinux_link() 


	if [ "${SRCARCH}" != "um" ]; then

		if [ -n "${CONFIG_THIN_ARCHIVES}" ]; then

			objects="--whole-archive built-in.o ${1} --no-whole-archive"

			objects="--whole-archive			\

				built-in.o				\

				--no-whole-archive			\

				--start-group				\

				${KBUILD_VMLINUX_LIBS}			\

				--end-group				\

				${1}"

		else

			objects="${KBUILD_VMLINUX_INIT}			\

				--start-group				\

				${KBUILD_VMLINUX_MAIN}			\

				${KBUILD_VMLINUX_LIBS}			\

				--end-group				\

				${1}"

		fi
@@ -96,11 +116,18 @@ vmlinux_link() 
			-T ${lds} ${objects}

	else

		if [ -n "${CONFIG_THIN_ARCHIVES}" ]; then

			objects="-Wl,--whole-archive built-in.o ${1} -Wl,--no-whole-archive"

			objects="-Wl,--whole-archive			\

				built-in.o				\

				-Wl,--no-whole-archive			\

				-Wl,--start-group			\

				${KBUILD_VMLINUX_LIBS}			\

				-Wl,--end-group				\

				${1}"

		else

			objects="${KBUILD_VMLINUX_INIT}			\

				-Wl,--start-group			\

				${KBUILD_VMLINUX_MAIN}			\

				${KBUILD_VMLINUX_LIBS}			\

				-Wl,--end-group				\

				${1}"

		fi

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