mirrors
/
linux-stable
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
1
0
Fork 0
Code Issues Releases Wiki Activity

kbuild: build init/built-in.a just once 

Kbuild builds init/built-in.a twice; first during the ordinary
directory descending, second from scripts/link-vmlinux.sh.

We do this because UTS_VERSION contains the build version and the
timestamp. We cannot update it during the normal directory traversal
since we do not yet know if we need to update vmlinux. UTS_VERSION is
temporarily calculated, but omitted from the update check. Otherwise,
vmlinux would be rebuilt every time.

When Kbuild results in running link-vmlinux.sh, it increments the
version number in the .version file and takes the timestamp at that
time to really fix UTS_VERSION.

However, updating the same file twice is a footgun. To avoid nasty
timestamp issues, all build artifacts that depend on init/built-in.a
are atomically generated in link-vmlinux.sh, where some of them do not
need rebuilding.

To fix this issue, this commit changes as follows:

[1] Split UTS_VERSION out to include/generated/utsversion.h from
    include/generated/compile.h

    include/generated/utsversion.h is generated just before the
    vmlinux link. It is generated under include/generated/ because
    some decompressors (s390, x86) use UTS_VERSION.

[2] Split init_uts_ns and linux_banner out to init/version-timestamp.c
    from init/version.c

    init_uts_ns and linux_banner contain UTS_VERSION. During the ordinary
    directory descending, they are compiled with __weak and used to
    determine if vmlinux needs relinking. Just before the vmlinux link,
    they are compiled without __weak to embed the real version and
    timestamp.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Masahiro Yamada 2022-08-28 11:39:53 +09:00
parent 561daaacb4
commit 2df8220cc5
12 changed files with 120 additions and 131 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/powerpc/boot/wrapper
View File

@ -433,7 +433,7 @@ fi
# Extract kernel version information, some platforms want to include
# it in the image header
version=`${CROSS}strings "$kernel" | grep '^Linux version [-0-9.]' | \
cut -d' ' -f3`
head -n1 | cut -d' ' -f3`
if [ -n "$version" ]; then
uboot_version="-n Linux-$version"
fi

1
arch/s390/boot/version.c
View File

@ -1,4 +1,5 @@
// SPDX-License-Identifier: GPL-2.0
#include <generated/utsversion.h>
#include <generated/utsrelease.h>
#include <generated/compile.h>
#include "boot.h"

1
arch/x86/boot/compressed/kaslr.c
View File

@ -29,6 +29,7 @@
#include <linux/uts.h>
#include <linux/utsname.h>
#include <linux/ctype.h>
#include <generated/utsversion.h>
#include <generated/utsrelease.h>
#define _SETUP

1
arch/x86/boot/version.c
View File

@ -11,6 +11,7 @@
*/
#include "boot.h"
#include <generated/utsversion.h>
#include <generated/utsrelease.h>
#include <generated/compile.h>

2
init/.gitignore vendored Normal file
View File

@ -0,0 +1,2 @@
# SPDX-License-Identifier: GPL-2.0-only
/utsversion-tmp.h

55
init/Makefile
View File

@ -19,20 +19,49 @@ mounts-y := do_mounts.o
mounts-$(CONFIG_BLK_DEV_RAM) += do_mounts_rd.o
mounts-$(CONFIG_BLK_DEV_INITRD) += do_mounts_initrd.o
# dependencies on generated files need to be listed explicitly
$(obj)/version.o: include/generated/compile.h
#
# UTS_VERSION
#
# compile.h changes depending on hostname, generation number, etc,
# so we regenerate it always.
# mkcompile_h will make sure to only update the
# actual file if its content has changed.
smp-flag-$(CONFIG_SMP) := SMP
preempt-flag-$(CONFIG_PREEMPT_BUILD) := PREEMPT
preempt-flag-$(CONFIG_PREEMPT_DYNAMIC) := PREEMPT_DYNAMIC
preempt-flag-$(CONFIG_PREEMPT_RT) := PREEMPT_RT
quiet_cmd_compile.h = CHK $@
cmd_compile.h = \
$(CONFIG_SHELL) $(srctree)/scripts/mkcompile_h $@ \
"$(UTS_MACHINE)" "$(CONFIG_SMP)" "$(CONFIG_PREEMPT_BUILD)" \
"$(CONFIG_PREEMPT_DYNAMIC)" "$(CONFIG_PREEMPT_RT)" \
"$(CONFIG_CC_VERSION_TEXT)" "$(LD)"
build-version = $(or $(KBUILD_BUILD_VERSION), $(build-version-auto))
build-timestamp = $(or $(KBUILD_BUILD_TIMESTAMP), $(build-timestamp-auto))
# Maximum length of UTS_VERSION is 64 chars
filechk_uts_version = \
utsver=$$(echo '$(pound)'"$(build-version)" $(smp-flag-y) $(preempt-flag-y) "$(build-timestamp)" | cut -b -64); \
echo '$(pound)'define UTS_VERSION \""$${utsver}"\"
#
# Build version.c with temporary UTS_VERSION
#
$(obj)/utsversion-tmp.h: FORCE
$(call filechk,uts_version)
clean-files += utsversion-tmp.h
$(obj)/version.o: include/generated/compile.h $(obj)/utsversion-tmp.h
CFLAGS_version.o := -include $(obj)/utsversion-tmp.h
filechk_compile.h = $(srctree)/scripts/mkcompile_h \
"$(UTS_MACHINE)" "$(CONFIG_CC_VERSION_TEXT)" "$(LD)"
include/generated/compile.h: FORCE
$(call cmd,compile.h)
$(call filechk,compile.h)
#
# Build version-timestamp.c with final UTS_VERSION
#
include/generated/utsversion.h: build-version-auto = $(shell $(srctree)/$(src)/build-version)
include/generated/utsversion.h: build-timestamp-auto = $(shell LC_ALL=C date)
include/generated/utsversion.h: FORCE
$(call filechk,uts_version)
$(obj)/version-timestamp.o: include/generated/utsversion.h
CFLAGS_version-timestamp.o := -include include/generated/utsversion.h

10
init/build-version Executable file
View File

@ -0,0 +1,10 @@
#!/bin/sh
# SPDX-License-Identifier: GPL-2.0-only
prev_ver=$(cat .version 2>/dev/null) &&
ver=$(expr ${prev_ver} + 1 2>/dev/null) ||
ver=1
echo ${ver} > .version
echo ${ver}

31
init/version-timestamp.c Normal file
View File

@ -0,0 +1,31 @@
// SPDX-License-Identifier: GPL-2.0-only
#include <generated/compile.h>
#include <generated/utsrelease.h>
#include <linux/version.h>
#include <linux/proc_ns.h>
#include <linux/refcount.h>
#include <linux/uts.h>
#include <linux/utsname.h>
struct uts_namespace init_uts_ns = {
.ns.count = REFCOUNT_INIT(2),
.name = {
.sysname = UTS_SYSNAME,
.nodename = UTS_NODENAME,
.release = UTS_RELEASE,
.version = UTS_VERSION,
.machine = UTS_MACHINE,
.domainname = UTS_DOMAINNAME,
},
.user_ns = &init_user_ns,
.ns.inum = PROC_UTS_INIT_INO,
#ifdef CONFIG_UTS_NS
.ns.ops = &utsns_operations,
#endif
};
/* FIXED STRINGS! Don't touch! */
const char linux_banner[] =
"Linux version " UTS_RELEASE " (" LINUX_COMPILE_BY "@"
LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION "\n";

36
init/version.c
View File

@ -18,24 +18,6 @@
#include <generated/utsrelease.h>
#include <linux/proc_ns.h>
struct uts_namespace init_uts_ns = {
.ns.count = REFCOUNT_INIT(2),
.name = {
.sysname = UTS_SYSNAME,
.nodename = UTS_NODENAME,
.release = UTS_RELEASE,
.version = UTS_VERSION,
.machine = UTS_MACHINE,
.domainname = UTS_DOMAINNAME,
},
.user_ns = &init_user_ns,
.ns.inum = PROC_UTS_INIT_INO,
#ifdef CONFIG_UTS_NS
.ns.ops = &utsns_operations,
#endif
};
EXPORT_SYMBOL_GPL(init_uts_ns);
static int __init early_hostname(char *arg)
{
size_t bufsize = sizeof(init_uts_ns.name.nodename);
@ -51,11 +33,6 @@ static int __init early_hostname(char *arg)
}
early_param("hostname", early_hostname);
/* FIXED STRINGS! Don't touch! */
const char linux_banner[] =
"Linux version " UTS_RELEASE " (" LINUX_COMPILE_BY "@"
LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION "\n";
const char linux_proc_banner[] =
"%s version %s"
" (" LINUX_COMPILE_BY "@" LINUX_COMPILE_HOST ")"
@ -63,3 +40,16 @@ const char linux_proc_banner[] =
BUILD_SALT;
BUILD_LTO_INFO;
/*
* init_uts_ns and linux_banner contain the build version and timestamp,
* which are really fixed at the very last step of build process.
* They are compiled with __weak first, and without __weak later.
*/
struct uts_namespace init_uts_ns __weak;
const char linux_banner[] __weak;
#include "version-timestamp.c"
EXPORT_SYMBOL_GPL(init_uts_ns);

6
kernel/gen_kheaders.sh
View File

@ -31,8 +31,8 @@ if [ "$building_out_of_srctree" ]; then
fi
all_dirs="$all_dirs $dir_list"
# include/generated/compile.h is ignored because it is touched even when none
# of the source files changed.
# include/generated/utsversion.h is ignored because it is generated after this
# script is executed. (utsversion.h is unneeded for kheaders)
#
# When Kconfig regenerates include/generated/autoconf.h, its timestamp is
# updated, but the contents might be still the same. When any CONFIG option is
@ -42,7 +42,7 @@ all_dirs="$all_dirs $dir_list"
#
# Ignore them for md5 calculation to avoid pointless regeneration.
headers_md5="$(find $all_dirs -name "*.h" |
grep -v "include/generated/compile.h" |
grep -v "include/generated/utsversion.h" |
grep -v "include/generated/autoconf.h" |
xargs ls -l | md5sum | cut -d ' ' -f1)"

17
scripts/link-vmlinux.sh
View File

@ -75,6 +75,8 @@ vmlinux_link()
objs="${objs} .vmlinux.export.o"
fi
objs="${objs} init/version-timestamp.o"
if [ "${SRCARCH}" = "um" ]; then
wl=-Wl,
ld="${CC}"
@ -213,19 +215,6 @@ if [ "$1" = "clean" ]; then
exit 0
fi
# Update version
info GEN .version
if [ -r .version ]; then
VERSION=$(expr 0$(cat .version) + 1)
echo $VERSION > .version
else
rm -f .version
echo 1 > .version
fi;
# final build of init/
${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1
#link vmlinux.o
${MAKE} -f "${srctree}/scripts/Makefile.vmlinux_o"
@ -260,6 +249,8 @@ if is_enabled CONFIG_MODULES; then
${MAKE} -f "${srctree}/scripts/Makefile.vmlinux" .vmlinux.export.o
fi
${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
btf_vmlinux_bin_o=""
if is_enabled CONFIG_DEBUG_INFO_BTF; then
btf_vmlinux_bin_o=.btf.vmlinux.bin.o

89
scripts/mkcompile_h
View File

@ -1,14 +1,9 @@
#!/bin/sh
# SPDX-License-Identifier: GPL-2.0
TARGET=$1
ARCH=$2
SMP=$3
PREEMPT=$4
PREEMPT_DYNAMIC=$5
PREEMPT_RT=$6
CC_VERSION="$7"
LD=$8
UTS_MACHINE=$1
CC_VERSION="$2"
LD=$3
# Do not expand names
set -f
@ -17,17 +12,6 @@ set -f
LC_ALL=C
export LC_ALL
if [ -z "$KBUILD_BUILD_VERSION" ]; then
VERSION=$(cat .version 2>/dev/null || echo 1)
else
VERSION=$KBUILD_BUILD_VERSION
fi
if [ -z "$KBUILD_BUILD_TIMESTAMP" ]; then
TIMESTAMP=`date`
else
TIMESTAMP=$KBUILD_BUILD_TIMESTAMP
fi
if test -z "$KBUILD_BUILD_USER"; then
LINUX_COMPILE_BY=$(whoami | sed 's/\\/\\\\/')
else
@ -39,63 +23,12 @@ else
LINUX_COMPILE_HOST=$KBUILD_BUILD_HOST
fi
UTS_VERSION="#$VERSION"
CONFIG_FLAGS=""
if [ -n "$SMP" ] ; then CONFIG_FLAGS="SMP"; fi
LD_VERSION=$($LD -v | head -n1 | sed 's/(compatible with [^)]*)//' \
| sed 's/[[:space:]]*$//')
if [ -n "$PREEMPT_RT" ] ; then
CONFIG_FLAGS="$CONFIG_FLAGS PREEMPT_RT"
elif [ -n "$PREEMPT_DYNAMIC" ] ; then
CONFIG_FLAGS="$CONFIG_FLAGS PREEMPT_DYNAMIC"
elif [ -n "$PREEMPT" ] ; then
CONFIG_FLAGS="$CONFIG_FLAGS PREEMPT"
fi
# Truncate to maximum length
UTS_LEN=64
UTS_VERSION="$(echo $UTS_VERSION $CONFIG_FLAGS $TIMESTAMP | cut -b -$UTS_LEN)"
# Generate a temporary compile.h
{ echo /\* This file is auto generated, version $VERSION \*/
if [ -n "$CONFIG_FLAGS" ] ; then echo "/* $CONFIG_FLAGS */"; fi
echo \#define UTS_MACHINE \"$ARCH\"
echo \#define UTS_VERSION \"$UTS_VERSION\"
printf '#define LINUX_COMPILE_BY "%s"\n' "$LINUX_COMPILE_BY"
echo \#define LINUX_COMPILE_HOST \"$LINUX_COMPILE_HOST\"
LD_VERSION=$($LD -v | head -n1 | sed 's/(compatible with [^)]*)//' \
| sed 's/[[:space:]]*$//')
printf '#define LINUX_COMPILER "%s"\n' "$CC_VERSION, $LD_VERSION"
} > .tmpcompile
# Only replace the real compile.h if the new one is different,
# in order to preserve the timestamp and avoid unnecessary
# recompilations.
# We don't consider the file changed if only the date/time changed,
# unless KBUILD_BUILD_TIMESTAMP was explicitly set (e.g. for
# reproducible builds with that value referring to a commit timestamp).
# A kernel config change will increase the generation number, thus
# causing compile.h to be updated (including date/time) due to the
# changed comment in the
# first line.
if [ -z "$KBUILD_BUILD_TIMESTAMP" ]; then
IGNORE_PATTERN="UTS_VERSION"
else
IGNORE_PATTERN="NOT_A_PATTERN_TO_BE_MATCHED"
fi
if [ -r $TARGET ] && \
grep -v $IGNORE_PATTERN $TARGET > .tmpver.1 && \
grep -v $IGNORE_PATTERN .tmpcompile > .tmpver.2 && \
cmp -s .tmpver.1 .tmpver.2; then
rm -f .tmpcompile
else
echo " UPD $TARGET"
mv -f .tmpcompile $TARGET
fi
rm -f .tmpver.1 .tmpver.2
cat <<EOF
#define UTS_MACHINE "${UTS_MACHINE}"
#define LINUX_COMPILE_BY "${LINUX_COMPILE_BY}"
#define LINUX_COMPILE_HOST "${LINUX_COMPILE_HOST}"
#define LINUX_COMPILER "${CC_VERSION}, ${LD_VERSION}"
EOF