Using macros in inline assembly allows us to work around bugs
in GCC's inlining decisions.
Compile macros.S and use it to assemble all C files.
Currently only x86 will use it.
Background:
The inlining pass of GCC doesn't include an assembler, so it's not aware
of basic properties of the generated code, such as its size in bytes,
or that there are such things as discontiuous blocks of code and data
due to the newfangled linker feature called 'sections' ...
Instead GCC uses a lazy and fragile heuristic: it does a linear count of
certain syntactic and whitespace elements in inlined assembly block source
code, such as a count of new-lines and semicolons (!), as a poor substitute
for "code size and complexity".
Unsurprisingly this heuristic falls over and breaks its neck whith certain
common types of kernel code that use inline assembly, such as the frequent
practice of putting useful information into alternative sections.
As a result of this fresh, 20+ years old GCC bug, GCC's inlining decisions
are effectively disabled for inlined functions that make use of such asm()
blocks, because GCC thinks those sections of code are "large" - when in
reality they are often result in just a very low number of machine
instructions.
This absolute lack of inlining provess when GCC comes across such asm()
blocks both increases generated kernel code size and causes performance
overhead, which is particularly noticeable on paravirt kernels, which make
frequent use of these inlining facilities in attempt to stay out of the
way when running on baremetal hardware.
Instead of fixing the compiler we use a workaround: we set an assembly macro
and call it from the inlined assembly block. As a result GCC considers the
inline assembly block as a single instruction. (Which it often isn't but I digress.)
This uglifies and bloats the source code - for example just the refcount
related changes have this impact:
Makefile | 9 +++++++--
arch/x86/Makefile | 7 +++++++
arch/x86/kernel/macros.S | 7 +++++++
scripts/Kbuild.include | 4 +++-
scripts/mod/Makefile | 2 ++
5 files changed, 26 insertions(+), 3 deletions(-)
Yay readability and maintainability, it's not like assembly code is hard to read
and maintain ...
We also hope that GCC will eventually get fixed, but we are not holding
our breath for that. Yet we are optimistic, it might still happen, any decade now.
[ mingo: Wrote new changelog describing the background. ]
Tested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Nadav Amit <namit@vmware.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kbuild@vger.kernel.org
Link: http://lkml.kernel.org/r/20181003213100.189959-3-namit@vmware.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Commit cafa0010cd ("Raise the minimum required gcc version to 4.6")
bumped the minimum GCC version to 4.6 for all architectures.
Remove the workaround code.
It was the only user of cc-if-fullversion. Remove the macro as well.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: linux-kbuild@vger.kernel.org
Link: https://lkml.kernel.org/r/1535348714-25457-1-git-send-email-yamada.masahiro@socionext.com
Commit a0f97e06a4 ("kbuild: enable 'make CFLAGS=...' to add
additional options to CC") renamed CFLAGS to KBUILD_CFLAGS.
Commit 222d394d30 ("kbuild: enable 'make AFLAGS=...' to add
additional options to AS") renamed AFLAGS to KBUILD_AFLAGS.
Commit 06c5040cdb ("kbuild: enable 'make CPPFLAGS=...' to add
additional options to CPP") renamed CPPFLAGS to KBUILD_CPPFLAGS.
For some reason, LDFLAGS was not renamed.
Using a well-known variable like LDFLAGS may result in accidental
override of the variable.
Kbuild generally uses KBUILD_ prefixed variables for the internally
appended options, so here is one more conversion to sanitize the
naming convention.
I did not touch Makefiles under tools/ since the tools build system
is a different world.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
- show clearer error messages where pkg-config is needed, but not
installed
- rename SYMBOL_AUTO to SYMBOL_NO_WRITE to reflect its semantics
- create all necessary directories by Kconfig tool itself instead
of Makefile
- update the .config unconditionally when syncconfig is invoked
- use 'include' directive instead of '-include' where
include/config/{auto,tristate}.conf is mandatory
- do not try to update the .config when running install targets
- add .DELETE_ON_ERROR to delete partially updated files
- misc cleanups and fixes
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Merge tag 'kconfig-v4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kconfig updates from Masahiro Yamada:
- show clearer error messages where pkg-config is needed, but not
installed
- rename SYMBOL_AUTO to SYMBOL_NO_WRITE to reflect its semantics
- create all necessary directories by Kconfig tool itself instead of
Makefile
- update the .config unconditionally when syncconfig is invoked
- use 'include' directive instead of '-include' where
include/config/{auto,tristate}.conf is mandatory
- do not try to update the .config when running install targets
- add .DELETE_ON_ERROR to delete partially updated files
- misc cleanups and fixes
* tag 'kconfig-v4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
kconfig: remove P_ENV property type
kconfig: remove unused sym_get_env_prop() function
kconfig: fix the rule of mainmenu_stmt symbol
init/Kconfig: Use short unix-style option instead of --longname
Kbuild: Makefile.modbuiltin: include auto.conf and tristate.conf mandatory
kbuild: remove auto.conf from prerequisite of phony targets
kbuild: do not update config for 'make kernelrelease'
kbuild: do not update config when running install targets
kbuild: add .DELETE_ON_ERROR special target
kbuild: use 'include' directive to load auto.conf from top Makefile
kconfig: allow all config targets to write auto.conf if missing
kconfig: make syncconfig update .config regardless of sym_change_count
kconfig: create directories needed for syncconfig by itself
kconfig: remove unneeded directory generation from local*config
kconfig: split out useful helpers in confdata.c
kconfig: rename file_write_dep and move it to confdata.c
kconfig: fix typos in description of "choice" in kconfig-language.txt
kconfig: handle format string before calling conf_message_callback()
kconfig: rename SYMBOL_AUTO to SYMBOL_NO_WRITE
kconfig: check for pkg-config on make {menu,n,g,x}config
- verify depmod is installed before modules_install
- support build salt in case build ids must be unique between builds
- allow users to specify additional host compiler flags via HOST*FLAGS,
and rename internal variables to KBUILD_HOST*FLAGS
- update buildtar script to drop vax support, add arm64 support
- update builddeb script for better debarch support
- document the pit-fall of if_changed usage
- fix parallel build of UML with O= option
- make 'samples' target depend on headers_install to fix build errors
- remove deprecated host-progs variable
- add a new coccinelle script for refcount_t vs atomic_t check
- improve double-test coccinelle script
- misc cleanups and fixes
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Merge tag 'kbuild-v4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- verify depmod is installed before modules_install
- support build salt in case build ids must be unique between builds
- allow users to specify additional host compiler flags via HOST*FLAGS,
and rename internal variables to KBUILD_HOST*FLAGS
- update buildtar script to drop vax support, add arm64 support
- update builddeb script for better debarch support
- document the pit-fall of if_changed usage
- fix parallel build of UML with O= option
- make 'samples' target depend on headers_install to fix build errors
- remove deprecated host-progs variable
- add a new coccinelle script for refcount_t vs atomic_t check
- improve double-test coccinelle script
- misc cleanups and fixes
* tag 'kbuild-v4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (41 commits)
coccicheck: return proper error code on fail
Coccinelle: doubletest: reduce side effect false positives
kbuild: remove deprecated host-progs variable
kbuild: make samples really depend on headers_install
um: clean up archheaders recipe
kbuild: add %asm-generic to no-dot-config-targets
um: fix parallel building with O= option
scripts: Add Python 3 support to tracing/draw_functrace.py
builddeb: Add automatic support for sh{3,4}{,eb} architectures
builddeb: Add automatic support for riscv* architectures
builddeb: Add automatic support for m68k architecture
builddeb: Add automatic support for or1k architecture
builddeb: Add automatic support for sparc64 architecture
builddeb: Add automatic support for mips{,64}r6{,el} architectures
builddeb: Add automatic support for mips64el architecture
builddeb: Add automatic support for ppc64 and powerpcspe architectures
builddeb: Introduce functions to simplify kconfig tests in set_debarch
builddeb: Drop check for 32-bit s390
builddeb: Change architecture detection fallback to use dpkg-architecture
builddeb: Skip architecture detection when KBUILD_DEBARCH is set
...
A bunch of good stuff in here:
- Wire up support for qspinlock, replacing our trusty ticket lock code
- Add an IPI to flush_icache_range() to ensure that stale instructions
fetched into the pipeline are discarded along with the I-cache lines
- Support for the GCC "stackleak" plugin
- Support for restartable sequences, plus an arm64 port for the selftest
- Kexec/kdump support on systems booting with ACPI
- Rewrite of our syscall entry code in C, which allows us to zero the
GPRs on entry from userspace
- Support for chained PMU counters, allowing 64-bit event counters to be
constructed on current CPUs
- Ensure scheduler topology information is kept up-to-date with CPU
hotplug events
- Re-enable support for huge vmalloc/IO mappings now that the core code
has the correct hooks to use break-before-make sequences
- Miscellaneous, non-critical fixes and cleanups
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Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 updates from Will Deacon:
"A bunch of good stuff in here. Worth noting is that we've pulled in
the x86/mm branch from -tip so that we can make use of the core
ioremap changes which allow us to put down huge mappings in the
vmalloc area without screwing up the TLB. Much of the positive
diffstat is because of the rseq selftest for arm64.
Summary:
- Wire up support for qspinlock, replacing our trusty ticket lock
code
- Add an IPI to flush_icache_range() to ensure that stale
instructions fetched into the pipeline are discarded along with the
I-cache lines
- Support for the GCC "stackleak" plugin
- Support for restartable sequences, plus an arm64 port for the
selftest
- Kexec/kdump support on systems booting with ACPI
- Rewrite of our syscall entry code in C, which allows us to zero the
GPRs on entry from userspace
- Support for chained PMU counters, allowing 64-bit event counters to
be constructed on current CPUs
- Ensure scheduler topology information is kept up-to-date with CPU
hotplug events
- Re-enable support for huge vmalloc/IO mappings now that the core
code has the correct hooks to use break-before-make sequences
- Miscellaneous, non-critical fixes and cleanups"
* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (90 commits)
arm64: alternative: Use true and false for boolean values
arm64: kexec: Add comment to explain use of __flush_icache_range()
arm64: sdei: Mark sdei stack helper functions as static
arm64, kaslr: export offset in VMCOREINFO ELF notes
arm64: perf: Add cap_user_time aarch64
efi/libstub: Only disable stackleak plugin for arm64
arm64: drop unused kernel_neon_begin_partial() macro
arm64: kexec: machine_kexec should call __flush_icache_range
arm64: svc: Ensure hardirq tracing is updated before return
arm64: mm: Export __sync_icache_dcache() for xen-privcmd
drivers/perf: arm-ccn: Use devm_ioremap_resource() to map memory
arm64: Add support for STACKLEAK gcc plugin
arm64: Add stack information to on_accessible_stack
drivers/perf: hisi: update the sccl_id/ccl_id when MT is supported
arm64: fix ACPI dependencies
rseq/selftests: Add support for arm64
arm64: acpi: fix alignment fault in accessing ACPI
efi/arm: map UEFI memory map even w/o runtime services enabled
efi/arm: preserve early mapping of UEFI memory map longer for BGRT
drivers: acpi: add dependency of EFI for arm64
...
Currently, filechk unconditionally opens the first prerequisite and
redirects it as the stdin of a filechk_* rule. Hence, every target
using $(call filechk,...) must list something as the first prerequisite
even if it is unneeded.
'< $<' is actually unneeded in most cases. Each rule can explicitly
adds it if necessary.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
If Make gets a fatal signal while a shell is executing, it may delete
the target file that the recipe was supposed to update. This is needed
to make sure that it is remade from scratch when Make is next run; if
Make is interrupted after the recipe has begun to write the target file,
it results in an incomplete file whose time stamp is newer than that
of the prerequisites files. Make automatically deletes the incomplete
file on interrupt unless the target is marked .PRECIOUS.
The situation is just the same as when the shell fails for some reasons.
Usually when a recipe line fails, if it has changed the target file at
all, the file is corrupted, or at least it is not completely updated.
Yet the file’s time stamp says that it is now up to date, so the next
time Make runs, it will not try to update that file.
However, Make does not cater to delete the incomplete target file in
this case. We need to add .DELETE_ON_ERROR somewhere in the Makefile
to request it.
scripts/Kbuild.include seems a suitable place to add it because it is
included from almost all sub-makes.
Please note .DELETE_ON_ERROR is not effective for phony targets.
The external module building should never ever touch the kernel tree.
The following recipe fails if include/generated/autoconf.h is missing.
However, include/config/auto.conf is not deleted since it is a phony
target.
PHONY += include/config/auto.conf
include/config/auto.conf:
$(Q)test -e include/generated/autoconf.h -a -e $@ || ( \
echo >&2; \
echo >&2 " ERROR: Kernel configuration is invalid."; \
echo >&2 " include/generated/autoconf.h or $@ are missing.";\
echo >&2 " Run 'make oldconfig && make prepare' on kernel src to fix it."; \
echo >&2 ; \
/bin/false)
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Not all toolchains have the baremetal elf targets, RedHat/Fedora ones
in particular. So, probe for whether it's available and use the previous
(linux) targets if it isn't.
Reported-by: Laura Abbott <labbott@redhat.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Paul Kocialkowski <contact@paulk.fr>
Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>
In preparation for enabling command line CFLAGS, re-name HOSTCFLAGS to
KBUILD_HOSTCFLAGS as the internal use only flags. This should not have
any visible effects.
Signed-off-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
The comment line for addtree says "skip if -I has no parameter".
What it actually does is "drop if -I has no parameter". For example,
if you have the compiler flag '-I foo' (a space between), it will be
converted to 'foo'. This completely changes the meaning.
What we want is, "do nothing" for -I without parameter so that
'-I foo' is kept as-is.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
The kbuild cache was introduced to remember the result of shell
commands, some of which are expensive to compute, such as
$(call cc-option,...).
However, this turned out not so clever as I had first expected.
Actually, it is problematic. For example, "$(CC) -print-file-name"
is cached. If the compiler is updated, the stale search path causes
build error, which is difficult to figure out. Another problem
scenario is cache files could be touched while install targets are
running under the root permission. We can patch them if desired,
but the build infrastructure is getting uglier and uglier.
Now, we are going to move compiler flag tests to the configuration
phase. If this is completed, the result of compiler tests will be
naturally cached in the .config file. We will not have performance
issues of incremental building since this testing only happens at
Kconfig time.
To start this work with a cleaner code base, remove the kbuild
cache first.
Revert the following commits:
Commit 9a234a2e38 ("kbuild: create directory for make cache only when necessary")
Commit e17c400ae1 ("kbuild: shrink .cache.mk when it exceeds 1000 lines")
Commit 4e56207130 ("kbuild: Cache a few more calls to the compiler")
Commit 3298b690b2 ("kbuild: Add a cache for generated variables")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
filechk displays two short logs; CHK for creating a temporary file,
and UPD for really updating the target.
IMHO, the build system can be quiet when the target file has not
been updated.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
I tried building using a freshly built Make (4.2.1-69-g8a731d1), but
already the objtool build broke with
orc_dump.c: In function ‘orc_dump’:
orc_dump.c:106:2: error: ‘elf_getshnum’ is deprecated [-Werror=deprecated-declarations]
if (elf_getshdrnum(elf, &nr_sections)) {
Turns out that with that new Make, the backslash was not removed, so cpp
didn't see a #include directive, grep found nothing, and
-DLIBELF_USE_DEPRECATED was wrongly put in CFLAGS.
Now, that new Make behaviour is documented in their NEWS file:
* WARNING: Backward-incompatibility!
Number signs (#) appearing inside a macro reference or function invocation
no longer introduce comments and should not be escaped with backslashes:
thus a call such as:
foo := $(shell echo '#')
is legal. Previously the number sign needed to be escaped, for example:
foo := $(shell echo '\#')
Now this latter will resolve to "\#". If you want to write makefiles
portable to both versions, assign the number sign to a variable:
C := \#
foo := $(shell echo '$C')
This was claimed to be fixed in 3.81, but wasn't, for some reason.
To detect this change search for 'nocomment' in the .FEATURES variable.
This also fixes up the two make-cmd instances to replace # with $(pound)
rather than with \#. There might very well be other places that need
similar fixup in preparation for whatever future Make release contains
the above change, but at least this builds an x86_64 defconfig with the
new make.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=197847
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
The idea of using fixdep was inspired by Kconfig, but autoksyms
belongs to a different group. So, I want to move those touched
files under include/config/ksym/ to include/ksym/.
The directory include/ksym/ can be removed by 'make clean' because
it is meaningless for the external module building.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Currently, linker options are tested by the coordination of $(CC) and
$(LD) because $(LD) needs some object to link.
As commit 86a9df597c ("kbuild: fix linker feature test macros when
cross compiling with Clang") addressed, we need to make sure $(CC)
and $(LD) agree the underlying architecture of the passed object.
This could be a bit complex when we combine tools from different groups.
For example, we can use clang for $(CC), but we still need to rely on
GCC toolchain for $(LD).
So, I was searching for a way of standalone testing of linker options.
A trick I found is to use '-v'; this not only prints the version string,
but also tests if the given option is recognized.
If a given option is supported,
$ aarch64-linux-gnu-ld -v --fix-cortex-a53-843419
GNU ld (Linaro_Binutils-2017.11) 2.28.2.20170706
$ echo $?
0
If unsupported,
$ aarch64-linux-gnu-ld -v --fix-cortex-a53-843419
GNU ld (crosstool-NG linaro-1.13.1-4.7-2013.04-20130415 - Linaro GCC 2013.04) 2.23.1
aarch64-linux-gnu-ld: unrecognized option '--fix-cortex-a53-843419'
aarch64-linux-gnu-ld: use the --help option for usage information
$ echo $?
1
Gold works likewise.
$ aarch64-linux-gnu-ld.gold -v --fix-cortex-a53-843419
GNU gold (Linaro_Binutils-2017.11 2.28.2.20170706) 1.14
masahiro@pug:~/ref/linux$ echo $?
0
$ aarch64-linux-gnu-ld.gold -v --fix-cortex-a53-999999
GNU gold (Linaro_Binutils-2017.11 2.28.2.20170706) 1.14
aarch64-linux-gnu-ld.gold: --fix-cortex-a53-999999: unknown option
aarch64-linux-gnu-ld.gold: use the --help option for usage information
$ echo $?
1
LLD too.
$ ld.lld -v --gc-sections
LLD 7.0.0 (http://llvm.org/git/lld.git 4a0e4190e74cea19f8a8dc625ccaebdf8b5d1585) (compatible with GNU linkers)
$ echo $?
0
$ ld.lld -v --fix-cortex-a53-843419
LLD 7.0.0 (http://llvm.org/git/lld.git 4a0e4190e74cea19f8a8dc625ccaebdf8b5d1585) (compatible with GNU linkers)
$ echo $?
0
$ ld.lld -v --fix-cortex-a53-999999
ld.lld: error: unknown argument: --fix-cortex-a53-999999
LLD 7.0.0 (http://llvm.org/git/lld.git 4a0e4190e74cea19f8a8dc625ccaebdf8b5d1585) (compatible with GNU linkers)
$ echo $?
1
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
* Use BREs where EREs aren't necessary.
* Pass -E instead of -r to use EREs. This will be standardized in the
next POSIX revision[0]. GNU sed supports this since 4.2 (May 2009),
and busybox since 1.22.0 (Jan 2014).
* Use the [:space:] character class instead of ` \t` in bracket
expressions. In bracket expressions, POSIX says that <backslash> loses
its special meaning, so a conforming implementation cannot expand \t
to <tab>[1].
* In BREs, use interval expressions (\{n,m\}) instead of non-standard
features like \+ and \?.
* Use a loop instead of -s flag.
There are still plenty of other cases of non-standard sed invocations
(use of ERE features in BREs, in-place editing), but this fixes some
core ones.
[0] http://austingroupbugs.net/view.php?id=528
[1] http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_03_05
Signed-off-by: Michael Forney <forney@google.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Currently, the existence of $(dir $(make-cache)) is always checked,
and created if it is missing.
We can avoid unnecessary system calls by some tricks.
[1] If KBUILD_SRC is unset, we are building in the source tree.
The output directory checks can be entirely skipped.
[2] If at least one cache data is found, it means the cache file
was included. Obviously its directory exists. Skip "mkdir -p".
[3] If Makefile does not contain any call of __run-and-store, it will
not create a cache file. No need to create its directory.
[4] The "mkdir -p" should be only invoked by the first call of
__run-and-store
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
I was not seeing my linker flags getting added when using ld-option when
cross compiling with Clang. Upon investigation, this seems to be due to
a difference in how GCC vs Clang handle cross compilation.
GCC is configured at build time to support one backend, that is implicit
when compiling. Clang is explicit via the use of `-target <triple>` and
ships with all supported backends by default.
GNU Make feature test macros that compile then link will always fail
when cross compiling with Clang unless Clang's triple is passed along to
the compiler. For example:
$ clang -x c /dev/null -c -o temp.o
$ aarch64-linux-android/bin/ld -E temp.o
aarch64-linux-android/bin/ld:
unknown architecture of input file `temp.o' is incompatible with
aarch64 output
aarch64-linux-android/bin/ld:
warning: cannot find entry symbol _start; defaulting to
0000000000400078
$ echo $?
1
$ clang -target aarch64-linux-android- -x c /dev/null -c -o temp.o
$ aarch64-linux-android/bin/ld -E temp.o
aarch64-linux-android/bin/ld:
warning: cannot find entry symbol _start; defaulting to 00000000004002e4
$ echo $?
0
This causes conditional checks that invoke $(CC) without the target
triple, then $(LD) on the result, to always fail.
Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
The cache files are only cleaned away by "make clean". If you continue
incremental builds, the cache files will grow up little by little.
It is not a big deal in general use cases because compiler flags do not
change quite often.
However, if you do build-test for various architectures, compilers, and
kernel configurations, you will end up with huge cache files soon.
When the cache file exceeds 1000 lines, shrink it down to 500 by "tail".
The Least Recently Added lines are cut. (not Least Recently Used)
I hope it will work well enough.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
While timing a "no-op" build of the kernel (incrementally building the
kernel even though nothing changed) in the Chrome OS build system I
found that it was much slower than I expected.
Digging into things a bit, I found that quite a bit of the time was
spent invoking the C compiler even though we weren't actually building
anything. Currently in the Chrome OS build system the C compiler is
called through a number of wrappers (one of which is written in
python!) and can take upwards of 100 ms to invoke even if we're not
doing anything difficult, so these invocations of the compiler were
taking a lot of time. Worse the invocations couldn't seem to take
advantage of the multiple cores on my system.
Certainly it seems like we could make the compiler invocations in the
Chrome OS build system faster, but only to a point. Inherently
invoking a program as big as a C compiler is a fairly heavy
operation. Thus even if we can speed the compiler calls it made sense
to track down what was happening.
It turned out that all the compiler invocations were coming from
usages like this in the kernel's Makefile:
KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks,)
Due to the way cc-option and similar statements work the above
contains an implicit call to the C compiler. ...and due to the fact
that we're storing the result in KBUILD_CFLAGS, a simply expanded
variable, the call will happen every time the Makefile is parsed, even
if there are no users of KBUILD_CFLAGS.
Rather than redoing this computation every time, it makes a lot of
sense to cache the result of all of the Makefile's compiler calls just
like we do when we compile a ".c" file to a ".o" file. Conceptually
this is quite a simple idea. ...and since the calls to invoke the
compiler and similar tools are centrally located in the Kbuild.include
file this doesn't even need to be super invasive.
Implementing the cache in a simple-to-use and efficient way is not
quite as simple as it first sounds, though. To get maximum speed we
really want the cache in a format that make can natively understand
and make doesn't really have an ability to load/parse files. ...but
make _can_ import other Makefiles, so the solution is to store the
cache in Makefile format. This requires coming up with a valid/unique
Makefile variable name for each value to be cached, but that's
solvable with some cleverness.
After this change, we'll automatically create a ".cache.mk" file that
will contain our cached variables. We'll load this on each invocation
of make and will avoid recomputing anything that's already in our
cache. The cache is stored in a format that it shouldn't need any
invalidation since anything that might change should affect the "key"
and any old cached value won't be used.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
This is a bunch of trivial fixes and cleanups.
Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
cc-option uses KBUILD_CFLAGS and KBUILD_CPPFLAGS when it determines
whether an option is supported or not. This is fine for options used to
build the kernel itself, however some components like the x86 boot code
use a different set of flags.
Add the new macro __cc-option which is a more generic version of
cc-option with additional parameters. One parameter is the compiler
with which the check should be performed, the other the compiler options
to be used instead KBUILD_C*FLAGS.
Refactor cc-option and hostcc-option to use __cc-option and move
hostcc-option to scripts/Kbuild.include.
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Michal Marek <mmarek@suse.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Documentation/kbuild/makefiles.txt says the change for align options
occurred at GCC 3.0, and Documentation/process/changes.rst says the
minimal supported GCC version is 3.2, so it should be safe to hard-code
-falign* options.
Fix the only user arch/x86/Makefile_32.cpu and remove cc-option-align.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
- Improve Clang support
- Clean up various Makefiles
- Improve build log visibility (objtool, alpha, ia64)
- Improve compiler flag evaluation for better build performance
- Fix GCC version-dependent warning
- Fix genksyms
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Merge tag 'kbuild-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- improve Clang support
- clean up various Makefiles
- improve build log visibility (objtool, alpha, ia64)
- improve compiler flag evaluation for better build performance
- fix GCC version-dependent warning
- fix genksyms
* tag 'kbuild-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (23 commits)
kbuild: dtbinst: remove unnecessary __dtbs_install_prep target
ia64: beatify build log for gate.so and gate-syms.o
alpha: make short build log available for division routines
alpha: merge build rules of division routines
alpha: add $(src)/ rather than $(obj)/ to make source file path
Makefile: evaluate LDFLAGS_BUILD_ID only once
objtool: make it visible in make V=1 output
kbuild: clang: add -no-integrated-as to KBUILD_[AC]FLAGS
kbuild: Add support to generate LLVM assembly files
kbuild: Add better clang cross build support
kbuild: drop -Wno-unknown-warning-option from clang options
kbuild: fix asm-offset generation to work with clang
kbuild: consolidate redundant sed script ASM offset generation
frv: Use OFFSET macro in DEF_*REG()
kbuild: avoid conflict between -ffunction-sections and -pg on gcc-4.7
kbuild: Consolidate header generation from ASM offset information
kbuild: use -Oz instead of -Os when using clang
kbuild, LLVMLinux: Add -Werror to cc-option to support clang
Kbuild: make designated_init attribute fatal
kbuild: drop unneeded patterns '.*.orig' and '.*.rej' from distclean
...
Clang will warn about unknown warnings but will not return false
unless -Werror is set. GCC will return false if an unknown
warning is passed.
Adding -Werror make both compiler behave the same.
[arnd: it turns out we need the same patch for testing whether -ffunction-sections
works right with gcc. I've build tested extensively with this patch
applied, so let's just merge this one now.]
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Behan Webster <behanw@converseincode.com>
Reviewed-by: Jan-Simon Möller <dl9pf@gmx.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
The GCC '-maccumulate-outgoing-args' flag is enabled for most configs,
mostly because of issues which are no longer relevant. For most
configs, and with most recent versions of GCC, it's no longer needed.
Clarify which cases need it, and only enable it for those cases. Also
produce a compile-time error for the ftrace graph + mcount + '-Os' case,
which will otherwise cause runtime failures.
The main benefit of '-maccumulate-outgoing-args' is that it prevents an
ugly prologue for functions which have aligned stacks. But removing the
option also has some benefits: more readable argument saves, smaller
text size, and (presumably) slightly improved performance.
Here are the object size savings for 32-bit and 64-bit defconfig
kernels:
text data bss dec hex filename
10006710 3543328 1773568 15323606 e9d1d6 vmlinux.x86-32.before
9706358 3547424 1773568 15027350 e54c96 vmlinux.x86-32.after
text data bss dec hex filename
10652105 4537576 843776 16033457 f4a6b1 vmlinux.x86-64.before
10639629 4537576 843776 16020981 f475f5 vmlinux.x86-64.after
That comes out to a 3% text size improvement on x86-32 and a 0.1% text
size improvement on x86-64.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170316193133.zrj6gug53766m6nn@treble
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Add a new command cpp_its_S introduced in commit cf2a5e0bb4 ("MIPS:
Support generating Flattened Image Trees (.itb)") to ksym_dep_filter
handler - otherwise a warning is produced during the build of MIPS
platforms (when vmlinux.*.itb target is chosen).
Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com>
Cc: Michal Marek <mmarek@suse.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/15278/
Signed-off-by: James Hogan <james.hogan@imgtec.com>
When building with separate object directories and driver specific
Makefiles that add additional header include paths, Kbuild adjusts
the gcc flags so that we include both the directory in the source
tree and in the object tree.
However, due to another bug I fixed earlier, this did not actually
include the correct directory in the object tree, so we know that
we only really need the source tree here. Also, including the
object tree sometimes causes warnings about nonexisting directories
when the include path only exists in the source.
This changes the logic to only emit the -I argument for the srctree,
not for objects. We still need both $(srctree)/$(src) and $(obj)
though, so I'm adding them manually.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michal Marek <mmarek@suse.com>
When we build with O=objdir and objdir is directly below the source tree,
$(srctree) becomes '..'.
When a Makefile adds a CFLAGS option like -Ipath/to/headers and
we are building with a separate object directory, Kbuild tries to
add two -I options, one for the source tree and one for the object
tree. An absolute path is treated as a special case, and don't add
this one twice. This also normally catches -I$(srctree)/$(src)
as $(srctree) usually is an absolute directory like /home/arnd/linux/.
The combination of the two behaviors however results in an invalid
path name to be included: we get both ../$(src) and ../../$(src),
the latter one pointing outside of the source tree, usually to a
nonexisting directory. Building with 'make W=1' makes this obvious:
cc1: error: ../../arch/arm/mach-s3c24xx/include: No such file or directory [-Werror=missing-include-dirs]
This adds another special case, treating path names starting with ../
like those starting with / so we don't try to prefix that with
$(srctree).
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michal Marek <mmarek@suse.com>
Currently, arg-check is implemented as follows:
arg-check = $(strip $(filter-out $(cmd_$(1)), $(cmd_$@)) \
$(filter-out $(cmd_$@), $(cmd_$(1))) )
This does not care about the order of arguments that appear in
$(cmd_$(1)) and $(cmd_$@). So, if_changed and friends never rebuild
the target if only the argument order is changed. This is a problem
when the link order is changed.
Apparently,
obj-y += foo.o
obj-y += bar.o
and
obj-y += bar.o
obj-y += foo.o
should be distinguished because the link order determines the probe
order of drivers. So, built-in.o should be rebuilt when the order
of objects is changed.
This commit fixes arg-check to compare the old/current commands
including the argument order.
Of course, this change has a side effect; Kbuild will react to the
change of compile option order. For example, "-DFOO -DBAR" and
"-DBAR -DFOO" should give no difference to the build result, but
false positive should be better than false negative.
I am moving space_escape to the top of Kbuild.include just for a
matter of preference. In practical terms, space_escape can be
defined after arg-check because arg-check uses "=" flavor, not ":=".
Having said that, collecting convenient variables in one place makes
sense from the point of readability.
Chaining "%%%SPACE%%%" to "_-_SPACE_-_" is also a matter of taste
at this point. Actually, it can be arbitrary as long as it is an
unlikely used string. The only problem I see in "%%%SPACE%%%" is
that "%" is a special character in "$(patsubst ...)" context. This
commit just uses "$(subst ...)" for arg-check, but I am fixing it now
in case we might want to use it in $(patsubst ...) context in the
future.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
In kernel/cgroup.c there is:
#define SUBSYS(_x) \
DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key); \
DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key); \
EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key); \
EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key);
The expansion of this macro causes multiple EXPORT_SYMBOL_GPL() instances
to appear on the same preprocessor line output, confusing the sed script
expecting only one of them per line. Unfortunately this can't be fixed
nicely in the sed script as sed's regexp can't do non greedy matching.
Fix this by turning any semicolon into a line break before filtering.
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Michal Marek <mmarek@suse.com>
The following renames occurred recently:
cmd_cc_i_c --> cmd_cpp_i_c
cmd_as_s_S --> cmd_cpp_s_S
The respective cc_*_c and as_*_S patterns no longer match the above
therefore additional patterns are needed.
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Michal Marek <mmarek@suse.com>
Like with kconfig options, we now have the ability to compile in and
out individual EXPORT_SYMBOL() declarations based on the content of
include/generated/autoksyms.h. However we don't want the entire
world to be rebuilt whenever that file is touched.
Let's apply the same build dependency trick used for CONFIG_* symbols
where the time stamp of empty files whose paths matching those symbols
is used to trigger fine grained rebuilds. In our case the key is the
symbol name passed to EXPORT_SYMBOL().
However, unlike config options, we cannot just use fixdep to parse
the source code for EXPORT_SYMBOL(ksym) because several variants exist
and parsing them all in a separate tool, and keeping it in synch, is
not trivially maintainable. Furthermore, there are variants such as
EXPORT_SYMBOL_GPL(pci_user_read_config_##size);
that are instanciated via a macro for which we can't easily determine
the actual exported symbol name(s) short of actually running the
preprocessor on them.
Storing the symbol name string in a special ELF section doesn't work
for targets that output assembly or preprocessed source.
So the best way is really to leverage the preprocessor by having it
output actual symbol names anchored by a special sequence that can be
easily filtered out. Then the list of symbols is simply fed to fixdep
to be merged with the other dependencies.
That implies the preprocessor is executed twice for each source file.
A previous attempt relied on a warning pragma for each EXPORT_SYMBOL()
instance that was filtered apart from stderr by the build system with
a sed script during the actual compilation pass. Unfortunately the
preprocessor/compiler diagnostic output isn't stable between versions
and this solution, although more efficient, was deemed too fragile.
Because of the lowercasing performed by fixdep, there might be name
collisions triggering spurious rebuilds for similar symbols. But this
shouldn't be a big issue in practice. (This is the case for CONFIG_*
symbols and I didn't want to be different here, whatever the original
reason for doing so.)
To avoid needless build overhead, the exported symbol name gathering is
performed only when CONFIG_TRIM_UNUSED_KSYMS is selected.
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
The generation and postprocessing of automatic dependency rules is
duplicated in rule_cc_o_c, rule_as_o_S and if_changed_dep. Since
this is not a trivial one-liner action, it is now abstracted under
cmd_and_fixdep to simplify things and make future changes in this area
easier.
In the rule_cc_o_c and rule_as_o_S cases that means the order of some
commands has been altered, namely fixdep and related file manipulations
are executed earlier, but they didn't depend on those commands that now
execute later.
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Under certain conditions, Kbuild shows "... is up to date" where
if_changed or friends are used.
For example, the incremental build of ARM64 Linux shows this message
when the kernel image has not been updated.
$ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-
CHK include/config/kernel.release
CHK include/generated/uapi/linux/version.h
CHK include/generated/utsrelease.h
CHK include/generated/bounds.h
CHK include/generated/timeconst.h
CHK include/generated/asm-offsets.h
CALL scripts/checksyscalls.sh
CHK include/generated/compile.h
CHK kernel/config_data.h
make[1]: `arch/arm64/boot/Image.gz' is up to date.
Building modules, stage 2.
MODPOST 0 modules
The following is the build rule in arch/arm64/boot/Makefile:
$(obj)/Image.gz: $(obj)/Image FORCE
$(call if_changed,gzip)
If the Image.gz is newer than the Image and the command line has not
changed (i.e., $(any-prereq) and $(arg-check) are both empty), the
build rule $(call if_changed,gzip) is evaluated to be empty, then
GNU Make reports the target is up to date. In order to make GNU Make
quiet, we need to give it something to do, for example, "@:". This
should be fixed in the Kbuild core part rather than in each Makefile.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
We cannot detect clang before including the arch Makefile, because that
can set the default cross compiler. We also cannot detect clang after
including the arch Makefile, because powerpc wants to know about clang.
Solve this by using an deferred variable. This costs us a few shell
invocations, but this is only a constant number.
Reported-by: Behan Webster <behanw@converseincode.com>
Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michal Marek <mmarek@suse.com>
Since commit 1329e8cc69 ("modsign: Extract signing cert from
CONFIG_MODULE_SIG_KEY if needed"), the build system has carefully coped
with the signing key being specified as a relative path in either the
source or or the build trees.
However, the actual signing of modules has not worked if the filename
is relative to the source tree.
Fix that by moving the config_filename helper into scripts/Kbuild.include
so that it can be used from elsewhere, and then using it in the top-level
Makefile to find the signing key file.
Kill the intermediate $(MODPUBKEY) and $(MODSECKEY) variables too, while
we're at it. There's no need for them.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
The macro "try-run" can have an argument for each of true and false
cases. Having an argument for the false case of cc-ifversion (and
ld-ifversion) would be useful too.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
The macros cc-version, cc-fullversion and ld-version take no argument.
It is not necessary to add $(call ...) to invoke them.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Helge Deller <deller@gmx.de> [parisc]
Signed-off-by: Michal Marek <mmarek@suse.cz>
The macro "cc-version" takes no argument. Drop $(CC) from the
"cc-ifversion" definition.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
Pull kbuild updates from Michal Marek:
"Here are the kbuild changes for v3.19-rc1:
- Cleanups and deduplication in the main Makefile and
scripts/Makefile.*
- Sort the output of *config targets in make help
- Old <linux/version.h> is always removed to avoid a surprise during
bisecting
- Warning fix in kconfig"
* 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
kbuild: remove redundant -rR flag of hdr-inst
kbuild: Fix make help-<board series> on powerpc
kbuild: Automatically remove stale <linux/version.h> file
kconfig: Fix warning "‘jump’ may be used uninitialized"
Makefile: sort list of defconfig targets in make help output
kbuild: Remove duplicate $(cmd) definition in Makefile.clean
kbuild: collect shorthands into scripts/Kbuild.include
Passing -rR for "make headers_install" is redundant because
the top Makefile has already set -rR to MAKEFLAGS.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
The shorthand "clean" is defined in both the top Makefile and
scripts/Makefile.clean. Likewise, the "hdr-inst" is defined in
both the top Makefile and scripts/Makefile.headersinst.
To reduce code duplication, this commit collects them into
scripts/Kbuild.include like the "build" and "modbuiltin" shorthands.
It requires scripts/Makefile.clean to include scripts/Kbuild.include,
but its impact on the performance of "make clean" should be
negligible.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
Move dtbs install rules to Makefile.dtbinst. This change is needed to
implement support for dts vendor subdirs. The change makes Makefiles
easier and smaller as no longer the dtbs_install rule needs to be
defined. Another advantage is that install goals are not encoded in
targets anymore (%.dtb_dtbinst_).
Signed-off-by: Robert Richter <rrichter@cavium.com>
$(if $(KBUILD_SRC),$(srctree)/) was a useful strategy
to omit a long absolute path for in-source-tree build
prior to commit 890676c65d
(kbuild: Use relative path when building in the source tree).
Now $(srctree) is "." when building in the source tree.
It would not be annoying to add "$(srctree)/" all the time.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
Commit c353acba ("kbuild: make: fix if_changed when command contains
backslashes") attempted to handle backslashes in *.cmd files, but it
only handled double backslashes for some reason. Changing make-cmd to also
handle single backslashes fixes rebuilds with dash, but it breaks bash
again. The reason is that the two shells disagree about the
interpretation of backslash sequences in the echo builtin. The way out
of this is to print the command with printf '%s\n'. While at it,
document what the individual parts of make-cmd do and why.
Reported-and-tested-by: Konstantin Khlebnikov <koct9i@gmail.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>
Pull kbuild changes from Michal Marek:
- cleanups in the main Makefiles and Documentation/DocBook/Makefile
- make O=... directory is automatically created if needed
- mrproper/distclean removes the old include/linux/version.h to make
life easier when bisecting across the commit that moved the version.h
file
* 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
kbuild: docbook: fix the include error when executing "make help"
kbuild: create a build directory automatically for out-of-tree build
kbuild: remove redundant '.*.cmd' pattern from make distclean
kbuild: move "quote" to Kbuild.include to be consistent
kbuild: docbook: use $(obj) and $(src) rather than specific path
kbuild: unconditionally clobber include/linux/version.h on distclean
kbuild: docbook: specify KERNELDOC dependency correctly
kbuild: docbook: include cmd files more simply
kbuild: specify build_docproc as a phony target
