Commit Graph

131 Commits

Author SHA1 Message Date
Masahiro Yamada 127668cf76 kbuild: clean up link rule of composite modules
cmd_link_multi-link is used only for cmd_link_multi-m.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-03-26 02:01:29 +09:00
Masahiro Yamada 5e18f0290f kbuild: clean up archive rule of built-in.a
With the incremental linking entirely dropped, we can simplify
the Makefile.

While I am here, I renamed cmd_link_o_target to cmd_ar_builtin.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-03-26 02:01:28 +09:00
Masahiro Yamada 7657f60e8f kbuild: remove partial section mismatch detection for built-in.a
When built-in.o was incrementally linked with 'ld -r', the section
mismatch analysis for the individual built-in.o was possible when
CONFIG_DEBUG_SECTION_MISMATCH was enabled.

With the migration to the thin archive, built-in.a (former, built-in.o)
is no longer an ELF file.  So, the modpost does nothing useful.
scripts/mod/modpost.c just checks the header to bail out, as follows:

        /* Is this a valid ELF file? */
        if ((hdr->e_ident[EI_MAG0] != ELFMAG0) ||
            (hdr->e_ident[EI_MAG1] != ELFMAG1) ||
            (hdr->e_ident[EI_MAG2] != ELFMAG2) ||
            (hdr->e_ident[EI_MAG3] != ELFMAG3)) {
                /* Not an ELF file - silently ignore it */
                return 0;
        }

We have the full analysis in the final link stage anyway, so we would
not miss the section mismatching.

I do not see a good reason to require extra linking only for the
purpose of the per-directory analysis.  Just get rid of this part.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-03-26 02:01:28 +09:00
Masahiro Yamada f98fe47ce5 kbuild: link $(real-obj-y) instead of $(obj-y) into built-in.a
In Kbuild, Makefiles can add the same object to obj-y multiple
times.  So,

   obj-y += foo.o
   obj-y += foo.o

is fine.

However, this is not true when the same object is added multiple
times via composite objects.  For example,

   obj-y    += foo.o bar.o
   foo-objs := foo-bar-common.o foo-only.o
   bar-objs := foo-bar-common.o bar-only.o

causes build error because two instances of foo-bar-common.o are
linked into the vmlinux.

Makefiles tend to invent ugly work-around, for example
  - lib/zstd/Makefile
  - drivers/net/ethernet/cavium/liquidio/Makefile

The technique used in Kbuild to avoid the multiple definition error
is to use $(filter $(obj-y), $^).  Here, $^ lists the names of all
the prerequisites with duplicated names removed.

By replacing it with $(filter $(real-obj-y), $^) we can do likewise
for composite objects.  For built-in objects, we do not need to keep
the composite object structure.  We can simply expand them, and link
$(real-obj-y) to built-in.a.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-03-26 02:01:27 +09:00
Masahiro Yamada f5f336812c kbuild: rename real-objs-y/m to real-obj-y/m
When I was refactoring Makefiles, I stupidly mistook 'real-obj-y' for
'real-objs-y' over and over again.  Finally, I decide to rename it to
'real-obj-y'.  This is consistent with 'obj-y', 'subdir-obj-y'.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-03-26 02:01:26 +09:00
Masahiro Yamada c0152e9a6b kbuild: move modname and modname-multi close to modname_flags
Just a cosmetic change to put related code close together.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Cao jin <caoj.fnst@cn.fujitsu.com>
2018-03-26 02:01:26 +09:00
Masahiro Yamada fe852ac200 kbuild: simplify modname calculation
modname can be calculated much more simply.  If modname-multi is
empty, it is a single-used object.  So, modname = $(basetarget).
Otherwise, modname = $(modname-multi).

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Cao jin <caoj.fnst@cn.fujitsu.com>
2018-03-26 02:01:25 +09:00
Nicholas Piggin f49821ee32 kbuild: rename built-in.o to built-in.a
Incremental linking is gone, so rename built-in.o to built-in.a, which
is the usual extension for archive files.

This patch does two things, first is a simple search/replace:

git grep -l 'built-in\.o' | xargs sed -i 's/built-in\.o/built-in\.a/g'

The second is to invert nesting of nested text manipulations to avoid
filtering built-in.a out from libs-y2:

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

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-03-26 02:01:19 +09:00
Nicholas Piggin 6358d6e8b9 kbuild: remove incremental linking option
This removes the old `ld -r` incremental link option, which has not
been selected by any architecture since June 2017.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-03-26 02:01:19 +09:00
Michael Forney 1fe7d2bb24 kbuild: Improve portability of some sed invocations
* 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>
2018-03-26 02:01:18 +09:00
Peter Zijlstra d5028ba8ee objtool, retpolines: Integrate objtool with retpoline support more closely
Disable retpoline validation in objtool if your compiler sucks, and otherwise
select the validation stuff for CONFIG_RETPOLINE=y (most builds would already
have it set due to ORC).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-02-21 16:54:32 +01:00
Peter Zijlstra ca41b97ed9 objtool: Add module specific retpoline rules
David allowed retpolines in .init.text, except for modules, which will
trip up objtool retpoline validation, fix that.

Requested-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-02-21 09:05:05 +01:00
Peter Zijlstra b5bc2231b8 objtool: Add retpoline validation
David requested a objtool validation pass for CONFIG_RETPOLINE=y enabled
builds, where it validates no unannotated indirect  jumps or calls are
left.

Add an additional .discard.retpoline_safe section to allow annotating
the few indirect sites that are required and safe.

Requested-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-02-21 09:05:04 +01:00
Linus Torvalds 88dc7fca18 Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 pti bits and fixes from Thomas Gleixner:
 "This last update contains:

   - An objtool fix to prevent a segfault with the gold linker by
     changing the invocation order. That's not just for gold, it's a
     general robustness improvement.

   - An improved error message for objtool which spares tearing hairs.

   - Make KASAN fail loudly if there is not enough memory instead of
     oopsing at some random place later

   - RSB fill on context switch to prevent RSB underflow and speculation
     through other units.

   - Make the retpoline/RSB functionality work reliably for both Intel
     and AMD

   - Add retpoline to the module version magic so mismatch can be
     detected

   - A small (non-fix) update for cpufeatures which prevents cpu feature
     clashing for the upcoming extra mitigation bits to ease
     backporting"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  module: Add retpoline tag to VERMAGIC
  x86/cpufeature: Move processor tracing out of scattered features
  objtool: Improve error message for bad file argument
  objtool: Fix seg fault with gold linker
  x86/retpoline: Add LFENCE to the retpoline/RSB filling RSB macros
  x86/retpoline: Fill RSB on context switch for affected CPUs
  x86/kasan: Panic if there is not enough memory to boot
2018-01-17 11:54:56 -08:00
Josh Poimboeuf 2a0098d706 objtool: Fix seg fault with gold linker
Objtool segfaults when the gold linker is used with
CONFIG_MODVERSIONS=y and CONFIG_UNWINDER_ORC=y.

With CONFIG_MODVERSIONS=y, the .o file gets passed to the linker before
being passed to objtool.  The gold linker seems to strip unused ELF
symbols by default, which confuses objtool and causes the seg fault when
it's trying to generate ORC metadata.

Objtool should really be running immediately after GCC anyway, without a
linker call in between.  Change the makefile ordering so that objtool is
called before the linker.

Reported-and-tested-by: Markus <M4rkusXXL@web.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: ee9f8fce99 ("x86/unwind: Add the ORC unwinder")
Link: http://lkml.kernel.org/r/355f04da33581f4a3bf82e5b512973624a1e23a2.1516025651.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-01-16 01:27:27 +01:00
Ingo Molnar 0fd2e9c53d Merge commit 'upstream-x86-entry' into WIP.x86/mm
Pull in a minimal set of v4.15 entry code changes, for a base for the MM isolation patches.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-12-17 12:58:53 +01:00
Linus Torvalds 5e2fda4776 Kbuild updates for v4.15 (2nd)
- Use pwd instead of /bin/pwd for portability
 
 - Clean up Makefiles
 
 - Fix ld-option for clang
 
 - Fix malloc'ed data size in Kconfig
 
 - Fix parallel building along with coccicheck
 
 - Fix a minor issue of package building
 
 - Prompt to use "rpm-pkg" instead of "rpm"
 
 - Clean up *.i and *.lst patterns by "make clean"
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Merge tag 'kbuild-v4.15-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull more Kbuild updates from Masahiro Yamada:

 - use 'pwd' instead of '/bin/pwd' for portability

 - clean up Makefiles

 - fix ld-option for clang

 - fix malloc'ed data size in Kconfig

 - fix parallel building along with coccicheck

 - fix a minor issue of package building

 - prompt to use "rpm-pkg" instead of "rpm"

 - clean up *.i and *.lst patterns by "make clean"

* tag 'kbuild-v4.15-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kbuild: drop $(extra-y) from real-objs-y
  kbuild: clean up *.i and *.lst patterns by make clean
  kbuild: rpm: prompt to use "rpm-pkg" if "rpm" target is used
  kbuild: pkg: use --transform option to prefix paths in tar
  coccinelle: fix parallel build with CHECK=scripts/coccicheck
  kconfig/symbol.c: use correct pointer type argument for sizeof
  kbuild: Set KBUILD_CFLAGS before incl. arch Makefile
  kbuild: remove all dummy assignments to obj-
  kbuild: create built-in.o automatically if parent directory wants it
  kbuild: /bin/pwd -> pwd
2017-11-25 08:06:30 -10:00
Linus Torvalds 1d3bc6363a A few late-arriving docs updates that have no real reason to wait. There's
a new "Co-Developed-by" tag described by Greg, and a build enhancement from
 Willy to generate docs warnings during a kernel build (but only when
 additional warnings have been requested in general).
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Merge tag 'docs-4.15-2' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "A few late-arriving docs updates that have no real reason to wait.

  There's a new "Co-Developed-by" tag described by Greg, and a build
  enhancement from Willy to generate docs warnings during a kernel build
  (but only when additional warnings have been requested in general)"

* tag 'docs-4.15-2' of git://git.lwn.net/linux:
  Add optional check for bad kernel-doc comments
  Documentation: fix profile= options in kernel-parameters.txt
  documentation/svga.txt: update outdated file
  kokr/memory-barriers.txt: Fix typo in paring example
  kokr/memory-barriers/txt: Replace uses of "transitive"
  Documentation/process: add Co-Developed-by: tag for patches with multiple authors
2017-11-23 21:01:32 -10:00
Matthew Wilcox 3a025e1d1c Add optional check for bad kernel-doc comments
Implement a '-none' output mode for kernel-doc which will only output
warning messages, and suppresses the warning message about there being
no kernel-doc in the file.

If the build has requested additional warnings, automatically check all
.c files.  This patch does not check .h files.  Enabling the warning
by default would add about 1300 warnings, so it's default off for now.
People who care can use this to check they didn't break the docs and
maybe we'll get all the warnings fixed and be able to enable this check
by default in the future.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-11-20 12:09:11 -07:00
Masahiro Yamada f7adc3124d kbuild: create built-in.o automatically if parent directory wants it
"obj-y += foo/" syntax requires Kbuild to visit the "foo" subdirectory
and link built-in.o from that directory.  This means foo/Makefile is
responsible for creating built-in.o even if there is no object to
link (in this case, built-in.o is an empty archive).

We have had several fixups like commit 4b024242e8 ("kbuild: Fix
linking error built-in.o no such file or directory"), then ended up
with a complex condition as follows:

  ifneq ($(strip $(obj-y) $(obj-m) $(obj-) $(subdir-m) $(lib-target)),)
  builtin-target := $(obj)/built-in.o
  endif

We still have more cases not covered by the above, so we need to add
  obj- := dummy.o
in several places just for creating empty built-in.o.

A key point is, the parent Makefile knows whether built-in.o is needed
or not.  If a subdirectory needs to create built-in.o, its parent can
tell the fact when descending.

If non-empty $(need-builtin) flag is passed from the parent, built-in.o
should be created.  $(obj-y) should be still checked to support the
single target "%/".  All of ugly tricks will go away.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
2017-11-18 11:38:58 +09:00
Linus Torvalds 09bd7c75e5 Kbuild updates for v4.15
One of the most remarkable improvements in this cycle is, Kbuild is
 now able to cache the result of shell commands.  Some variables are
 expensive to compute, for example, $(call cc-option,...) invokes the
 compiler.  It is not efficient to redo this computation every time,
 even when we are not actually building anything.  Kbuild creates a
 hidden file ".cache.mk" that contains invoked shell commands and
 their results.  The speed-up should be noticeable.
 
 Summary:
 
 - Fix arch build issues (hexagon, sh)
 
 - Clean up various Makefiles and scripts
 
 - Fix wrong usage of {CFLAGS,LDFLAGS}_MODULE in arch Makefiles
 
 - Cache variables that are expensive to compute
 
 - Improve cc-ldopton and ld-option for Clang
 
 - Optimize output directory creation
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Merge tag 'kbuild-v4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:
 "One of the most remarkable improvements in this cycle is, Kbuild is
  now able to cache the result of shell commands. Some variables are
  expensive to compute, for example, $(call cc-option,...) invokes the
  compiler. It is not efficient to redo this computation every time,
  even when we are not actually building anything. Kbuild creates a
  hidden file ".cache.mk" that contains invoked shell commands and their
  results. The speed-up should be noticeable.

  Summary:

   - Fix arch build issues (hexagon, sh)

   - Clean up various Makefiles and scripts

   - Fix wrong usage of {CFLAGS,LDFLAGS}_MODULE in arch Makefiles

   - Cache variables that are expensive to compute

   - Improve cc-ldopton and ld-option for Clang

   - Optimize output directory creation"

* tag 'kbuild-v4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (30 commits)
  kbuild: move coccicheck help from scripts/Makefile.help to top Makefile
  sh: decompressor: add shipped files to .gitignore
  frv: .gitignore: ignore vmlinux.lds
  selinux: remove unnecessary assignment to subdir-
  kbuild: specify FORCE in Makefile.headersinst as .PHONY target
  kbuild: remove redundant mkdir from ./Kbuild
  kbuild: optimize object directory creation for incremental build
  kbuild: create object directories simpler and faster
  kbuild: filter-out PHONY targets from "targets"
  kbuild: remove redundant $(wildcard ...) for cmd_files calculation
  kbuild: create directory for make cache only when necessary
  sh: select KBUILD_DEFCONFIG depending on ARCH
  kbuild: fix linker feature test macros when cross compiling with Clang
  kbuild: shrink .cache.mk when it exceeds 1000 lines
  kbuild: do not call cc-option before KBUILD_CFLAGS initialization
  kbuild: Cache a few more calls to the compiler
  kbuild: Add a cache for generated variables
  kbuild: add forward declaration of default target to Makefile.asm-generic
  kbuild: remove KBUILD_SUBDIR_ASFLAGS and KBUILD_SUBDIR_CCFLAGS
  hexagon/kbuild: replace CFLAGS_MODULE with KBUILD_CFLAGS_MODULE
  ...
2017-11-17 17:45:29 -08:00
Masahiro Yamada c4da7ed0e7 kbuild: optimize object directory creation for incremental build
The previous commit largely optimized the object directory creation.
We can optimize it more for incremental build.

There are already *.cmd files in the output directory.  The existing
*.cmd files have been picked up by $(wildcard ...).  Obviously,
directories containing them exist too, so we can skip "mkdir -p".

With this, Kbuild runs almost zero "mkdir -p" in incremental building.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-11-16 09:07:36 +09:00
Masahiro Yamada 8a78756eb5 kbuild: create object directories simpler and faster
For the out-of-tree build, scripts/Makefile.build creates output
directories, but this operation is not efficient.

scripts/Makefile.lib calculates obj-dirs as follows:

  obj-dirs := $(dir $(multi-objs) $(obj-y))

Please notice $(sort ...) is not used here.  Usually the result is
as many "./" as objects here.

For a lot of duplicated paths, the following command is invoked.

  _dummy := $(foreach d,$(obj-dirs), $(shell [ -d $(d) ] || mkdir -p $(d)))

Then, the costly shell command is run over and over again.

I see many points for optimization:

[1] Use $(sort ...) to cut down duplicated paths before passing them
    to system call
[2] Use single $(shell ...) instead of repeating it with $(foreach ...)
    This will reduce forking.
[3] We can calculate obj-dirs more simply.  Most of objects are already
    accumulated in $(targets).  So, $(dir $(targets)) is fine and more
    comprehensive.

I also removed ugly code in arch/x86/entry/vdso/Makefile.  This is now
really unnecessary.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
2017-11-16 09:07:35 +09:00
Masahiro Yamada 591f668997 kbuild: filter-out PHONY targets from "targets"
The variable "targets" contains object paths for which existing .*.cmd
files should be included.

scripts/Makefile.build automatically adds $(MAKECMDGOALS) to "targets"
as follows:

  targets += $(extra-y) $(MAKECMDGOALS) $(always)

The $(MAKECMDGOALS) is a PHONY target in several places.  PHONY targets
never create .*.cmd files.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-11-16 09:07:35 +09:00
Masahiro Yamada 2982c95357 kbuild: remove redundant $(wildcard ...) for cmd_files calculation
I do not see any reason why $(wildcard ...) needs to be called twice
for computing cmd_files.  Remove the first one.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-11-16 09:07:34 +09:00
Ingo Molnar b3d9a13681 Merge branch 'linus' into x86/asm, to pick up fixes and resolve conflicts
Conflicts:
	arch/x86/kernel/cpu/Makefile

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-11-07 10:53:06 +01:00
Linus Torvalds 5cb0512c02 Kbuild: don't pass "-C" to preprocessor when processing linker scripts
For some odd historical reason, we preprocessed the linker scripts with
"-C", which keeps comments around.  That makes no sense, since the
comments are not meaningful for the build anyway.

And it actually breaks things, since linker scripts can't have C++ style
"//" comments in them, so keeping comments after preprocessing now
limits us in odd and surprising ways in our header files for no good
reason.

The -C option goes back to pre-git and pre-bitkeeper times, but seems to
have been historically used (along with "-traditional") for some
odd-ball architectures (ia64, MIPS and SH).  It probably didn't matter
back then either, but might possibly have been used to minimize the
difference between the original file and the pre-processed result.

The reason for this may be lost in time, but let's not perpetuate it
only because we can't remember why we did this crazy thing.

This was triggered by the recent addition of SPDX lines to the source
tree, where people apparently were confused about why header files
couldn't use the C++ comment format.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg KH <gregkh@linuxfoundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-02 14:10:37 -07:00
Greg Kroah-Hartman b24413180f License cleanup: add SPDX GPL-2.0 license identifier to files with no license
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne.  Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed.  Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
 - Files considered eligible had to be source code files.
 - Make and config files were included as candidates if they contained >5
   lines of source
 - File already had some variant of a license header in it (even if <5
   lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

 - when both scanners couldn't find any license traces, file was
   considered to have no license information in it, and the top level
   COPYING file license applied.

   For non */uapi/* files that summary was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0                                              11139

   and resulted in the first patch in this series.

   If that file was a */uapi/* path one, it was "GPL-2.0 WITH
   Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0 WITH Linux-syscall-note                        930

   and resulted in the second patch in this series.

 - if a file had some form of licensing information in it, and was one
   of the */uapi/* ones, it was denoted with the Linux-syscall-note if
   any GPL family license was found in the file or had no licensing in
   it (per prior point).  Results summary:

   SPDX license identifier                            # files
   ---------------------------------------------------|------
   GPL-2.0 WITH Linux-syscall-note                       270
   GPL-2.0+ WITH Linux-syscall-note                      169
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
   LGPL-2.1+ WITH Linux-syscall-note                      15
   GPL-1.0+ WITH Linux-syscall-note                       14
   ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
   LGPL-2.0+ WITH Linux-syscall-note                       4
   LGPL-2.1 WITH Linux-syscall-note                        3
   ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
   ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1

   and that resulted in the third patch in this series.

 - when the two scanners agreed on the detected license(s), that became
   the concluded license(s).

 - when there was disagreement between the two scanners (one detected a
   license but the other didn't, or they both detected different
   licenses) a manual inspection of the file occurred.

 - In most cases a manual inspection of the information in the file
   resulted in a clear resolution of the license that should apply (and
   which scanner probably needed to revisit its heuristics).

 - When it was not immediately clear, the license identifier was
   confirmed with lawyers working with the Linux Foundation.

 - If there was any question as to the appropriate license identifier,
   the file was flagged for further research and to be revisited later
   in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights.  The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
 - a full scancode scan run, collecting the matched texts, detected
   license ids and scores
 - reviewing anything where there was a license detected (about 500+
   files) to ensure that the applied SPDX license was correct
 - reviewing anything where there was no detection but the patch license
   was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
   SPDX license was correct

This produced a worksheet with 20 files needing minor correction.  This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg.  Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected.  This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.)  Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-02 11:10:55 +01:00
Josh Poimboeuf 11af847446 x86/unwind: Rename unwinder config options to 'CONFIG_UNWINDER_*'
Rename the unwinder config options from:

  CONFIG_ORC_UNWINDER
  CONFIG_FRAME_POINTER_UNWINDER
  CONFIG_GUESS_UNWINDER

to:

  CONFIG_UNWINDER_ORC
  CONFIG_UNWINDER_FRAME_POINTER
  CONFIG_UNWINDER_GUESS

... in order to give them a more logical config namespace.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/73972fc7e2762e91912c6b9584582703d6f1b8cc.1507924831.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-10-14 10:12:12 +02:00
Josh Poimboeuf da541b2002 objtool: Skip unreachable warnings for GCC 4.4 and older
The kbuild bot occasionally reports warnings like:

  drivers/scsi/pcmcia/aha152x_core.o: warning: objtool: seldo_run()+0x130: unreachable instruction

These warnings are always with GCC 4.4.  That version of GCC sometimes
places unreachable instructions after calls to noreturn functions.

The unreachable warnings aren't very important anyway.  Just ignore them
for old versions of GCC.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/bc89b807d965b98ec18a0bb94f96a594bd58f2f2.1506551639.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-09-28 07:23:02 +02:00
Linus Torvalds b0c79f49c3 Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 asm updates from Ingo Molnar:

 - Introduce the ORC unwinder, which can be enabled via
   CONFIG_ORC_UNWINDER=y.

   The ORC unwinder is a lightweight, Linux kernel specific debuginfo
   implementation, which aims to be DWARF done right for unwinding.
   Objtool is used to generate the ORC unwinder tables during build, so
   the data format is flexible and kernel internal: there's no
   dependency on debuginfo created by an external toolchain.

   The ORC unwinder is almost two orders of magnitude faster than the
   (out of tree) DWARF unwinder - which is important for perf call graph
   profiling. It is also significantly simpler and is coded defensively:
   there has not been a single ORC related kernel crash so far, even
   with early versions. (knock on wood!)

   But the main advantage is that enabling the ORC unwinder allows
   CONFIG_FRAME_POINTERS to be turned off - which speeds up the kernel
   measurably:

   With frame pointers disabled, GCC does not have to add frame pointer
   instrumentation code to every function in the kernel. The kernel's
   .text size decreases by about 3.2%, resulting in better cache
   utilization and fewer instructions executed, resulting in a broad
   kernel-wide speedup. Average speedup of system calls should be
   roughly in the 1-3% range - measurements by Mel Gorman [1] have shown
   a speedup of 5-10% for some function execution intense workloads.

   The main cost of the unwinder is that the unwinder data has to be
   stored in RAM: the memory cost is 2-4MB of RAM, depending on kernel
   config - which is a modest cost on modern x86 systems.

   Given how young the ORC unwinder code is it's not enabled by default
   - but given the performance advantages the plan is to eventually make
   it the default unwinder on x86.

   See Documentation/x86/orc-unwinder.txt for more details.

 - Remove lguest support: its intended role was that of a temporary
   proof of concept for virtualization, plus its removal will enable the
   reduction (removal) of the paravirt API as well, so Rusty agreed to
   its removal. (Juergen Gross)

 - Clean up and fix FSGS related functionality (Andy Lutomirski)

 - Clean up IO access APIs (Andy Shevchenko)

 - Enhance the symbol namespace (Jiri Slaby)

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (47 commits)
  objtool: Handle GCC stack pointer adjustment bug
  x86/entry/64: Use ENTRY() instead of ALIGN+GLOBAL for stub32_clone()
  x86/fpu/math-emu: Add ENDPROC to functions
  x86/boot/64: Extract efi_pe_entry() from startup_64()
  x86/boot/32: Extract efi_pe_entry() from startup_32()
  x86/lguest: Remove lguest support
  x86/paravirt/xen: Remove xen_patch()
  objtool: Fix objtool fallthrough detection with function padding
  x86/xen/64: Fix the reported SS and CS in SYSCALL
  objtool: Track DRAP separately from callee-saved registers
  objtool: Fix validate_branch() return codes
  x86: Clarify/fix no-op barriers for text_poke_bp()
  x86/switch_to/64: Rewrite FS/GS switching yet again to fix AMD CPUs
  selftests/x86/fsgsbase: Test selectors 1, 2, and 3
  x86/fsgsbase/64: Report FSBASE and GSBASE correctly in core dumps
  x86/fsgsbase/64: Fully initialize FS and GS state in start_thread_common
  x86/asm: Fix UNWIND_HINT_REGS macro for older binutils
  x86/asm/32: Fix regs_get_register() on segment registers
  x86/xen/64: Rearrange the SYSCALL entries
  x86/asm/32: Remove a bunch of '& 0xffff' from pt_regs segment reads
  ...
2017-09-04 09:52:57 -07:00
Cao jin 312a3d0918 kbuild: trivial cleanups on the comments
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>
2017-08-10 00:58:20 +09:00
Josh Poimboeuf ee9f8fce99 x86/unwind: Add the ORC unwinder
Add the new ORC unwinder which is enabled by CONFIG_ORC_UNWINDER=y.
It plugs into the existing x86 unwinder framework.

It relies on objtool to generate the needed .orc_unwind and
.orc_unwind_ip sections.

For more details on why ORC is used instead of DWARF, see
Documentation/x86/orc-unwinder.txt - but the short version is
that it's a simplified, fundamentally more robust debugninfo
data structure, which also allows up to two orders of magnitude
faster lookups than the DWARF unwinder - which matters to
profiling workloads like perf.

Thanks to Andy Lutomirski for the performance improvement ideas:
splitting the ORC unwind table into two parallel arrays and creating a
fast lookup table to search a subset of the unwind table.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
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: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/0a6cbfb40f8da99b7a45a1a8302dc6aef16ec812.1500938583.git.jpoimboe@redhat.com
[ Extended the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-07-26 13:18:20 +02:00
Josh Poimboeuf 867ac9d737 objtool: Fix gcov check for older versions of GCC
Objtool tries to silence 'unreachable instruction' warnings when it
detects gcov is enabled, because gcov produces a lot of unreachable
instructions and they don't really matter.

However, the 0-day bot is still reporting some unreachable instruction
warnings with CONFIG_GCOV_KERNEL=y on GCC 4.6.4.

As it turns out, objtool's gcov detection doesn't work with older
versions of GCC because they don't create a bunch of symbols with the
'gcov.' prefix like newer versions of GCC do.

Move the gcov check out of objtool and instead just create a new
'--no-unreachable' flag which can be passed in by the kernel Makefile
when CONFIG_GCOV_KERNEL is defined.

Also rename the 'nofp' variable to 'no_fp' for consistency with the new
'no_unreachable' variable.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 9cfffb1168 ("objtool: Skip all "unreachable instruction" warnings for gcov kernels")
Link: http://lkml.kernel.org/r/c243dc78eb2ffdabb6e927844dea39b6033cd395.1500939244.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-07-25 11:12:45 +02:00
Nicholas Piggin 9a6cfca4f4 kbuild: thin archives use P option to ar
The P option makes ar do full path name matching and can prevent ar
from discarding files with duplicate names in some cases of creating
thin archives from thin archives. The sh architecture in particular
loses some object files from its kernel/cpu/sh*/ directories without
this option.

This could be a bug in binutils ar, but the P option should not cause
any negative effects so it is safe to use to work around this with.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-06-30 09:03:03 +09:00
Jiri Slaby e8a3118e1f objtool: make it visible in make V=1 output
It is currently impossible to see what is going on with objtool when
building, so call echo-cmd to see the actions:
  gcc -Wp,-MD,arch/x86/entry/.entry_64.o.d  -nostdinc -isystem ...
  ./tools/objtool/objtool check "arch/x86/entry/entry_64.o";

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Michal Marek <mmarek@suse.com>
Cc: linux-kbuild@vger.kernel.org
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-05-03 13:39:37 +09:00
Vinícius Tinti 433db3e260 kbuild: Add support to generate LLVM assembly files
Add rules to kbuild in order to generate LLVM assembly files with the .ll
extension when using clang.

  # from c code
  make CC=clang kernel/pid.ll

Signed-off-by: Vinícius Tinti <viniciustinti@gmail.com>
Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-04-25 08:13:52 +09:00
Ard Biesheuvel 56067812d5 kbuild: modversions: add infrastructure for emitting relative CRCs
This add the kbuild infrastructure that will allow architectures to emit
vmlinux symbol CRCs as 32-bit offsets to another location in the kernel
where the actual value is stored. This works around problems with CRCs
being mistaken for relocatable symbols on kernels that self relocate at
runtime (i.e., powerpc with CONFIG_RELOCATABLE=y)

For the kbuild side of things, this comes down to the following:

 - introducing a Kconfig symbol MODULE_REL_CRCS

 - adding a -R switch to genksyms to instruct it to emit the CRC symbols
   as references into the .rodata section

 - making modpost distinguish such references from absolute CRC symbols
   by the section index (SHN_ABS)

 - making kallsyms disregard non-absolute symbols with a __crc_ prefix

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-03 08:28:25 -08:00
Linus Torvalds 41e0e24b45 Merge branch 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild
Pull kbuild updates from Michal Marek:

 - prototypes for x86 asm-exported symbols (Adam Borowski) and a warning
   about missing CRCs (Nick Piggin)

 - asm-exports fix for LTO (Nicolas Pitre)

 - thin archives improvements (Nick Piggin)

 - linker script fix for CONFIG_LD_DEAD_CODE_DATA_ELIMINATION (Nick
   Piggin)

 - genksyms support for __builtin_va_list keyword

 - misc minor fixes

* 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  x86/kbuild: enable modversions for symbols exported from asm
  kbuild: fix scripts/adjust_autoksyms.sh* for the no modules case
  scripts/kallsyms: remove last remnants of --page-offset option
  make use of make variable CURDIR instead of calling pwd
  kbuild: cmd_export_list: tighten the sed script
  kbuild: minor improvement for thin archives build
  kbuild: modpost warn if export version crc is missing
  kbuild: keep data tables through dead code elimination
  kbuild: improve linker compatibility with lib-ksyms.o build
  genksyms: Regenerate parser
  kbuild/genksyms: handle va_list type
  kbuild: thin archives for multi-y targets
  kbuild: kallsyms allow 3-pass generation if symbols size has changed
2016-12-17 16:24:13 -08:00
Nicolas Pitre 76bee23411 kbuild: cmd_export_list: tighten the sed script
When LTO is used, some ___ksymtab_string sections are seen by this sed
script, creating lines containing a single ) such as:

EXPORT(foo)
)
)
EXPORT(bar)

Let's make it so the + character is also required for any line to be
printed.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-12-11 11:51:43 +01:00
Nicholas Piggin 9da2f584b5 kbuild: improve linker compatibility with lib-ksyms.o build
lib-ksyms.o is created by linking an empty input file with a linker
script containing the interesting bits. Currently the empty input file
is an archive containing nothing, however this causes the gold linker
to segfault.

I have opened a bug against gold

  https://sourceware.org/bugzilla/show_bug.cgi?id=20767

However this can be worked around by assembling an empty file to link
with instead. The resulting lib-ksyms.o is slightly larger (seemingly
due to empty .text, .data, .bss setions added), but final linked
output should not be changed.

Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-11-29 15:58:57 +01:00
Nicholas Piggin fe026a851b kbuild: thin archives for multi-y targets
THIN_ARCHIVES builds archives for built-in.o targets, have it build
multi-y targets as archives as well.

This saves another ~15% of the size of intermediate artifacts in the
build tree. After this patch, the linker is only used in final link,
and special cases like vdsos.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-11-29 15:53:19 +01:00
Nicholas Piggin cc6acc11ca kbuild: be more careful about matching preprocessed asm ___EXPORT_SYMBOL
The CRC code for asm exports grabs the preprocessed asm, finds the
___EXPORT_SYMBOL and turns those into EXPORT_SYMBOL in a C program
that can be preprocessed and parsed to create the CRC signatures from
the type.

The existing regex matching and replacement is too strict, and doesn't
deal well with whitespace among other things. The line
" EXPORT_SYMBOL(sym)" in a .S file would not match due to initial
whitespace, for example, which resulted in x86's ___preempt_schedule
failing to get CRCs.

Reported-by: Philip Müller <philm@manjaro.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-11-09 22:29:53 +01:00
Nicholas Piggin 4efca4ed05 kbuild: modversions for EXPORT_SYMBOL() for asm
Allow architectures to create asm/asm-prototypes.h file that
provides C prototypes for exported asm functions, which enables
proper CRC versions to be generated for them.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-11-01 16:20:17 +01:00
Nicholas Piggin 989cea5c14 kbuild: prevent lib-ksyms.o rebuilds
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reported-by: Russell King <rmk+kernel@armlinux.org.uk>
Tested-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-10-22 21:49:30 +02:00
Stephen Rothwell a5967db9af kbuild: allow architectures to use thin archives instead of ld -r
ld -r is an incremental link used to create built-in.o files in build
subdirectories. It produces relocatable object files containing all
its input files, and these are are then pulled together and relocated
in the final link. Aside from the bloat, this constrains the final
link relocations, which has bitten large powerpc builds with
unresolvable relocations in the final link.

Alan Modra has recommended the kernel use thin archives for linking.
This is an alternative and means that the linker has more information
available to it when it links the kernel.

This patch enables a config option architectures can select, which
causes all built-in.o files to be built as thin archives. built-in.o
files in subdirectories do not get symbol table or index attached,
which improves speed and size. The final link pass creates a
built-in.o archive in the root output directory which includes the
symbol table and index. The linker then uses takes this file to link.

The --whole-archive linker option is required, because the linker now
has visibility to every individual object file, and it will otherwise
just completely avoid including those without external references
(consider a file with EXPORT_SYMBOL or initcall or hardware exceptions
as its only entry points). The traditional built works "by luck" as
built-in.o files are large enough that they're going to get external
references. However this optimisation is unpredictable for the kernel
(due to above external references), ineffective at culling unused, and
costly because the .o files have to be searched for references.
Superior alternatives for link-time culling should be used instead.

Build characteristics for inclink vs thinarc, on a small powerpc64le
pseries VM with a modest .config:

                                  inclink       thinarc
sizes
vmlinux                        15 618 680    15 625 028
sum of all built-in.o          56 091 808     1 054 334
sum excluding root built-in.o                   151 430

find -name built-in.o | xargs rm ; time make vmlinux
real                              22.772s       21.143s
user                              13.280s       13.430s
sys                                4.310s        2.750s

- Final kernel pulled in only about 6K more, which shows how
  ineffective the object file culling is.
- Build performance looks improved due to less pagecache activity.
  On IO constrained systems it could be a bigger win.
- Build size saving is significant.

Side note, the toochain understands archives, so there's some tricks,
$ ar t built-in.o          # list all files you linked with
$ size built-in.o          # and their sizes
$ objdump -d built-in.o    # disassembly (unrelocated) with filenames

Implementation by sfr, minor tweaks by npiggin.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-09-09 10:31:19 +02:00
Al Viro 7f2084fa55 [kbuild] handle exports in lib-y objects reliably
Collect the symbols exported by anything that goes into lib.a and
add an empty object (lib-exports.o) with explicit undefs for each
of those to obj-y.

That allows to relax the rules regarding the use of exports in
lib-* objects - right now an object with export can be in lib-*
only if we are guaranteed that there always will be users in
built-in parts of the tree, otherwise it needs to be in obj-*.
As the result, we have an unholy mix of lib- and obj- in lib/Makefile
and (especially) in arch/*/lib/Makefile.  Moreover, a change in
generic part of the kernel can lead to mysteriously missing exports
on some configs.  With this change we don't have to worry about
that anymore.

One side effect is that built-in.o now pulls everything with exports
from the corresponding lib.a (if such exists).  That's exactly what
we want for linking vmlinux and fortunately it's almost the only thing
built-in.o is used in.  arch/ia64/hp/sim/boot/bootloader is the only
exception and it's easy to get rid of now - just turn everything in
arch/ia64/lib into lib-* and don't bother with arch/ia64/lib/built-in.o
anymore.

[AV: stylistic fix from Michal folded in]

Acked-by: Michal Marek <mmarek@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-08-07 23:46:30 -04:00
Emese Revfy 2440387431 Shared library support
Infrastructure for building independent shared library targets.

Based on work created by the PaX Team.

Signed-off-by: Emese Revfy <re.emese@gmail.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-06-07 22:57:10 +02:00
Masahiro Yamada e0f41e52dd kbuild: rename cmd_as_s_S to cmd_cpp_s_S
This command just preprocesses .S files into .s files, so cmd_cpp_s_S
seems more suitable.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-04-20 10:49:09 +02:00
Masahiro Yamada 23d4384870 kbuild: rename cmd_cc_i_c to cmd_cpp_i_c
This command just preprocesses .c files into .i files, so cmd_cpp_i_c
seems more suitable.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-04-20 10:48:19 +02:00