By default, sparse assumes a 64bit machine when compiled on x86-64
and 32bit when compiled on anything else.
This can of course create all sort of problems for the other archs, like
issuing false warnings ('shift too big (32) for type unsigned long'), or
worse, failing to emit legitimate warnings.
Fix this by adding the -m32/-m64 flag, depending on CONFIG_64BIT,
to CHECKFLAGS in the main Makefile (and so for all archs).
Also, remove the now unneeded -m32/-m64 in arch specific Makefiles.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Pull x86 build updates from Ingo Molnar:
"The biggest change is the forcing of asm-goto support on x86, which
effectively increases the GCC minimum supported version to gcc-4.5 (on
x86)"
* 'x86-build-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/build: Don't pass in -D__KERNEL__ multiple times
x86: Remove FAST_FEATURE_TESTS
x86: Force asm-goto
x86/build: Drop superfluous ALIGN from the linker script
Some .<target>.cmd files under arch/x86 are showing two instances of
-D__KERNEL__, like arch/x86/boot/ and arch/x86/realmode/rm/.
__KERNEL__ is already defined in KBUILD_CPPFLAGS in the top Makefile,
so it can be dropped safely.
Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kbuild@vger.kernel.org
Link: http://lkml.kernel.org/r/20180316084944.3997-1-caoj.fnst@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We want to start using asm-goto to guarantee the absence of dynamic
branches (and thus speculation).
A primary prerequisite for this is of course that the compiler
supports asm-goto. This effecively lifts the minimum GCC version to
build an x86 kernel to gcc-4.5.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: torvalds@linux-foundation.org
Link: https://lkml.kernel.org/r/20180319201327.GJ4043@hirez.programming.kicks-ass.net
Binutils 2.31 will enable -z separate-code by default for x86 to avoid
mixing code pages with data to improve cache performance as well as
security. To reduce x86-64 executable and shared object sizes, the
maximum page size is reduced from 2MB to 4KB. But x86-64 kernel must
be aligned to 2MB. Pass -z max-page-size=0x200000 to linker to force
2MB page size regardless of the default page size used by linker.
Tested with Linux kernel 4.15.6 on x86-64.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.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/CAMe9rOp4_%3D_8twdpTyAP2DhONOCeaTOsniJLoppzhoNptL8xzA@mail.gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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>
Pull x86 fixlet from Thomas Gleixner.
Remove a warning about lack of compiler support for retpoline that most
people can't do anything about, so it just annoys them needlessly.
* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/retpoline: Remove compile time warning
Remove the compile time warning when CONFIG_RETPOLINE=y and the compiler
does not have retpoline support. Linus rationale for this is:
It's wrong because it will just make people turn off RETPOLINE, and the
asm updates - and return stack clearing - that are independent of the
compiler are likely the most important parts because they are likely the
ones easiest to target.
And it's annoying because most people won't be able to do anything about
it. The number of people building their own compiler? Very small. So if
their distro hasn't got a compiler yet (and pretty much nobody does), the
warning is just annoying crap.
It is already properly reported as part of the sysfs interface. The
compile-time warning only encourages bad things.
Fixes: 76b043848f ("x86/retpoline: Add initial retpoline support")
Requested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: thomas.lendacky@amd.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kees Cook <keescook@google.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
Link: https://lkml.kernel.org/r/CA+55aFzWgquv4i6Mab6bASqYXg3ErV3XDFEYf=GEcCDQg5uAtw@mail.gmail.com
Pull x86 pti updates from Thomas Gleixner:
"This contains:
- a PTI bugfix to avoid setting reserved CR3 bits when PCID is
disabled. This seems to cause issues on a virtual machine at least
and is incorrect according to the AMD manual.
- a PTI bugfix which disables the perf BTS facility if PTI is
enabled. The BTS AUX buffer is not globally visible and causes the
CPU to fault when the mapping disappears on switching CR3 to user
space. A full fix which restores BTS on PTI is non trivial and will
be worked on.
- PTI bugfixes for EFI and trusted boot which make sure that the user
space visible page table entries have the NX bit cleared
- removal of dead code in the PTI pagetable setup functions
- add PTI documentation
- add a selftest for vsyscall to verify that the kernel actually
implements what it advertises.
- a sysfs interface to expose vulnerability and mitigation
information so there is a coherent way for users to retrieve the
status.
- the initial spectre_v2 mitigations, aka retpoline:
+ The necessary ASM thunk and compiler support
+ The ASM variants of retpoline and the conversion of affected ASM
code
+ Make LFENCE serializing on AMD so it can be used as speculation
trap
+ The RSB fill after vmexit
- initial objtool support for retpoline
As I said in the status mail this is the most of the set of patches
which should go into 4.15 except two straight forward patches still on
hold:
- the retpoline add on of LFENCE which waits for ACKs
- the RSB fill after context switch
Both should be ready to go early next week and with that we'll have
covered the major holes of spectre_v2 and go back to normality"
* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (28 commits)
x86,perf: Disable intel_bts when PTI
security/Kconfig: Correct the Documentation reference for PTI
x86/pti: Fix !PCID and sanitize defines
selftests/x86: Add test_vsyscall
x86/retpoline: Fill return stack buffer on vmexit
x86/retpoline/irq32: Convert assembler indirect jumps
x86/retpoline/checksum32: Convert assembler indirect jumps
x86/retpoline/xen: Convert Xen hypercall indirect jumps
x86/retpoline/hyperv: Convert assembler indirect jumps
x86/retpoline/ftrace: Convert ftrace assembler indirect jumps
x86/retpoline/entry: Convert entry assembler indirect jumps
x86/retpoline/crypto: Convert crypto assembler indirect jumps
x86/spectre: Add boot time option to select Spectre v2 mitigation
x86/retpoline: Add initial retpoline support
objtool: Allow alternatives to be ignored
objtool: Detect jumps to retpoline thunks
x86/pti: Make unpoison of pgd for trusted boot work for real
x86/alternatives: Fix optimize_nops() checking
sysfs/cpu: Fix typos in vulnerability documentation
x86/cpu/AMD: Use LFENCE_RDTSC in preference to MFENCE_RDTSC
...
Enable the use of -mindirect-branch=thunk-extern in newer GCC, and provide
the corresponding thunks. Provide assembler macros for invoking the thunks
in the same way that GCC does, from native and inline assembler.
This adds X86_FEATURE_RETPOLINE and sets it by default on all CPUs. In
some circumstances, IBRS microcode features may be used instead, and the
retpoline can be disabled.
On AMD CPUs if lfence is serialising, the retpoline can be dramatically
simplified to a simple "lfence; jmp *\reg". A future patch, after it has
been verified that lfence really is serialising in all circumstances, can
enable this by setting the X86_FEATURE_RETPOLINE_AMD feature bit in addition
to X86_FEATURE_RETPOLINE.
Do not align the retpoline in the altinstr section, because there is no
guarantee that it stays aligned when it's copied over the oldinstr during
alternative patching.
[ Andi Kleen: Rename the macros, add CONFIG_RETPOLINE option, export thunks]
[ tglx: Put actual function CALL/JMP in front of the macros, convert to
symbolic labels ]
[ dwmw2: Convert back to numeric labels, merge objtool fixes ]
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: thomas.lendacky@amd.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kees Cook <keescook@google.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: https://lkml.kernel.org/r/1515707194-20531-4-git-send-email-dwmw@amazon.co.uk
Patch series "kmemcheck: kill kmemcheck", v2.
As discussed at LSF/MM, kill kmemcheck.
KASan is a replacement that is able to work without the limitation of
kmemcheck (single CPU, slow). KASan is already upstream.
We are also not aware of any users of kmemcheck (or users who don't
consider KASan as a suitable replacement).
The only objection was that since KASAN wasn't supported by all GCC
versions provided by distros at that time we should hold off for 2
years, and try again.
Now that 2 years have passed, and all distros provide gcc that supports
KASAN, kill kmemcheck again for the very same reasons.
This patch (of 4):
Remove kmemcheck annotations, and calls to kmemcheck from the kernel.
[alexander.levin@verizon.com: correctly remove kmemcheck call from dma_map_sg_attrs]
Link: http://lkml.kernel.org/r/20171012192151.26531-1-alexander.levin@verizon.com
Link: http://lkml.kernel.org/r/20171007030159.22241-2-alexander.levin@verizon.com
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tim Hansen <devtimhansen@gmail.com>
Cc: Vegard Nossum <vegardno@ifi.uio.no>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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>
With the following commit:
8f91869766 ("x86/build: Fix stack alignment for CLang")
cc-option is only used to determine the name of the stack alignment option
supported by the compiler, but not to verify that the actual parameter
<option>=N is valid in combination with the other CFLAGS.
This causes problems (as reported by the kbuild robot) with older GCC versions
which only support stack alignment on a boundary of 16 bytes or higher.
Also use (__)cc_option to add the stack alignment option to CFLAGS to
make sure only valid options are added.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bernhard.Rosenkranzer@linaro.org
Cc: Greg Hackmann <ghackmann@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michael Davidson <md@google.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hines <srhines@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dianders@chromium.org
Fixes: 8f91869766 ("x86/build: Fix stack alignment for CLang")
Link: http://lkml.kernel.org/r/20170817182047.176752-1-mka@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Commit:
d77698df39 ("x86/build: Specify stack alignment for clang")
intended to use the same stack alignment for clang as with gcc.
The two compilers use different options to configure the stack alignment
(gcc: -mpreferred-stack-boundary=n, clang: -mstack-alignment=n).
The above commit assumes that the clang option uses the same parameter
type as gcc, i.e. that the alignment is specified as 2^n. However clang
interprets the value of this option literally to use an alignment of n,
in consequence the stack remains misaligned.
Change the values used with -mstack-alignment to be the actual alignment
instead of a power of two.
cc-option isn't used here with the typical pattern of KBUILD_CFLAGS +=
$(call cc-option ...). The reason is that older gcc versions don't
support the -mpreferred-stack-boundary option, since cc-option doesn't
verify whether the alternative option is valid it would incorrectly
select the clang option -mstack-alignment..
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bernhard.Rosenkranzer@linaro.org
Cc: Greg Hackmann <ghackmann@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michael Davidson <md@google.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hines <srhines@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dianders@chromium.org
Link: http://lkml.kernel.org/r/20170817004740.170588-1-mka@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Subarchitecture support (mflags-y) was removed from x86 in this commit:
6bda2c8b32 ("x86: remove subarchitecture support")
So drop the mflags-y usage from the Makefile.
Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.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/1502105384-23214-1-git-send-email-caoj.fnst@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
For gcc stack alignment is configured with -mpreferred-stack-boundary=N,
clang has the option -mstack-alignment=N for that purpose. Use the same
alignment as with gcc.
If the alignment is not specified clang assumes an alignment of
16 bytes, as required by the standard ABI. However as mentioned in
d9b0cde91c ("x86-64, gcc: Use -mpreferred-stack-boundary=3 if
supported") the standard kernel entry on x86-64 leaves the stack
on an 8-byte boundary, as a consequence clang will keep the stack
misaligned.
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
cc-option is used to enable compiler options for the boot code if they
are available. The macro uses KBUILD_CFLAGS and KBUILD_CPPFLAGS for the
check, however these flags aren't used to build the boot code, in
consequence cc-option can yield wrong results. For example
-mpreferred-stack-boundary=2 is never set with a 64-bit compiler,
since the setting is only valid for 16 and 32-bit binaries. This
is also the case for 32-bit kernel builds, because the option -m32 is
added to KBUILD_CFLAGS after the assignment of REALMODE_CFLAGS.
Use __cc-option instead of cc-option for the boot mode options.
The macro receives the compiler options as parameter instead of using
KBUILD_C*FLAGS, for the boot code we pass REALMODE_CFLAGS.
Also use separate statements for the __cc-option checks instead
of performing them in the initial assignment of REALMODE_CFLAGS since
the variable is an input of the macro.
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reuse mce_amd_inj's debugfs interface so that mce-inject can
benefit from it too. The old functionality is still preserved under
CONFIG_X86_MCELOG_LEGACY.
Tested-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Yazen Ghannam <yazen.ghannam@amd.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/20170613162835.30750-4-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
At least Make 3.82 dislikes the tab in front of the $(warning) function:
arch/x86/Makefile:162: *** recipe commences before first target. Stop.
Let's be gentle.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1944fcd8-e3df-d1f7-c0e4-60aeb1917a24@siemens.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Clang does not support this machine dependent option.
Older versions of GCC (pre 3.0) may not support this option, added in
2000, but it's unlikely they can still compile a working kernel.
Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com>
Reviewed-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/20170509032946.20444-1-nick.desaulniers@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull x86 build update from Ingo Molnar:
"A single CLang support related fix"
* 'x86-build-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/kbuild: Use cc-option to enable -falign-{jumps/loops}
For pre-4.6.0 versions of GCC, which don't have '-mfentry', the
'-maccumulate-outgoing-args' option is required for function graph
tracing in order to avoid GCC bug 42109.
However, GCC ignores '-maccumulate-outgoing-args' when '-Os' is
also set.
Currently we force a build error to prevent that scenario, but that
breaks randconfigs. So change the error to a warning which also
disables CONFIG_CC_OPTIMIZE_FOR_SIZE.
Reported-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kbuild test robot <fengguang.wu@intel.com>
Cc: kbuild-all@01.org
Link: http://lkml.kernel.org/r/20170418214429.o7fbwbmf4nqosezy@treble
Signed-off-by: Ingo Molnar <mingo@kernel.org>
clang currently does not support these optimizations, only enable them
when they are available.
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Cc: Greg Hackmann <ghackmann@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michael Davidson <md@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: grundler@chromium.org
Link: http://lkml.kernel.org/r/20170413172609.118122-1-mka@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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>
Optimize RAID6 gen_syndrom functions to take advantage of
the 512-bit ZMM integer instructions introduced in AVX512.
AVX512 optimized gen_syndrom functions, which is simply based
on avx2.c written by Yuanhan Liu and sse2.c written by hpa.
The patch was tested and benchmarked before submission on
a hardware that has AVX512 flags to support such instructions
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jim Kukunas <james.t.kukunas@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Megha Dey <megha.dey@linux.intel.com>
Signed-off-by: Gayatri Kammela <gayatri.kammela@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Before, the stack protector flag was sanity checked before .config had
been reprocessed. This meant the build couldn't be aborted early, and
only a warning could be emitted followed later by the compiler blowing
up with an unknown flag. This has caused a lot of confusion over time,
so this splits the flag selection from sanity checking and performs the
sanity checking after the make has been restarted from a reprocessed
.config, so builds can be aborted as early as possible now.
Additionally moves the x86-specific sanity check to the same location,
since it suffered from the same warn-then-wait-for-compiler-failure
problem.
Link: http://lkml.kernel.org/r/20160712223043.GA11664@www.outflux.net
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Michal Marek <mmarek@suse.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We have 4 types of x86 platforms that disable RTC:
* Intel MID
* Lguest - uses paravirt
* Xen dom-U - uses paravirt
* x86 on legacy systems annotated with an ACPI legacy flag
We can consolidate all of these into a platform specific legacy
quirk set early in boot through i386_start_kernel() and through
x86_64_start_reservations(). This deals with the RTC quirks which
we can rely on through the hardware subarch, the ACPI check can
be dealt with separately.
For Xen things are bit more complex given that the @X86_SUBARCH_XEN
x86_hardware_subarch is shared on for Xen which uses the PV path for
both domU and dom0. Since the semantics for differentiating between
the two are Xen specific we provide a platform helper to help override
default legacy features -- x86_platform.set_legacy_features(). Use
of this helper is highly discouraged, its only purpose should be
to account for the lack of semantics available within your given
x86_hardware_subarch.
As per 0-day, this bumps the vmlinux size using i386-tinyconfig as
follows:
TOTAL TEXT init.text x86_early_init_platform_quirks()
+70 +62 +62 +43
Only 8 bytes overhead total, as the main increase in size is
all removed via __init.
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
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: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: andrew.cooper3@citrix.com
Cc: andriy.shevchenko@linux.intel.com
Cc: bigeasy@linutronix.de
Cc: boris.ostrovsky@oracle.com
Cc: david.vrabel@citrix.com
Cc: ffainelli@freebox.fr
Cc: george.dunlap@citrix.com
Cc: glin@suse.com
Cc: jlee@suse.com
Cc: josh@joshtriplett.org
Cc: julien.grall@linaro.org
Cc: konrad.wilk@oracle.com
Cc: kozerkov@parallels.com
Cc: lenb@kernel.org
Cc: lguest@lists.ozlabs.org
Cc: linux-acpi@vger.kernel.org
Cc: lv.zheng@intel.com
Cc: matt@codeblueprint.co.uk
Cc: mbizon@freebox.fr
Cc: rjw@rjwysocki.net
Cc: robert.moore@intel.com
Cc: rusty@rustcorp.com.au
Cc: tiwai@suse.de
Cc: toshi.kani@hp.com
Cc: xen-devel@lists.xensource.com
Link: http://lkml.kernel.org/r/1460592286-300-5-git-send-email-mcgrof@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull crypto update from Herbert Xu:
"API:
- Add support for cipher output IVs in testmgr
- Add missing crypto_ahash_blocksize helper
- Mark authenc and des ciphers as not allowed under FIPS.
Algorithms:
- Add CRC support to 842 compression
- Add keywrap algorithm
- A number of changes to the akcipher interface:
+ Separate functions for setting public/private keys.
+ Use SG lists.
Drivers:
- Add Intel SHA Extension optimised SHA1 and SHA256
- Use dma_map_sg instead of custom functions in crypto drivers
- Add support for STM32 RNG
- Add support for ST RNG
- Add Device Tree support to exynos RNG driver
- Add support for mxs-dcp crypto device on MX6SL
- Add xts(aes) support to caam
- Add ctr(aes) and xts(aes) support to qat
- A large set of fixes from Russell King for the marvell/cesa driver"
* 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6: (115 commits)
crypto: asymmetric_keys - Fix unaligned access in x509_get_sig_params()
crypto: akcipher - Don't #include crypto/public_key.h as the contents aren't used
hwrng: exynos - Add Device Tree support
hwrng: exynos - Fix missing configuration after suspend to RAM
hwrng: exynos - Add timeout for waiting on init done
dt-bindings: rng: Describe Exynos4 PRNG bindings
crypto: marvell/cesa - use __le32 for hardware descriptors
crypto: marvell/cesa - fix missing cpu_to_le32() in mv_cesa_dma_add_op()
crypto: marvell/cesa - use memcpy_fromio()/memcpy_toio()
crypto: marvell/cesa - use gfp_t for gfp flags
crypto: marvell/cesa - use dma_addr_t for cur_dma
crypto: marvell/cesa - use readl_relaxed()/writel_relaxed()
crypto: caam - fix indentation of close braces
crypto: caam - only export the state we really need to export
crypto: caam - fix non-block aligned hash calculation
crypto: caam - avoid needlessly saving and restoring caam_hash_ctx
crypto: caam - print errno code when hash registration fails
crypto: marvell/cesa - fix memory leak
crypto: marvell/cesa - fix first-fragment handling in mv_cesa_ahash_dma_last_req()
crypto: marvell/cesa - rearrange handling for sw padded hashes
...
Commit:
131484c8da ("x86/debug: Remove perpetually broken, unmaintainable dwarf annotations")
removed all the manual DWARF annotations outside the vDSO. It also removed
the macros we used for the manual annotations.
Re-add these macros so that we can clean up the vDSO annotations.
Signed-off-by: Andy 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: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/4c70bb98a8b773c8ccfaabf6745e569ff43e7f65.1444091584.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This patch provides the configuration and build support to
include and build the optimized SHA1 and SHA256 update transforms
for the kernel's crypto library.
Originally-by: Chandramouli Narayanan <mouli_7982@yahoo.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Pull x86 asm changes from Ingo Molnar:
"The biggest changes in this cycle were:
- Revamp, simplify (and in some cases fix) Time Stamp Counter (TSC)
primitives. (Andy Lutomirski)
- Add new, comprehensible entry and exit handlers written in C.
(Andy Lutomirski)
- vm86 mode cleanups and fixes. (Brian Gerst)
- 32-bit compat code cleanups. (Brian Gerst)
The amount of simplification in low level assembly code is already
palpable:
arch/x86/entry/entry_32.S | 130 +----
arch/x86/entry/entry_64.S | 197 ++-----
but more simplifications are planned.
There's also the usual laudry mix of low level changes - see the
changelog for details"
* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (83 commits)
x86/asm: Drop repeated macro of X86_EFLAGS_AC definition
x86/asm/msr: Make wrmsrl() a function
x86/asm/delay: Introduce an MWAITX-based delay with a configurable timer
x86/asm: Add MONITORX/MWAITX instruction support
x86/traps: Weaken context tracking entry assertions
x86/asm/tsc: Add rdtscll() merge helper
selftests/x86: Add syscall_nt selftest
selftests/x86: Disable sigreturn_64
x86/vdso: Emit a GNU hash
x86/entry: Remove do_notify_resume(), syscall_trace_leave(), and their TIF masks
x86/entry/32: Migrate to C exit path
x86/entry/32: Remove 32-bit syscall audit optimizations
x86/vm86: Rename vm86->v86flags and v86mask
x86/vm86: Rename vm86->vm86_info to user_vm86
x86/vm86: Clean up vm86.h includes
x86/vm86: Move the vm86 IRQ definitions to vm86.h
x86/vm86: Use the normal pt_regs area for vm86
x86/vm86: Eliminate 'struct kernel_vm86_struct'
x86/vm86: Move fields from 'struct kernel_vm86_struct' to 'struct vm86'
x86/vm86: Move vm86 fields out of 'thread_struct'
...
This is an x86-specific module and would benefit from being
closer to the arch code. Move it there. Update copyright while
at it.
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/1439396985-12812-14-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
As per:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
GCC only allows -mpreferred-stack-boundary=3 on x86_64 if -mno-sse is set.
That means that cc-option will not detect -mpreferred-stack-boundary=3
support, because we test for it before setting -mno-sse.
Fix it by reordering the Makefile bits.
Compile-tested only. This should help avoid code generation
issues such as the one that was worked around in:
b96fecbfa8 ("x86/fpu: Fix boot crash in the early FPU code")
I'm a bit concerned that we could still have problems on older
GCC versions given that our asm code does not respect GCC's idea
of the ABI-required stack alignment.
Signed-off-by: Andy 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: H. Peter Anvin <hpa@zytor.com>
Cc: Jan Kara <jack@suse.cz>
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/f5297c192969adfa0d28b84cf8a22d59573db26d.1436126872.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The build time generated syscall definitions are entry code related, move
them into the arch/x86/entry/ directory.
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
So the dwarf2 annotations in low level assembly code have
become an increasing hindrance: unreadable, messy macros
mixed into some of the most security sensitive code paths
of the Linux kernel.
These debug info annotations don't even buy the upstream
kernel anything: dwarf driven stack unwinding has caused
problems in the past so it's out of tree, and the upstream
kernel only uses the much more robust framepointers based
stack unwinding method.
In addition to that there's a steady, slow bitrot going
on with these annotations, requiring frequent fixups.
There's no tooling and no functionality upstream that
keeps it correct.
So burn down the sick forest, allowing new, healthier growth:
27 files changed, 350 insertions(+), 1101 deletions(-)
Someone who has the willingness and time to do this
properly can attempt to reintroduce dwarf debuginfo in x86
assembly code plus dwarf unwinding from first principles,
with the following conditions:
- it should be maximally readable, and maximally low-key to
'ordinary' code reading and maintenance.
- find a build time method to insert dwarf annotations
automatically in the most common cases, for pop/push
instructions that manipulate the stack pointer. This could
be done for example via a preprocessing step that just
looks for common patterns - plus special annotations for
the few cases where we want to depart from the default.
We have hundreds of CFI annotations, so automating most of
that makes sense.
- it should come with build tooling checks that ensure that
CFI annotations are sensible. We've seen such efforts from
the framepointer side, and there's no reason it couldn't be
done on the dwarf side.
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: Frédéric Weisbecker <fweisbec@gmail.com
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Packing loops tightly (-falign-loops=1) is beneficial to code size:
text data bss dec filename
12566391 1617840 1089536 15273767 vmlinux.align.16-byte
12224951 1617840 1089536 14932327 vmlinux.align.1-byte
11976567 1617840 1089536 14683943 vmlinux.align.1-byte.funcs-1-byte
11903735 1617840 1089536 14611111 vmlinux.align.1-byte.funcs-1-byte.loops-1-byte
Which reduces the size of the kernel by another 0.6%, so the
the total combined size reduction of the alignment-packing
patches is ~5.5%.
The x86 decoder bandwidth and caching arguments laid out in:
be6cb02779 ("x86: Align jump targets to 1-byte boundaries")
apply to loop alignment as well.
Furtermore, modern CPU uarchs have a loop cache/buffer that
is a L0 cache before even any uop cache, covering a few
dozen most recently executed instructions.
This loop cache generally does not have the 16-byte alignment
restrictions of the uop cache.
Now loop alignment can still be beneficial if:
- a loop is cache-hot and its surroundings are not.
- if the loop is so cache hot that the instruction
flow becomes x86 decoder bandwidth limited
But loop alignment is harmful if:
- a loop is cache-cold
- a loop's surroundings are cache-hot as well
- two cache-hot loops are close to each other
- if the loop fits into the loop cache
- if the code flow is not decoder bandwidth limited
and I'd argue that the latter five scenarios are much
more common in the kernel, as our hottest loops are
typically:
- pointer chasing: this should fit into the loop cache
in most cases and is typically data cache and address
generation limited
- generic memory ops (memset, memcpy, etc.): these generally
fit into the loop cache as well, and are likewise data
cache limited.
So this patch packs loop addresses tightly as well.
Acked-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/20150410123017.GB19918@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The following NOP in a hot function caught my attention:
> 5a: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1)
That's a dead NOP that bloats the function a bit, added for the
default 16-byte alignment that GCC applies for jump targets.
I realize that x86 CPU manufacturers recommend 16-byte jump
target alignments (it's in the Intel optimization manual),
to help their relatively narrow decoder prefetch alignment
and uop cache constraints, but the cost of that is very
significant:
text data bss dec filename
12566391 1617840 1089536 15273767 vmlinux.align.16-byte
12224951 1617840 1089536 14932327 vmlinux.align.1-byte
By using 1-byte jump target alignment (i.e. no alignment at all)
we get an almost 3% reduction in kernel size (!) - and a
probably similar reduction in I$ footprint.
Now, the usual justification for jump target alignment is the
following:
- modern decoders tend to have 16-byte (effective) decoder
prefetch windows. (AMD documents it higher but measurements
suggest the effective prefetch window on curretn uarchs is
still around 16 bytes)
- on Intel there's also the uop-cache with cachelines that have
16-byte granularity and limited associativity.
- older x86 uarchs had a penalty for decoder fetches that crossed
16-byte boundaries. These limits are mostly gone from recent
uarchs.
So if a forward jump target is aligned to cacheline boundary then
prefetches will start from a new prefetch-cacheline and there's
higher chance for decoding in fewer steps and packing tightly.
But I think that argument is flawed for typical optimized kernel
code flows: forward jumps often go to 'cold' (uncommon) pieces
of code, and aligning cold code to cache lines does not bring a
lot of advantages (they are uncommon), while it causes
collateral damage:
- their alignment 'spreads out' the cache footprint, it shifts
followup hot code further out
- plus it slows down even 'cold' code that immediately follows 'hot'
code (like in the above case), which could have benefited from the
partial cacheline that comes off the end of hot code.
But even in the cache-hot case the 16 byte alignment brings
disadvantages:
- it spreads out the cache footprint, possibly making the code
fall out of the L1 I$.
- On Intel CPUs, recent microarchitectures have plenty of
uop cache (typically doubling every 3 years) - while the
size of the L1 cache grows much less aggressively. So
workloads are rarely uop cache limited.
The only situation where alignment might matter are tight
loops that could fit into a single 16 byte chunk - but those
are pretty rare in the kernel: if they exist they tend
to be pointer chasing or generic memory ops, which both tend
to be cache miss (or cache allocation) intensive and are not
decoder bandwidth limited.
So the balance of arguments strongly favors packing kernel
instructions tightly versus maximizing for decoder bandwidth:
this patch changes the jump target alignment from 16 bytes
to 1 byte (tightly packed, unaligned).
Acked-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/20150410120846.GA17101@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
GCC 5 added a compiler option, -mskip-rax-setup, for x86-64. It skips
setting up the RAX register when SSE is disabled and there are no
variable arguments passed in vector registers. (According to the x86_64
ABI, %al is used as a hidden register containing the number of vector
registers used).
Since the kernel doesn't pass vector registers to functions with
variable arguments, this option can be used to optimize the x86-64
kernel.
This GCC feature was suggested by Rasmus Villemoes <linux@rasmusvillemoes.dk>.
This is the corresponding kernel change using it.
For kernel v3.17:
text data bss dec filename
11455921 2204048 5853184 19513153 vmlinux #with -mskip-rax-setup
11480079 2204048 5853184 19537311 vmlinux
For Kernel v4.0+ - custom config:
text data bss dec filename
10231778 3479800 16617472 30329050 vmlinux-gcc5+-mskip-rax-setup
10268797 3547448 16621568 30437813 vmlinux
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
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: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Prior to this commit, it was impossible to use relative path to
include Makefiles from the top level Makefile because the option
"--include-dir=$(srctree)" becomes effective when Make enters into
sub Makefiles.
To use relative path in any places, this commit moves the option
above the "sub-make" target.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
Just like for AVX2 (which simply needs an #if -> #ifdef conversion),
SSSE3 assembler support should be checked for before using it.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Jim Kukunas <james.t.kukunas@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NeilBrown <neilb@suse.de>
Pull x86 build update from Ingo Molnar:
"A single commit that simplifies the no-FPU-ops build options"
* 'x86-build-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/kbuild: Eliminate duplicate command line options
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Merge tag 'tiny/for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/josh/linux
Pull "tinification" patches from Josh Triplett.
Work on making smaller kernels.
* tag 'tiny/for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/josh/linux:
bloat-o-meter: Ignore syscall aliases SyS_ and compat_SyS_
mm: Support compiling out madvise and fadvise
x86: Support compiling out human-friendly processor feature names
x86: Drop support for /proc files when !CONFIG_PROC_FS
x86, boot: Don't compile early_serial_console.c when !CONFIG_EARLY_PRINTK
x86, boot: Don't compile aslr.c when !CONFIG_RANDOMIZE_BASE
x86, boot: Use the usual -y -n mechanism for objects in vmlinux
x86: Add "make tinyconfig" to configure the tiniest possible kernel
x86, platform, kconfig: move kvmconfig functionality to a helper
The options -mno-mmx and -mno-sse are unconditionally added to
KBUILD_CFLAGS in both branches of an ifeq and through a
$(cc-option) further down. We can safely remove the first
instances.
In fact, since the -mno-mmx and -mno-sse options were introduced
simultaneous with the other two options in the $(cc-option)
[according to http://www.gnu.org/software/gcc/gcc-3.1/changes.html],
and since the former were unconditionally used, one can deduce that
only gcc versions knowing about all four are supported. So also
eliminate the $(cc-option) wrap.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Peter Foley <pefoley2@pefoley.com>
Link: http://lkml.kernel.org/r/1410365139-24440-1-git-send-email-linux@rasmusvillemoes.dk
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Without this patch the kexec-purgatory.c and purgatory.ro files are not
removed after make mrproper.
Signed-off-by: Michael Welling <mwelling@ieee.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Luc Van Oostenryck