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Filename Latest commit message Latest commit date
Andy Lutomirski 715bd9d12f x86/vdso: Fix asm constraints on vDSO syscall fallbacks
The syscall fallbacks in the vDSO have incorrect asm constraints.
They are not marked as writing to their outputs -- instead, they are
marked as clobbering "memory", which is useless.  In particular, gcc
is smart enough to know that the timespec parameter hasn't escaped,
so a memory clobber doesn't clobber it.  And passing a pointer as an
asm *input* does not tell gcc that the pointed-to value is changed.

Add in the fact that the asm instructions weren't volatile, and gcc
was free to omit them entirely unless their sole output (the return
value) is used.  Which it is (phew!), but that stops happening with
some upcoming patches.

As a trivial example, the following code:

void test_fallback(struct timespec *ts)
{
	vdso_fallback_gettime(CLOCK_MONOTONIC, ts);
}

compiles to:

00000000000000c0 <test_fallback>:
  c0:   c3                      retq

To add insult to injury, the RCX and R11 clobbers on 64-bit
builds were missing.

The "memory" clobber is also unnecessary -- no ordering with respect to
other memory operations is needed, but that's going to be fixed in a
separate not-for-stable patch.

Fixes: 2aae950b21 ("x86_64: Add vDSO for x86-64 with gettimeofday/clock_gettime/getcpu")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/2c0231690551989d2fafa60ed0e7b5cc8b403908.1538422295.git.luto@kernel.org
2018-10-02 08:28:15 +02:00
arch x86/vdso: Fix asm constraints on vDSO syscall fallbacks 2018-10-02 08:28:15 +02:00
block blk-mq: I/O and timer unplugs are inverted in blktrace 2018-09-27 13:12:44 -06:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto DMAengine updates for v4.19-rc1 2018-08-18 15:55:59 -07:00
Documentation Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2018-09-28 18:04:50 -07:00
drivers for-linus-20180929 2018-09-29 14:52:14 -07:00
firmware
fs filesystem-dax for 4.19-rc6 2018-09-30 06:19:38 -07:00
include spi: Fixes for v4.19 2018-09-28 18:04:06 -07:00
init Kbuild updates for v4.19 (2nd) 2018-08-25 13:40:38 -07:00
ipc ipc/shm: properly return EIDRM in shm_lock() 2018-09-04 16:45:02 -07:00
kernel Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-09-29 11:32:03 -07:00
lib lib/Kconfig.debug: fix three typos in help text 2018-09-04 16:45:02 -07:00
LICENSES
mm mm: slowly shrink slabs with a relatively small number of objects 2018-09-20 22:01:11 +02:00
net ip_tunnel: be careful when accessing the inner header 2018-09-24 12:27:04 -07:00
samples
scripts linux-kselftest-4.19-rc5 2018-09-17 07:24:28 +02:00
security Revert "uapi/linux/keyctl.h: don't use C++ reserved keyword as a struct member name" 2018-09-25 13:28:58 +02:00
sound ASoC: Fixes for v4.19 2018-09-17 18:59:21 +02:00
tools powerpc fixes for 4.19 #3 2018-09-28 17:43:32 -07:00
usr initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
virt KVM: Remove obsolete kvm_unmap_hva notifier backend 2018-09-07 15:06:02 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild
Kconfig
MAINTAINERS A trivial fix for auxdisplay 2018-09-30 06:20:33 -07:00
Makefile Linux 4.19-rc6 2018-09-30 07:15:35 -07:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.