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Thomas Gleixner 2023963916 ARM: futex: Address build warning 
[ Upstream commit 8101b5a153 ]

Stephen reported the following build warning on a ARM multi_v7_defconfig
build with GCC 9.2.1:

kernel/futex.c: In function 'do_futex':
kernel/futex.c:1676:17: warning: 'oldval' may be used uninitialized in this function [-Wmaybe-uninitialized]
 1676 |   return oldval == cmparg;
      |          ~~~~~~~^~~~~~~~~
kernel/futex.c:1652:6: note: 'oldval' was declared here
 1652 |  int oldval, ret;
      |      ^~~~~~

introduced by commit a08971e948 ("futex: arch_futex_atomic_op_inuser()
calling conventions change").

While that change should not make any difference it confuses GCC which
fails to work out that oldval is not referenced when the return value is
not zero.

GCC fails to properly analyze arch_futex_atomic_op_inuser(). It's not the
early return, the issue is with the assembly macros. GCC fails to detect
that those either set 'ret' to 0 and set oldval or set 'ret' to -EFAULT
which makes oldval uninteresting. The store to the callsite supplied oldval
pointer is conditional on ret == 0.

The straight forward way to solve this is to make the store unconditional.

Aside of addressing the build warning this makes sense anyway because it
removes the conditional from the fastpath. In the error case the stored
value is uninteresting and the extra store does not matter at all.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/87pncao2ph.fsf@nanos.tec.linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-05-27 17:37:35 +02:00
arch ARM: futex: Address build warning 2020-05-27 17:37:35 +02:00
block block, bfq: fix use-after-free in bfq_idle_slice_timer_body 2020-04-17 10:48:42 +02:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto gcc-10: avoid shadowing standard library 'free()' in crypto 2020-05-20 08:18:46 +02:00
Documentation arm64: errata: Hide CTR_EL0.DIC on systems affected by Neoverse-N1 #1542419 2020-04-29 16:31:08 +02:00
drivers platform/x86: asus-nb-wmi: Do not load on Asus T100TA and T200TA 2020-05-27 17:37:35 +02:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs ceph: fix double unlock in handle_cap_export() 2020-05-27 17:37:34 +02:00
include x86: Fix early boot crash on gcc-10, third try 2020-05-20 08:18:49 +02:00
init x86: Fix early boot crash on gcc-10, third try 2020-05-20 08:18:49 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:18:40 +02:00
kernel Stop the ad-hoc games with -Wno-maybe-initialized 2020-05-20 08:18:45 +02:00
lib ubsan: build ubsan.c more conservatively 2020-05-27 17:37:27 +02:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm shmem: fix possible deadlocks on shmlock_user_lock 2020-05-20 08:18:32 +02:00
net netfilter: nft_set_rbtree: Introduce and use nft_rbtree_interval_start() 2020-05-20 08:18:44 +02:00
samples vmalloc: fix remap_vmalloc_range() bounds checks 2020-04-29 16:31:27 +02:00
scripts gcc-common.h: Update for GCC 10 2020-05-27 17:37:30 +02:00
security ima: Fix return value of ima_write_policy() 2020-05-27 17:37:29 +02:00
sound Revert "ALSA: hda/realtek: Fix pop noise on ALC225" 2020-05-20 08:18:52 +02:00
tools objtool: Fix stack offset tracking for indirect CFAs 2020-05-14 07:57:23 +02:00
usr initramfs: restore default compression behavior 2020-04-13 10:44:59 +02:00
virt KVM: arm64: Fix 32bit PC wrap-around 2020-05-14 07:57:20 +02:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 16:38:49 +01:00
Makefile Linux 4.19.124 2020-05-20 08:18:54 +02:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

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.