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Arnd Bergmann b8fd230ae0 ARM: 9081/1: fix gcc-10 thumb2-kernel regression 
commit dad7b9896a upstream.

When building the kernel wtih gcc-10 or higher using the
CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=y flag, the compiler picks a slightly
different set of registers for the inline assembly in cpu_init() that
subsequently results in a corrupt kernel stack as well as remaining in
FIQ mode. If a banked register is used for the last argument, the wrong
version of that register gets loaded into CPSR_c.  When building in Arm
mode, the arguments are passed as immediate values and the bug cannot
happen.

This got introduced when Daniel reworked the FIQ handling and was
technically always broken, but happened to work with both clang and gcc
before gcc-10 as long as they picked one of the lower registers.
This is probably an indication that still very few people build the
kernel in Thumb2 mode.

Marek pointed out the problem on IRC, Arnd narrowed it down to this
inline assembly and Russell pinpointed the exact bug.

Change the constraints to force the final mode switch to use a non-banked
register for the argument to ensure that the correct constant gets loaded.
Another alternative would be to always use registers for the constant
arguments to avoid the #ifdef that has now become more complex.

Cc: <stable@vger.kernel.org> # v3.18+
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Reported-by: Marek Vasut <marek.vasut@gmail.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Fixes: c0e7f7ee71 ("ARM: 8150/3: fiq: Replace default FIQ handler")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-06-30 08:47:16 -04:00
arch ARM: 9081/1: fix gcc-10 thumb2-kernel regression 2021-06-30 08:47:16 -04:00
block blk-mq: Swap two calls in blk_mq_exit_queue() 2021-05-19 10:13:14 +02:00
certs certs: Fix blacklist flag type confusion 2021-03-04 11:37:59 +01:00
crypto async_xor: check src_offs is not NULL before updating it 2021-06-16 12:01:40 +02:00
Documentation mm/slub: clarify verification reporting 2021-06-23 14:42:53 +02:00
drivers drm/amdgpu: wait for moving fence after pinning 2021-06-30 08:47:16 -04:00
fs fanotify: fix copy_event_to_user() fid error clean up 2021-06-23 14:42:41 +02:00
include mm/swap: fix pte_same_as_swp() not removing uffd-wp bit when compare 2021-06-23 14:42:53 +02:00
init pid: take a reference when initializing cad_pid 2021-06-10 13:39:26 +02:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-26 12:06:54 +02:00
kernel module: limit enabling module.sig_enforce 2021-06-30 08:47:15 -04:00
lib lib/lz4: explicitly support in-place decompression 2021-06-10 13:39:29 +02:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm/slub.c: include swab.h 2021-06-23 14:42:54 +02:00
net net: bridge: fix vlan tunnel dst refcnt when egressing 2021-06-23 14:42:53 +02:00
samples samples: vfio-mdev: fix error handing in mdpy_fb_probe() 2021-06-10 13:39:15 +02:00
scripts scripts/clang-tools: switch explicitly to Python 3 2021-06-03 09:00:52 +02:00
security KEYS: trusted: Fix memory leak on object td 2021-05-19 10:12:50 +02:00
sound ASoC: qcom: lpass-cpu: Fix pop noise during audio capture begin 2021-06-23 14:42:49 +02:00
tools perf beauty: Update copy of linux/socket.h with the kernel sources 2021-06-23 14:42:54 +02:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt Revert "irqbypass: do not start cons/prod when failed connect" 2021-06-03 09:00:34 +02:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: generate Module.symvers only when vmlinux exists 2021-05-19 10:12:59 +02:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS f2fs: move ioctl interface definitions to separated file 2021-05-19 10:13:00 +02:00
Makefile Linux 5.10.46 2021-06-23 14:42:55 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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.

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.