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Will Deacon 6a684e0025 ARM: 8898/1: mm: Don't treat faults reported from cache maintenance as writes 
[ Upstream commit 834020366d ]

Translation faults arising from cache maintenance instructions are
rather unhelpfully reported with an FSR value where the WnR field is set
to 1, indicating that the faulting access was a write. Since cache
maintenance instructions on 32-bit ARM do not require any particular
permissions, this can cause our private 'cacheflush' system call to fail
spuriously if a translation fault is generated due to page aging when
targetting a read-only VMA.

In this situation, we will return -EFAULT to userspace, although this is
unfortunately suppressed by the popular '__builtin___clear_cache()'
intrinsic provided by GCC, which returns void.

Although it's tempting to write this off as a userspace issue, we can
actually do a little bit better on CPUs that support LPAE, even if the
short-descriptor format is in use. On these CPUs, cache maintenance
faults additionally set the CM field in the FSR, which we can use to
suppress the write permission checks in the page fault handler and
succeed in performing cache maintenance to read-only areas even in the
presence of a translation fault.

Reported-by: Orion Hodson <oth@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2019-10-07 18:57:11 +02:00
arch ARM: 8898/1: mm: Don't treat faults reported from cache maintenance as writes 2019-10-07 18:57:11 +02:00
block block: fix null pointer dereference in blk_mq_rq_timed_out() 2019-10-05 13:10:08 +02:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: chacha20poly1305 - fix atomic sleep when using async algorithm 2019-07-26 09:14:19 +02:00
Documentation ovl: fix regression caused by overlapping layers detection 2019-09-21 07:17:14 +02:00
drivers HID: wacom: Fix several minor compiler warnings 2019-10-07 18:57:10 +02:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs ext4: fix potential use after free after remounting with noblock_validity 2019-10-07 18:57:05 +02:00
include scsi: core: Reduce memory required for SCSI logging 2019-10-07 18:57:04 +02:00
init initramfs: don't free a non-existent initrd 2019-10-01 08:26:09 +02:00
ipc ipc/mqueue.c: only perform resource calculation if user valid 2019-08-06 19:06:52 +02:00
kernel livepatch: Nullify obj->mod in klp_module_coming()'s error path 2019-10-07 18:57:10 +02:00
lib lib: logic_pio: Add logic_pio_unregister_range() 2019-09-06 10:22:19 +02:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm/compaction.c: clear total_{migrate,free}_scanned before scanning a new zone 2019-10-05 13:10:13 +02:00
net cfg80211: Purge frame registrations on iftype change 2019-10-05 13:10:10 +02:00
samples samples, bpf: suppress compiler warning 2019-07-14 08:11:04 +02:00
scripts randstruct: Check member structs in is_pure_ops_struct() 2019-10-05 13:10:02 +02:00
security keys: Fix missing null pointer check in request_key_auth_describe() 2019-09-21 07:17:13 +02:00
sound ASoC: Intel: Fix use of potentially uninitialized variable 2019-10-05 13:10:06 +02:00
tools libtraceevent: Change users plugin directory 2019-10-05 13:09:53 +02:00
usr initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
virt KVM: coalesced_mmio: add bounds checking 2019-09-21 07:16:44 +02:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 platform/x86: Add Intel AtomISP2 dummy / power-management driver 2019-04-20 09:16:02 +02:00
Makefile Linux 4.19.77 2019-10-05 13:10:13 +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.