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Filename Latest commit message Latest commit date
Nick Desaulniers 12051b318b
mips: avoid explicit UB in assignment of mips_io_port_base
The code in question is modifying a variable declared const through
pointer manipulation.  Such code is explicitly undefined behavior, and
is the lone issue preventing malta_defconfig from booting when built
with Clang:

If an attempt is made to modify an object defined with a const-qualified
type through use of an lvalue with non-const-qualified type, the
behavior is undefined.

LLVM is removing such assignments. A simple fix is to not declare
variables const that you plan on modifying.  Limiting the scope would be
a better method of preventing unwanted writes to such a variable.

Further, the code in question mentions "compiler bugs" without any links
to bug reports, so it is difficult to know if the issue is resolved in
GCC. The patch was authored in 2006, which would have been GCC 4.0.3 or
4.1.1. The minimal supported version of GCC in the Linux kernel is
currently 4.6.

For what its worth, there was UB before the commit in question, it just
added a barrier and got lucky IRT codegen. I don't think there's any
actual compiler bugs related, just runtime bugs due to UB.

Link: https://github.com/ClangBuiltLinux/linux/issues/610
Fixes: 966f4406d9 ("[MIPS] Work around bad code generation for <asm/io.h>.")
Reported-by: Nathan Chancellor <natechancellor@gmail.com>
Debugged-by: Nathan Chancellor <natechancellor@gmail.com>
Suggested-by: Eli Friedman <efriedma@quicinc.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: ralf@linux-mips.org
Cc: jhogan@kernel.org
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Hassan Naveed <hnaveed@wavecomp.com>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Serge Semin <fancer.lancer@gmail.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: clang-built-linux@googlegroups.com
2019-08-24 15:10:58 +01:00
arch mips: avoid explicit UB in assignment of mips_io_port_base 2019-08-24 15:10:58 +01:00
block
certs
crypto
Documentation dt-bindings: Add doc for the Ingenic TCU drivers 2019-08-08 15:30:06 -07:00
drivers irqchip/irq-ingenic-tcu: Fix COMPILE_TEST building 2019-08-19 22:15:37 +01:00
fs SMB3 fixes: two fixes for stable, one that had dependency on earlier patch in this merge window and can now go in, and a perf improvement in SMB3 open 2019-07-21 10:01:17 -07:00
include clk: jz4740: Add TCU clock 2019-08-08 15:30:08 -07:00
init Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
ipc Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
kernel dma-mapping fixes for 5.3-rc1 2019-07-20 12:09:52 -07:00
lib Kbuild updates for v5.3 (2nd) 2019-07-20 09:34:55 -07:00
LICENSES
mm Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
net Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
samples
scripts Kbuild updates for v5.3 (2nd) 2019-07-20 09:34:55 -07:00
security Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
sound ASoC: jz4740: Drop lb60 board code 2019-07-30 10:41:53 -07:00
tools New feature to add support for NTB virtual MSI interrupts, the ability 2019-07-21 09:46:59 -07:00
usr Kbuild updates for v5.3 (2nd) 2019-07-20 09:34:55 -07:00
virt KVM: Boost vCPUs that are delivering interrupts 2019-07-20 09:00:45 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS Remove references to dead website. 2019-07-19 12:22:04 -07:00
Kbuild
Kconfig
MAINTAINERS Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-20 11:24:49 -07:00
Makefile Linus 5.3-rc1 2019-07-21 14:05:38 -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.

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.