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Sean Christopherson f28b11a2ab x86/fault: Reword initial BUG message for unhandled page faults
Reword the NULL pointer dereference case to simply state that a NULL
pointer was dereferenced, i.e. drop "unable to handle" as that implies
that there are instances where the kernel actual does handle NULL
pointer dereferences, which is not true barring funky exception fixup.

For the non-NULL case, replace "kernel paging request" with "page fault"
as the kernel can technically oops on faults that originated in user
code.  Dropping "kernel" also allows future patches to provide detailed
information on where the fault occurred, e.g. user vs. kernel, without
conflicting with the initial BUG message.

In both cases, replace "at address=" with wording more appropriate to
the oops, as "at" may be interpreted as stating that the address is the
RIP of the instruction that faulted.

Last, and probably least, further qualify the NULL-pointer path by
checking that the fault actually originated in kernel code.  It's
technically possible for userspace to map address 0, and not printing
a super specific message is the least of our worries if the kernel does
manage to oops on an actual NULL pointer dereference from userspace.

Before:
    BUG: unable to handle kernel NULL pointer dereference at ffffbeef00000000
    BUG: unable to handle kernel paging request at ffffbeef00000000

After:
    BUG: kernel NULL pointer dereference, address = 0000000000000008
    BUG: unable to handle page fault for address = ffffbeef00000000

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/20181221213657.27628-2-sean.j.christopherson@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
History 2019-04-19 19:31:15 +02:00
arch x86/fault: Reword initial BUG message for unhandled page faults 2019-04-19 19:31:15 +02:00
block blk-mq: fix sbitmap ws_active for shared tags 2019-03-25 13:05:47 -06:00
certs kexec, KEYS: Make use of platform keyring for signature verify 2019-02-04 17:34:07 -05:00
crypto lib/lzo: separate lzo-rle from lzo 2019-03-07 18:32:03 -08:00
Documentation x86/mm: Fix the 56-bit addresses memory map in Documentation/x86/x86_64/mm.txt 2019-04-16 09:00:34 +02:00
drivers dmaengine-5.10-rc3 2019-03-31 07:42:39 -07:00
fs Merge branch 'work.aio' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-04-01 08:28:36 -07:00
include A collection of x86 and ARM bugfixes, and some improvements to documentation. 2019-03-31 08:55:59 -07:00
init init/main: add checks for the return value of memblock_alloc*() 2019-03-12 10:04:02 -07:00
ipc Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 14:08:19 -07:00
kernel Merge branch 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-03-31 08:22:12 -07:00
lib for-linus-20190329 2019-03-29 14:43:07 -07:00
LICENSES LICENSES: Add GCC runtime library exception text 2019-01-16 14:54:15 -07:00
mm mm/migrate.c: add missing flush_dcache_page for non-mapped page migrate 2019-03-29 10:01:37 -07:00
net A patch to avoid choking on multipage bvecs in the messenger and 2019-03-29 14:41:09 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-03-11 08:54:01 -07:00
scripts Merge branch 'akpm' (patches from Andrew) 2019-03-29 16:02:28 -07:00
security LSM: Revive CONFIG_DEFAULT_SECURITY_* for "make oldconfig" 2019-03-29 14:08:49 -07:00
sound sound fixes for 5.1-rc3 2019-03-29 14:53:33 -07:00
tools A collection of x86 and ARM bugfixes, and some improvements to documentation. 2019-03-31 08:55:59 -07:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt KVM/ARM fixes for 5.1 2019-03-28 19:07:30 +01:00
.clang-format Merge branch 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 13:43:42 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support for DT binding schema checks 2018-12-13 09:41:32 -06:00
.mailmap mailmap: add Changbin Du 2019-03-29 10:01:37 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Char/Misc driver patches for 5.1-rc1 2019-03-06 14:18:59 -08:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-03-31 07:48:58 -07:00
Makefile Linux 5.1-rc3 2019-03-31 14:39:29 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.