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Filename Latest commit message Latest commit date
Michael Ellerman 9227f04314 powerpc/udbg: Reduce the footgun potential of EARLY_DEBUG_LPAR(_HVSI)
For debugging very early boot problems we have CONFIG_PPC_EARLY_DEBUG,
which allows configuring the kernel such that it unconditionally writes
to a particular type of console, regardless of whether that console
exists or not. This is useful sometimes when the kernel crashes before
it can even determine what platform it's on, and therefore what consoles
exist.

However if you boot a kernel built this way on a different platform, it
will generally crash because it writes to a console that doesn't exist.

A particularly nasty instance of this is if you enable the hypervisor
console early debug, and then boot that kernel on bare metal. The result
is that the kernel calls "the hypervisor" very early in boot, but the
kernel *is* the hypervisor, so we jump to the system call handler and
start executing all sorts of code that isn't ready to be run. This may
lead to a machine check or check stop depending on how lucky you are.

Luckily there is an easy way to avoid this particular case. We simply
read the MSR before installing the hooks, and if we see MSR_HV is set
then we are the hypervisor and we definitely should not use the
hypervisor console.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2017-07-31 16:56:45 +10:00
arch powerpc/configs: Add a powernv_be_defconfig 2017-07-31 16:56:37 +10:00
block
certs
crypto
Documentation TTY/Serial fixes for 4.13-rc2 2017-07-22 09:00:24 -07:00
drivers powerpc/udbg: Reduce the footgun potential of EARLY_DEBUG_LPAR(_HVSI) 2017-07-31 16:56:45 +10:00
firmware
fs NFS client bugfixes for 4.13 2017-07-21 16:26:01 -07:00
include powerpc/perf: Add thread IMC PMU support 2017-07-25 22:55:46 +10:00
init
ipc
kernel Three minor updates 2017-07-21 13:59:51 -07:00
lib
mm
net NFS client bugfixes for 4.13 2017-07-21 16:26:01 -07:00
samples
scripts Properly alphabetize MAINTAINERS file 2017-07-23 16:06:21 -07:00
security
sound
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-21 11:12:48 -07:00
usr
virt
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Properly alphabetize MAINTAINERS file 2017-07-23 16:06:21 -07:00
Makefile Linux 4.13-rc2 2017-07-23 16:15:17 -07:00
README

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

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.