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69393cb03c
Xmon should be either fully or partially disabled depending on the
kernel lockdown state.
Put xmon into read-only mode for lockdown=integrity and prevent user
entry into xmon when lockdown=confidentiality. Xmon checks the lockdown
state on every attempted entry:
(1) during early xmon'ing
(2) when triggered via sysrq
(3) when toggled via debugfs
(4) when triggered via a previously enabled breakpoint
The following lockdown state transitions are handled:
(1) lockdown=none -> lockdown=integrity
set xmon read-only mode
(2) lockdown=none -> lockdown=confidentiality
clear all breakpoints, set xmon read-only mode,
prevent user re-entry into xmon
(3) lockdown=integrity -> lockdown=confidentiality
clear all breakpoints, set xmon read-only mode,
prevent user re-entry into xmon
Suggested-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Christopher M. Riedl <cmr@informatik.wtf>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190907061124.1947-3-cmr@informatik.wtf
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.