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Inheriting the DEXCR across exec can have security and usability concerns. If a program is compiled with hash instructions it generally expects to run with NPHIE enabled. But if the parent process disables NPHIE then if it's not careful it will be disabled for any children too and the protection offered by hash checks is basically worthless. This patch introduces a per-process reset value that new execs in a particular process tree are initialized with. This enables fine grained control over what DEXCR value child processes run with by default. For example, containers running legacy binaries that expect hash instructions to act as NOPs could configure the reset value of the container root to control the default reset value for all members of the container. Signed-off-by: Benjamin Gray <bgray@linux.ibm.com> [mpe: Add missing SPDX tag on dexcr.c] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20240417112325.728010-4-bgray@linux.ibm.com
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 reStructuredText 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.