Merging upstream version 6.7.7.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 0 insertions, 58 deletions

diff --git a/Documentation/powerpc/dexcr.rst b/Documentation/powerpc/dexcr.rst
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-.. SPDX-License-Identifier: GPL-2.0-or-later
-
-==========================================
-DEXCR (Dynamic Execution Control Register)
-==========================================
-
-Overview
-========
-
-The DEXCR is a privileged special purpose register (SPR) introduced in
-PowerPC ISA 3.1B (Power10) that allows per-cpu control over several dynamic
-execution behaviours. These behaviours include speculation (e.g., indirect
-branch target prediction) and enabling return-oriented programming (ROP)
-protection instructions.
-
-The execution control is exposed in hardware as up to 32 bits ('aspects') in
-the DEXCR. Each aspect controls a certain behaviour, and can be set or cleared
-to enable/disable the aspect. There are several variants of the DEXCR for
-different purposes:
-
-DEXCR
-    A privileged SPR that can control aspects for userspace and kernel space
-HDEXCR
-    A hypervisor-privileged SPR that can control aspects for the hypervisor and
-    enforce aspects for the kernel and userspace.
-UDEXCR
-    An optional ultravisor-privileged SPR that can control aspects for the ultravisor.
-
-Userspace can examine the current DEXCR state using a dedicated SPR that
-provides a non-privileged read-only view of the userspace DEXCR aspects.
-There is also an SPR that provides a read-only view of the hypervisor enforced
-aspects, which ORed with the userspace DEXCR view gives the effective DEXCR
-state for a process.
-
-
-Configuration
-=============
-
-The DEXCR is currently unconfigurable. All threads are run with the
-NPHIE aspect enabled.
-
-
-coredump and ptrace
-===================
-
-The userspace values of the DEXCR and HDEXCR (in this order) are exposed under
-``NT_PPC_DEXCR``. These are each 64 bits and readonly, and are intended to
-assist with core dumps. The DEXCR may be made writable in future. The top 32
-bits of both registers (corresponding to the non-userspace bits) are masked off.
-
-If the kernel config ``CONFIG_CHECKPOINT_RESTORE`` is enabled, then
-``NT_PPC_HASHKEYR`` is available and exposes the HASHKEYR value of the process
-for reading and writing. This is a tradeoff between increased security and
-checkpoint/restore support: a process should normally have no need to know its
-secret key, but restoring a process requires setting its original key. The key
-therefore appears in core dumps, and an attacker may be able to retrieve it from
-a coredump and effectively bypass ROP protection on any threads that share this
-key (potentially all threads from the same parent that have not run ``exec()``).