No description
  • C 96.8%
  • Assembly 0.9%
  • Rust 0.7%
  • Shell 0.6%
  • Python 0.5%
  • Other 0.3%
Find a file
Mark Rutland 39138093f1 arm64: alternatives: make clean_dcache_range_nopatch() noinstr-safe
When patching kernel alternatives, we need to be careful not to execute
kernel code which is itself subject to patching. In general, if code is
executed after the instructions in memory have been patched but prior to
the cache maintenance and barriers completing, it could lead to
UNPREDICTABLE results.

As our regular cache maintenance routines are patched with alternatives,
we have a clean_dcache_range_nopatch() function which is *intended* to
avoid patchable code and therefore supposed to be safe in the middle of
patching alternatives. Unfortunately, it's not marked as 'noinstr', and
so can be instrumented with patchable code.

Additionally, it calls read_sanitised_ftr_reg() (which may be
instrumented with patchable code) to find the sanitized value of
CTR_EL0.DminLine, and is therefore not safe to call during patching.

Luckily, since commit:

  675b0563d6 ("arm64: cpufeature: expose arm64_ftr_reg struct for CTR_EL0")

... we can read the sanitised CTR_EL0 value directly, and avoid the call
to read_sanitised_ftr_reg().

This patch marks clean_dcache_range_nopatch() as noinstr, and has it
read the sanitized CTR_EL0 value directly, avoiding the issues above.

As a bonus, this is also an optimization. As read_sanitised_ftr_reg()
performs a binary search to find the CTR_EL0 value, reading the value
directly avoids this binary search per applied alternative, avoiding
some unnecessary work.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230616103150.1238132-1-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
History 2023-06-21 16:07:45 +01:00
arch
block
certs
crypto
Documentation
drivers
fs
include
init
io_uring
ipc
kernel
lib
LICENSES
mm
net
rust
samples
scripts
security
sound
tools
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
.rustfmt.toml
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile
README

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.