kernel/linux
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2026-10-14 05:55:17 +00:00
Code Issues Releases Packages Activity
No description
840,021 commits 116 branches 5,791 tags 5.6 GiB
  • C 96.9%
  • Assembly 0.9%
  • Rust 0.6%
  • Shell 0.6%
  • Python 0.5%
  • Other 0.3%
Find a file
Christophe Leroy 6c284228eb powerpc: Fix kexec failure on book3s/32 
In the old days, _PAGE_EXEC didn't exist on 6xx aka book3s/32.
Therefore, allthough __mapin_ram_chunk() was already mapping kernel
text with PAGE_KERNEL_TEXT and the rest with PAGE_KERNEL, the entire
memory was executable. Part of the memory (first 512kbytes) was
mapped with BATs instead of page table, but it was also entirely
mapped as executable.

In commit 385e89d5b2 ("powerpc/mm: add exec protection on
powerpc 603"), we started adding exec protection to some 6xx, namely
the 603, for pages mapped via pagetables.

Then, in commit 63b2bc6195 ("powerpc/mm/32s: Use BATs for
STRICT_KERNEL_RWX"), the exec protection was extended to BAT mapped
memory, so that really only the kernel text could be executed.

The problem here is that kexec is based on copying some code into
upper part of memory then executing it from there in order to install
a fresh new kernel at its definitive location.

However, the code is position independant and first part of it is
just there to deactivate the MMU and jump to the second part. So it
is possible to run this first part inplace instead of running the
copy. Once the MMU is off, there is no protection anymore and the
second part of the code will just run as before.

Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Fixes: 63b2bc6195 ("powerpc/mm/32s: Use BATs for STRICT_KERNEL_RWX")
Cc: stable@vger.kernel.org # v5.1+
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
History 2019-06-07 16:24:47 +10:00
arch
block
certs
crypto
Documentation
drivers
fs
include
init
ipc
kernel
lib
LICENSES
mm
net
samples
scripts
security
sound
tools
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS The usual smattering of fixes and tunings that came in too late for the 2019-05-26 13:45:15 -07:00
Makefile
README

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.