33bd8d153c
There is no added security by making the inittext section non-writable, however it does split part of the kernel mapping into 4K mappings instead of 1M mappings: ---[ Kernel Image Start ]--- 0x000003ffe0000000-0x000003ffe0e00000 14M PMD RO X 0x000003ffe0e00000-0x000003ffe0ec7000 796K PTE RO X 0x000003ffe0ec7000-0x000003ffe0f00000 228K PTE RO NX 0x000003ffe0f00000-0x000003ffe1300000 4M PMD RO NX 0x000003ffe1300000-0x000003ffe1353000 332K PTE RO NX 0x000003ffe1353000-0x000003ffe1400000 692K PTE RW NX 0x000003ffe1400000-0x000003ffe1500000 1M PMD RW NX 0x000003ffe1500000-0x000003ffe1700000 2M PTE RW NX <--- 0x000003ffe1700000-0x000003ffe1800000 1M PMD RW NX 0x000003ffe1800000-0x000003ffe187e000 504K PTE RW NX ---[ Kernel Image End ]--- Keep the inittext writable and enable instruction execution protection (aka noexec) later to prevent this. This also allows to use the generic free_initmem() implementation. ---[ Kernel Image Start ]--- 0x000003ffe0000000-0x000003ffe0e00000 14M PMD RO X 0x000003ffe0e00000-0x000003ffe0ec7000 796K PTE RO X 0x000003ffe0ec7000-0x000003ffe0f00000 228K PTE RO NX 0x000003ffe0f00000-0x000003ffe1300000 4M PMD RO NX 0x000003ffe1300000-0x000003ffe1353000 332K PTE RO NX 0x000003ffe1353000-0x000003ffe1400000 692K PTE RW NX 0x000003ffe1400000-0x000003ffe1800000 4M PMD RW NX <--- 0x000003ffe1800000-0x000003ffe187e000 504K PTE RW NX ---[ Kernel Image End ]--- Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@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.