bac4cffc7c
On 603 MMU, TLB missed are handled by SW and there are separated DTLB and ITLB. It is therefore possible to implement execute-only protection by not loading DTLB when read access is not permitted. To do that, _PAGE_READ flag is needed but there is no bit available for it in PTE. On the other hand the only real use of _PAGE_USER is to implement PAGE_NONE by clearing _PAGE_USER. As _PAGE_NONE can also be implemented by clearing _PAGE_READ, remove _PAGE_USER and add _PAGE_READ. Then use the virtual address to know whether user rights or kernel rights are to be used. With that change, 603 MMU now honors execute-only protection. For hash (604) MMU it is more tricky because hash table is common to load/store and execute. Nevertheless it is still possible to check whether _PAGE_READ is set before loading hash table for a load/store access. At least it can't be read unless it is executed first. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/b7702dd5a041ec59055ed2880f4952e94c087a2e.1695659959.git.christophe.leroy@csgroup.eu
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.