97e3d26b5e
Seth found that the CPU-entry-area; the piece of per-cpu data that is mapped into the userspace page-tables for kPTI is not subject to any randomization -- irrespective of kASLR settings. On x86_64 a whole P4D (512 GB) of virtual address space is reserved for this structure, which is plenty large enough to randomize things a little. As such, use a straight forward randomization scheme that avoids duplicates to spread the existing CPUs over the available space. [ bp: Fix le build. ] Reported-by: Seth Jenkins <sethjenkins@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Signed-off-by: Borislav Petkov <bp@suse.de>
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.