82046702e2
The notion of a 'preferred' load offset for the kernel dates back to the times when the kernel's primary mapping overlapped with the linear region, and memory below it could not be used at all. Today, the arm64 kernel does not really care where it is loaded in physical memory, as long as the alignment requirements are met, and so there is no point in unconditionally moving the kernel to a new location in memory at boot. Instead, we can - check for a KASLR seed, and randomly reallocate the kernel if one is provided - otherwise, check whether the alignment requirements are met for the current placement of the kernel, and just run it in place if they are - finally, do an ordinary page allocation and reallocate the kernel to a suitably aligned buffer anywhere in memory. By the same reasoning, there is no need to take TEXT_OFFSET into account if it is a round multiple of the minimum alignment, which is the usual case for relocatable kernels with TEXT_OFFSET randomization disabled. Otherwise, it suffices to use the relative misaligment of TEXT_OFFSET when reallocating the kernel. Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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.