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5c46f2768c
Currently there are several minor problems with randomization base generation code: 1. It might misbehave in low memory conditions. In particular there might be enough space for the kernel on [0, block_sum] but after if (base < safe_addr) base = safe_addr; it might not be enough anymore. 2. It does not correctly handle minimal address constraint. In condition if (base < safe_addr) base = safe_addr; a synthetic value is compared with an address. If we have a memory setup with memory holes due to offline memory regions, and safe_addr is close to the end of the first online memory block - we might position the kernel in invalid memory. 3. block_sum calculation logic contains off-by-one error. Let's say we have a memory block in which the kernel fits perfectly (end - start == kernel_size). In this case: if (end - start < kernel_size) continue; block_sum += end - start - kernel_size; block_sum is not increased, while it is a valid kernel position. So, address problems listed and explain algorithm used. Besides that restructuring the code makes it possible to extend kernel positioning algorithm further. Currently we pick position in between single [min, max] range (min = safe_addr, max = memory_limit). In future we can do that for multiple ranges as well (by calling count_valid_kernel_positions for each range). Reviewed-by: Philipp Rudo <prudo@linux.ibm.com> Reviewed-by: Alexander Egorenkov <egorenar@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 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.