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The separate vmalloc area size check against _REGION2_SIZE is needed in case user provided insanely large value using vmalloc= kernel command line parameter. That could lead to overflow and selecting 3 page table levels instead of 4. Use size_add() for the overflow check and get rid of the extra vmalloc area check. With the current values of CONFIG_MAX_PHYSMEM_BITS and PAGES_PER_SECTION the sum of maximal possible size of identity mapping and vmemmap area (derived from these macros) plus modules area size MODULES_LEN can not overflow. Thus, that sum is used as first addend while vmalloc area size is second addend for size_add(). Suggested-by: Heiko Carstens <hca@linux.ibm.com> Acked-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@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.