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When we have CONFIG_STRICT_KERNEL_RWX enabled, we want to split the linear mapping at the text/data boundary so we can map the kernel text read only. But the current logic uses small pages for the entire text section, regardless of whether a larger page size would fit. eg. with the boundary at 16M we could use 2M pages, but instead we use 64K pages up to the 16M boundary: Mapped 0x0000000000000000-0x0000000001000000 with 64.0 KiB pages Mapped 0x0000000001000000-0x0000000040000000 with 2.00 MiB pages Mapped 0x0000000040000000-0x0000000100000000 with 1.00 GiB pages This is because the test is checking if addr is < __init_begin and addr + mapping_size is >= _stext. But that is true for all pages between _stext and __init_begin. Instead what we want to check is if we are crossing the text/data boundary, which is at __init_begin. With that fixed we see: Mapped 0x0000000000000000-0x0000000000e00000 with 2.00 MiB pages Mapped 0x0000000000e00000-0x0000000001000000 with 64.0 KiB pages Mapped 0x0000000001000000-0x0000000040000000 with 2.00 MiB pages Mapped 0x0000000040000000-0x0000000100000000 with 1.00 GiB pages ie. we're correctly using 2MB pages below __init_begin, but we still drop down to 64K pages unnecessarily at the boundary. Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.