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To resume from hibernate, the contents of memory are restored from the swap image. This may overwrite any page, including the running kernel and its page tables. Hibernate copies the code it uses to do the restore into a single page that it knows won't be overwritten, and maps it with page tables built from pages that won't be overwritten. Today the address it uses for this mapping is arbitrary, but to allow kexec to reuse this code, it needs to be idmapped. To idmap the page we must avoid the kernel helpers that have VA_BITS baked in. Convert create_single_mapping() to take a single PA, and idmap it. The page tables are built in the reverse order to normal using pfn_pte() to stir in any bits between 52:48. T0SZ is always increased to cover 48bits, or 52 if the copy code has bits 52:48 in its PA. Signed-off-by: James Morse <james.morse@arm.com> [Adopted the original patch from James to trans_pgd interface, so it can be commonly used by both Kexec and Hibernate. Some minor clean-ups.] Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com> Link: https://lore.kernel.org/linux-arm-kernel/20200115143322.214247-4-james.morse@arm.com/ Link: https://lore.kernel.org/r/20210125191923.1060122-9-pasha.tatashin@soleen.com Signed-off-by: Will Deacon <will@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.