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Calling 32-bit EFI runtime services from a 64-bit OS involves switching back to the flat mapping with a stack carved out of memory that is 32-bit addressable. There is no need to actually execute the 64-bit part of this routine from the flat mapping as well, as long as the entry and return address fit in 32 bits. There is also no need to preserve part of the calling context in global variables: we can simply push the old stack pointer value to the new stack, and keep the return address from the code32 section in EBX. While at it, move the conditional check whether to invoke the mixed mode version of SetVirtualAddressMap() into the 64-bit implementation of the wrapper routine. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Arvind Sankar <nivedita@alum.mit.edu> Cc: Matthew Garrett <mjg59@google.com> Cc: linux-efi@vger.kernel.org Link: https://lkml.kernel.org/r/20200103113953.9571-11-ardb@kernel.org Signed-off-by: Ingo Molnar <mingo@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.