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When pre-processing the instructions, it is trivial to detect what subprograms are using R6, R7, R8 or R9 as destination registers. If a subprogram uses none of those, then we do not need to jump to the subroutines dedicated to saving and restoring callee-saved registers in its prologue and epilogue. This patch introduces detection of callee-saved registers in subprograms and prevents the JIT from adding calls to those subroutines whenever we can: we save some instructions in the translated program, and some time at runtime on BPF-to-BPF calls and returns. If no subprogram needs to save those registers, we can avoid appending the subroutines at the end of the program. Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com> Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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.