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When calling BPF helpers, we load the function address to call into a register. This can result in upto 5 instructions. Optimize this by instead using the kernel toc in r2 and adjusting offset to the BPF helper. This works since all BPF helpers are part of kernel text, and all BPF programs/functions utilize the kernel TOC. Further more: - load the actual function entry address in elf v1, rather than loading it through the function descriptor address. - load the Local Entry Point (LEP) in elf v2 skipping TOC setup. - consolidate code across elf abi v1 and v2 by using r12 on both. Reported-by: Anton Blanchard <anton@ozlabs.org> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1233c7544e60dcb021c52b1f840b0f21a87b33ed.1644834730.git.naveen.n.rao@linux.vnet.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.