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.
Luke Nelson
authored
This patch optimizes the code generated by emit_a32_arsh_r64, which handles the BPF_ALU64 BPF_ARSH BPF_X instruction. The original code uses a conditional B followed by an unconditional ORR. The optimization saves one instruction by removing the B instruction and using a conditional ORR (with an inverted condition). Example of the code generated for BPF_ALU64_REG(BPF_ARSH, BPF_REG_0, BPF_REG_1), before optimization: 34: rsb ip, r2, #32 38: subs r9, r2, #32 3c: lsr lr, r0, r2 40: orr lr, lr, r1, lsl ip 44: bmi 0x4c 48: orr lr, lr, r1, asr r9 4c: asr ip, r1, r2 50: mov r0, lr 54: mov r1, ip and after optimization: 34: rsb ip, r2, #32 38: subs r9, r2, #32 3c: lsr lr, r0, r2 40: orr lr, lr, r1, lsl ip 44: orrpl lr, lr, r1, asr r9 48: asr ip, r1, r2 4c: mov r0, lr 50: mov r1, ip Tested on QEMU using lib/test_bpf and test_verifier. Co-developed-by:Xi Wang <xi.wang@gmail.com> Signed-off-by:
Luke Nelson <luke.r.nels@gmail.com> Signed-off-by:
Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20200501020210.32294-2-luke.r.nels@gmail.com
| Name | Last commit | Last update |
|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README |