mbox series

[00/13] ARM BPF jit compiler improvements

Message ID 20180710123340.GK17271@n2100.armlinux.org.uk
Headers show
Series ARM BPF jit compiler improvements | expand

Message

Russell King (Oracle) July 10, 2018, 12:33 p.m. UTC 
Hi,

This series improves the ARM BPF JIT compiler by:
- enumerating the stack layout rather than using constants that happen
  to be multiples of four
- rejig the BPF "register" accesses to use negative numbers instead of
  positive, which could be confused with register numbers in the bpf2a32
  array.
- since we maintain the ARM FP register as a pointer to the top of our
  scratch space (or, with frame pointers enabled, a valid ARM frame
  pointer register), we can access our scratch space using FP, which is
  constant across all BPF programs, including tail-called programs.
- use immediate forms of ARM instructions where possible, rather than
  first loading the immediate into an ARM register.
- use load-with-shift instruction rather than seperate shift instruction
  followed by load
- avoid reloading index and array in the tail-call code
- use double-word load/store instructions where available

 arch/arm/net/bpf_jit_32.c | 927 +++++++++++++++++++++++-----------------------
 arch/arm/net/bpf_jit_32.h |  44 +--
 2 files changed, 493 insertions(+), 478 deletions(-)