1. 10 10月, 2017 27 次提交
  2. 09 10月, 2017 12 次提交
  3. 08 10月, 2017 1 次提交
    • A
      bpf: fix liveness marking · 8fe2d6cc
      Alexei Starovoitov 提交于
      while processing Rx = Ry instruction the verifier does
      regs[insn->dst_reg] = regs[insn->src_reg]
      which often clears write mark (when Ry doesn't have it)
      that was just set by check_reg_arg(Rx) prior to the assignment.
      That causes mark_reg_read() to keep marking Rx in this block as
      REG_LIVE_READ (since the logic incorrectly misses that it's
      screened by the write) and in many of its parents (until lucky
      write into the same Rx or beginning of the program).
      That causes is_state_visited() logic to miss many pruning opportunities.
      
      Furthermore mark_reg_read() logic propagates the read mark
      for BPF_REG_FP as well (though it's readonly) which causes
      harmless but unnecssary work during is_state_visited().
      Note that do_propagate_liveness() skips FP correctly,
      so do the same in mark_reg_read() as well.
      It saves 0.2 seconds for the test below
      
      program               before  after
      bpf_lb-DLB_L3.o       2604    2304
      bpf_lb-DLB_L4.o       11159   3723
      bpf_lb-DUNKNOWN.o     1116    1110
      bpf_lxc-DDROP_ALL.o   34566   28004
      bpf_lxc-DUNKNOWN.o    53267   39026
      bpf_netdev.o          17843   16943
      bpf_overlay.o         8672    7929
      time                  ~11 sec  ~4 sec
      
      Fixes: dc503a8a ("bpf/verifier: track liveness for pruning")
      Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
      Acked-by: NEdward Cree <ecree@solarflare.com>
      Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      8fe2d6cc