[v3,0/3] bpf,x64: implement jump padding in jit

Message

Gary Lin Jan. 14, 2021, 9:54 a.m. UTC

This patch series implements jump padding to x64 jit to cover some
corner cases that used to consume more than 20 jit passes and caused
failure.

v3:
  - Copy the instructions of prologue separately or the size calculation
    of the first BPF instruction would include the prologue.
  - Replace WARN_ONCE() with pr_err() and EFAULT
  - Use MAX_PASSES in the for loop condition check
  - Remove the "padded" flag from x64_jit_data. For the extra pass of
    subprogs, padding is always enabled since it won't hurt the images
    that converge without padding.
v2:
  - Simplify the sample code in the commit description and provide the
    jit code
  - Check the expected padding bytes with WARN_ONCE
  - Move the 'padded' flag to 'struct x64_jit_data'
  - Remove the EXPECTED_FAIL flag from bpf_fill_maxinsns11() in test_bpf
  - Add 2 verifier tests

Gary Lin (3):
  bpf,x64: pad NOPs to make images converge more easily
  test_bpf: remove EXPECTED_FAIL flag from bpf_fill_maxinsns11
  selftests/bpf: Add verifier test for x64 jit jump padding

 arch/x86/net/bpf_jit_comp.c                 | 86 +++++++++++++++------
 lib/test_bpf.c                              |  7 +-
 tools/testing/selftests/bpf/test_verifier.c | 43 +++++++++++
 tools/testing/selftests/bpf/verifier/jit.c  | 16 ++++
 4 files changed, 122 insertions(+), 30 deletions(-)