[PATCH bpf-next 0/3] bpf: Allow 'may_goto 0' instruction

[Yonghong Song <yonghong.song@linux.dev>]

Emil Tsalapatis from Meta reported such a case where 'may_goto 0' insn is
generated by clang-19 compiler and this caused verification failure
since 'may_goto 0' is rejected by verifier.

In fact, 'may_goto 0' insn is actually a no-op and it won't hurt
verification. The only side effect is that the verifier will convert
the insn to a sequence of codes like
   /* r10 - 8 stores the implicit loop count */
   r11 = *(u64 *)(r10 -8)
   if r11 == 0x0 goto pc+2
   r11 -= 1
   *(u64 *)(r10 -8) = r11

With this patch set 'may_goto 0' insns are allowed in verification which
also removes those insns.

Yonghong Song (3):
  bpf: Allow 'may_goto 0' instruction
  bpf: Remove 'may_goto 0' instruction
  selftests/bpf: Add some tests related to 'may_goto 0' insns

 kernel/bpf/verifier.c                         | 41 +++++++-
 .../selftests/bpf/prog_tests/verifier.c       |  4 +
 .../selftests/bpf/progs/verifier_may_goto_1.c | 97 +++++++++++++++++++
 .../selftests/bpf/progs/verifier_may_goto_2.c | 28 ++++++
 4 files changed, 167 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_may_goto_1.c
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_may_goto_2.c

-- 
2.43.5