Hey Ilya,
On 8/12/21 1:12 PM, Ilya Leoshkevich wrote:
"access skb fields ok" verifier test fails on s390 with the "verifier
bug. zext_dst is set, but no reg is defined" message. The first insns
of the test prog are:
0: 61 01 00 00 00 00 00 00 ldxw %r0,[%r1+0]
8: 35 00 00 01 00 00 00 00 jge %r0,0,1
10: 61 01 00 08 00 00 00 00 ldxw %r0,[%r1+8]
and the 3rd one is dead (this does not look intentional to me, but this
is a separate topic).
sanitize_dead_code() converts dead insns into "ja -1", but keeps
zext_dst. When opt_subreg_zext_lo32_rnd_hi32() tries to parse such
an insn, it sees this discrepancy and bails. This problem can be seen
only with JITs whose bpf_jit_needs_zext() returns true.
Fix by clearning dead insns' zext_dst.
Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
I presume this would rather be bpf tree material, no? Do you also have a
Fixes tag I could add?
And one last small request: if this is not already covered by test_verifier
selftest, could you add one along with the fix?
Thanks a lot,
Daniel
