On Fri, May 13, 2016 at 10:57:18AM +0100, Will Deacon wrote:
> On Thu, May 12, 2016 at 11:37:58PM -0700, Zi Shen Lim wrote:
> > Original implementation commit e54bcde3d69d ("arm64: eBPF JIT compiler")
> > had the relevant code paths, but due to an oversight always fail jiting.
> >
> > As a result, we had been falling back to BPF interpreter whenever a BPF
> > program has JMP_JSET_{X,K} instructions.
> >
> > With this fix, we confirm that the corresponding tests in lib/test_bpf
> > continue to pass, and also jited.
> >
> > ...
> > [ 2.784553] test_bpf: #30 JSET jited:1 188 192 197 PASS
> > [ 2.791373] test_bpf: #31 tcpdump port 22 jited:1 325 677 625 PASS
> > [ 2.808800] test_bpf: #32 tcpdump complex jited:1 323 731 991 PASS
> > ...
> > [ 3.190759] test_bpf: #237 JMP_JSET_K: if (0x3 & 0x2) return 1 jited:1
> > 110 PASS
> > [ 3.192524] test_bpf: #238 JMP_JSET_K: if (0x3 & 0xffffffff) return 1
> > jited:1 98 PASS
> > [ 3.211014] test_bpf: #249 JMP_JSET_X: if (0x3 & 0x2) return 1 jited:1
> > 120 PASS
> > [ 3.212973] test_bpf: #250 JMP_JSET_X: if (0x3 & 0xffffffff) return 1
> > jited:1 89 PASS
> > ...
> >
> > Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler")
> > Signed-off-by: Zi Shen Lim <zlim....@gmail.com>
> > ---
> > arch/arm64/net/bpf_jit_comp.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> > index 031ed08..d0d5190 100644
> > --- a/arch/arm64/net/bpf_jit_comp.c
> > +++ b/arch/arm64/net/bpf_jit_comp.c
> > @@ -478,6 +478,7 @@ emit_cond_jmp:
> > case BPF_JGE:
> > jmp_cond = A64_COND_CS;
> > break;
> > + case BPF_JSET:
> > case BPF_JNE:
> > jmp_cond = A64_COND_NE;
> > break;
>
> Are you sure about this? filter.txt says:
>
> jne - Jump on K != A
> ...
> jset - Jump on k & A
>
> so it looks weird wiring them both to the same thing. I'm not sure you
> can express this as a simple CMP + B.<cond>.
Ah, sorry, I see how this works now. I overlooked the BPF_JMP | BPF_JSET |
BPF_X case emitting a TST instruction. In which case:
Acked-by: Will Deacon <will.dea...@arm.com>
I'm assuming David will queue this?
Will
