On 2016/06/20 03:56PM, Thadeu Lima de Souza Cascardo wrote:
> On Sun, Jun 19, 2016 at 11:19:14PM +0530, Naveen N. Rao wrote:
> > On 2016/06/17 10:00AM, Thadeu Lima de Souza Cascardo wrote:
> > >
> > > Hi, Michael and Naveen.
> > >
> > > I noticed independently that there is a problem with BPF JIT and ABIv2,
> > > and
> > > worked out the patch below before I noticed Naveen's patchset and the
> > > latest
> > > changes in ppc tree for a better way to check for ABI versions.
> > >
> > > However, since the issue described below affect mainline and stable
> > > kernels,
> > > would you consider applying it before merging your two patchsets, so that
> > > we can
> > > more easily backport the fix?
> >
> > Hi Cascardo,
> > Given that this has been broken on ABIv2 since forever, I didn't bother
> > fixing it. But, I can see why this would be a good thing to have for
> > -stable and existing distros. However, while your patch below may fix
> > the crash you're seeing on ppc64le, it is not sufficient -- you'll need
> > changes in bpf_jit_asm.S as well.
>
> Hi, Naveen.
>
> Any tips on how to exercise possible issues there? Or what changes you think
> would be sufficient?
The calling convention is different with ABIv2 and so we'll need changes
in bpf_slow_path_common() and sk_negative_common().
However, rather than enabling classic JIT for ppc64le, are we better off
just disabling it?
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -128,7 +128,7 @@ config PPC
select IRQ_FORCED_THREADING
select HAVE_RCU_TABLE_FREE if SMP
select HAVE_SYSCALL_TRACEPOINTS
- select HAVE_CBPF_JIT
+ select HAVE_CBPF_JIT if CPU_BIG_ENDIAN
select HAVE_ARCH_JUMP_LABEL
select ARCH_HAVE_NMI_SAFE_CMPXCHG
select ARCH_HAS_GCOV_PROFILE_ALL
Michael,
Let me know your thoughts on whether you intend to take this patch or
Cascardo's patch for -stable before the eBPF patches. I can redo my
patches accordingly.
- Naveen
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