On Fri, Sep 9, 2022 at 4:21 AM Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> wrote:
>
> On Fri, 9 Sept 2022 at 10:25, Dave Marchevsky <davemarchevsky@xxxxxx> wrote:
> >
> > On 9/7/22 8:35 PM, Alexei Starovoitov wrote:
> > > On Sun, Sep 04, 2022 at 10:41:31PM +0200, Kumar Kartikeya Dwivedi wrote:
> > >> diff --git a/include/linux/poison.h b/include/linux/poison.h
> > >> index d62ef5a6b4e9..753e00b81acf 100644
> > >> --- a/include/linux/poison.h
> > >> +++ b/include/linux/poison.h
> > >> @@ -81,4 +81,7 @@
> > >> /********** net/core/page_pool.c **********/
> > >> #define PP_SIGNATURE (0x40 + POISON_POINTER_DELTA)
> > >>
> > >> +/********** kernel/bpf/helpers.c **********/
> > >> +#define BPF_PTR_POISON ((void *)((0xeB9FUL << 2) + POISON_POINTER_DELTA))
> > >> +
> > >
> > > That was part of Dave's patch set as well.
> > > Please keep his SOB and authorship and keep it as separate patch.
> >
> > My patch picked a different constant :). But on that note, it also added some
> > checking in verifier.c so that verification fails if any arg or retval type
> > was BPF_PTR_POISON after it should've been replaced. Perhaps it's worth shipping
> > that patch ("bpf: Add verifier check for BPF_PTR_POISON retval and arg")
> > separately? Would allow both rbtree series and this lock-focused patch to drop
> > BPF_PTR_POISON changes after rebase.
>
> Yeah, feel free to post it separately. I'm using the constant in this
> patch for a different purpose (I separate the BPF_PTR_POISON case into
> its own different argument type, and then check that it is always set
> for it in check_btf_id_ok, to ensure DYN_BTF_ID is not setting some
> static real BTF ID).
>
> But why change the constant, eB9F looks very close to eBPF already :).
+1. It's already in many spots:
git grep eB9F
