Re: [PATCH] pickles: btf: improve magic num endianness logic

[David Faust]

On 1/4/22 14:48, Jose E. Marchesi wrote:
> Hi David.
>
> > The magic number should always read as 0xeb9f (like eBPF). When mapping
> > a BTF_Header, if 0x9feb is read instead then the current endianness is
> > simply the opposite that of the BTF information.
> >
> > This fixes an issue where attempting to map a little-endian BTF_Header
> > while in big-endian mode, the endianness would not correctly be
> > changed.
>
> OK for both master and maint/poke-1.
> Thanks.

Pushed to both. Thanks.

> > 2022-01-04  David Faust  <david.faust@oracle.com>
> >
> >         * pickles/btf.pk (BTF_Header): Adjust constraint on magic number
> >         to properly set endianness as needed.
> > ---
> >   ChangeLog      | 5 +++++
> >   pickles/btf.pk | 6 +++---
> >   2 files changed, 8 insertions(+), 3 deletions(-)
> >
> > diff --git a/ChangeLog b/ChangeLog
> > index b725a005..b889ab5e 100644
> > --- a/ChangeLog
> > +++ b/ChangeLog
> > @@ -1,3 +1,8 @@
> > +2022-01-04  David Faust  <david.faust@oracle.com>
> > +
> > +       * pickles/btf.pk (BTF_Header): Adjust constraint on magic number
> > +       to properly set endianness as needed.
> > +
> >   2022-01-04  Jose E. Marchesi  <jemarch@gnu.org>
> >   
> >   	* libpoke/pkl-gen.c: Remove obsolete comments.  The GEN contexts
> > diff --git a/pickles/btf.pk b/pickles/btf.pk
> > index 51110044..7b8cc0f5 100644
> > --- a/pickles/btf.pk
> > +++ b/pickles/btf.pk
> > @@ -199,9 +199,9 @@ type BTF_Type =
> >   type BTF_Header =
> >     struct
> >     {
> > -    uint<16> magic : ((magic == 0x9feb && set_endian (ENDIAN_BIG)
> > -                       || (magic == 0xeb9f && set_endian (ENDIAN_LITTLE))))
> > -                   = (get_endian == ENDIAN_BIG ? 0x9feb : 0xeb9f);
> > +    uint<16> magic : (magic == 0xeb9f)
> > +                       || (magic == 0x9feb && set_endian (!get_endian))
> > +                   = 0xeb9f;
> >       uint<8> version;
> >       uint<8> flags;
> >       offset<uint<32>,B> hdr_len; /* Size of this header.  */