Re: git: d6c0538dae8d - main - ddb: Remove SOFTWARE_SSTEP support

On Mon, Jan 10, 2022 at 02:14:54PM -0700, Warner Losh wrote:
> On Mon, Jan 10, 2022 at 12:48 PM John Baldwin <jhb@freebsd.org> wrote:
> 
> > On 1/7/22 8:27 AM, Warner Losh wrote:
> > > The branch main has been updated by imp:
> > >
> > > URL:
> > https://cgit.FreeBSD.org/src/commit/?id=d6c0538dae8d138219dfd051994a44c50e741212
> > >
> > > commit d6c0538dae8d138219dfd051994a44c50e741212
> > > Author:     Warner Losh <imp@FreeBSD.org>
> > > AuthorDate: 2022-01-07 16:25:33 +0000
> > > Commit:     Warner Losh <imp@FreeBSD.org>
> > > CommitDate: 2022-01-07 16:25:33 +0000
> > >
> > >      ddb: Remove SOFTWARE_SSTEP support
> > >
> > >      It was needed for mips only, and only kinda sorta worked for mips.
> > It
> > >      can be brought back if we grow another architecture that need it.
> > >
> > >      Sponsored by:           Netflix
> >
> > RISC-V would need it in theory (no hardware single step), but no one has
> > felt the
> > need to implement the backend support for it.  I think 32-bit arm doesn't
> > support
> > hardware single step either (but again, no one has bothered to add the
> > backend
> > support).
> >
> 
> Generally, I agree with these thoughts. I went ahead with the removal
> because I
> knew it would be easy to bring back, even years from now should someone[tm]
> have an implementation for those platforms (though I thought 32-bit arm did
> have
> single step in hardware).
> 
> Should I put it back? Or should we wait until someone shows up with support
> for
> a supported platform?
> 

It was used for arm, but only older arm, ie v4/v5, pretty sure newer
cores do have hardware breakpoints.

Regards,

Olivier