Re: [PATCH v4 0/5] Powerpc/Watchpoint: Few important fixes

[Ravi Bangoria]

On 10/12/19 1:01 PM, Christophe Leroy wrote:
> Le 10/10/2019 Ã 08:25, Ravi Bangoria a ÃcritÂ:
> > On 10/10/19 10:14 AM, Ravi Bangoria wrote:
> > > > > @Christophe, Is patch5 works for you on 8xx?
> > > >
> > > > Getting the following :
> > > >
> > > > root@vgoip:~# ./ptrace-hwbreak
> > > > test: ptrace-hwbreak
> > > > tags: git_version:v5.4-rc2-710-gf0082e173fe4-dirty
> > > > PTRACE_SET_DEBUGREG, WO, len: 1: Ok
> > > > PTRACE_SET_DEBUGREG, WO, len: 2: Ok
> > > > PTRACE_SET_DEBUGREG, WO, len: 4: Ok
> > > > PTRACE_SET_DEBUGREG, WO, len: 8: Ok
> > > > PTRACE_SET_DEBUGREG, RO, len: 1: Ok
> > > > PTRACE_SET_DEBUGREG, RO, len: 2: Ok
> > > > PTRACE_SET_DEBUGREG, RO, len: 4: Ok
> > > > PTRACE_SET_DEBUGREG, RO, len: 8: Ok
> > > > PTRACE_SET_DEBUGREG, RW, len: 1: Ok
> > > > PTRACE_SET_DEBUGREG, RW, len: 2: Ok
> > > > PTRACE_SET_DEBUGREG, RW, len: 4: Ok
> > > > PTRACE_SET_DEBUGREG, RW, len: 8: Ok
> > > > PPC_PTRACE_SETHWDEBUG, MODE_EXACT, WO, len: 1: Ok
> > > > PPC_PTRACE_SETHWDEBUG, MODE_EXACT, RO, len: 1: Ok
> > > > PPC_PTRACE_SETHWDEBUG, MODE_EXACT, RW, len: 1: Ok
> > > > PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW ALIGNED, WO, len: 6: Ok
> > > > PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW ALIGNED, RO, len: 6: Fail
> > > > failure: ptrace-hwbreak
> > >
> > > Thanks Christophe. I don't have any 8xx box. I checked qemu and it seems
> > > qemu emulation for 8xx is not yet supported. So I can't debug this. Can
> > > you please check why it's failing?
> >
> > PPC_PTRACE_SETHWDEBUG internally uses DAWR register and probably 8xx does
> > not emulate DAWR logic, it only uses DABR to emulate double-word watchpoint.
> > In that case, all testcases that uses PPC_PTRACE_SETHWDEBUG should be
> > disabled for 8xx. I'll change [PATCH 5] accordingly and resend.
>
> I think the MODE_EXACT ones are OK with the 8xx at the time being.

Ok. I'll disable other tests for 8xx.

Also, I was bit wrong in above point. Actually, PPC_PTRACE_SETHWDEBUG with RANGE
breakpoint also support DABR but the length will be 8 only. So I've to change my
patch 1 also a bit (ptrace stuff). I'll resend the series with these changes.

> > Also, do you think I should fix hw_breakpoint_validate_len() from [PARCH 1]
> > for 8xx? I re-checked you recent patch* to allow any address range size for
> > 8xx. With that patch, hw_breakpoint_validate_len() won't get called at all
> > for 8xx.
>
> At the time being, the 8xx emulates DABR so it has the same limitations as BOOK3S.
> My patch needs to be rebased on top of your series and I think it needs some modifications, as it seems it doesn't properly handle size 1 and size 2 breakpoints at least.
> So I think that you should leave your Patch1 as is, and I'll modify the validate_len() logic while rebasing my patch.

Sure. Thanks for helping!

Ravi