RE: [PATCH 1/1] aarch64: fix a crash during maintenance print cooked-registers

["Gerlicher, Klaus" <klaus.gerlicher@intel.com>]

Hi Luis,

"info all-registers" ignores registers w/o name but "maint print cooked-registers" does not and I think that hasn't changed. I think maintenance commands aren't supposed to hide anything since they are used more in GDB development than by a GDB user.

Anyway, thanks for the quick feedback, I'll push this some time soon.

Thanks
Klaus

> -----Original Message-----
> From: Luis Machado <luis.machado@arm.com>
> Sent: Monday, February 3, 2025 3:28 PM
> To: Gerlicher, Klaus <klaus.gerlicher@intel.com>; gdb-
> patches@sourceware.org
> Subject: Re: [PATCH 1/1] aarch64: fix a crash during maintenance print
> cooked-registers
> 
> Hi,
> 
> On 2/3/25 13:52, Klaus Gerlicher wrote:
> > Hi all, Luis,
> >
> > I found this accidently while looking at Thiago's GDBserver improvements.
> Luis
> > I think added the pseudo register in question, so maybe he can comment
> > on this issue. I used a aarch64 qemu 9.2.
> 
> Thanks for catching this.
> 
> >
> > Thanks
> > Klaus
> >
> > On aarch64 with pauth enabled I can see a crash when
> > using "maintenance print cooked-registers".
> >
> > This happens because the register dump code tries to read
> > a pseudo reg that is not handled here because it is supposedly
> > only used in unwinding.
> 
> Indeed. ra_sign_state is only used to track which frames have PAC enabled or
> not.
> 
> I was wondering why I had not caught this before, and I just noticed my VM
> had pauth disabled. :-(
> 
> Enabling it, now I see the crash. In any case...
> 
> >
> > Fix this by returning a zero value typed as a built-in uint64.
> > ---
> >  gdb/aarch64-tdep.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
> > index 840f9877361..6e712b12b86 100644
> > --- a/gdb/aarch64-tdep.c
> > +++ b/gdb/aarch64-tdep.c
> > @@ -3290,6 +3290,9 @@ aarch64_pseudo_read_value (gdbarch *gdbarch,
> const frame_info_ptr &next_frame,
> >      return aarch64_pseudo_read_value_1 (next_frame, pseudo_reg_num,
> >  					pseudo_offset -
> AARCH64_SVE_V0_REGNUM);
> >
> > +  if (tdep->has_pauth () && pseudo_reg_num == tdep-
> >ra_sign_state_regnum)
> > +    return value::zero (builtin_type (gdbarch)->builtin_uint64, lval_register);
> > +
> >    gdb_assert_not_reached ("regnum out of bound");
> >  }
> >
> 
> ... the fix above looks OK to me. Though it makes me wonder why we starting
> hitting this.
> 
> Internally we don't assign a name to this register so it technically doesn't show
> up in any
> listing. Maybe something changed and we now list even pseudo registers
> without a name?
> 
> Approved-By: Luis Machado <luis.machado@arm.com>
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