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

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

> -----Original Message-----
> From: Luis Machado <luis.machado@arm.com>
> Sent: Monday, February 3, 2025 3:41 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
> 
> On 2/3/25 14:38, Gerlicher, Klaus wrote:
> > 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.
> 
> That make sense. Probably an oversight on our end when we first enabled
> this.
> 
> >
> > Anyway, thanks for the quick feedback, I'll push this some time soon.
> 
> Sounds good. Thanks.
> 
> >
> > 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>
> > Intel Deutschland GmbH
> > Registered Address: Am Campeon 10, 85579 Neubiberg, Germany
> > Tel: +49 89 99 8853-0, www.intel.de
> > Managing Directors: Sean Fennelly, Jeffrey Schneiderman, Tiffany Doon Silva
> > Chairperson of the Supervisory Board: Nicole Lau
> > Registered Office: Munich
> > Commercial Register: Amtsgericht Muenchen HRB 186928

Intel Deutschland GmbH
Registered Address: Am Campeon 10, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de
Managing Directors: Sean Fennelly, Jeffrey Schneiderman, Tiffany Doon Silva
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928