RE: [PATCH 11/12] gdb, gdbarch: Introduce gdbarch method to get the shadow stack pointer.

["Schimpe, Christina" <christina.schimpe@intel.com>]

> -----Original Message-----
> From: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
> Sent: Friday, February 21, 2025 6:11 AM
> To: Schimpe, Christina <christina.schimpe@intel.com>
> Cc: gdb-patches@sourceware.org
> Subject: Re: [PATCH 11/12] gdb, gdbarch: Introduce gdbarch method to get
> the shadow stack pointer.
> 
> Hello Christina,
> 
> "Schimpe, Christina" <christina.schimpe@intel.com> writes:
> 
> >> -----Original Message-----
> >> From: Schimpe, Christina
> >> Sent: Sunday, February 16, 2025 11:45 AM
> >> To: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
> >> Cc: gdb-patches@sourceware.org
> >> Subject: RE: [PATCH 11/12] gdb, gdbarch: Introduce gdbarch method to
> >> get the shadow stack pointer.
> >>
> >> > -----Original Message-----
> >> > From: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
> >> > Sent: Saturday, February 15, 2025 4:45 AM
> >> > To: Schimpe, Christina <christina.schimpe@intel.com>
> >> > Cc: gdb-patches@sourceware.org
> >> > Subject: Re: [PATCH 11/12] gdb, gdbarch: Introduce gdbarch method
> >> > to get the shadow stack pointer.
> >> >
> >> > Hello Christina,
> >> >
> >> > Thiago Jung Bauermann <thiago.bauermann@linaro.org> writes:
> >> >
> >> > > "Schimpe, Christina" <christina.schimpe@intel.com> writes:
> >> > >
> >> > >> Would something like that be acceptable as well?
> >> > >>
> >> > >> Method(
> >> > >>       comment="""
> >> > >> If possible, return the shadow stack pointer. On some
> >> > >> architectures, the shadow stack pointer is available even if the
> >> > >> feature is disabled.  To return the shadow stack enablement
> >> > >> state configure
> >> > SHADOW_STACK_ENABLED.
> >> > >>   """,
> >> > >> type="std::optional<CORE_ADDR>",
> >> > >> name="get_shadow_stack_pointer", params=[("bool &",
> >> > >> "shadow_stack_enabled")],
> >> > >> predefault="default_get_shadow_stack_pointer",
> >> > >> invalid=False,
> >> > >> )
> >> > >
> >> > > Yes, this looks good.
> >> >
> >> > I was rebasing my Guarded Control Stack code on top of this series,
> >> > and noticed that I will need to access the thread's regcache for
> >> > the
> >> > aarch64 implementation of this gdbarch method. Then I noticed that
> >> > the
> >> > x86_64 version also needs it, and calls "get_thread_regcache
> >> (inferior_thread ())".
> >> > It would be better to pass the regcache as an argument instead.
> >>
> >> Hi Thiago,
> >>
> >> Do you mean instead or in addition?
> >> I thought you also need the parameter ("bool &",
> "shadow_stack_enabled").
> 
> Sorry for not answering your previous email. I switched my focus to the
> variable-length registers thread and forgot that I hadn't answered this
> question yet.
> 
> > Since you wrote instead I now have the regcache argument only in the v2 of
> this series.
> 
> I wrote "instead" meaning "instead of calling get_thread_regcache inside of
> the method implementation". Sorry for being unclear.
> 
> > https://sourceware.org/pipermail/gdb-patches/2025-February/215650.html
> 
> Strange, for some reason the threading on the patch series got broken up
> into three parts. I thought I had missed some of the patches but now I see I
> received the whole series.
> 
> > Please let me know if you see any problems with that.
> 
> For AArch64 GCS I need the shadow_stack_enabled argument so that callers
> can tell whether the shadow stack is enabled or disabled.

Ah ok, no problem.  It will be part of the next version then. 😊

Christina
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