RE: [PATCH 0/9] Add new command to print the shadow stack backtrace

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

> -----Original Message-----
> From: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
> Sent: Monday, October 13, 2025 3:19 AM
> To: Schimpe, Christina <christina.schimpe@intel.com>
> Cc: gdb-patches@sourceware.org
> Subject: Re: [PATCH 0/9] Add new command to print the shadow stack
> backtrace
> 
> Thiago Jung Bauermann <thiago.bauermann@linaro.org> writes:
> 
> > I tested your patches and there's a bug unfortunately:
> >
> > FAIL: gdb.arch/aarch64-gcs-disp-step.exp: continue to breakpoint at
> > blr
> > FAIL: gdb.arch/aarch64-gcs-disp-step.exp: continue until exit
> > FAIL: gdb.arch/aarch64-gcs.exp: call inferior function
> > FAIL: gdb.arch/aarch64-gcs-return.exp: test inferior call and
> > continue: call (int) call2()
> > FAIL: gdb.arch/aarch64-gcs-return.exp: test inferior call and
> > continue: continue until exit
> > FAIL: gdb.arch/aarch64-gcs-return.exp: test frame level update: check
> > gcspr of frame 1
> > FAIL: gdb.arch/aarch64-gcs-return.exp: test frame level update: check
> > gcspr of frame 2
> > FAIL: gdb.arch/aarch64-gcs-return.exp: test return from current frame:
> > continue until exit
> >
> > In each FAIL above a GCS error happens unexpectedly in the inferior.
> > It appears that GDB isn't updating the shadow stack correctly. I still
> > have to see what exactly is the problem.
> 
> The problem turned out to be simple. I just had to set the regnum for the
> GCSPR in the gdbarch:
> 
> diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c index
> 95af82c26327..9e866fc319d4 100644
> --- a/gdb/aarch64-tdep.c
> +++ b/gdb/aarch64-tdep.c
> @@ -4780,6 +4780,10 @@ aarch64_gdbarch_init (struct gdbarch_info info,
> struct gdbarch_list *arches)
>    /* Register a hook for converting a memory tag to a string.  */
>    set_gdbarch_memtag_to_string (gdbarch, aarch64_memtag_to_string);
> 
> +  if (tdep->has_gcs ())
> +    /* AArch64's shadow stack pointer is the GCSPR.  */
> +    set_gdbarch_ssp_regnum (gdbarch, tdep->gcs_reg_base);
> +
>    /* ABI */
>    set_gdbarch_short_bit (gdbarch, 16);
>    set_gdbarch_int_bit (gdbarch, 32);
> 
> --
> Thiago

Ah, I forgot about that. Cool that it works now. 😊

Thanks,
Christina

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