Re: [PATCH v3 2/5] [PATCH 2/5] gdb: Improve SIGSEGV diagnostics for POE faults

On 14/07/2026 21:15, [email protected] wrote:
> From: Srinath Parvathaneni <[email protected]>
> 
> When a SIGSEGV is caused by a Permission Overlay violation, include
> additional information in GDB's error message to help identify the
> failing address along with the responsible protection key causing
> this fault.
> 
> Example:
> (gdb) c
> Continuing.
> 
> Program received signal SIGSEGV, Segmentation fault
> Protection Key Violation while accessing address 0x0000fffff7ff3000 with Protection Key = 1.
> 0x0000aaaaaaaa0a3c in main () at poe_sigsegv.c:26
> 
> Approved-by: Thiago Jung Bauermann <[email protected]>
> ---
>   gdb/aarch64-linux-tdep.c | 21 ++++++++++++++++++---
>   1 file changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c
> index f11eccc1bc1..b8a02ab9972 100644
> --- a/gdb/aarch64-linux-tdep.c
> +++ b/gdb/aarch64-linux-tdep.c
> @@ -53,6 +53,7 @@
>   
>   #include "arch/aarch64-fpmr-linux.h"
>   #include "arch/aarch64-gcs-linux.h"
> +#include "arch/aarch64-poe-linux.h"
>   #include "arch/aarch64-mte.h"
>   #include "arch/aarch64-mte-linux.h"
>   #include "arch/aarch64-pauth-linux.h"
> @@ -2675,11 +2676,12 @@ aarch64_linux_report_signal_info (struct gdbarch *gdbarch,
>   {
>     aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
>   
> -  if (!(tdep->has_mte () || tdep->has_gcs ()) || siggnal != GDB_SIGNAL_SEGV)
> +  if (!(tdep->has_mte () || tdep->has_gcs () || tdep->has_poe ())
> +      || siggnal != GDB_SIGNAL_SEGV)
>       return;
>   
>     CORE_ADDR fault_addr = 0;
> -  long si_code = 0, si_errno = 0;
> +  long si_code = 0, si_errno = 0, si_pkey = -1;
>   
>     try
>       {
> @@ -2687,6 +2689,9 @@ aarch64_linux_report_signal_info (struct gdbarch *gdbarch,
>   	 violation.  */
>         si_code = parse_and_eval_long ("$_siginfo.si_code");
>         si_errno = parse_and_eval_long ("$_siginfo.si_errno");
> +      if (tdep->has_poe ())
> +	si_pkey = parse_and_eval_long
> +	  ("$_siginfo._sifields._sigfault._._addr_pkey.si_pkey");
>   
>         fault_addr
>   	= parse_and_eval_long ("$_siginfo._sifields._sigfault.si_addr");
> @@ -2703,6 +2708,8 @@ aarch64_linux_report_signal_info (struct gdbarch *gdbarch,
>       meaning = _("Memory tag violation");
>     else if (si_code == AARCH64_SEGV_CPERR && si_errno == 0)
>       meaning = _("Guarded Control Stack error");
> +  else if (si_code == AARCH64_SEGV_PKUERR)
> +    meaning = _("Protection Key Violation");
>     else
>       return;
>   
> @@ -2734,6 +2741,14 @@ aarch64_linux_report_signal_info (struct gdbarch *gdbarch,
>   	  uiout->field_string ("logical-tag", hex_string (ltag));
>   	}
>       }
> +  /* For POE SEGSEGV, show additional information.  */

Is this really supposed to be POE SEGSEGV or is it a typo?

> +  else if (si_code == AARCH64_SEGV_PKUERR)
> +    {
> +      uiout->text (_(" while accessing address "));
> +      uiout->field_core_addr ("fault-addr", gdbarch, fault_addr);
> +      uiout->text (" with Protection Key = ");

Missing internationalization above.

> +      uiout->field_signed ("protection-key", si_pkey);
> +    }
>     else if (si_code != AARCH64_SEGV_CPERR)
>       {
>         uiout->text ("\n");
> @@ -3054,7 +3069,7 @@ aarch64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
>   					 aarch64_linux_decode_memtag_section);
>       }
>   
> -  if (tdep->has_mte () || tdep->has_gcs ())
> +  if (tdep->has_mte () || tdep->has_gcs () || tdep->has_poe ())
>       set_gdbarch_report_signal_info (gdbarch, aarch64_linux_report_signal_info);
>   
>     /* Initialize the aarch64_linux_record_tdep.  */