[PATCH v2 3/7] gdb: Improve SIGSEGV diagnostics for POE faults

[<srinath.parvathaneni@arm.com>]

From: Srinath Parvathaneni <srinath.parvathaneni@arm.com>

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
---
 gdb/aarch64-linux-tdep.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c
index 4a6bc3158c8..b8a02ab9972 100644
--- a/gdb/aarch64-linux-tdep.c
+++ b/gdb/aarch64-linux-tdep.c
@@ -2676,11 +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
     {
@@ -2688,6 +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");
@@ -2704,6 +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;
 
@@ -2735,6 +2741,14 @@ aarch64_linux_report_signal_info (struct gdbarch *gdbarch,
 	  uiout->field_string ("logical-tag", hex_string (ltag));
 	}
     }
+  /* For POE SEGSEGV, show additional information.  */
+  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 = ");
+      uiout->field_signed ("protection-key", si_pkey);
+    }
   else if (si_code != AARCH64_SEGV_CPERR)
     {
       uiout->text ("\n");
@@ -3055,7 +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.  */
-- 
2.43.0