[PATCH v2 4/7] gdbserver/aarch64: Add POR_EL0 register support

[<srinath.parvathaneni@arm.com>]

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

Add support for transferring the POR_EL0 register between the Linux
kernel and GDB during remote debugging.

This patch implements the necessary `fill` and `store` operations using
the `NT_ARM_POE` regset, allowing GDB to read and write the POR_EL0
register when debugging a remote target that supports FEAT_S1POE.
---
 gdbserver/linux-aarch64-low.cc | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/gdbserver/linux-aarch64-low.cc b/gdbserver/linux-aarch64-low.cc
index a2588a6e2a9..d326341e63a 100644
--- a/gdbserver/linux-aarch64-low.cc
+++ b/gdbserver/linux-aarch64-low.cc
@@ -45,6 +45,7 @@
 #include "linux-aarch32-tdesc.h"
 #include "linux-aarch64-tdesc.h"
 #include "nat/aarch64-fpmr-linux.h"
+#include "nat/aarch64-poe-linux.h"
 #include "nat/aarch64-gcs-linux.h"
 #include "nat/aarch64-mte-linux-ptrace.h"
 #include "nat/aarch64-scalable-linux-ptrace.h"
@@ -250,6 +251,26 @@ aarch64_store_fpregset (struct regcache *regcache, const void *buf)
   supply_register (regcache, AARCH64_FPCR_REGNUM, &regset->fpcr);
 }
 
+/* Fill BUF with the POE (POR_EL0) register set from the regcache.  */
+
+static void
+aarch64_fill_por_el0_regset (struct regcache *regcache, void *buf)
+{
+  uint64_t *poe = (uint64_t *) buf;
+  int poe_regnum = find_regno (regcache->tdesc, "por_el0");
+  collect_register (regcache, poe_regnum, poe);
+}
+
+/* Store the POE (POR_EL0) register set to regcache.  */
+
+static void
+aarch64_store_por_el0_regset (struct regcache *regcache, const void *buf)
+{
+  uint64_t *poe = (uint64_t *) buf;
+  int poe_regnum = find_regno (regcache->tdesc, "por_el0");
+  supply_register (regcache, poe_regnum, poe);
+}
+
 /* Fill BUF with the FPMR register set from the regcache.  */
 
 static void
@@ -901,6 +922,10 @@ static struct regset_info aarch64_regsets[] =
   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_ARM_FPMR,
     0, OPTIONAL_REGS,
     aarch64_fill_fpmr_regset, aarch64_store_fpmr_regset },
+  /* POE register (POR_EL0).  */
+  { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_ARM_POE,
+    0, OPTIONAL_REGS,
+    aarch64_fill_por_el0_regset, aarch64_store_por_el0_regset },
   /* TLS register.  */
   { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_ARM_TLS,
     0, OPTIONAL_REGS,
@@ -980,6 +1005,10 @@ aarch64_adjust_register_sets (const struct aarch64_features &features)
 	  if (features.fpmr)
 	    regset->size = sizeof (uint64_t);
 	  break;
+	case NT_ARM_POE:
+	  if (features.poe)
+	    regset->size = sizeof (uint64_t);
+	  break;
 	default:
 	  gdb_assert_not_reached ("Unknown register set found.");
 	}
@@ -1010,6 +1039,7 @@ aarch64_target::low_arch_setup ()
       features.tls = aarch64_tls_register_count (tid);
       features.gcs = features.gcs_linux = linux_get_hwcap (pid, 8) & HWCAP_GCS;
       features.fpmr = linux_get_hwcap2 (pid, 8) & HWCAP2_FPMR;
+      features.poe = linux_get_hwcap2 (pid, 8) & HWCAP2_POE;
 
       /* Scalable Matrix Extension feature and size check.  */
       if (linux_get_hwcap2 (pid, 8) & HWCAP2_SME)
-- 
2.43.0