[PATCH 4/8] gdbserver/linux-aarch64: Factor out function to get aarch64_features

[Thiago Jung Bauermann <thiago.bauermann@linaro.org>]

It will be used in a subsequent commit.  There's no functional change.
---
 gdbserver/linux-aarch64-low.cc | 45 ++++++++++++++++++++++------------
 1 file changed, 29 insertions(+), 16 deletions(-)

diff --git a/gdbserver/linux-aarch64-low.cc b/gdbserver/linux-aarch64-low.cc
index 576925838f49..9b57be73818e 100644
--- a/gdbserver/linux-aarch64-low.cc
+++ b/gdbserver/linux-aarch64-low.cc
@@ -652,6 +652,28 @@ aarch64_target::low_delete_process (arch_process_info *info)
   xfree (info);
 }
 
+/* Matches HWCAP_PACA in kernel header arch/arm64/include/uapi/asm/hwcap.h.  */
+#define AARCH64_HWCAP_PACA (1 << 30)
+
+static gdb::optional<struct aarch64_features>
+aarch64_get_arch_features (const thread_info *thread)
+{
+  struct aarch64_features features;
+  int vq = aarch64_sve_get_vq (thread->id.lwp ());
+
+  if (vq < 0)
+    return {};
+
+  features.vq = vq;
+  /* A-profile PAC is 64-bit only.  */
+  features.pauth = linux_get_hwcap (thread, 8) & AARCH64_HWCAP_PACA;
+  /* A-profile MTE is 64-bit only.  */
+  features.mte = linux_get_hwcap2 (thread, 8) & HWCAP2_MTE;
+  features.tls = true;
+
+  return features;
+}
+
 void
 aarch64_target::low_new_thread (lwp_info *lwp)
 {
@@ -804,9 +826,6 @@ aarch64_adjust_register_sets (const struct aarch64_features &features)
     }
 }
 
-/* Matches HWCAP_PACA in kernel header arch/arm64/include/uapi/asm/hwcap.h.  */
-#define AARCH64_HWCAP_PACA (1 << 30)
-
 /* Implementation of linux target ops method "low_arch_setup".  */
 
 void
@@ -822,24 +841,18 @@ aarch64_target::low_arch_setup ()
 
   if (is_elf64)
     {
-      struct aarch64_features features;
-      int vq = aarch64_sve_get_vq (tid);
+      gdb::optional<struct aarch64_features> features
+	  = aarch64_get_arch_features (current_thread);
 
-      /* If ptrace fails we can't determine vq, but the low_arch_setup method
-	  always succeeds so all we can do here is assert that vq is valid.  */
-      gdb_assert (vq >= 0);
-      features.vq = vq;
-      /* A-profile PAC is 64-bit only.  */
-      features.pauth = linux_get_hwcap (current_thread, 8) & AARCH64_HWCAP_PACA;
-      /* A-profile MTE is 64-bit only.  */
-      features.mte = linux_get_hwcap2 (current_thread, 8) & HWCAP2_MTE;
-      features.tls = true;
+      /* If ptrace fails we can't determine vq, but low_arch_setup always
+	 succeeds so all we can do here is assert that features is valid.  */
+      gdb_assert (features.has_value ());
 
-      current_process ()->tdesc = aarch64_linux_read_description (features);
+      current_process ()->tdesc = aarch64_linux_read_description (*features);
 
       /* Adjust the register sets we should use for this particular set of
 	 features.  */
-      aarch64_adjust_register_sets (features);
+      aarch64_adjust_register_sets (*features);
     }
   else
     current_process ()->tdesc = aarch32_linux_read_description ();