[PATCH v2] gdb/hppa: guess g packet size

[Sven Schnelle <svens@stackframe.org>]

With qemu supporting 64 bit now, add some code to determine the
register size of a hppa remote target.

Signed-off-by: Sven Schnelle <svens@stackframe.org>
---

Changes in v2:

- adjust coding style
- use target_desc_up, make it static
- use nullptr instead of NULL

 gdb/hppa-tdep.c | 51 +++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 45 insertions(+), 6 deletions(-)

diff --git a/gdb/hppa-tdep.c b/gdb/hppa-tdep.c
index 96cb797c023..bd250408951 100644
--- a/gdb/hppa-tdep.c
+++ b/gdb/hppa-tdep.c
@@ -33,6 +33,8 @@
 #include "trad-frame.h"
 #include "frame-unwind.h"
 #include "frame-base.h"
+#include "remote.h"
+#include "target-descriptions.h"
 
 #include "gdbcore.h"
 #include "cli/cli-cmds.h"
@@ -43,6 +45,14 @@
 
 static bool hppa_debug = false;
 
+/* Properties (for struct target_desc) describing the g/G packet
+   layout.  */
+#define PROPERTY_GP32 "internal: transfers-32bit-registers"
+#define PROPERTY_GP64 "internal: transfers-64bit-registers"
+
+static target_desc_up hppa_tdesc32;
+static target_desc_up hppa_tdesc64;
+
 /* Some local constants.  */
 static const int hppa32_num_regs = 128;
 static const int hppa64_num_regs = 96;
@@ -2978,6 +2988,17 @@ hppa_skip_trampoline_code (const frame_info_ptr &frame, CORE_ADDR pc)
 
    -- chastain 2003-12-18  */
 
+static void
+hppa_register_g_packet_guesses (struct gdbarch *gdbarch)
+{
+  /* If the size matches the set of 32-bit or 64-bit integer registers,
+     assume that's what we've got.  */
+  register_remote_g_packet_guess (gdbarch, hppa32_num_regs * 4, hppa_tdesc32.get());
+  register_remote_g_packet_guess (gdbarch, hppa64_num_regs * 8, hppa_tdesc64.get());
+
+  /* Otherwise we don't have a useful guess.  */
+}
+
 static struct gdbarch *
 hppa_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 {
@@ -2991,15 +3012,28 @@ hppa_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
     = gdbarch_alloc (&info, gdbarch_tdep_up (new hppa_gdbarch_tdep));
   hppa_gdbarch_tdep *tdep = gdbarch_tdep<hppa_gdbarch_tdep> (gdbarch);
 
-  /* Determine from the bfd_arch_info structure if we are dealing with
-     a 32 or 64 bits architecture.  If the bfd_arch_info is not available,
-     then default to a 32bit machine.  */
-  if (info.bfd_arch_info != NULL)
-    tdep->bytes_per_address =
-      info.bfd_arch_info->bits_per_address / info.bfd_arch_info->bits_per_byte;
+  /* Determine from the target description if we are dealing with
+     a 32 or 64 bits architecture. If the target description is not
+     available, then check whether bfd_arch_info could be used.
+     Otherwise default to a 32bit machine.
+  */
+  if (info.target_desc != nullptr)
+    {
+      if (tdesc_property (info.target_desc, PROPERTY_GP64) != nullptr)
+	tdep->bytes_per_address = 8;
+      else if (tdesc_property (info.target_desc, PROPERTY_GP32) != nullptr)
+	tdep->bytes_per_address = 4;
+    }
+  else if (info.bfd_arch_info != nullptr)
+    {
+      tdep->bytes_per_address =
+	info.bfd_arch_info->bits_per_address / info.bfd_arch_info->bits_per_byte;
+    }
   else
     tdep->bytes_per_address = 4;
 
+  hppa_register_g_packet_guesses (gdbarch);
+
   tdep->find_global_pointer = hppa_find_global_pointer;
 
   /* Some parts of the gdbarch vector depend on whether we are running
@@ -3122,6 +3156,11 @@ hppa_dump_tdep (struct gdbarch *gdbarch, struct ui_file *file)
 INIT_GDB_FILE (hppa_tdep)
 {
   gdbarch_register (bfd_arch_hppa, hppa_gdbarch_init, hppa_dump_tdep);
+  hppa_tdesc32 = allocate_target_description ();
+  set_tdesc_property (hppa_tdesc32.get(), PROPERTY_GP32, "");
+
+  hppa_tdesc64 = allocate_target_description ();
+  set_tdesc_property (hppa_tdesc64.get(), PROPERTY_GP64, "");
 
   add_cmd ("unwind", class_maintenance, unwind_command,
 	   _("Print unwind table entry at given address."),
-- 
2.51.0