gdb: xtensa: support disabling use of 'g' packet

The xt-ocd from Xtensa's official toolchain may not support
'g' packet. So this allows building GDB which won't query
registers using 'g' packets but instead using 'p' packets only.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

Author: dcpleung

gdb/configure

@@ -977,6 +977,7 @@ with_libbabeltrace_prefix
 with_libbabeltrace_type
 enable_libctf
 enable_xtensa_use_target_regnum
+enable_xtensa_remote_g_packet
 enable_unit_tests
 '
       ac_precious_vars='build_alias
@@ -1665,6 +1666,8 @@ Optional Features:
   --enable-libctf         Handle .ctf type-info sections [default=yes]
   --enable-xtensa-use-target-regnum
                           Use remote target register numbers (Xtensa target)
+  --disable-xtensa-remote-g-packet
+                          Disable g packet for remote Xtensa target
   --enable-unit-tests     Enable the inclusion of unit tests when compiling
                           GDB
 
@@ -11503,7 +11506,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11506 "configure"
+#line 11509 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11609,7 +11612,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11612 "configure"
+#line 11615 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -33656,6 +33659,23 @@ if test x"$enable_xtensa_use_target_regnum" = xyes; then
   CPPFLAGS="$CPPFLAGS -DXTENSA_USE_TGT_REGNUM"
 fi
 
+# Use g packet for remote Xtensa target
+# Check whether --enable-xtensa-remote-g-packet was given.
+if test "${enable_xtensa_remote_g_packet+set}" = set; then :
+  enableval=$enable_xtensa_remote_g_packet; case $enableval in
+    yes | no)
+      enable_xtensa_use_g_packet=$enableval ;;
+    *)
+      as_fn_error $? "bad value $enableval for --enable-xtensa-remote-g-packet" "$LINENO" 5 ;;
+  esac
+else
+  enable_xtensa_use_g_packet=yes
+fi
+
+if test x"$enable_xtensa_use_g_packet" = xno; then
+  CPPFLAGS="$CPPFLAGS -DXTENSA_DISABLE_REMOTE_G_PACKET"
+fi
+
 NM_H=
 rm -f nm.h
 if test "${nativefile}" != ""; then

gdb/configure.ac

@@ -2244,6 +2244,20 @@ if test x"$enable_xtensa_use_target_regnum" = xyes; then
   CPPFLAGS="$CPPFLAGS -DXTENSA_USE_TGT_REGNUM"
 fi
 
+# Use g packet for remote Xtensa target
+AC_ARG_ENABLE(xtensa-remote-g-packet,
+AS_HELP_STRING([--disable-xtensa-remote-g-packet], [Disable g packet for remote Xtensa target]),
+  [case $enableval in
+    yes | no)
+      enable_xtensa_use_g_packet=$enableval ;;
+    *)
+      AC_MSG_ERROR([bad value $enableval for --enable-xtensa-remote-g-packet]) ;;
+  esac],
+  [enable_xtensa_use_g_packet=yes])
+if test x"$enable_xtensa_use_g_packet" = xno; then
+  CPPFLAGS="$CPPFLAGS -DXTENSA_DISABLE_REMOTE_G_PACKET"
+fi
+
 NM_H=
 rm -f nm.h
 if test "${nativefile}" != ""; then

gdb/xtensa-tdep.c

@@ -3161,6 +3161,16 @@ xtensa_remote_register_number (struct gdbarch *gdbarch, int regnum)
 }
 #endif
 
+static int
+xtensa_remote_supports_g_packet (struct gdbarch *gdbarch)
+{
+#ifdef XTENSA_DISABLE_REMOTE_G_PACKET
+  return 0;
+#else
+  return 1;
+#endif
+}
+
 /* Module "constructor" function.  */
 
 extern xtensa_register_t xtensa_rmap[];
@@ -3261,6 +3271,8 @@ xtensa_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   set_solib_svr4_fetch_link_map_offsets
     (gdbarch, svr4_ilp32_fetch_link_map_offsets);
 
+  set_gdbarch_remote_supports_g_packet (gdbarch, xtensa_remote_supports_g_packet);
+
   /* Hook in the ABI-specific overrides, if they have been registered.  */
   gdbarch_init_osabi (info, gdbarch);