[gdbarch] New method "execute_dwarf_cfa_vendor_op" and migrate SPARC to it

Recently a feature called "return address signing" has been added to GCC to
prevent stack smash stack on AArch64.  For details please refer:

  https://gcc.gnu.org/ml/gcc-patches/2017-01/msg00376.html

GDB needs to be aware of this feature so it can restore the original return
address which is critical for unwinding.

On compiler side, whenever return address, i.e. LR register, is mangled or
restored by hardware instruction, compiler is expected to generate a
DW_CFA_AARCH64_negate_ra_state to toggle return address signing status.

DW_CFA_AARCH64_negate_ra_state is using the same CFI number and
therefore need to be multiplexed with DW_CFA_GNU_window_save which was designed
for SPARC.

A new gdbarch method "execute_dwarf_cfa_vendor_op" is introduced by this patch.
It's parameters has been restricted to those only needed by SPARC and AArch64
for multiplexing DW_CFA_GNU_window_save which is a CFI operation takes none
operand.  Should any further DWARF CFI operation want to be multiplexed in the
future,  the parameter list can be extended.  Below is the current function
prototype.

   typedef int (gdbarch_execute_dwarf_cfa_vendor_op_ftype)
     (struct gdbarch *gdbarch, gdb_byte op, struct dwarf2_frame_state *fs);

DW_CFA_GNU_window_save support for SPARC is migrated to this new gdbarch
method by this patch.

gdb/
	* gdbarch.sh: New gdbarch method execute_dwarf_cfa_vendor_op.
	* gdbarch.c: Regenerated.
	* gdbarch.h: Regenerated.
	* dwarf2-frame.c (dwarf2_frame_state_alloc_regs): Made the
	visibility external.
	(execute_cfa_program): Call execute_dwarf_cfa_vendor_op for CFI
	between DW_CFA_lo_user and DW_CFA_high_user inclusive.
	(enum cfa_how_kind): Move to ...
	(struct dwarf2_frame_state_reg_info): Likewise.
	(struct dwarf2_frame_state): Likewise.
	* dwarf2-frame.h: ... here.
	(dwarf2_frame_state_alloc_regs): New declaration.
	* sparc-tdep.c (sparc_execute_dwarf_cfa_vendor_op): New function.
	(sparc32_gdbarch_init): Register execute_dwarf_cfa_vendor_op hook.

1 files changed, 23 insertions, 0 deletions

diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
index 56643256da..41c086685d 100644
--- a/gdb/gdbarch.c
+++ b/gdb/gdbarch.c
@@ -275,6 +275,7 @@ struct gdbarch
   int have_nonsteppable_watchpoint;
   gdbarch_address_class_type_flags_ftype *address_class_type_flags;
   gdbarch_address_class_type_flags_to_name_ftype *address_class_type_flags_to_name;
+  gdbarch_execute_dwarf_cfa_vendor_op_ftype *execute_dwarf_cfa_vendor_op;
   gdbarch_address_class_name_to_type_flags_ftype *address_class_name_to_type_flags;
   gdbarch_register_reggroup_p_ftype *register_reggroup_p;
   gdbarch_fetch_pointer_argument_ftype *fetch_pointer_argument;
@@ -436,6 +437,7 @@ gdbarch_alloc (const struct gdbarch_info *info,
   gdbarch->make_symbol_special = default_make_symbol_special;
   gdbarch->adjust_dwarf2_addr = default_adjust_dwarf2_addr;
   gdbarch->adjust_dwarf2_line = default_adjust_dwarf2_line;
+  gdbarch->execute_dwarf_cfa_vendor_op = default_execute_dwarf_cfa_vendor_op;
   gdbarch->register_reggroup_p = default_register_reggroup_p;
   gdbarch->skip_permanent_breakpoint = default_skip_permanent_breakpoint;
   gdbarch->displaced_step_hw_singlestep = default_displaced_step_hw_singlestep;
@@ -634,6 +636,7 @@ verify_gdbarch (struct gdbarch *gdbarch)
   /* Skip verify of have_nonsteppable_watchpoint, invalid_p == 0 */
   /* Skip verify of address_class_type_flags, has predicate.  */
   /* Skip verify of address_class_type_flags_to_name, has predicate.  */
+  /* Skip verify of execute_dwarf_cfa_vendor_op, invalid_p == 0 */
   /* Skip verify of address_class_name_to_type_flags, has predicate.  */
   /* Skip verify of register_reggroup_p, invalid_p == 0 */
   /* Skip verify of fetch_pointer_argument, has predicate.  */
@@ -975,6 +978,9 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
                       "gdbarch_dump: elfcore_write_linux_prpsinfo = <%s>\n",
                       host_address_to_string (gdbarch->elfcore_write_linux_prpsinfo));
   fprintf_unfiltered (file,
+                      "gdbarch_dump: execute_dwarf_cfa_vendor_op = <%s>\n",
+                      host_address_to_string (gdbarch->execute_dwarf_cfa_vendor_op));
+  fprintf_unfiltered (file,
                       "gdbarch_dump: fast_tracepoint_valid_at = <%s>\n",
                       host_address_to_string (gdbarch->fast_tracepoint_valid_at));
   fprintf_unfiltered (file,
@@ -3523,6 +3529,23 @@ set_gdbarch_address_class_type_flags_to_name (struct gdbarch *gdbarch,
   gdbarch->address_class_type_flags_to_name = address_class_type_flags_to_name;
 }
 
+bool
+gdbarch_execute_dwarf_cfa_vendor_op (struct gdbarch *gdbarch, gdb_byte op, struct dwarf2_frame_state *fs)
+{
+  gdb_assert (gdbarch != NULL);
+  gdb_assert (gdbarch->execute_dwarf_cfa_vendor_op != NULL);
+  if (gdbarch_debug >= 2)
+    fprintf_unfiltered (gdb_stdlog, "gdbarch_execute_dwarf_cfa_vendor_op called\n");
+  return gdbarch->execute_dwarf_cfa_vendor_op (gdbarch, op, fs);
+}
+
+void
+set_gdbarch_execute_dwarf_cfa_vendor_op (struct gdbarch *gdbarch,
+                                         gdbarch_execute_dwarf_cfa_vendor_op_ftype execute_dwarf_cfa_vendor_op)
+{
+  gdbarch->execute_dwarf_cfa_vendor_op = execute_dwarf_cfa_vendor_op;
+}
+
 int
 gdbarch_address_class_name_to_type_flags_p (struct gdbarch *gdbarch)
 {