[PATCH 11/12] gdb, gdbarch: Introduce gdbarch method to get the shadow stack pointer.

["Schimpe, Christina" <christina.schimpe@intel.com>]

This patch is required by the following commit.
---
 gdb/arch-utils.c          |  8 ++++++++
 gdb/arch-utils.h          |  5 +++++
 gdb/gdbarch-gen.c         | 22 ++++++++++++++++++++++
 gdb/gdbarch-gen.h         |  6 ++++++
 gdb/gdbarch_components.py | 10 ++++++++++
 5 files changed, 51 insertions(+)

diff --git a/gdb/arch-utils.c b/gdb/arch-utils.c
index a2ed2a2c011..3aedb3f2600 100644
--- a/gdb/arch-utils.c
+++ b/gdb/arch-utils.c
@@ -1218,6 +1218,14 @@ default_gdbarch_return_value
 				readbuf, writebuf);
 }
 
+/* See arch-utils.h.  */
+
+std::optional<CORE_ADDR>
+default_get_shadow_stack_pointer (gdbarch *gdbarch)
+{
+  return {};
+}
+
 obstack *gdbarch_obstack (gdbarch *arch)
 {
   return &arch->obstack;
diff --git a/gdb/arch-utils.h b/gdb/arch-utils.h
index b59e2ad70c2..471be9c282d 100644
--- a/gdb/arch-utils.h
+++ b/gdb/arch-utils.h
@@ -325,4 +325,9 @@ extern enum return_value_convention default_gdbarch_return_value
       struct regcache *regcache, struct value **read_value,
       const gdb_byte *writebuf);
 
+/* Default implementation of gdbarch default_get_shadow_stack_pointer
+   method.  */
+extern std::optional<CORE_ADDR> default_get_shadow_stack_pointer
+  (gdbarch *gdbarch);
+
 #endif /* GDB_ARCH_UTILS_H */
diff --git a/gdb/gdbarch-gen.c b/gdb/gdbarch-gen.c
index c33c476dfdb..72638f01ad7 100644
--- a/gdb/gdbarch-gen.c
+++ b/gdb/gdbarch-gen.c
@@ -261,6 +261,7 @@ struct gdbarch
   gdbarch_read_core_file_mappings_ftype *read_core_file_mappings = default_read_core_file_mappings;
   gdbarch_use_target_description_from_corefile_notes_ftype *use_target_description_from_corefile_notes = default_use_target_description_from_corefile_notes;
   gdbarch_shadow_stack_push_ftype *shadow_stack_push = nullptr;
+  gdbarch_get_shadow_stack_pointer_ftype *get_shadow_stack_pointer = default_get_shadow_stack_pointer;
 };
 
 /* Create a new ``struct gdbarch'' based on information provided by
@@ -533,6 +534,7 @@ verify_gdbarch (struct gdbarch *gdbarch)
   /* Skip verify of read_core_file_mappings, invalid_p == 0.  */
   /* Skip verify of use_target_description_from_corefile_notes, invalid_p == 0.  */
   /* Skip verify of shadow_stack_push, has predicate.  */
+  /* Skip verify of get_shadow_stack_pointer, invalid_p == 0.  */
   if (!log.empty ())
     internal_error (_("verify_gdbarch: the following are invalid ...%s"),
 		    log.c_str ());
@@ -1404,6 +1406,9 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
   gdb_printf (file,
 	      "gdbarch_dump: shadow_stack_push = <%s>\n",
 	      host_address_to_string (gdbarch->shadow_stack_push));
+  gdb_printf (file,
+	      "gdbarch_dump: get_shadow_stack_pointer = <%s>\n",
+	      host_address_to_string (gdbarch->get_shadow_stack_pointer));
   if (gdbarch->dump_tdep != NULL)
     gdbarch->dump_tdep (gdbarch, file);
 }
@@ -5539,3 +5544,20 @@ set_gdbarch_shadow_stack_push (struct gdbarch *gdbarch,
 {
   gdbarch->shadow_stack_push = shadow_stack_push;
 }
+
+std::optional<CORE_ADDR>
+gdbarch_get_shadow_stack_pointer (struct gdbarch *gdbarch)
+{
+  gdb_assert (gdbarch != NULL);
+  gdb_assert (gdbarch->get_shadow_stack_pointer != NULL);
+  if (gdbarch_debug >= 2)
+    gdb_printf (gdb_stdlog, "gdbarch_get_shadow_stack_pointer called\n");
+  return gdbarch->get_shadow_stack_pointer (gdbarch);
+}
+
+void
+set_gdbarch_get_shadow_stack_pointer (struct gdbarch *gdbarch,
+				      gdbarch_get_shadow_stack_pointer_ftype get_shadow_stack_pointer)
+{
+  gdbarch->get_shadow_stack_pointer = get_shadow_stack_pointer;
+}
diff --git a/gdb/gdbarch-gen.h b/gdb/gdbarch-gen.h
index ff14a3666b9..ff511b4a9e0 100644
--- a/gdb/gdbarch-gen.h
+++ b/gdb/gdbarch-gen.h
@@ -1783,6 +1783,8 @@ extern void set_gdbarch_use_target_description_from_corefile_notes (struct gdbar
    technologies.  For example, Intel's Control-flow Enforcement Technology (CET)
    provides a shadow stack and indirect branch tracking.
    To enable inferior calls the function shadow_stack_push has to be provided.
+   The method get_shadow_stack_pointer has to be provided to enable displaced
+   stepping.
 
    Push the address NEW_ADDR on the shadow stack and update the shadow stack
    pointer. */
@@ -1792,3 +1794,7 @@ extern bool gdbarch_shadow_stack_push_p (struct gdbarch *gdbarch);
 typedef void (gdbarch_shadow_stack_push_ftype) (struct gdbarch *gdbarch, CORE_ADDR new_addr);
 extern void gdbarch_shadow_stack_push (struct gdbarch *gdbarch, CORE_ADDR new_addr);
 extern void set_gdbarch_shadow_stack_push (struct gdbarch *gdbarch, gdbarch_shadow_stack_push_ftype *shadow_stack_push);
+
+typedef std::optional<CORE_ADDR> (gdbarch_get_shadow_stack_pointer_ftype) (struct gdbarch *gdbarch);
+extern std::optional<CORE_ADDR> gdbarch_get_shadow_stack_pointer (struct gdbarch *gdbarch);
+extern void set_gdbarch_get_shadow_stack_pointer (struct gdbarch *gdbarch, gdbarch_get_shadow_stack_pointer_ftype *get_shadow_stack_pointer);
diff --git a/gdb/gdbarch_components.py b/gdb/gdbarch_components.py
index 52f265e8e0e..df70cb082a4 100644
--- a/gdb/gdbarch_components.py
+++ b/gdb/gdbarch_components.py
@@ -2822,6 +2822,8 @@ Some targets support special hardware-assisted control-flow protection
 technologies.  For example, Intel's Control-flow Enforcement Technology (CET)
 provides a shadow stack and indirect branch tracking.
 To enable inferior calls the function shadow_stack_push has to be provided.
+The method get_shadow_stack_pointer has to be provided to enable displaced
+stepping.
 
 Push the address NEW_ADDR on the shadow stack and update the shadow stack
 pointer.
@@ -2831,3 +2833,11 @@ pointer.
     params=[("CORE_ADDR", "new_addr")],
     predicate=True,
 )
+
+Method(
+    type="std::optional<CORE_ADDR>",
+    name="get_shadow_stack_pointer",
+    params=[],
+    predefault="default_get_shadow_stack_pointer",
+    invalid=False,
+)
-- 
2.34.1

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