[PATCH v4 01/25] New target methods for memory tagging support

[Luis Machado via Gdb-patches <gdb-patches@sourceware.org>]

Updates on v4:

- Updated the return types of fetch/store member functions from int to bool.
- Implemented target-debug type print helpers.
- Renamed global memtag to memory_tagging.

Updates on v3:

- Updated the code documentation for the fetch_memtags and store_memtags
  methods.

Updates on v2:

- Added type parameter to fetch_memtags/store_memtags hooks.

--

This patch starts adding some of the generic pieces to accomodate memory
tagging.

We have three new target methods:

- supports_memory_tagging: Checks if the target supports memory tagging. This
  defaults to false for targets that don't support memory tagging.

- fetch_memtags: Fetches the allocation tags associated with a particular
  memory range [address, address + length).

  The default is to return 0 without returning any tags. This should only
  be called if memory tagging is supported.

- store_memtags: Stores a set of allocation tags for a particular memory
  range [address, address + length).

  The default is to return 0. This should only
  be called if memory tagging is supported.

It also adds a control option for enabling/disabling memory tagging
manually: set memory-tagging on/off.

The default is "on", with GDB making its use conditional to the
architecture supporting memory tagging.

gdb/ChangeLog:

YYYY-MM-DD  Luis Machado  <luis.machado@linaro.org>

	* printcmd.c (memory_tagging): New static global.
	(show_memory_tagging): New function.
	(_initialize_printcmd): Add set/show memory-tagging command.
	* remote.c (remote_target) <supports_memory_tagging>: New method
	override.
	<fetch_memtags>: New method override.
	<store_memtags>: New method override.
	(remote_target::supports_memory_tagging): New method.
	(remote_target::fetch_memtags): New method.
	(remote_target::store_memtags): New method.
	* target-delegates.c: Regenerate.
	* target.h (struct target_ops) <supports_memory_tagging>: New virtual
	method.
	<fetch_memtags>: New virtual method.
	<store_memtags>: New virtual method.
	(target_supports_memory_tagging): Define.
	(target_fetch_memtags): Define.
	(target_store_memtags): Define.
	* target-debug.h (target_debug_print_size_t)
	(target_debug_print_const_gdb_byte_vector_r)
	(target_debug_print_gdb_byte_vector_r): New functions.
---
 gdb/printcmd.c         | 28 +++++++++++++
 gdb/remote.c           | 34 +++++++++++++++
 gdb/target-debug.h     | 24 +++++++++++
 gdb/target-delegates.c | 95 ++++++++++++++++++++++++++++++++++++++++++
 gdb/target.h           | 41 ++++++++++++++++++
 5 files changed, 222 insertions(+)

diff --git a/gdb/printcmd.c b/gdb/printcmd.c
index de083a2a76..974b0480c7 100644
--- a/gdb/printcmd.c
+++ b/gdb/printcmd.c
@@ -85,6 +85,24 @@ static CORE_ADDR last_examine_address;
 
 static value_ref_ptr last_examine_value;
 
+/* If TRUE (default), and the architecture supports it, GDB will attempt to use
+   the memory tagging infrastructure to validate certain memory accesses.  It
+   will also report memory tag violations alongside a SIGSEGV signal.
+
+   If FALSE, GDB will not use memory tagging in any way, and debugging will
+   work in the standard way.  */
+static bool memory_tagging = true;
+
+static void
+show_memory_tagging (struct ui_file *file, int from_tty,
+		     struct cmd_list_element *c,
+		     const char *value)
+{
+  fprintf_filtered (file,
+		    _("Use of memory tagging infrastructure is \"%s\".\n"),
+		    value);
+}
+
 /* Largest offset between a symbolic value and an address, that will be
    printed as `0x1234 <symbol+offset>'.  */
 
@@ -2980,4 +2998,14 @@ Construct a GDB command and then evaluate it.\n\
 Usage: eval \"format string\", ARG1, ARG2, ARG3, ..., ARGN\n\
 Convert the arguments to a string as \"printf\" would, but then\n\
 treat this string as a command line, and evaluate it."));
+
+  add_setshow_boolean_cmd ("memory-tagging", class_support,
+			   &memory_tagging, _("\
+Set whether the debugger should use memory tagging infrastructure."), _("\
+Show whether the debugger should use memory tagging infrastructure."), _("\
+If on, gdb will attempt to validate memory tags and will warn the user if\n\
+certain operations have illegal tags."),
+			    NULL,
+			    show_memory_tagging,
+			    &setlist, &showlist);
 }
diff --git a/gdb/remote.c b/gdb/remote.c
index 71f814efb3..c7f09c4269 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -686,6 +686,14 @@ class remote_target : public process_stratum_target
   int remove_exec_catchpoint (int) override;
   enum exec_direction_kind execution_direction () override;
 
+  bool supports_memory_tagging () override;
+
+  bool fetch_memtags (CORE_ADDR address, size_t len,
+		     gdb::byte_vector &tags, int type) override;
+
+  bool store_memtags (CORE_ADDR address, size_t len,
+		     const gdb::byte_vector &tags, int type) override;
+
 public: /* Remote specific methods.  */
 
   void remote_download_command_source (int num, ULONGEST addr,
@@ -14389,6 +14397,32 @@ set_range_stepping (const char *ignore_args, int from_tty,
     }
 }
 
+/* Implement the "supports_memory_tagging" target_ops method.  */
+
+bool
+remote_target::supports_memory_tagging ()
+{
+  return false;
+}
+
+/* Implement the "fetch_memtags" target_ops method.  */
+
+bool
+remote_target::fetch_memtags (CORE_ADDR address, size_t len,
+			      gdb::byte_vector &tags, int type)
+{
+  return 0;
+}
+
+/* Implement the "store_memtags" target_ops method.  */
+
+bool
+remote_target::store_memtags (CORE_ADDR address, size_t len,
+			      const gdb::byte_vector &tags, int type)
+{
+  return 0;
+}
+
 void _initialize_remote ();
 void
 _initialize_remote ()
diff --git a/gdb/target-debug.h b/gdb/target-debug.h
index c5abfd46c6..16531470ef 100644
--- a/gdb/target-debug.h
+++ b/gdb/target-debug.h
@@ -212,4 +212,28 @@ target_debug_print_signals (gdb::array_view<const unsigned char> sigs)
   fputs_unfiltered (" }", gdb_stdlog);
 }
 
+static void
+target_debug_print_size_t (size_t size)
+{
+  fprintf_unfiltered (gdb_stdlog, "%s", pulongest (size));
+}
+
+static void
+target_debug_print_const_gdb_byte_vector_r (const gdb::byte_vector &vector)
+{
+  fputs_unfiltered ("{", gdb_stdlog);
+
+  for (size_t i = 0; i < vector.size (); i++)
+    {
+      fprintf_unfiltered (gdb_stdlog, " %s",
+			  phex_nz (vector[i], 1));
+    }
+  fputs_unfiltered (" }", gdb_stdlog);
+}
+
+static void
+target_debug_print_gdb_byte_vector_r (gdb::byte_vector &vector)
+{
+  target_debug_print_gdb_byte_vector_r (vector);
+}
 #endif /* TARGET_DEBUG_H */
diff --git a/gdb/target-delegates.c b/gdb/target-delegates.c
index 437b19b858..e4563e4dac 100644
--- a/gdb/target-delegates.c
+++ b/gdb/target-delegates.c
@@ -173,6 +173,9 @@ struct dummy_target : public target_ops
   const struct frame_unwind *get_tailcall_unwinder () override;
   void prepare_to_generate_core () override;
   void done_generating_core () override;
+  bool supports_memory_tagging () override;
+  bool fetch_memtags (CORE_ADDR arg0, size_t arg1, gdb::byte_vector &arg2, int arg3) override;
+  bool store_memtags (CORE_ADDR arg0, size_t arg1, const gdb::byte_vector &arg2, int arg3) override;
 };
 
 struct debug_target : public target_ops
@@ -344,6 +347,9 @@ struct debug_target : public target_ops
   const struct frame_unwind *get_tailcall_unwinder () override;
   void prepare_to_generate_core () override;
   void done_generating_core () override;
+  bool supports_memory_tagging () override;
+  bool fetch_memtags (CORE_ADDR arg0, size_t arg1, gdb::byte_vector &arg2, int arg3) override;
+  bool store_memtags (CORE_ADDR arg0, size_t arg1, const gdb::byte_vector &arg2, int arg3) override;
 };
 
 void
@@ -4413,3 +4419,92 @@ debug_target::done_generating_core ()
   fputs_unfiltered (")\n", gdb_stdlog);
 }
 
+bool
+target_ops::supports_memory_tagging ()
+{
+  return this->beneath ()->supports_memory_tagging ();
+}
+
+bool
+dummy_target::supports_memory_tagging ()
+{
+  return false;
+}
+
+bool
+debug_target::supports_memory_tagging ()
+{
+  bool result;
+  fprintf_unfiltered (gdb_stdlog, "-> %s->supports_memory_tagging (...)\n", this->beneath ()->shortname ());
+  result = this->beneath ()->supports_memory_tagging ();
+  fprintf_unfiltered (gdb_stdlog, "<- %s->supports_memory_tagging (", this->beneath ()->shortname ());
+  fputs_unfiltered (") = ", gdb_stdlog);
+  target_debug_print_bool (result);
+  fputs_unfiltered ("\n", gdb_stdlog);
+  return result;
+}
+
+bool
+target_ops::fetch_memtags (CORE_ADDR arg0, size_t arg1, gdb::byte_vector &arg2, int arg3)
+{
+  return this->beneath ()->fetch_memtags (arg0, arg1, arg2, arg3);
+}
+
+bool
+dummy_target::fetch_memtags (CORE_ADDR arg0, size_t arg1, gdb::byte_vector &arg2, int arg3)
+{
+  tcomplain ();
+}
+
+bool
+debug_target::fetch_memtags (CORE_ADDR arg0, size_t arg1, gdb::byte_vector &arg2, int arg3)
+{
+  bool result;
+  fprintf_unfiltered (gdb_stdlog, "-> %s->fetch_memtags (...)\n", this->beneath ()->shortname ());
+  result = this->beneath ()->fetch_memtags (arg0, arg1, arg2, arg3);
+  fprintf_unfiltered (gdb_stdlog, "<- %s->fetch_memtags (", this->beneath ()->shortname ());
+  target_debug_print_CORE_ADDR (arg0);
+  fputs_unfiltered (", ", gdb_stdlog);
+  target_debug_print_size_t (arg1);
+  fputs_unfiltered (", ", gdb_stdlog);
+  target_debug_print_gdb_byte_vector_r (arg2);
+  fputs_unfiltered (", ", gdb_stdlog);
+  target_debug_print_int (arg3);
+  fputs_unfiltered (") = ", gdb_stdlog);
+  target_debug_print_bool (result);
+  fputs_unfiltered ("\n", gdb_stdlog);
+  return result;
+}
+
+bool
+target_ops::store_memtags (CORE_ADDR arg0, size_t arg1, const gdb::byte_vector &arg2, int arg3)
+{
+  return this->beneath ()->store_memtags (arg0, arg1, arg2, arg3);
+}
+
+bool
+dummy_target::store_memtags (CORE_ADDR arg0, size_t arg1, const gdb::byte_vector &arg2, int arg3)
+{
+  tcomplain ();
+}
+
+bool
+debug_target::store_memtags (CORE_ADDR arg0, size_t arg1, const gdb::byte_vector &arg2, int arg3)
+{
+  bool result;
+  fprintf_unfiltered (gdb_stdlog, "-> %s->store_memtags (...)\n", this->beneath ()->shortname ());
+  result = this->beneath ()->store_memtags (arg0, arg1, arg2, arg3);
+  fprintf_unfiltered (gdb_stdlog, "<- %s->store_memtags (", this->beneath ()->shortname ());
+  target_debug_print_CORE_ADDR (arg0);
+  fputs_unfiltered (", ", gdb_stdlog);
+  target_debug_print_size_t (arg1);
+  fputs_unfiltered (", ", gdb_stdlog);
+  target_debug_print_const_gdb_byte_vector_r (arg2);
+  fputs_unfiltered (", ", gdb_stdlog);
+  target_debug_print_int (arg3);
+  fputs_unfiltered (") = ", gdb_stdlog);
+  target_debug_print_bool (result);
+  fputs_unfiltered ("\n", gdb_stdlog);
+  return result;
+}
+
diff --git a/gdb/target.h b/gdb/target.h
index 416b8089fa..a35e07d0a3 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -1260,6 +1260,38 @@ struct target_ops
     /* Cleanup after generating a core file.  */
     virtual void done_generating_core ()
       TARGET_DEFAULT_IGNORE ();
+
+    /* Returns true if the target supports memory tagging, false otherwise.  */
+    virtual bool supports_memory_tagging ()
+      TARGET_DEFAULT_RETURN (false);
+
+    /* Return the allocated memory tags of type TYPE associated with
+       [ADDRESS, ADDRESS + LEN) in TAGS.
+
+       LEN is the number of bytes in the memory range.  TAGS is a vector of
+       bytes containing the tags found in the above memory range.
+
+       It is up to the architecture/target to interpret the bytes in the TAGS
+       vector and read the tags appropriately.
+
+       Returns true if fetching the tags succeeded and false otherwise.  */
+    virtual bool fetch_memtags (CORE_ADDR address, size_t len,
+			       gdb::byte_vector &tags, int type)
+      TARGET_DEFAULT_NORETURN (tcomplain ());
+
+    /* Write the allocation tags of type TYPE contained in TAGS to the memory
+       range [ADDRESS, ADDRESS + LEN).
+
+       LEN is the number of bytes in the memory range.  TAGS is a vector of
+       bytes containing the tags to be stored to the memory range.
+
+       It is up to the architecture/target to interpret the bytes in the TAGS
+       vector and store them appropriately.
+
+       Returns true if storing the tags succeeded and false otherwise.  */
+    virtual bool store_memtags (CORE_ADDR address, size_t len,
+			       const gdb::byte_vector &tags, int type)
+      TARGET_DEFAULT_NORETURN (tcomplain ());
   };
 
 /* Deleter for std::unique_ptr.  See comments in
@@ -2312,6 +2344,15 @@ extern gdb::unique_xmalloc_ptr<char> target_fileio_read_stralloc
 #define target_augmented_libraries_svr4_read() \
   (current_top_target ()->augmented_libraries_svr4_read) ()
 
+#define target_supports_memory_tagging() \
+  ((current_top_target ()->supports_memory_tagging) ())
+
+#define target_fetch_memtags(address, len, tags, type) \
+  (current_top_target ()->fetch_memtags) ((address), (len), (tags), (type))
+
+#define target_store_memtags(address, len, tags, type) \
+  (current_top_target ()->store_memtags) ((address), (len), (tags), (type))
+
 /* Command logging facility.  */
 
 #define target_log_command(p)					\
-- 
2.25.1