Re: [PATCH v5 01/25] New target methods for memory tagging support

[Lancelot SIX <lsix@lancelotsix.com>]

On Wed, Jan 27, 2021 at 05:20:48PM -0300, Luis Machado via Gdb-patches wrote:
> Updates on v5:
> 
> - Remove the memory_tagging global (in favor of setting a specific print
>   option) and related functions.
> 
> 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.
> 
> gdb/ChangeLog:
> 
> YYYY-MM-DD  Luis Machado  <luis.machado@linaro.org>
> 
> 	* 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/remote.c           | 34 +++++++++++++++
>  gdb/target-debug.h     | 24 +++++++++++
>  gdb/target-delegates.c | 95 ++++++++++++++++++++++++++++++++++++++++++
>  gdb/target.h           | 41 ++++++++++++++++++
>  4 files changed, 194 insertions(+)
> 
> diff --git a/gdb/remote.c b/gdb/remote.c
> index bc995edc53..b130f1ddae 100644
> --- a/gdb/remote.c
> +++ b/gdb/remote.c
> @@ -690,6 +690,14 @@ 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,
> @@ -14472,6 +14480,32 @@ show_remote_timeout (struct ui_file *file, int from_tty,
>  		    value);
>  }
>  
> +/* 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;

If you return a bool, you should probably return false.

> +}
> +
> +/* 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;

Similarly, return false.

> +}
> +
>  void _initialize_remote ();
>  void
>  _initialize_remote ()
> diff --git a/gdb/target-debug.h b/gdb/target-debug.h
> index 6910338865..5bc384a39a 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);

I think you meant target_debug_print_const_gdb_byte_vector_r here.

Lancelot.

> +}
>  #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 917476d16a..19395f1258 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
>