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

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

On 1/27/21 8:26 PM, Lancelot SIX wrote:
> 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.
> 

Missed it, since this gets replaced by the full implementation later. 
I'll address it locally. Thanks for spotting that.

>> +}
>> +
>>   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.
> 

That's correct. I'll fix this locally.

Thanks!

> 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
>>