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

Luis Machado via Gdb-patches
2021-01-28T10:02:53Z

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
>>