[PATCH] record: Add wrappers for malloc() functions

[Sebastian Huber]

On 02/09/2019 08:00, Chris Johns wrote:
>>> I do not see any upside adding this library or wrapping specific functions
>>> this way.
>> The benefits are:
>>
>> * Slightly more compact (the event indicates the function and the data can be
>> used for the caller address instead, the generic function entry/exit needs two
>> events for this).
> Could you please explain this, sorry I am not sure what this means? If the code
> is what needs to be generated then why not generate?

The record items is defined like this:

/**
  * @brief The record data integer type.
  *
  * It is big enough to store 32-bit integers and pointers.
  */
typedef unsigned long rtems_record_data;

/**
  * @brief The native record item.
  */
typedef struct __attribute__((__packed__)) {
   uint32_t          event;
   rtems_record_data data;
} rtems_record_item;

The event member contains a 22-bit time stamp and a 10-bit event number.

The malloc entry/exit wrapper with a special event number looks like this:

void *__wrap_malloc( size_t size )
{
   void *ptr;

   rtems_record_produce_2(
     RTEMS_RECORD_MALLOC_ENTRY,
     (rtems_record_data) RTEMS_RETURN_ADDRESS(),
     RTEMS_RECORD_ARG_0,
     size
   )
   ptr = __real_malloc( size );
     rtems_record_produce_2(
     RTEMS_RECORD_MALLOC_EXIT,
     (rtems_record_data) RTEMS_RETURN_ADDRESS(),
     RTEMS_RECORD_RETURN_0,
     (rtems_record_data) ptr
   )
   return ptr;
}

If you have to encode the function in the event data, then you need two 
extra items:

void *__wrap_malloc( size_t size )
{
   rtems_record_item items[ 3 ];
   void *ptr;

   items[ 0 ].event = RTEMS_RECORD_FUNCTION_ENTRY;
   items[ 1 ].data = (rtems_record_data) __real_malloc;
   items[ 1 ].event = RTEMS_RECORD_CALLER;
   items[ 1 ].data = (rtems_record_data) RTEMS_RETURN_ADDRESS();
   items[ 2 ].event = RTEMS_RECORD_ARG_0;
   items[ 2 ].data = size;
   rtems_record_produce_n( items, RTEMS_ARRAY_SIZE( items ) );
   ptr = __real_malloc( size );
   items[ 0 ].event = RTEMS_RECORD_FUNCTION_EXIT;
   items[ 1 ].data = (rtems_record_data) __real_malloc;
   items[ 1 ].event = RTEMS_RECORD_CALLER;
   items[ 1 ].data = (rtems_record_data) RTEMS_RETURN_ADDRESS();
   items[ 2 ].event = RTEMS_RECORD_RETURN_0;
   items[ 2 ].data = (rtems_record_data) ptr;
   rtems_record_produce_n( items, RTEMS_ARRAY_SIZE( items ) );
   return ptr;
}

For this simple one argument function, this is a 50% increase.

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber at embedded-brains.de
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