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

[Sebastian Huber]

On 01/09/2019 04:29, Chris Johns wrote:
> On 30/8/19 11:07 pm, Sebastian Huber wrote:
>> Introduce new library librtemsrecordwrap.a which contains wrappers for
>> operating system functions which produce entry/exit events.
> 
> Why not enhance the trace linker to handle the recorder you have developed? It
> has been able to wrap malloc and friends for a while now, it is just lacking
> support for your recent tracing effort.
> 
> Currently the trace linker does not uses the DWARF information to determine the
> function signature as the DWARF support was added to the tool kit after it was
> created and it has not been updated. The idea is to have DWARF provide the
> signature of any suitable function so it can be wrapped.

With the DWARF information at hand it should be possible to generate 
generic record events for function calls with up to 10 input arguments 
(RTEMS_RECORD_ARG_[0-9]) and up to 10 return values 
(RTEMS_RECORD_RETURN_[0-9]). We need two events for generic function 
entry/exit:

RTEMS_RECORD_FUNCTION_ENTRY
RTEMS_RECORD_FUNCTION_EXIT

The event data for these two is the function address.

> 
> 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).

* It works without extra tools to build the application.

* It can be tested through the RTEMS test suite.

* You don't need the ELF file to produce a report.

The only strong argument is the first one. A future support in the trace 
linker could use the librtemsrecordwrap.a and only generate generic 
stubs for other functions.

Adding the DWARF support could be a GSoC 2020 project.

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
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E-Mail  : sebastian.huber at embedded-brains.de
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