Tiny coverage

This is a small source repository to simplify the code coverage tasks on embedded systems.

#Directory structure

• gcov: code coverage library
• sample/rtems: sample code for RTEMS operating system
• gdb: gdb script to automate the code coverage counters retrieval

#Usage

Let us take the sample code inside sample/rtems. This folder contains two files. One file bubble.c that is the software we want to profile and, a wrapper.c that wraps the main function to ensure the code coverage counters are transmitted back to the host.

In the case of RTEMS, the main function is called Init. The wrapper method __wrap_Init() wraps that function to ensure __gcov_exit() is called when finished.

extern void __real_Init(void *ignored);

#define real_function   __real_Init

void __wrap_Init(void *ignored)
{

    printf("%s: Coverage initialized\n", __func__);
    /*	call the real funcion	*/
    real_function(ignored);

    // Send the gathered coverage info
    __gcov_exit();

    // These lines here bellow are not really important as are specific of RTEMS OS
    printf("rtems_task_delete\n");
    rtems_task_delete( RTEMS_SELF );

}

##Profiling in 3 steps

First, we need to compile the source files on which we want to perform the code coverage. For that we'll include the flags -ftest-coverage and -fprofile-arcs to tell GCC to instrument the code.

${CROSS-COMPILE}-gcc -c sample/bubble.c -ftest-coverage -fprofile-arcs

where CROSS-COMPILE is the prefix for your GCC cross compiler (in this case would be spar-rtems-)

Second, compile the rest of our project and wrap if necessary our application entry point. In this case the Init function.

${CROSS-COMPILE}-gcc -g -o bubble bubble.o sample/wrapper.c  gcov/* -Xlinker --wrap -Xlinker Init -I./gcov

Third, we can use GDB to connect to our embedded hardware and let it receive the coverage profile information.

The following code is an example of a possible GDB script that could be used.

tar extended-remote :10001
load bubble.cov

b base.c:85  # break on coverage_helper_breakme() function
commands 1
    silent
    set $filename = tmp->info->filename
    set $dataBegin = buffer
    set $dataEnd = buffer + sizeInBytes
    eval "dump binary memory %s 0x%lx 0x%lx", $dataBegin, $dataEnd, $filename 
    eval "echo dump binary memory %s 0x%lx 0x%lx", $dataBegin, $dataEnd, $filename 
    echo \n
    c
end
c

Now, just use GDB to connect to your target hardware and execute your application

gdb -x gdb/automate_coverage.gdb bubble

The corresponding .gcda files with the information about the code coverage should have been created. You can now process them using lcov at will.