Packing a file into an ELF executable

I'm currently looking for a way to add data to an already compiled ELF executable, i.e. embedding a file into the executable without recompiling it.

I could easily do that by using cat myexe mydata > myexe_with_mydata, but I couldn't access the data from the executable because I don't know the size of the original executable.

Does anyone have an idea of how I could implement this ? I thought of adding a section to the executable or using a special marker (0xBADBEEFC0FFEE for example) to detect the beginning of the data in the executable, but I do not know if there is a more beautiful way to do it.

Thanks in advance.