Assignment 3 ELF Loader

Main idea

When the executable is started is generates page faults for each memory acces to a new page.
There is a signal handler that gets triggered every time a page fault is generated.
The signal handler first has to see in which segment the page fault occured.
- This is done in signal_handler by comparing the address at which the page fault occured to the start address and end address of each segment
- If there is no segment then it's a true invalid acces and Segmentation fault is delivered
After the segment is found, we have to find informations about the page that contains the address of the page fault
If the page was already mapped then the access didn't have the right permisions and Segmentation fault is delivered
If the page isn't mapped then we map it:
- For bss address we map with the MAP_ANONYMOUS flag on
To see what kind of mapping it has to be made we compare the page_start and page_end to the file_size of that segment
- If file_size is between those two then the page could have .bss data as well and we have to map accordingly