Clearing parts of virtual memory?

Question

I want to clear some virtual memory because I need to load segments from an elf file.

(I'm writing a program that loads and executes an ELF file).

As I understand I have to use munmap

unsigned int blok = sectionHeads[i].adr - (sectionHeads[i].adr % getpagesize());

if (munmap((void *)blok,getpagesize()) == -1) 
{ 
  printf("fail\n");
} 
else 
{ 
  printf("succ\n");
}

blok is a multiple of the address from which I want to free the memory. (or so I think, English is not my mother tongue so it's very possible I misunderstood the meaning of "multiple of").

I want to free the memory because later on I need that space.

When I run the program it doesn't go beyond munmap();

What am I doing wrong?

The only constraint that I found in the munmap documentation is that the address parameter has to be a multiple of the system pagesize.

Is there an easier way to free this memory?

Note: The project requirement is that I free the memory if it is needed but it doesn't say how.

Answer 1

You might be unmapping the memory that your code is running in. You can check this in a debugger by puttimg a breakpoint at the if statement and comparing the value of blok to the current program counter.