[B2-devel] Re: Memory mapping

[<ni...@in...>]

I asked:
> What is this mmap() actually doing, apart from allocating memory?

Christian answered:
> It can allocate memory at a program-specified address
> (and optionally read- or write-protect the area).

	Sure. What I actually meant was, what is this mmap() doing:

RAMBaseHost = (uint8 *)mmap(0, mapped_ram_rom_size,
                            PROT_READ | PROT_WRITE,
			    MAP_PRIVATE, zero_fd, 0);

	From my reading of the manpage:

* The load address (0) is ignored because MAP_FIXED isn't set

* MAP_PRIVATE makes a copy of mapped_ram_rom_size bytes from
  zero_fd when the process first writes to the memory block



	So, how is this really any different to:

RAMBaseHost = (uint8 *)malloc(mapped_ram_rom_size);
memset(RAMBaseHost, mapped_ram_rom_size, sizeof(uint8));

	or

RAMBaseHost = (uint8 *)calloc(mapped_ram_rom_size, sizeof(uint8));

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