[syslinux] Comboot Menu

[H. Peter Anvin]

ganapathy murali krishnan wrote:
> So, the following should be a very simple memory manager?
> 
> 
> --- BEGIN PSEUDO CODE ---
> 
> START = SS:SP+1 (1 byte above SS:SP)
> END = Value(DS:0002)-1
> myptr = pointer to START
> 
> (void *) myalloc(int numbytes)
> {
>     void * ans;
>     ans = myptr;
>     myptr = myptr + numbytes;
> }
> 
> --- END PSEUDO CODE ---
> 
> As long I never have to deallocated memory, the above should be a
> workable memory managing system?
> 

No, that would trash your stack!  Instead you need to do (DS+1000h):0 as
the beginning.

Instead you probably would want to do:

static void huge *myptr;

void farmalloc_init(void)
{
	myptr = (void huge *)((unsigned long)(__DS + 0x1000) << 16);
}

void far * farmalloc(int bytes)
{
	void far *ans;
	ans = myptr;
	myptr += bytes;

	return ans;
}