[gPXE-devel] Expand heap size

[Michael Brown]

On Monday 07 Jun 2010 15:19:16 Guo-Fu Tseng wrote:
> > 3. By increasing the total memory footprint beyond 1MB, you lose the
> > guarantee of residing entirely within a region with A20=0.  iPXE will
> > work in a region with A20=1, but gPXE may fail.
> 
> By placing the heap to the highest memory address, we can ensure that
> all addresses other than heap would still be at region with A20=0.
> Since gPXE have not apply your A20 patchset right now.
> 
> This is the part that I'm not sure, have not traced all your code yet.
> But I'm guessing that the A20=0 limitation is for 16-bit code only.
> And the parts that uses heap which written in C are running on 32-bit
> protected-mode(for arch i386 with librm). So I'm hoping that it can
> make gPXE safer this way.

No; the A20=0 limitation in gPXE applies to 32-bit code as well as 16-bit 
code.

Michael