[syslinux] Re: mboot.c32, weird e820 map on HP blade machine, possible memory corruption

[H. Peter Anvin]

Tim Deegan wrote:
> Hi Ram,
> 
> Just saw your latest message about optimization levels.  Does explicitly
> clearing the registers help?  Shouldn't make a difference, since es:edi
> is the only address we pass, but...
> 
> --- old/mboot.c 2006-03-15 10:12:43.000000000 +0000
> +++ ./mboot.c   2006-03-15 10:13:21.000000000 +0000
> @@ -359,6 +359,7 @@
>      while(((void *)(e820 + 1)) < __com32.cs_bounce +
>      __com32.cs_bounce_size) 
>      {
>          memset(e820, 0, sizeof (*e820));
> +        memset(&regs_in, 0, sizeof regs_in);
>          e820->size = sizeof(*e820) - sizeof(e820->size);
>        
>          /* Ask the BIOS to fill in this descriptor */
> 

Explicitly clearing registers is usually a good idea, I've found.  It 
cuts down on weirdness.

One thing I think in particular might be important is to set eflags, 
which mboot.c currently doesn't do.  eflags set to a random value is 
usually bad news.

	-hpa