Hi,
On Thu, Nov 12, 2009 at 01:20:58PM +0200, Naphtali Sprei wrote:
I've found a problem with the usage of SeaBIOS/gPXE in Qemu. The
scenario is when failing to boot from network and falling back to
booting from hard-disk (-boot nc). The cause of the problem is that
both SeaBIOS and gPXE (in it's installation phase) uses same stack
area, 0x7c00. The gPXE code corrupts the SeaBIOS stack, so when
gPXE returns to SeaBIOS chaos occurs.
Output: "qemu: fatal: Trying to execute code outside RAM or ROM at
0x00000000eb300000"
Thanks for reporting this.
We can move the SeaBIOS stack, but it's not clear to me where to move
it to. Bochs bios puts the top of the stack at 0x10000, but this
could potentially conflict with the OS load to 0x7c00. So, in SeaBIOS
the top of stack was moved to 0x7c00 to prevent this conflict.
Maybe the gPXE developers know where the bios typically places its
stack.
However, I'm not sure why gPXE doesn't just use the stack it was
given, or allocate the stack space it needs with PMM.