On 14/02/16 15:26, Michael S. Tsirkin wrote:
I'm not aware of any standard describing the content of %ds when jumping to
a boot sector at 0000:7c00. Every boot sector that I have encountered
explicitly initialises %ds (and %es, and %ss:%sp) to known values.
Sounds reasonable wrt %ds, but I think %ss:%sp at least is initialized by PXE,
isn't it?
PXE spec says (4.4.5 Client State at Bootstrap Execution Time (Remote.0)):
On entry to the NBP:
! CS:IP must contain the value 0:7C00h.
! ES:BX must contain the address of the PXENV+ structure.
! SS:[SP+4] must contain the segment:offset address of the !PXE structure.
! EDX is no longer used.
! SS:SP is to contain the address of the beginning of the unused portion of the
PXE services stack.
! There must be at least 1.5KB of free stack space for the NBP.
That's for execution of a PXE NBP, rather than a (SAN-booted) disk boot
sector.
Michael
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