On Sun, Feb 14, 2016 at 03:40:51PM +0000, Michael Brown wrote: > 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
I actually thought the initial post was about iPXE calling NBP (starting at location 07C00h) with a non-zero DS, not about booting from disk. Rephrasing the original question, do you think %DS should be zeroed when NBP is called then? -- MST _______________________________________________ SeaBIOS mailing list [email protected] http://www.seabios.org/mailman/listinfo/seabios
