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[romprefix] Cope with PnP BIOSes that fail to set %es:%di on entry 

Some BIOSes support the BIOS Boot Specification (BBS) but fail to set
%es:%di correctly when calling the option ROM initialisation entry
point.  This causes gPXE to identify the BIOS as non-PnP (and so
non-BBS), leaving the user unable to control the boot order.

Fix by scanning for the $PnP signature ourselves, rather than relying
on the BIOS having passed in %es:%di correctly.

Tested-by: Helmut Adrigan <helmut.adrigan@chello.at>
pull/1/head
Michael Brown 2009-08-08 14:36:10 +01:00
parent ad66465b3c
commit 7a3a159af5
1 changed files with 20 additions and 7 deletions
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27
src/arch/i386/prefix/romprefix.S
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@ -238,24 +238,37 @@ no_pci3:
popl %edx
popl %ebx
/* Check for PnP BIOS */
testw $0x0f, %bx /* PnP signature must be aligned - bochs */
jnz no_bbs /* uses unalignment to indicate 'fake' PnP. */
cmpl $PNP_SIGNATURE, %es:0(%bx)
jne no_bbs
/* Check for PnP BIOS. Although %es:di should point to the
* PnP BIOS signature on entry, some BIOSes fail to do this.
*/
movw $( 0xf000 - 1 ), %bx
pnp_scan:
incw %bx
jz no_pnp
movw %bx, %es
cmpl $PNP_SIGNATURE, %es:0
jne pnp_scan
xorw %dx, %dx
xorw %si, %si
movzbw %es:5, %cx
1: es lodsb
addb %al, %dl
loop 1b
jnz pnp_scan
/* Is PnP: print PnP message */
movw $init_message_pnp, %si
xorw %di, %di
call print_message
/* Check for BBS */
pushw %es:0x1b(%bx) /* Real-mode data segment */
pushw %es:0x1b /* Real-mode data segment */
pushw %ds /* &(bbs_version) */
pushw $bbs_version
pushw $PNP_GET_BBS_VERSION
lcall *%es:0xd(%bx)
lcall *%es:0xd
addw $8, %sp
testw %ax, %ax
je got_bbs
no_pnp: /* Not PnP-compliant - therefore cannot be BBS-compliant */
no_bbs: /* Not BBS-compliant - must hook INT 19 */
movw $init_message_int19, %si
xorw %di, %di