When chainloading, set ES:DI to point to the $PnP ICS if available.

Arguably these really should be kept from the original invocation instead
of saved.  This is doable for PXELINUX, but might be very hard to do for
the disk-based ones.  Think hard about it.

diff --git a/bootsect.inc b/bootsect.inc
index b1360a5..d52aefb 100644 (file)
--- a/bootsect.inc
+++ b/bootsect.inc
@@ -132,10 +132,39 @@ replace_bootstrap:
                pop di
 .stackok:
 
-               mov [es:di+28],edx
-               mov [es:di+12],esi
-               mov [es:di+6],bx
+               mov [es:di+28],edx      ; New EDX
+               mov [es:di+12],esi      ; New ESI
+               mov [es:di+6],bx        ; New DS
 
+               ; Hunt for $PnP header if one exists
+               mov ax,0F000h
+               mov fs,ax
+               xor bx,bx
+.findpnp:
+               cmp dword [fs:bx], "$PnP"
+               jz .foundpnp
+               inc bx
+               jnz .findpnp
+               jmp .donepnp            ; No $PnP header found
+.foundpnp:
+               movzx cx,byte [fs:bx+5] ; Size of $PnP header
+               cmp cl,21h
+               jb .findpnp             ; Invalid $PnP header (too short)
+               push bx
+               xor ax,ax
+.checkpnp:
+               add al,byte [fs:bx]
+               inc bx
+               loop .checkpnp
+               pop bx
+               and al,al
+               jnz .findpnp
+
+               ; Found a valid $PnP header, point ES:DI to it
+               mov [es:di+8], bx       ; New DI
+               mov [es:di+4], fs       ; New ES
+
+.donepnp:
                pop ax                  ; Copy list count
                pop bx                  ; Copy from...