Fix the shuffle and boot interface. It was probably always broken.

diff --git a/bootsect.inc b/bootsect.inc
index 7c288da..3a5fd1b 100644 (file)
--- a/bootsect.inc
+++ b/bootsect.inc
@@ -92,8 +92,8 @@ load_bootsec:
 ;
 
 replace_bootstrap_one:
-               push word trackbuf              ; Address of descriptor list
                push word 1                     ; Length of descriptor list
+               push word trackbuf              ; Address of descriptor list
                ; Fall through
 
 ;
@@ -149,7 +149,8 @@ replace_bootstrap:
                cmp dword [fs:bx], "$PnP"
                jz .foundpnp
                inc bx
-               jnz .findpnp
+               cmp bx,-3               ; Don't get a segment overflow error!
+               jb .findpnp
                jmp .donepnp            ; No $PnP header found
 .foundpnp:
                movzx cx,byte [fs:bx+5] ; Size of $PnP header
@@ -171,8 +172,8 @@ replace_bootstrap:
 %endif
 
 .donepnp:
-               pop ax                  ; Copy list count
                pop bx                  ; Copy from...
+               pop ax                  ; Copy list count
 
                cli
                mov cx,es

diff --git a/comboot.doc b/comboot.doc
index b61fb08..bc6433c 100644 (file)
--- a/comboot.doc
+++ b/comboot.doc
@@ -548,7 +548,7 @@ AX=0011h [3.05] Maximum number of shuffle descriptors
        Typical values are 682 and 1365.
 
 
-AX=0012h [3.05] Cleanup, shuffle and boot
+AX=0012h [3.40] Cleanup, shuffle and boot
        Input:  AX      0012h
                DX      derivative-specific flags (see function 000Ch)
                ES:DI   shuffle descriptor list (must be in low memory)
@@ -589,6 +589,8 @@ AX=0012h [3.05] Cleanup, shuffle and boot
        (except DS, ESI and EDX) and the stack will be set up as they
        were set up by the PXE ROM.
 
+       This interface was probably broken before version 3.40.
+
 
 AX=0013h [3.08] Idle loop call
        Input:  AX      0013h

diff --git a/comboot.inc b/comboot.inc
index d0ac808..70d7d7b 100644 (file)
--- a/comboot.inc
+++ b/comboot.inc
@@ -606,11 +606,12 @@ comapi_maxshuffle:
 ; INT 22h AX=0012h     Cleanup, shuffle and boot
 ;
 comapi_shuffle:
-               call comapi_cleanup
-               mov cx,P_CX
-               cmp cx,(2*trackbufsize)/12
+               cmp P_CX,(2*trackbufsize)/12
                ja .error
 
+               call comapi_cleanup
+
+               mov cx, P_CX
                push cx                         ; On stack: descriptor count
 
                lea cx,[ecx+ecx*2]              ; CX *= 3
@@ -799,11 +800,12 @@ comapi_readdisk   equ comapi_err
 ; INT 22h AX=001Ah     Cleanup, shuffle and boot to flat protected mode
 ;
 comapi_shufflepm:
-               call comapi_cleanup
-               mov cx,P_CX
-               cmp cx,(2*trackbufsize)/12
+               cmp P_CX,(2*trackbufsize)/12
                ja .error
 
+               call comapi_cleanup
+
+               mov cx, P_CX
                push cx                         ; On stack: descriptor count
 
                lea cx,[ecx+ecx*2]              ; CX *= 3
@@ -816,8 +818,7 @@ comapi_shufflepm:
 
                mov fs,P_DS
                mov si,P_SI
-               xor edi,edi
-               mov di,PMTrampolineBuf
+               mov edi,PMTrampolineBuf
                mov al,0B8h                     ; MOV EAX opcode
                mov cx,9
 .maketramp:
@@ -825,8 +826,8 @@ comapi_shufflepm:
                inc ax                          ; Next register opcode
                fs movsd                        ; immediate value
                loop .maketramp
-               mov byte [di-9],0E9h            ; Last opcode is JMP
-               sub dword [di-8],edi            ; Make JMP target relative
+               mov byte [di-5],0E9h            ; Last opcode is JMP
+               sub [di-4],edi                  ; Make JMP target relative
 
                mov dword [EntryPoint],trampoline_to_pm
                xor bx,bx                       ; DS on entry