Use small synthesized thunks for the PXE/PXENV calls; fix the stack-

switching code.

diff --git a/pxelinux.asm b/pxelinux.asm
index 7798f21..f95fd04 100644 (file)
--- a/pxelinux.asm
+++ b/pxelinux.asm
@@ -189,7 +189,6 @@ KernelSize  resd 1                  ; Size of kernel (bytes)
 SavedSSSP      resd 1                  ; Our SS:SP while running a COMBOOT image
 PMESP          resd 1                  ; Protected-mode ESP
 InitStack      resd 1                  ; Pointer to reset stack
-PXEEntry       resd 1                  ; !PXE API entry point
 RebootTime     resd 1                  ; Reboot timeout, if set by option
 KernelClust    resd 1                  ; Kernel size in clusters
 StrucPtr       resd 1                  ; Pointer to PXENV+ or !PXE structure
@@ -1421,10 +1420,15 @@ unmangle_name:  call strcpy
 ; calling convention.  This is a separate local routine so
 ; we can hook special things from it if necessary.
 ;
+
 pxenv:
-               call far [cs:PXENVEntry]
+.jump:         call 0:pxe_thunk                ; Default to calling the thunk
+               cld
                ret
 
+; Must be after function def due to NASM bug
+PXENVEntry     equ pxenv.jump+1
+
 ;
 ; pxe_thunk
 ;
@@ -1437,12 +1441,15 @@ pxenv:
 pxe_thunk:     push es
                push di
                push bx
-               call far [cs:PXEEntry]
+.jump:         call 0:0
                add sp,byte 6
                cmp ax,byte 1
                cmc                             ; Set CF unless ax == 0
                retf
 
+; Must be after function def due to NASM bug
+PXEEntry       equ pxe_thunk.jump+1
+
 ;
 ; getfssec: Get multiple clusters from a file, given the starting cluster.
 ;
@@ -1690,8 +1697,7 @@ unload_pxe:
                mov ax,ss
                mov gs,ax
                sub ax,[BaseStack+4]            ; Are we using the base stack
-                                               ; (as opposed to the COMBOOT stack)?
-               je .is_base_stack
+               je .is_base_stack               ; (as opposed to the COMBOOT stack)?
 
                lgs si,[SavedSSSP]              ; COMBOOT stack
 .is_base_stack:
@@ -1702,11 +1708,11 @@ unload_pxe:
                mov [BaseStack+4],es
                sub cx,si
                sub di,cx
-               mov [SavedSSSP],cx              ; New SP
+               mov [SavedSSSP],di              ; New SP
                mov [SavedSSSP+2],es
                gs rep movsb
 
-               and ax,ax                       ; Remeber which stack
+               and ax,ax                       ; Remember which stack
                jne .combootstack
 
                ; Update the base stack pointer since it's in use
@@ -2145,12 +2151,6 @@ exten_table_end:
                dd 0, 0                 ; Need 8 null bytes here
 
 ;
-; PXENV entry point.  If we use the !PXE API, this will point to a thunk
-; function that converts to the !PXE calling convention.
-;
-PXENVEntry     dw pxe_thunk,0
-
-;
 ; PXE unload sequences
 ;
 new_api_unload: