Force 8086-asm; use direct call far real_XMSexec instead of push/push…

…/retf.

Fixes #15

include/cswap.h

@@ -29,15 +29,14 @@ extern unsigned char far dosCMDNAME[128];
 /*extern unsigned char far dosCMDTAIL[128];*/
 #define dosCMDTAIL  ((char far*)MK_FP(_psp, 0x80))
 
-extern word residentCS;
-
 extern int cdecl XMSexec(void);	
 
 #ifdef __WATCOMC__
 typedef unsigned long xmsfunc(unsigned request, unsigned dx, void *si);
 #pragma aux xmsfunc = parm [ax] [dx] [si] modify [bx cx]
 extern xmsfunc far *far XMSdriverAdress;
 #elif defined(__GNUC__)
+extern far void real_XMSexec(void);
 extern unsigned far *far XMSdriverAdress;
 static inline unsigned long XMSrequest(unsigned request, unsigned dx, void *si)
 {

include/stuff.inc

@@ -1,3 +1,5 @@
+cpu 8086
+
 ;; Multi-Push/Pop
 ;; Both take the registers in the same order, "F"==Flags
 ;; Push pushes left to right; pop right to left

shell/cswap.asm

@@ -84,7 +84,9 @@ mySP DW 0
 
 execRetval dw 0
 
-;	global real_XMSexec
+%ifidn __OUTPUT_FORMAT__,elf
+	cglobal real_XMSexec
+%endif
 real_XMSexec:
 		int 21h	; shrink/free: first thing done from resident code
 
@@ -320,7 +322,6 @@ XMSrequest:
 ;;	SS at the end of the XMSexec function
 		cglobal	XMSexec
 XMSexec:
-		cextern residentCS
 						; save ALL registers needed later
 %ifidn __OUTPUT_FORMAT__,elf 	; GCC: need to preserve es
 		push es
@@ -345,7 +346,12 @@ XMSexec:
 		mov bx,[SwapResidentSize]
 
 		mov dx, ds
-		mov cx, [residentCS]
+%ifidn __OUTPUT_FORMAT__,elf 	; GCC/ELF: can't use seg so use pointer from C
+		cextern preal_XMSexec
+		mov cx, [cs:preal_XMSexec+2]
+%else
+		mov cx, seg mySS
+%endif
 		mov ds, cx
 
         mov [mySS],ss  ; 2E
@@ -355,11 +361,11 @@ XMSexec:
         mov  sp,localStack
 
 		push dx			; save DS of transient portion
-		push cs			; save segment of transient portion
-		push WORD ret_from_resident
-		push cx
-		push WORD real_XMSexec
-		retf
+%ifidn __OUTPUT_FORMAT__,elf 	; GCC/ELF: can't use direct call far
+		call far [cs:preal_XMSexec]
+%else
+		call far real_XMSexec
+%endif
 
 ret_from_resident:
 		mov ax,[execRetval]

shell/cswapc.c

@@ -78,7 +78,11 @@ static enum {
 	,INIT_FAILED
 	,INIT_SUCCEEDED
 } initialized = INIT_NO;
-word residentCS;
+#ifdef __GNUC__
+/* For other compilers this is defined in cswap.asm but NASM can't deal
+   with relocations in ELF */
+void far * far preal_XMSexec __attribute__((section(".text"))) = real_XMSexec;
+#endif
 
 int XMSisactive(void)
 {	return initialized == INIT_SUCCEEDED;

shell/init.c

@@ -180,9 +180,6 @@ int initialize(void)
 /* Set up the host environment of COMMAND.COM */
 
 	/* Give us shell privileges */
-#ifdef FEATURE_XMS_SWAP
-	residentCS = _CS;
-#endif
 	myPID = _psp;
 	termAddr = pspTermAddr;
 	pspTermAddr = terminateFreeCOMHook;