[librm] Convert prot_call() to a real-mode near call

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/interface/syslinux/comboot_call.c

 	__asm__ __volatile__ (
 		TEXT16_CODE ( "\nint20_wrapper:\n\t"
 		              "pushl %0\n\t"
-		              "pushw %%cs\n\t"
 		              "call prot_call\n\t"
 			      "clc\n\t"
 			      "call patch_cf\n\t"
 	__asm__ __volatile__ (
 		TEXT16_CODE ( "\nint21_wrapper:\n\t"
 		              "pushl %0\n\t"
-		              "pushw %%cs\n\t"
 		              "call prot_call\n\t"
 			      "clc\n\t"
 			      "call patch_cf\n\t"
 	__asm__  __volatile__ (
 		TEXT16_CODE ( "\nint22_wrapper:\n\t"
 		              "pushl %0\n\t"
-		              "pushw %%cs\n\t"
 		              "call prot_call\n\t"
 			      "clc\n\t"
 			      "call patch_cf\n\t"

src/arch/x86/core/dumpregs.c

 		TEXT16_CODE ( ".globl dump_regs\n\t"
 			      "\ndump_regs:\n\t"
 			      "pushl $_dump_regs\n\t"
-			      "pushw %%cs\n\t"
 			      "call prot_call\n\t"
 			      "ret\n\t" ) : : );
 

src/arch/x86/interface/pcbios/bios_console.c

 			      "cmpb $0, %%cs:bios_inject_lock\n\t"
 			      "jnz 1f\n\t"
 			      "pushl %0\n\t"
-			      "pushw %%cs\n\t"
 			      "call prot_call\n\t"
 			      "\n1:\n\t"
 			      "popfw\n\t"

src/arch/x86/interface/pcbios/int13.c

 			     "orb $0, %%al\n\t" 
 			     "stc\n\t"
 			     "pushl %0\n\t"
-			     "pushw %%cs\n\t"
 			     "call prot_call\n\t"
 			     /* Chain if OF not set */
 			     "jo 1f\n\t"

src/arch/x86/interface/pxe/pxe_entry.S

 	.code16
 pxenv_entry:
 	pushl	$pxe_api_call
-	pushw	%cs
 	call	prot_call
 	lret
 	.size	pxenv_entry, . - pxenv_entry

src/arch/x86/prefix/dskprefix.S

 	.section ".text16", "awx", @progbits
 1:
 	pushl	$main
-	pushw	%cs
 	call	prot_call
 
 	/* Uninstall iPXE */

src/arch/x86/prefix/exeprefix.S

 
 	/* Run iPXE */
 	pushl	$main
-	pushw	%cs
 	call	prot_call
 
 	/* Uninstall iPXE */

src/arch/x86/prefix/hdprefix.S

 	.section ".text16", "awx", @progbits
 1:
 	pushl	$main
-	pushw	%cs
 	call	prot_call
 
 	/* Uninstall iPXE */

src/arch/x86/prefix/libprefix.S

 	 */
 	progress "  relocate\n"
 	pushl	$relocate
-	pushw	%cs
 	call	prot_call
 
 	/* Jump back to .prefix segment */

src/arch/x86/prefix/lkrnprefix.S

 
 	/* Run iPXE */
 	pushl	$main
-	pushw	%cs
 	call	prot_call
 
 	/* Uninstall iPXE */

src/arch/x86/prefix/nbiprefix.S

 	.section ".text16", "awx", @progbits
 1:
 	pushl	$main
-	pushw	%cs
 	call	prot_call
 
 	/* Uninstall iPXE */

src/arch/x86/prefix/pxeprefix.S

 
 	/* Run main program */
 	pushl	$main
-	pushw	%cs
 	call	prot_call
 
 	/* Uninstall iPXE */

src/arch/x86/prefix/romprefix.S

 
 	/* Call main() */
 	pushl	$main
-	pushw	%cs
 	call	prot_call
 
 	/* Set up flat real mode for return to BIOS */

src/arch/x86/prefix/undiloader.S

 1:
 	/* Call UNDI loader C code */
 	pushl	$pxe_loader_call
-	pushw	%cs
 	call	prot_call
 
 1:	/* Restore registers and return */

src/arch/x86/transitions/librm.S

 
 	/* Initialise IDT */
 	pushl	$init_idt
-	pushw	%cs
 	call	prot_call
 
 	/* Restore registers */
 	.long 0 /* Base */
 
 /****************************************************************************
- * prot_call (real-mode far call, 16-bit real-mode far return address)
+ * prot_call (real-mode near call, 16-bit real-mode near return address)
  *
  * Call a specific C function in the protected-mode code.  The
  * prototype of the C function must be
  *
  * Example usage:
  *	pushl	$pxe_api_call
- *	pushw	%cs
  *	call	prot_call
  * to call in to the C function
  *      void pxe_api_call ( struct i386_all_regs *ix86 );
 PC_OFFSET_GDT:		.space	6
 PC_OFFSET_IDT:		.space	6
 PC_OFFSET_IX86:		.space	SIZEOF_I386_ALL_REGS
-PC_OFFSET_RETADDR:	.space	4
+PC_OFFSET_PADDING:	.space	2 /* for alignment */
+PC_OFFSET_RETADDR:	.space	2
 PC_OFFSET_FUNCTION:	.space	4
 PC_OFFSET_END:
 	.previous
 	.globl prot_call
 prot_call:
 	/* Preserve registers, flags and GDT on external RM stack */
+	pushfw	/* padding */
 	pushfl
 	pushal
 	pushw	%gs
 	 */
 	addr32 movl -20(%esp), %esp
 	popfl
-	lret	$4
+	popfw	/* padding */
+	ret	$4
 
 /****************************************************************************
  * real_call (protected-mode near call, 32-bit virtual return address)
 	movb	$0x8f, real_ds + 6
 	/* Call dummy protected-mode function */
 	pushl	$flatten_dummy
-	pushw	%cs
 	call	prot_call
 	/* Restore GDT */
 	movb	$0x00, real_cs + 6

src/arch/x86/transitions/librm_test.c

 		__asm__ __volatile__ ( REAL_CODE ( "rdtsc\n\t"
 						   "movl %k0, %k2\n\t"
 						   "pushl %k3\n\t"
-						   "pushw %%cs\n\t"
 						   "call prot_call\n\t"
 						   "rdtsc\n\t" )
 				       : "=a" ( stopped ), "=d" ( discard_d ),