COM32: Try to support both farcall and intcall

8 files changed, 104 insertions, 30 deletions

diff --git a/com32.inc b/com32.inc
index 3d445c10..969bfce4 100644
--- a/com32.inc
+++ b/com32.inc
@@ -1,7 +1,7 @@
 ;; $Id$
 ;; -----------------------------------------------------------------------
 ;;   
-;;   Copyright 1994-2002 H. Peter Anvin - All Rights Reserved
+;;   Copyright 1994-2003 H. Peter Anvin - All Rights Reserved
 ;;
 ;;   This program is free software; you can redistribute it and/or modify
 ;;   it under the terms of the GNU General Public License as published by
@@ -140,12 +140,13 @@ com32_call_start:
 
 		; Now everything is set up for interrupts...
 
+		push dword com32_farcall	; Farcall entry point
 		push dword (1 << 16)		; 64K bounce buffer
 		push dword (comboot_seg << 4)	; Bounce buffer address
-		push dword com32_syscall	; Syscall entry point
+		push dword com32_intcall	; Intcall entry point
 		movzx esi,word [word CmdOptPtr]
 		push esi			; Command line pointer
-		push dword 4			; Argument count
+		push dword 5			; Argument count
 		sti				; Interrupts OK now
 		call pm_entry			; Run the program...
 		; ... on return, fall through to com32_exit ...
@@ -217,8 +218,12 @@ com32_sys_rm:
 		pop ds
 		popad
 		popfd
+		mov [cs:Com32SysSP],sp
 		retf				; Invoke routine
 .return:
+		; We clean up SP here because we don't know if the
+		; routine returned with RET, RETF or IRET
+		mov sp,[cs:Com32SysSP]
 		pushfd
 		pushad
 		push ds
@@ -253,7 +258,7 @@ com32_int_resume:
 		iret
 
 ;
-; Syscall invocation.  We manifest a structure on the real-mode stack,
+; Intcall/farcall invocation.  We manifest a structure on the real-mode stack,
 ; containing the com32sys_t structure from <com32.h> as well as
 ; the following entries (from low to high address):
 ; - Target offset
@@ -262,27 +267,37 @@ com32_int_resume:
 ; - Return segment (== real mode cs == 0)
 ; - Return flags
 ;
+com32_farcall:
+		pushfd				; Save IF among other things...
+		pushad				; We only need to save some, but...
+
+		mov eax,[esp+10*4]		; CS:IP
+		jmp com32_syscall
+
+
+com32_intcall:
+		pushfd				; Save IF among other things...
+		pushad				; We only need to save some, but...
+
+		movzx eax,byte [esp+10*4]	; INT number
+		mov eax,[eax*4]			; Get CS:IP from low memory
+
 com32_syscall:
-		pushfd			; Save IF among other things...
-		pushad			; We only need to save some, but...
 		cld
 
 		movzx edi,word [word SavedSSSP]
-		movzx eax,word [word SavedSSSP+2]
+		movzx ebx,word [word SavedSSSP+2]
 		sub edi,54		; Allocate 54 bytes
 		mov [word SavedSSSP],di
-		shl eax,4
-		add edi,eax		; Create linear address
+		shl ebx,4
+		add edi,ebx		; Create linear address
 
 		mov esi,[esp+11*4]	; Source regs
 		xor ecx,ecx
 		mov cl,11		; 44 bytes to copy
 		rep movsd
 
-		movzx eax,byte [esp+10*4] ; Interrupt number
-		; ecx == 0 here; adding it to the EA makes the
-		; encoding smaller
-		mov eax,[ecx+eax*4]	; Get IVT entry
+		; EAX is already set up to be CS:IP
 		stosd			; Save in stack frame
 		mov eax,com32_sys_rm.return	; Return seg:offs
 		stosd			; Save in stack frame
@@ -295,7 +310,8 @@ com32_syscall:
 		jmp com32_enter_rm	; Go to real mode
 
 		; On return, the 44-byte return structure is on the
-		; real-mode stack.
+		; real-mode stack, plus the 10 additional bytes used
+		; by the target address (see above.)
 com32_sys_resume:
 		movzx esi,word [word SavedSSSP]
 		movzx eax,word [word SavedSSSP+2]
@@ -309,7 +325,7 @@ com32_sys_resume:
 		mov cl,11		; 44 bytes
 		rep movsd		; Copy register block
 
-		add dword [word SavedSSSP],44	; Remove from stack
+		add dword [word SavedSSSP],54	; Remove from stack
 
 		popad
 		popfd
diff --git a/com32/include/com32.h b/com32/include/com32.h
index c080ce7f..e61cb3c2 100644
--- a/com32/include/com32.h
+++ b/com32/include/com32.h
@@ -49,9 +49,10 @@ typedef struct {
 extern struct com32_sys_args {
   uint32_t cs_sysargs;
   char *cs_cmdline;
-  void (*cs_syscall)(uint8_t, com32sys_t *, com32sys_t *);
+  void (*cs_intcall)(uint8_t, com32sys_t *, com32sys_t *);
   void *cs_bounce;
   uint32_t cs_bounce_size;
+  void (*cs_farcall)(uint32_t, com32sys_t *, com32sys_t *);
 } __com32;
 
 /*
diff --git a/comboot.doc b/comboot.doc
index c66a179c..d262e562 100644
--- a/comboot.doc
+++ b/comboot.doc
@@ -79,11 +79,12 @@ notification to the program how much memory is available.
 The following arguments are passed to the program on the stack:
 
  Address  Size	Meaning
- [ESP+4]  dword	Number of additional arguments (currently 4)
+ [ESP+4]  dword	Number of additional arguments (currently 5)
  [ESP+8]  dword	Pointer to the command line arguments (null-terminated string)
- [ESP+12] dword Pointer to system call helper function
+ [ESP+12] dword Pointer to INT call helper function
  [ESP+16] dword Pointer to low memory bounce buffer
  [ESP+20] dword Size of low memory bounce buffer
+ [ESP+24] dword Pointer to FAR call helper function (new in 2.05)
 
 This corresponds to the following C prototype, available in the file
 com32/include/com32.h:
@@ -91,14 +92,15 @@ com32/include/com32.h:
 /* The standard prototype for _start() */
 int _start(unsigned int __nargs,
 	   char *__cmdline,
-	   void (*__syscall)(uint8_t, com32sys_t *, com32sys_t *),
+	   void (*__intcall)(uint8_t, com32sys_t *, com32sys_t *),
 	   void *__bounce_ptr,
-	   unsigned int __bounce_len);
+	   unsigned int __bounce_len,
+	   void (*__farcall)(uint32_t, uint16_t, com32sys_t *, com32sys_t *));
 
-The system call helper function can be used to issue BIOS or SYSLINUX
-API calls, and takes the interrupt number as first argument.  The
-second argument is a pointer to the input register definition, an
-instance of the following structure (also available in com32.h):
+The intcall helper function can be used to issue BIOS or SYSLINUX API
+calls, and takes the interrupt number as first argument.  The second
+argument is a pointer to the input register definition, an instance of
+the following structure (also available in com32.h):
 
 typedef union {
   uint32_t l;
@@ -132,6 +134,10 @@ Since BIOS or SYSLINUX API calls can generally only manipulate data
 below address 0x100000, a "bounce buffer" in low memory, at least 64K
 in size, is available, to copy data in and out.
 
+The farcall helper function behaves similarly, but takes as its first
+argument the CS:IP (in the form (CS << 16) + IP) of procedure to be
+invoked via a FAR CALL.
+
 
 	++++ SYSLINUX API CALLS +++
 
diff --git a/isolinux.asm b/isolinux.asm
index 22f78576..111e2796 100644
--- a/isolinux.asm
+++ b/isolinux.asm
@@ -170,6 +170,7 @@ GraphXSize	resw 1			; Width of splash screen file
 VGAPos		resw 1			; Pointer into VGA memory
 VGACluster	resw 1			; Cluster pointer for VGA image file
 VGAFilePtr	resw 1			; Pointer into VGAFileBuf
+Com32SysSP	resw 1			; SP saved during COM32 syscall
 ConfigFile	resw 1			; Socket for config file
 PktTimeout	resw 1			; Timeout for current packet
 KernelExtPtr	resw 1			; During search, final null pointer
diff --git a/ldlinux.asm b/ldlinux.asm
index d6c2b05e..b68d1998 100644
--- a/ldlinux.asm
+++ b/ldlinux.asm
@@ -172,6 +172,7 @@ GraphXSize	resw 1			; Width of splash screen file
 VGAPos		resw 1			; Pointer into VGA memory
 VGACluster	resw 1			; Cluster pointer for VGA image file
 VGAFilePtr	resw 1			; Pointer into VGAFileBuf
+Com32SysSP	resw 1			; SP saved during COM32 syscall
 TextAttrBX      equ $
 TextAttribute   resb 1			; Text attribute for message file
 TextPage        resb 1			; Active display page
diff --git a/sample/c32entry.S b/sample/c32entry.S
index 251838d4..1ae57a2c 100644
--- a/sample/c32entry.S
+++ b/sample/c32entry.S
@@ -1,15 +1,64 @@
+#ident "$Id$"
+# -----------------------------------------------------------------------
+#   
+#   Copyright 2003 H. Peter Anvin - All Rights Reserved
+#
+#   Permission is hereby granted, free of charge, to any person
+#   obtaining a copy of this software and associated documentation
+#   files (the "Software"), to deal in the Software without
+#   restriction, including without limitation the rights to use,
+#   copy, modify, merge, publish, distribute, sublicense, and/or
+#   sell copies of the Software, and to permit persons to whom
+#   the Software is furnished to do so, subject to the following
+#   conditions:
+#   
+#   The above copyright notice and this permission notice shall
+#   be included in all copies or substantial portions of the Software.
+#   
+#   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+#   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+#   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+#   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+#   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+#   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+#   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+#   OTHER DEALINGS IN THE SOFTWARE.
+#
+# -----------------------------------------------------------------------
+
+# COM32 start up code - must be linked first in the binary
+
+	
 		.section ".text","ax"
 		.globl _start
 _start:
 		# This first instruction acts as COM32 magic number
 		movl $0x21cd4cff,%eax
+
+		# Upwards string operations
+		cld
+
+		# Zero the .bss segment
+		xorl %eax,%eax
+		movl $__bss_start,%edi		# Symbol provided by linker
+		movl $_end+3,%ecx		# Symbol provided by linker
+		subl %edi,%ecx
+		shrl $2,%ecx
+		rep ; stosl
+
+		# Copy COM32 invocation parameters
 		leal 4(%esp),%esi
 		movl $__com32,%edi
-		mov $5,%ecx
-		cld
-		rep ; movsl
+		movl $6,%ecx
+		cmpl (%esi),%ecx
+		jbe 1f
+		movl (%esi),%ecx
+1:		rep ; movsl
+
+		# Run program; we call this __start rather than main since we
+		# did not parse the command line or anything like that.
 		jmp __start
 
 		.section ".bss","a"
 		.globl __com32
-__com32:	.space 20
+__com32:	.space 24
diff --git a/sample/hello.c b/sample/hello.c
index a2b79dde..8730ba1a 100644
--- a/sample/hello.c
+++ b/sample/hello.c
@@ -38,7 +38,7 @@ int __start(void)
   for ( p = msg ; *p ; p++ ) {
     inreg.edx.b[0] = *p;
     inreg.eax.b[1] = 0x02;	/* Write Character */
-    __com32.cs_syscall(0x21, &inreg, NULL);
+    __com32.cs_intcall(0x21, &inreg, NULL);
   }
 
   return 0;
diff --git a/sample/hello2.c b/sample/hello2.c
index 26a8a759..871ad047 100644
--- a/sample/hello2.c
+++ b/sample/hello2.c
@@ -48,7 +48,7 @@ static void writemsg(const char *msg)
   inreg.eax.w[0] = 0x0002;	/* Write string */
   inreg.ebx.w[0] = OFFS(__com32.cs_bounce);
   inreg.es       = SEG(__com32.cs_bounce);
-  __com32.cs_syscall(0x22, &inreg, NULL);
+  __com32.cs_intcall(0x22, &inreg, NULL);
 };  
 
 int __start(void)