Memory protection without MultiTOS

[Andreas Schwab <schwab@issan.informatik.uni-dortmund.de>]

In an old mail ekl@sdf.lonestar.org (Evan K. Langlois) wrote:

|> Yes, for memory protection, your only choice is to run MultiTOS, or no GEM.
|> There is no way around that!

Actually, there is.  Here is a patch to allow running the old AES
under memory protection.  It turns all memory requests by the AES into
global accessible, so that the resource tree can be accessed by both
the program and the AES.  Also the first process started by the AES
(the real GEM process) is marked to have global memory protection.
Note that the accessories must run in global memory too, you have to
change the file header appropriately.  There are still problems with
accessories that dynamically request memory during runtime, since it
is allocated in the context of the running program and thus private by
default, but this is considered bad programming style anyway (XCONTROL
1.31 is such a beast :-/ ).

This is kind of a hack, especially the distinction between Malloc from
AES and VDI.  This only works if the AES code is located after the VDI
code in the roms, which is the case in all TOS versions i know of
(1.00, 1.02, 1.04, 3.06), but it may fall over with other versions.


--- orig/dosmem.c	Wed Feb  2 23:43:02 1994
+++ dosmem.c	Sat Jul  2 15:36:28 1994
@@ -120,8 +120,19 @@
 	if (((mode & F_PROTMODE) == 0) &&
 	    (curproc->ctxt[SYSCALL].pc > 0x00e00000L) &&
 	    (curproc->ctxt[SYSCALL].pc < 0x00efffffL)) {
+#ifndef MULTITOS
+	  extern long gem_start;
+	  if (gem_start && curproc->ctxt[SYSCALL].pc >= gem_start)
+	    {
+	      mode |= F_PROT_G + 0x10;
+	      TRACE (("m_xalloc: AES special (call from ROM)"));
+	    }
+	  else
+#endif
+	    {
 		mode |= (F_PROT_S + 0x10) | F_KEEP;
 		TRACE(("m_xalloc: VDI special (call from ROM)"));
+	    }
 	}
 /*
  * If the mode argument comes in a zero, then set it to the default
@@ -319,6 +330,9 @@
 	char localname[PNAMSIZ+1];
 	XATTR xattr;
 	int newpid;
+#ifndef MULTITOS
+	extern BASEPAGE *gem_base;
+#endif
 
 #ifdef DEBUG_INFO
 /* tfmt and tail_offs are used for debugging only */
@@ -387,6 +401,13 @@
 		    DEBUG (("Pexec: invalid protection mode changed to private"));
 		    flags = (flags & ~F_PROTMODE) | F_PROT_P;
 		}
+#ifndef MULTITOS
+		if ((flags & F_PROTMODE) == 0 && curproc->base == gem_base)
+		  {
+		    flags |= F_PROT_G;
+		    TRACE (("p_exec: AES special"));
+		  }
+#endif
 					/* and fall through */
 	case 5:
 		mkbase = 1;
--- orig/main.c	Fri Feb 11 20:37:16 1994
+++ main.c	Fri Jul  1 18:43:06 1994
@@ -125,6 +125,8 @@
 static int init_is_gem = 1;	/* set to 1 if init_prg is GEM */
 #else
 static int init_is_gem = 0;	/* set to 1 if init_prg is GEM */
+BASEPAGE *gem_base = 0;
+long gem_start = 0;
 #endif
 static const char *init_prg = 0;
 
@@ -893,6 +895,11 @@
 		  (char *)((long)F_FASTLOAD | F_ALTLOAD | F_ALTALLOC | F_PROT_S),
 		  (char *)"\0", init_env);
 		bp->p_tbase = *((long *) EXEC_OS );
+#ifndef MULTITOS
+		if (((long *) sysbase[5])[0] == 0x87654321)
+		  gem_start = ((long *) sysbase[5])[2];
+		gem_base = bp;
+#endif
 		r = p_exec(106, (char *)"GEM", bp, 0L);
 		pid = (int)r;
 		if (pid > 0) {

-- 
+------------------------------------------------------------------------+
Andreas Schwab                                      "And now for something
schwab@ls5.informatik.uni-dortmund.de                completely different"