From d0cb6629c14fb6076f5555537ea484bf134d8f42 Mon Sep 17 00:00:00 2001
From: Jim Wilcoxson <prirun@gmail.com>
Date: Thu, 16 Apr 2020 15:09:14 +0000
Subject: [PATCH] em.c: change MAXMB to DEFMB, remove MEMSIZE and MEMMASK It
 was confusing that MAXMB is the default memory size, so renamed it to DEFMB. 
 MEMSIZE was not necessary (half of MAXMB) and MEMMASK was used only in mapva
 to limit physcal addresses when segmentation was not enabled.  However, this
 appears to be a bug, because it would cause memory addresses larger than
 physical memory to wrap and succeed rather than generate a missing memory
 check.

---
 em.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/em.c b/em.c
index ac82e90..be6d001 100644
--- a/em.c
+++ b/em.c
@@ -576,9 +576,7 @@ static  jmp_buf bootjmp;               /* for longjumps to the fetch loop */
    speed up system boots and diagnostics during emulator testing.
 */
 
-#define MAXMB   32     /* must be a power of 2 */
-#define MEMSIZE MAXMB/2*1024*1024
-#define MEMMASK MEMSIZE-1
+#define DEFMB   32     /* must be a power of 2 */
 #define MEM physmem
 
 static unsigned short *physmem = NULL; /* system's physical memory */
@@ -1005,11 +1003,11 @@ static pa_t mapva(ea_t ea, ea_t rp, short intacc, unsigned short *access) {
     pa = stlbp->ppa | (ea & 0x3FF);
     TRACE(T_MAP,"        for ea %o/%o, iacc=%d, stlbix=%d, pa=%o	loaded at #%u\n", ea>>16, ea&0xffff, intacc, stlbix, pa, stlbp->load_ic);
   } else {
-    pa = ea & MEMMASK;
+    pa = ea;
   }
   if (pa < gv.memlimit)
     return pa;
-#ifdef DBG
+#if 0
   printf(" map: Memory address '%o (%o/%o) is out of range 0-'%o (%o/%o) at #%d!\n", pa, pa>>16, pa & 0xffff, gv.memlimit-1, (gv.memlimit-1)>>16, (gv.memlimit-1) & 0xffff, gv.instcount);
 #endif
 
@@ -4463,7 +4461,7 @@ int main (int argc, char **argv) {
   bootfile[0] = 0;
   gv.pmap32bits = 0;
   gv.csoffset = 0;
-  gv.memlimit = MEMSIZE;
+  gv.memlimit = DEFMB;
   tport = 0;
   nport = 0;
 
@@ -4540,7 +4538,7 @@ int main (int argc, char **argv) {
       if (i+1 < argc && argv[i+1][0] != '-') {
 	sscanf(argv[++i],"%d", &templ);
 	if (1 <= templ && templ <= 512)
-	  gv.memlimit = templ*1024/2*1024;
+	  gv.memlimit = templ;
 	else
 	  fatal("-mem arg range is 1 to 512 (megabytes)\n");
       } else
@@ -4694,7 +4692,9 @@ int main (int argc, char **argv) {
     gv.stlb[i].seg = 0xFFFF;        /* marker for invalid STLB entry */
   for (i=0; i < IOTLBENTS; i++)
     gv.iotlb[i].valid = 0;
-  physmem = malloc(gv.memlimit * sizeof(*physmem));
+  gv.memlimit *= 1024 * 1024;         /* memory size in bytes */
+  physmem = malloc(gv.memlimit);
+  gv.memlimit /= sizeof(*physmem);    /* max Prime word address */
   if (physmem == NULL) {
     perror("Error allocating Prime memory block");
     fatal("Can't allocate Prime memory block");