believe it or not, this was working

the macro expansion of "char *cp;" turned into char *(curproc[cpu()]); which declares a dynamically sized array of char* called curproc. so then &cp == &(curproc[cpu()]) was actually a stack variable as "expected". it was one past the end of the array, but the implicit alloca allocated more than was necessary. do not tell me that making cp a #define was a bad idea. there are worse problems to fix. more on that later.

believe it or not, this was working
666f58c7 · rsc · 90d975e9 · 666f58c7 · 666f58c7 · 666f58c7
--- a/dot-bochsrc
+++ b/dot-bochsrc
@@ -74,7 +74,8 @@
 # now supported, but we still recommend to use the BIOS distributed with
 # Bochs. Now the start address can be calculated from image size.
 #=======================================================================
-romimage: file=$BXSHARE/BIOS-bochs-latest, address=0xf0000
+#romimage: file=$BXSHARE/BIOS-bochs-latest
+romimage: file=/home/rsc/pub/bochs/bios/BIOS-bochs-latest
 #romimage: file=mybios.bin, address=0xfff80000 # 512k at memory top
 #romimage: file=mybios.bin # calculate start address from image size

@@ -107,7 +108,7 @@ romimage: file=$BXSHARE/BIOS-bochs-latest, address=0xf0000
 #  650Mhz Athlon K-7 with Linux 2.4.4/egcs-2.91.66  2 to  2.5 Mips
 #  400Mhz Pentium II with Linux 2.0.36/egcs-1.0.3   1 to  1.8 Mips
 #=======================================================================
-cpu: count=2, ips=10000000
+cpu: count=2, ips=10000000, quantum=1

 #=======================================================================
 # MEGS
@@ -403,7 +404,7 @@ debug: action=ignore
 #=======================================================================
 #debugger_log: /dev/null
 #debugger_log: debugger.out
-debugger_log: -
+debugger_log: bochsout.txt

 #=======================================================================
 # COM1, COM2, COM3, COM4:
@@ -675,6 +676,7 @@ keyboard_mapping: enabled=0, map=
 #   i440fxsupport: enabled=1, slot1=pcivga, slot2=ne2k
 #=======================================================================
 #i440fxsupport: enabled=1
+i440fxsupport: enabled=1

 #=======================================================================
 # USB1:

--- a/sysfile.c
+++ b/sysfile.c
@@ -49,11 +49,11 @@ sys_read(void)
 {
  struct file *f;
  int n;
-  char *cp;
+  char *p;

-  if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &cp, n) < 0)
+  if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0)
    return -1;
-  return fileread(f, cp, n);
+  return fileread(f, p, n);
 }

 int
@@ -61,11 +61,11 @@ sys_write(void)
 {
  struct file *f;
  int n;
-  char *cp;
+  char *p;

-  if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &cp, n) < 0)
+  if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0)
    return -1;
-  return filewrite(f, cp, n);
+  return filewrite(f, p, n);
 }

 int

--- a/usertests.c
+++ b/usertests.c
@@ -1234,7 +1234,9 @@ int
 main(int argc, char *argv[])
 {
  printf(1, "usertests starting\n");
-  
+
+for(;;) concreate();
+
  if(open("usertests.ran", 0) >= 0){
    printf(1, "already ran user tests -- rebuild fs.img\n");
    exit();