Implemented task privileges

equi.c

@@ -98,11 +98,12 @@ struct CLTEntry { /* one entry in the compilation lookup table */
 struct EquiCtx { /* one Equi program context */
   ushort id; /* task ID */
   uchar active; /* 0 - inactive/quit, 1 - active */
+  uchar privileged; /* whether or not the task is allowed to write to the entire command buffer */
   uchar CM; /* compilation mode flag */
   uchar IM; /* interpretation mode flag */
-  uchar lsp; /* literal stack pointer */
   ushort msp; /* main stack pointer */
   ushort rsp; /* return stack pointer */
+  ushort lsp; /* literal stack pointer */
   ushort cltp; /* compilation lookup table pointer */
   ushort cbp; /* compilation buffer pointer */
   ushort gpd_start; /* GPD area start for this task */
@@ -344,16 +345,16 @@ ushort tobig(ushort val) {
 
 /* Task-based memory address jump checker */
 uchar taskMemJumpAllowed(addr) {
-  /* task 0 is allowed to jump anywhere in the command buffer, others only in their own zone */
+  /* a privileged task is allowed to jump anywhere in the command buffer, others only in their own zone */
-  if(curtask->id)
+  if(curtask->privileged)
-    return (addr >= curtask->cmd_start) && (addr < curtask->cmd_start + curtask->cmd_size);
-  else
     return addr >= ram.cmd_start;
+  else
+    return (addr >= curtask->cmd_start) && (addr < curtask->cmd_start + curtask->cmd_size);
 }
 
 /* Task-based memory address write checker */
 uchar taskMemWriteAllowed(addr) {
-  /* task 0 is allowed to write anywhere in the command buffer, others only in their own zone */
+  /* a privileged task is allowed to write anywhere in the command buffer, others only in their own zone */
   return (addr >= curtask->gpd_start && addr < (curtask->gpd_start + GPD_AREA_SIZE)) || taskMemJumpAllowed(addr);
 }
 
@@ -426,8 +427,11 @@ struct EquiCtx* equi_find_next_task() {
 }
 
 /* Task loader method */
-struct EquiCtx* equi_load_task(ushort len, ushort progStart) {
+struct EquiCtx* equi_load_task(uchar priv, ushort len, ushort progStart) {
   ushort tid = equi_find_free_task_slot();
+  /* don't allow to load privileged tasks from non-privileged ones */
+  if(curtask && !curtask->privileged)
+    priv = 0;
   struct EquiCtx *taskptr = &ram.tasks[tid]; /* refer to the next available entry */
   taskptr->msp = taskptr->rsp = taskptr->lsp = taskptr->cltp = 0; /* init stacks and CLT */
   taskptr->pc = progStart - 1U; /* init program counter for preincrement logic */
@@ -436,6 +440,7 @@ struct EquiCtx* equi_load_task(ushort len, ushort progStart) {
   taskptr->id = tid; /* assign task ID */
   taskptr->gpd_start = (ushort) (taskptr->gpd - flatram); /* assign GPD area start */
   taskptr->CM = 0; /* unset compilation mode flag */
+  taskptr->privileged = priv; /* set privileged flag */
   return taskptr;
 }
 
@@ -658,9 +663,10 @@ void equi_main_loop() {
       case INS_PERSIST_WRITE: /* ( blk len maddr -- status) */
         pushMain(persistOp(pfd, popMain(), popMain(), popMain(), 1));
         break;
-      case INS_TASKLOAD: /* ( addr len -- ) */
+      case INS_TASKLOAD: /* ( addr len priv -- taskid ) */
-        newtaskptr = equi_load_task(popMain(), popMain());
+        newtaskptr = equi_load_task(popMain(), popMain(), popMain());
         newtaskptr->active = 1;
+        pushMain(newtaskptr->id);
         break;
       default: /* all characters not processed before are invalid instructions */
         trapout(INVALID_INSTRUCTION);
@@ -743,7 +749,7 @@ int main(int argc, char* argv[]) {
           cputc(LF); /* echo LF */
         }
         ram.cmdbuf[++ram.ibp] = INS_QUIT; /* end program with INS_QUIT */
-        curtask = equi_load_task(ram.ibp+1, (ushort)ram.cmd_start); /* load the code as task 0 */
+        curtask = equi_load_task(1, ram.ibp+1, (ushort)ram.cmd_start); /* load the code as task 0 - always privileged */
         ram.taskid = curtask->id; /* actualize the current task id */
         curtask->active = 1; /*activate the current task */
         equi_main_loop(); /* and run the interpreter loop */