soft page fault in syscall argument pointers

4298ddf2 · Nickolai Zeldovich · aad8c084 · 4298ddf2 · 4298ddf2 · 4298ddf2
--- a/defs.h
+++ b/defs.h
@@ -143,8 +143,8 @@ char*           strncpy(char*, const char*, int);
 int             argint(int, int*);
 int             argptr(int, char**, int);
 int             argstr(int, char**);
-int             fetchint(struct proc*, uint, int*);
+int             fetchint(uint, int*);
-int             fetchstr(struct proc*, uint, char**);
+int             fetchstr(uint, char**);
 void            syscall(void);
 // timer.c

--- a/syscall.c
+++ b/syscall.c
@@ -18,12 +18,12 @@
 // Fetch the int at addr from process p.
 int
-fetchint(struct proc *p, uint addr, int *ip)
+fetchint(uint addr, int *ip)
 {
-#if 0 /* XXX use pagefault() */
+  if(pagefault(proc->pgdir, proc->vmap, addr) < 0)
-  if(addr >= p->sz || addr+4 > p->sz)
+    return -1;
+  if(pagefault(proc->pgdir, proc->vmap, addr+3) < 0)
    return -1;
-#endif
  *ip = *(int*)(addr);
  return 0;
 }
@@ -32,23 +32,19 @@ fetchint(struct proc *p, uint addr, int *ip)
 // Doesn't actually copy the string - just sets *pp to point at it.
 // Returns length of string, not including nul.
 int
-fetchstr(struct proc *p, uint addr, char **pp)
+fetchstr(uint addr, char **pp)
 {
-  char *s, *ep;
+  char *s = (char *) addr;
-#if 0 /* XXX use pagefault() */
+  while(1){
-  if(addr >= p->sz)
+    if(pagefault(proc->pgdir, proc->vmap, (uint) s) < 0)
-    return -1;
+      return -1;
-#endif
+    if(*s == 0){
-  *pp = (char*)addr;
+      *pp = (char*)addr;
-#if 0 /* XXX use pagefault() */
-  ep = (char*)p->sz;
-#else
-  ep = (char *) 0xffffffff;
-#endif
-  for(s = *pp; s < ep; s++)
-    if(*s == 0)
      return s - *pp;
+    }
+    s++;
+  }
  return -1;
 }
@@ -56,7 +52,7 @@ fetchstr(struct proc *p, uint addr, char **pp)
 int
 argint(int n, int *ip)
 {
-  return fetchint(proc, proc->tf->esp + 4 + 4*n, ip);
+  return fetchint(proc->tf->esp + 4 + 4*n, ip);
 }
 // Fetch the nth word-sized system call argument as a pointer
@@ -69,10 +65,9 @@ argptr(int n, char **pp, int size)
  if(argint(n, &i) < 0)
    return -1;
-#if 0 /* XXX use pagefault() */
+  for(uint va = PGROUNDDOWN(i); va < i+size; va = va + PGSIZE)
-  if((uint)i >= proc->sz || (uint)i+size > proc->sz)
+    if(pagefault(proc->pgdir, proc->vmap, va) < 0)
-    return -1;
+      return -1;
-#endif
  *pp = (char*)i;
  return 0;
 }
@@ -87,7 +82,7 @@ argstr(int n, char **pp)
  int addr;
  if(argint(n, &addr) < 0)
    return -1;
-  return fetchstr(proc, addr, pp);
+  return fetchstr(addr, pp);
 }
 extern int sys_chdir(void);

--- a/sysfile.c
+++ b/sysfile.c
@@ -358,13 +358,13 @@ sys_exec(void)
  for(i=0;; i++){
    if(i >= NELEM(argv))
      return -1;
-    if(fetchint(proc, uargv+4*i, (int*)&uarg) < 0)
+    if(fetchint(uargv+4*i, (int*)&uarg) < 0)
      return -1;
    if(uarg == 0){
      argv[i] = 0;
      break;
    }
-    if(fetchstr(proc, uarg, &argv[i]) < 0)
+    if(fetchstr(uarg, &argv[i]) < 0)
      return -1;
  }
  return exec(path, argv);