exec questions

4587b358 · Robert Morris · faad047a · 4587b358 · 4587b358
--- a/exec.c
+++ b/exec.c
@@ -48,6 +48,9 @@ exec(char *path, char **argv)
  }
  iunlockput(ip);

+  // XXX rtm: what about the BSS? shouldn't there be some
+  // bzero()ing here?
+
  // Allocate and initialize stack at sz
  sz = spbottom = PGROUNDUP(sz);
  if(!(sz = allocuvm(pgdir, sz, sz + PGSIZE)))
@@ -62,6 +65,9 @@ exec(char *path, char **argv)
  sp = sz;
  argp = sz - arglen - 4*(argc+1);

+  // XXX rtm: does the following code work if the
+  // arguments &c do not fit in one page?
+
  // Copy argv strings and pointers to stack.
  *(uint*)(mem+argp-spbottom + 4*argc) = 0;  // argv[argc]
  for(i=argc-1; i>=0; i--){

--- a/kalloc.c
+++ b/kalloc.c
@@ -17,12 +17,12 @@ struct {
  struct run *freelist;
 } kmem;

+extern char end[]; // first address after kernel loaded from ELF file
+
 // Initialize free list of physical pages.
 void
 kinit(void)
 {
-  extern char end[];
-
  initlock(&kmem.lock, "kmem");
  char *p = (char*)PGROUNDUP((uint)end);
  for( ; p + PGSIZE - 1 < (char*) PHYSTOP; p += PGSIZE)
@@ -39,7 +39,7 @@ kfree(char *v)
 {
  struct run *r;

-  if(((uint) v) % PGSIZE || (uint)v < 1024*1024 || (uint)v >= PHYSTOP) 
+  if(((uint) v) % PGSIZE || v < end || (uint)v >= PHYSTOP) 
    panic("kfree");

  // Fill with junk to catch dangling refs.