exec tweaks

b3bebfce · Russ Cox · fd8e3681 · b3bebfce
--- a/exec.c
+++ b/exec.c
@@ -16,19 +16,21 @@ exec(char *path, char **argv)
  struct inode *ip;
  struct proghdr ph;
+  mem = 0;
+  sz = 0;
  if((ip = namei(path)) == 0)
    return -1;
  ilock(ip);
-  // Compute memory size of new process.
+  // Check ELF header
-  mem = 0;
-  sz = 0;
-  // Program segments.
  if(readi(ip, (char*)&elf, 0, sizeof(elf)) < sizeof(elf))
    goto bad;
  if(elf.magic != ELF_MAGIC)
    goto bad;
+  // Compute memory size of new process.
+  // Program segments.
  for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
    if(readi(ip, (char*)&ph, off, sizeof(ph)) != sizeof(ph))
      goto bad;
@@ -44,7 +46,10 @@ exec(char *path, char **argv)
  for(argc=0; argv[argc]; argc++)
    arglen += strlen(argv[argc]) + 1;
  arglen = (arglen+3) & ~3;
-  sz += arglen + 4*(argc+1);
+  sz += arglen;
+  sz += 4*(argc+1);  // argv data
+  sz += 4;  // argv
+  sz += 4;  // argc
  // Stack.
  sz += PAGE;