[src/trunk]: src/sys/kern Clarify stack size calculation in copyargs(). Comm...

[uebayasi <uebayasi%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/72f9f53812fb
branches:  trunk
changeset: 328643:72f9f53812fb
user:      uebayasi <uebayasi%NetBSD.org@localhost>
date:      Fri Apr 11 11:49:38 2014 +0000

description:
Clarify stack size calculation in copyargs().  Comments.

diffstat:

 sys/kern/kern_exec.c |  24 +++++++++++++++++++-----
 1 files changed, 19 insertions(+), 5 deletions(-)

diffs (57 lines):

diff -r 674384060a06 -r 72f9f53812fb sys/kern/kern_exec.c
--- a/sys/kern/kern_exec.c      Fri Apr 11 11:32:14 2014 +0000
+++ b/sys/kern/kern_exec.c      Fri Apr 11 11:49:38 2014 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_exec.c,v 1.381 2014/04/11 11:32:14 uebayasi Exp $ */
+/*     $NetBSD: kern_exec.c,v 1.382 2014/04/11 11:49:38 uebayasi Exp $ */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -59,7 +59,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_exec.c,v 1.381 2014/04/11 11:32:14 uebayasi Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_exec.c,v 1.382 2014/04/11 11:49:38 uebayasi Exp $");
 
 #include "opt_exec.h"
 #include "opt_execfmt.h"
@@ -1485,6 +1485,10 @@
        return error;
 }
 
+/*
+ * Copy argv and env strings from kernel buffer (argp) to the new stack.
+ * Those strings are located just after auxinfo.
+ */
 int
 copyargs(struct lwp *l, struct exec_package *pack, struct ps_strings *arginfo,
     char **stackp, void *argp)
@@ -1499,14 +1503,24 @@
        nullp = NULL;
        argc = arginfo->ps_nargvstr;
        envc = arginfo->ps_nenvstr;
+
+       /* argc on stack is long */
+       CTASSERT(sizeof(*cpp) == sizeof(argc));
+
+       dp = (char *)(cpp +
+           1 +                         /* argc */
+           argc +                      /* *argv[] */
+           1 +                         /* \0 */
+           envc +                      /* *env[] */
+           1 +                         /* \0 */
+           pack->ep_esch->es_arglen);  /* auxinfo */
+       sp = argp;
+
        if ((error = copyout(&argc, cpp++, sizeof(argc))) != 0) {
                COPYPRINTF("", cpp - 1, sizeof(argc));
                return error;
        }
 
-       dp = (char *)(cpp + argc + envc + 2 + pack->ep_esch->es_arglen);
-       sp = argp;
-
        /* XXX don't copy them out, remap them! */
        arginfo->ps_argvstr = cpp; /* remember location of argv for later */