[src/trunk]: src/sys/kern execve_runproc: Correct thinko in Rev. 1.386; the n...

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

details:   https://anonhg.NetBSD.org/src/rev/1145eed98a51
branches:  trunk
changeset: 795423:1145eed98a51
user:      uebayasi <uebayasi%NetBSD.org@localhost>
date:      Sat Apr 12 15:08:56 2014 +0000

description:
execve_runproc: Correct thinko in Rev. 1.386; the new SP always points to
after (higher adderss) argc/argv/env/aux/strings regardless of stack growing
direction .  Machines with grow-up stack will detect the top of
argc/argv/env/aux/strings by the address of *argv[] via ps_strings:ps_argvstr.

This means that old comments about RTLD_GAP are all obsolete.

With help from Nick Hudson.

diffstat:

 sys/kern/kern_exec.c |  25 ++++++++++++++++---------
 1 files changed, 16 insertions(+), 9 deletions(-)

diffs (61 lines):

diff -r 22d58a12965f -r 1145eed98a51 sys/kern/kern_exec.c
--- a/sys/kern/kern_exec.c      Sat Apr 12 13:28:41 2014 +0000
+++ b/sys/kern/kern_exec.c      Sat Apr 12 15:08:56 2014 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_exec.c,v 1.389 2014/04/12 07:38:32 uebayasi Exp $ */
+/*     $NetBSD: kern_exec.c,v 1.390 2014/04/12 15:08:56 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 1.389 2014/04/12 07:38:32 uebayasi Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_exec.c,v 1.390 2014/04/12 15:08:56 uebayasi Exp $");
 
 #include "opt_exec.h"
 #include "opt_execfmt.h"
@@ -246,7 +246,6 @@
        int                     ed_szsigcode;
        long                    ed_argc;
        long                    ed_envc;
-       vaddr_t                 ed_newstack;
 };
 
 /*
@@ -1202,9 +1201,6 @@
        /* Skip a few words reserved for _rtld(). */
        stack = STACK_GROW(stack, RTLD_GAP);
 
-       /* Remember the new stack address for setregs(). */
-       data->ed_newstack = (vaddr_t)stack;
-
        /* Now copy argc, args & environ to the new stack. */
        error = (*epp->ep_esch->es_copyargs)(l, epp,
            &data->ed_arginfo, &stack, data->ed_argp);
@@ -1308,10 +1304,21 @@
 
        doexechooks(p);
 
-       /* setup new registers and do misc. setup. */
-       (*epp->ep_esch->es_emul->e_setregs)(l, epp, data->ed_newstack);
+    {
+       /*
+        * Set initial SP at the top of the stack.
+        *
+        * Note that on machines where stack grows up (e.g. hppa), SP points to
+        * the end of arg/env strings.  Userland guesses the address of argc
+        * via ps_strings::ps_argvstr.
+        */
+       const vaddr_t newstack = (vaddr_t)STACK_GROW(vm->vm_minsaddr, epp->ep_ssize);
+
+       /* Setup new registers and do misc. setup. */
+       (*epp->ep_esch->es_emul->e_setregs)(l, epp, newstack);
        if (epp->ep_esch->es_setregs)
-               (*epp->ep_esch->es_setregs)(l, epp, data->ed_newstack);
+               (*epp->ep_esch->es_setregs)(l, epp, newstack);
+    }
 
        /* Provide a consistent LWP private setting */
        (void)lwp_setprivate(l, NULL);