[src/trunk]: src/lib/libpuffs fix crashes caused by using the results of getc...

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

details:   https://anonhg.NetBSD.org/src/rev/9d8516ed49c8
branches:  trunk
changeset: 771204:9d8516ed49c8
user:      chs <chs%NetBSD.org@localhost>
date:      Mon Nov 14 01:27:42 2011 +0000

description:
fix crashes caused by using the results of getcontext()
after the caller returns.

diffstat:

 lib/libpuffs/puffs.c |  25 +++++++++++++++++++++++--
 1 files changed, 23 insertions(+), 2 deletions(-)

diffs (49 lines):

diff -r a081cc9f9086 -r 9d8516ed49c8 lib/libpuffs/puffs.c
--- a/lib/libpuffs/puffs.c      Mon Nov 14 00:12:37 2011 +0000
+++ b/lib/libpuffs/puffs.c      Mon Nov 14 01:27:42 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: puffs.c,v 1.116 2011/05/03 13:16:47 manu Exp $ */
+/*     $NetBSD: puffs.c,v 1.117 2011/11/14 01:27:42 chs Exp $  */
 
 /*
  * Copyright (c) 2005, 2006, 2007  Antti Kantee.  All Rights Reserved.
@@ -31,7 +31,7 @@
 
 #include <sys/cdefs.h>
 #if !defined(lint)
-__RCSID("$NetBSD: puffs.c,v 1.116 2011/05/03 13:16:47 manu Exp $");
+__RCSID("$NetBSD: puffs.c,v 1.117 2011/11/14 01:27:42 chs Exp $");
 #endif /* !lint */
 
 #include <sys/param.h>
@@ -993,9 +993,30 @@
        if (puffs__cc_create(pu, puffs__theloop, &pcc) == -1) {
                goto out;
        }
+
+#if 0
        if (puffs__cc_savemain(pu) == -1) {
                goto out;
        }
+#else
+       /*
+        * XXX
+        * puffs__cc_savemain() uses getcontext() and then returns.
+        * the caller (this function) may overwrite the stack frame
+        * of puffs__cc_savemain(), so when we call setcontext() later and
+        * return from puffs__cc_savemain() again, the return address or
+        * saved stack pointer can be garbage.
+        * avoid this by calling getcontext() directly here.
+        */
+       extern int puffs_fakecc;
+       if (!puffs_fakecc) {
+               PU_CLRSFLAG(pu, PU_MAINRESTORE);
+               if (getcontext(&pu->pu_mainctx) == -1) {
+                       goto out;
+               }
+       }
+#endif
+
        if ((pu->pu_state & PU_MAINRESTORE) == 0)
                puffs_cc_continue(pcc);