* sysdeps/unix/sysv/linux/i386/makecontext.S (__makecontext): Avoid

	clobbering memory at or above uc_stack.ss_sp + uc_stack.ss_size.
	* stdlib/Makefile: Add rules to build and run tst-makecontext2.
	* stdlib/tst-makecontext2.c: New test.

ChangeLog

@@ -1,3 +1,10 @@
+2008-01-09  Jakub Jelinek  <jakub@redhat.com>
+
+	* sysdeps/unix/sysv/linux/i386/makecontext.S (__makecontext): Avoid
+	clobbering memory at or above uc_stack.ss_sp + uc_stack.ss_size.
+	* stdlib/Makefile: Add rules to build and run tst-makecontext2.
+	* stdlib/tst-makecontext2.c: New test.
+
 2008-01-07  Ulrich Drepper  <drepper@redhat.com>
 
 	* libio/stdio.h (vscanf): Fix definition for loser compilers.

stdlib/Makefile

@@ -1,4 +1,4 @@
-# Copyright (C) 1991-2006, 2007 Free Software Foundation, Inc.
+# Copyright (C) 1991-2006, 2007, 2008 Free Software Foundation, Inc.
 # This file is part of the GNU C Library.
 
 # The GNU C Library is free software; you can redistribute it and/or
@@ -68,7 +68,8 @@ tests		:= tst-strtol tst-strtod testmb testrand testsort testdiv   \
 		   tst-limits tst-rand48 bug-strtod tst-setcontext	    \
 		   test-a64l tst-qsort tst-system testmb2 bug-strtod2	    \
 		   tst-atof1 tst-atof2 tst-strtod2 tst-strtod3 tst-rand48-2 \
-		   tst-makecontext tst-strtod4 tst-strtod5 tst-qsort2
+		   tst-makecontext tst-strtod4 tst-strtod5 tst-qsort2	    \
+		   tst-makecontext2
 
 include ../Makeconfig
 
@@ -106,6 +107,7 @@ endif
 
 CFLAGS-tst-bsearch.c = $(stack-align-test-flags)
 CFLAGS-tst-qsort.c = $(stack-align-test-flags)
+CFLAGS-tst-makecontext2.c = $(stack-align-test-flags)
 
 include ../Rules
 

stdlib/tst-makecontext2.c

@@ -0,0 +1,80 @@
+/* Copyright (C) 2008 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <ucontext.h>
+#include <tst-stack-align.h>
+
+ucontext_t ucp, ucp2;
+char st1[262144] __attribute__((aligned (16)));
+
+void
+cf (int i, int j)
+{
+  if (i != 78 || j != 274)
+    {
+      printf ("i %d j %d\n", i, j);
+      exit (1);
+    }
+  else if (TEST_STACK_ALIGN ())
+    {
+      puts ("insufficiently aligned stack");
+      exit (2);
+    }
+}
+
+int
+do_test (void)
+{
+  for (size_t j = 32; j < 64; j += sizeof (long))
+    {
+      if (getcontext (&ucp) != 0)
+	{
+	  if (errno == ENOSYS)
+	    {
+	      puts ("context handling not supported");
+	      return 0;
+	    }
+
+	  puts ("getcontext failed");
+	  return 1;
+	}
+      ucp.uc_link = &ucp2;
+      ucp.uc_stack.ss_sp = st1;
+      ucp.uc_stack.ss_size = sizeof (st1) - j;
+      memset (&st1[sizeof (st1) - j], 0x55, j);
+      makecontext (&ucp, (void (*) (void)) cf, 2, 78, 274);
+      if (swapcontext (&ucp2, &ucp) != 0)
+	{
+	  puts ("setcontext failed");
+	  return 1;
+	}
+
+      for (size_t i = j; i > 0; i--)
+	if (st1[sizeof (st1) - j + i - 1] != 0x55)
+	  { printf ("fail %zd %zd\n", i, j); break; }
+    }
+
+  return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"

sysdeps/unix/sysv/linux/i386/makecontext.S

@@ -1,5 +1,5 @@
 /* Create new context.
-   Copyright (C) 2001, 2002, 2005 Free Software Foundation, Inc.
+   Copyright (C) 2001, 2002, 2005, 2007, 2008 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@redhat.com>, 2001.
 
@@ -41,13 +41,15 @@ ENTRY(__makecontext)
 	movl	12(%esp), %ecx
 	movl	%ecx, oEBX(%eax)
 
-	/* Make room on the new stack for the parameters.  */
+	/* Make room on the new stack for the parameters.
+	   Room for the arguments, return address (== L(exitcode)) and
+	   oLINK pointer is needed.  One of the pointer sizes is subtracted
+	   after aligning the stack.  */
 	negl	%ecx
-	leal	-8(%edx,%ecx,4), %edx
+	leal	-4(%edx,%ecx,4), %edx
 	negl	%ecx
 
 	/* Align the stack.  */
-	addl	$16, %edx
 	andl	$0xfffffff0, %edx
 	subl	$4, %edx