* [PATCH] Fix makecontext on i?86
@ 2008-01-09 13:44 Jakub Jelinek
0 siblings, 0 replies; only message in thread
From: Jakub Jelinek @ 2008-01-09 13:44 UTC (permalink / raw)
To: Ulrich Drepper; +Cc: Glibc hackers
Hi!
The BZ #5435 fix aligned stack in makecontext called functions, but
depending on alignment of uc_stack.ss_sp + uc_stack.ss_size and the number
of arguments can clobber 0, 4, 8 or 12 bytes above uc_stack.ss_sp +
uc_stack.ss_size. This patch fixes it and adds a testcase.
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.
--- libc/sysdeps/unix/sysv/linux/i386/makecontext.S.jj 2007-12-10 09:05:36.000000000 +0100
+++ libc/sysdeps/unix/sysv/linux/i386/makecontext.S 2008-01-09 14:33:44.000000000 +0100
@@ -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
--- libc/stdlib/tst-makecontext2.c.jj 2008-01-09 13:45:44.000000000 +0100
+++ libc/stdlib/tst-makecontext2.c 2008-01-09 14:21:14.000000000 +0100
@@ -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"
--- libc/stdlib/Makefile.jj 2007-10-10 12:50:11.000000000 +0200
+++ libc/stdlib/Makefile 2008-01-09 14:15:02.000000000 +0100
@@ -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 t
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
Jakub
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2008-01-09 13:44 [PATCH] Fix makecontext on i?86 Jakub Jelinek
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