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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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