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/* Make sure that the stackaddr returned by pthread_getattr_np is
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reachable.
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Copyright (C) 2012-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <stdio.h>
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#include <string.h>
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#include <sys/resource.h>
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#include <sys/param.h>
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#include <pthread.h>
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#include <alloca.h>
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#include <assert.h>
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#include <unistd.h>
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#include <inttypes.h>
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/* There is an obscure bug in the kernel due to which RLIMIT_STACK is sometimes
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returned as unlimited when it is not, which may cause this test to fail.
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There is also the other case where RLIMIT_STACK is intentionally set as
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unlimited or very high, which may result in a vma that is too large and again
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results in a test case failure. To avoid these problems, we cap the stack
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size to one less than 8M. See the following mailing list threads for more
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information about this problem:
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<https://sourceware.org/ml/libc-alpha/2012-06/msg00599.html>
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<https://sourceware.org/ml/libc-alpha/2012-06/msg00713.html>. */
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#define MAX_STACK_SIZE (8192 * 1024 - 1)
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static size_t pagesize;
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/* Check if the page in which TARGET lies is accessible. This will segfault
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if it fails. */
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static volatile char *
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allocate_and_test (char *target)
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{
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volatile char *mem = (char *) &mem;
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/* FIXME: mem >= target for _STACK_GROWSUP. */
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mem = alloca ((size_t) (mem - target));
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*mem = 42;
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return mem;
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}
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static int
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get_self_pthread_attr (const char *id, void **stackaddr, size_t *stacksize)
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{
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pthread_attr_t attr;
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int ret;
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pthread_t me = pthread_self ();
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if ((ret = pthread_getattr_np (me, &attr)) < 0)
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{
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printf ("%s: pthread_getattr_np failed: %s\n", id, strerror (ret));
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return 1;
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}
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if ((ret = pthread_attr_getstack (&attr, stackaddr, stacksize)) < 0)
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{
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printf ("%s: pthread_attr_getstack returned error: %s\n", id,
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strerror (ret));
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return 1;
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}
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return 0;
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}
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/* Verify that the stack size returned by pthread_getattr_np is usable when
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the returned value is subject to rlimit. */
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static int
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check_stack_top (void)
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{
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struct rlimit stack_limit;
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void *stackaddr;
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volatile void *mem;
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size_t stacksize = 0;
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int ret;
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uintptr_t pagemask = ~(pagesize - 1);
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puts ("Verifying that stack top is accessible");
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ret = getrlimit (RLIMIT_STACK, &stack_limit);
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if (ret)
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{
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perror ("getrlimit failed");
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return 1;
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}
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printf ("current rlimit_stack is %zu\n", (size_t) stack_limit.rlim_cur);
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if (get_self_pthread_attr ("check_stack_top", &stackaddr, &stacksize))
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return 1;
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/* Reduce the rlimit to a page less that what is currently being returned
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(subject to a maximum of MAX_STACK_SIZE) so that we ensure that
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pthread_getattr_np uses rlimit. The figure is intentionally unaligned so
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to verify that pthread_getattr_np returns an aligned stacksize that
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correctly fits into the rlimit. We don't bother about the case where the
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stack is limited by the vma below it and not by the rlimit because the
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stacksize returned in that case is computed from the end of that vma and is
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hence safe. */
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stack_limit.rlim_cur = MIN (stacksize - pagesize + 1, MAX_STACK_SIZE);
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printf ("Adjusting RLIMIT_STACK to %zu\n", (size_t) stack_limit.rlim_cur);
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if ((ret = setrlimit (RLIMIT_STACK, &stack_limit)) < 0)
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{
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perror ("setrlimit failed");
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return 1;
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}
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if (get_self_pthread_attr ("check_stack_top2", &stackaddr, &stacksize))
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return 1;
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printf ("Adjusted rlimit: stacksize=%zu, stackaddr=%p\n", stacksize,
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stackaddr);
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/* A lot of targets tend to write stuff on top of the user stack during
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context switches, so we cannot possibly safely go up to the very top of
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stack and test access there. It is however sufficient to simply check if
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the top page is accessible, so we target our access halfway up the top
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page. Thanks Chris Metcalf for this idea. */
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mem = allocate_and_test (stackaddr + pagesize / 2);
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/* Before we celebrate, make sure we actually did test the same page. */
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if (((uintptr_t) stackaddr & pagemask) != ((uintptr_t) mem & pagemask))
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{
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printf ("We successfully wrote into the wrong page.\n"
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"Expected %#" PRIxPTR ", but got %#" PRIxPTR "\n",
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(uintptr_t) stackaddr & pagemask, (uintptr_t) mem & pagemask);
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return 1;
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}
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puts ("Stack top tests done");
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return 0;
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}
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/* TODO: Similar check for thread stacks once the thread stack sizes are
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fixed. */
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static int
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do_test (void)
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{
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pagesize = sysconf (_SC_PAGESIZE);
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return check_stack_top ();
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}
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#define TEST_FUNCTION do_test ()
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#include "../test-skeleton.c"
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