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/* Make sure that the stackaddr returned by pthread_getattr_np is
reachable.
Copyright (C) 2012 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, see
<http://www.gnu.org/licenses/>. */
#include <stdio.h>
#include <string.h>
#include <sys/resource.h>
#include <pthread.h>
#include <alloca.h>
#include <assert.h>
/* There is an obscure bug in the kernel due to which RLIMIT_STACK is sometimes
returned as unlimited when it is not, which may cause this test to fail.
There is also the other case where RLIMIT_STACK is intentionally set as
unlimited or very high, which may result in a vma that is too large and again
results in a test case failure. To avoid these problems, we cap the stack
size to one less than 8M. See the following mailing list threads for more
information about this problem:
<http://sourceware.org/ml/libc-alpha/2012-06/msg00599.html>
<http://sourceware.org/ml/libc-alpha/2012-06/msg00713.html>. */
#define MAX_STACK_SIZE (8192 * 1024 - 1)
#define _MIN(l,o) ((l) < (o) ? (l) : (o))
/* Move the stack pointer so that stackaddr is accessible and then check if it
really is accessible. This will segfault if it fails. */
static void *
allocate_and_test (void *stackaddr)
{
void *mem = &mem;
/* FIXME: mem >= stackaddr for _STACK_GROWSUP. */
mem = alloca ((size_t) (mem - stackaddr));
assert (mem <= stackaddr);
/* We don't access mem here because the compiler may move the stack pointer
beyond what we expect, thus making our alloca send the stack pointer
beyond stackaddr. Using only stackaddr without the assert may make the
compiler think that this instruction is independent of the above alloca
and hence reshuffle to do this dereference before the alloca. */
*(int *)stackaddr = 42;
return stackaddr;
}
static int
get_self_pthread_attr (const char *id, void **stackaddr, size_t *stacksize)
{
pthread_attr_t attr;
int ret;
pthread_t me = pthread_self ();
if ((ret = pthread_getattr_np (me, &attr)))
{
printf ("%s: pthread_getattr_np failed: %s\n", id, strerror (ret));
return 1;
}
if ((ret = pthread_attr_getstack (&attr, stackaddr, stacksize)))
{
printf ("%s: pthread_attr_getstack returned error: %s\n", id,
strerror (ret));
return 1;
}
return 0;
}
/* Verify that the stack size returned by pthread_getattr_np is usable when
the returned value is subject to rlimit. */
static int
check_stack_top (void)
{
struct rlimit stack_limit;
void *stackaddr;
size_t stacksize = 0;
int ret;
puts ("Verifying that stack top is accessible");
ret = getrlimit (RLIMIT_STACK, &stack_limit);
if (ret)
{
perror ("getrlimit failed");
return 1;
}
printf ("current rlimit_stack is %zu\n", stack_limit.rlim_cur);
if (get_self_pthread_attr ("check_stack_top", &stackaddr, &stacksize))
return 1;
/* Reduce the rlimit to a page less that what is currently being returned
(subject to a maximum of MAX_STACK_SIZE) so that we ensure that
pthread_getattr_np uses rlimit. The figure is intentionally unaligned so
to verify that pthread_getattr_np returns an aligned stacksize that
correctly fits into the rlimit. We don't bother about the case where the
stack is limited by the vma below it and not by the rlimit because the
stacksize returned in that case is computed from the end of that vma and is
hence safe. */
stack_limit.rlim_cur = _MIN(stacksize - 4095, MAX_STACK_SIZE);
printf ("Adjusting RLIMIT_STACK to %zu\n", stack_limit.rlim_cur);
if ((ret = setrlimit (RLIMIT_STACK, &stack_limit)))
{
perror ("setrlimit failed");
return 1;
}
if (get_self_pthread_attr ("check_stack_top2", &stackaddr, &stacksize))
return 1;
printf ("Adjusted rlimit: stacksize=%zu, stackaddr=%p\n", stacksize,
stackaddr);
/* So that the compiler does not optimize out this call. */
stackaddr = allocate_and_test (stackaddr);
assert (*(int *)stackaddr == 42);
puts ("Stack top tests done");
return 0;
}
/* TODO: Similar check for thread stacks once the thread stack sizes are
fixed. */
static int
do_test (void)
{
return check_stack_top ();
}
#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"
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