nptl/tst-pthread-getattr.c

   1 /* Make sure that the stackaddr returned by pthread_getattr_np is
   2    reachable.
   3
   4    Copyright (C) 2012-2018 Free Software Foundation, Inc.
   5    This file is part of the GNU C Library.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, see
  19    <http://www.gnu.org/licenses/>.  */
  20
  21 #include <stdio.h>
  22 #include <string.h>
  23 #include <sys/resource.h>
  24 #include <sys/param.h>
  25 #include <pthread.h>
  26 #include <alloca.h>
  27 #include <assert.h>
  28 #include <unistd.h>
  29 #include <inttypes.h>
  30
  31 /* There is an obscure bug in the kernel due to which RLIMIT_STACK is sometimes
  32    returned as unlimited when it is not, which may cause this test to fail.
  33    There is also the other case where RLIMIT_STACK is intentionally set as
  34    unlimited or very high, which may result in a vma that is too large and again
  35    results in a test case failure.  To avoid these problems, we cap the stack
  36    size to one less than 8M.  See the following mailing list threads for more
  37    information about this problem:
  38    <https://sourceware.org/ml/libc-alpha/2012-06/msg00599.html>
  39    <https://sourceware.org/ml/libc-alpha/2012-06/msg00713.html>.  */
  40 #define MAX_STACK_SIZE (8192 * 1024 - 1)
  41
  42 static size_t pagesize;
  43
  44 /* Check if the page in which TARGET lies is accessible.  This will segfault
  45    if it fails.  */
  46 static volatile char *
  47 allocate_and_test (char *target)
  48 {
  49   volatile char *mem = (char *) &mem;
  50   /* FIXME:  mem >= target for _STACK_GROWSUP.  */
  51   mem = alloca ((size_t) (mem - target));
  52
  53   *mem = 42;
  54   return mem;
  55 }
  56
  57 static int
  58 get_self_pthread_attr (const char *id, void **stackaddr, size_t *stacksize)
  59 {
  60   pthread_attr_t attr;
  61   int ret;
  62   pthread_t me = pthread_self ();
  63
  64   if ((ret = pthread_getattr_np (me, &attr)) < 0)
  65     {
  66       printf ("%s: pthread_getattr_np failed: %s\n", id, strerror (ret));
  67       return 1;
  68     }
  69
  70   if ((ret = pthread_attr_getstack (&attr, stackaddr, stacksize)) < 0)
  71     {
  72       printf ("%s: pthread_attr_getstack returned error: %s\n", id,
  73               strerror (ret));
  74       return 1;
  75     }
  76
  77   return 0;
  78 }
  79
  80 /* Verify that the stack size returned by pthread_getattr_np is usable when
  81    the returned value is subject to rlimit.  */
  82 static int
  83 check_stack_top (void)
  84 {
  85   struct rlimit stack_limit;
  86   void *stackaddr;
  87   volatile void *mem;
  88   size_t stacksize = 0;
  89   int ret;
  90   uintptr_t pagemask = ~(pagesize - 1);
  91
  92   puts ("Verifying that stack top is accessible");
  93
  94   ret = getrlimit (RLIMIT_STACK, &stack_limit);
  95   if (ret)
  96     {
  97       perror ("getrlimit failed");
  98       return 1;
  99     }
 100
 101   printf ("current rlimit_stack is %zu\n", (size_t) stack_limit.rlim_cur);
 102
 103   if (get_self_pthread_attr ("check_stack_top", &stackaddr, &stacksize))
 104     return 1;
 105
 106   /* Reduce the rlimit to a page less that what is currently being returned
 107      (subject to a maximum of MAX_STACK_SIZE) so that we ensure that
 108      pthread_getattr_np uses rlimit.  The figure is intentionally unaligned so
 109      to verify that pthread_getattr_np returns an aligned stacksize that
 110      correctly fits into the rlimit.  We don't bother about the case where the
 111      stack is limited by the vma below it and not by the rlimit because the
 112      stacksize returned in that case is computed from the end of that vma and is
 113      hence safe.  */
 114   stack_limit.rlim_cur = MIN (stacksize - pagesize + 1, MAX_STACK_SIZE);
 115   printf ("Adjusting RLIMIT_STACK to %zu\n", (size_t) stack_limit.rlim_cur);
 116   if ((ret = setrlimit (RLIMIT_STACK, &stack_limit)) < 0)
 117     {
 118       perror ("setrlimit failed");
 119       return 1;
 120     }
 121
 122   if (get_self_pthread_attr ("check_stack_top2", &stackaddr, &stacksize))
 123     return 1;
 124
 125   printf ("Adjusted rlimit: stacksize=%zu, stackaddr=%p\n", stacksize,
 126           stackaddr);
 127
 128   /* A lot of targets tend to write stuff on top of the user stack during
 129      context switches, so we cannot possibly safely go up to the very top of
 130      stack and test access there.  It is however sufficient to simply check if
 131      the top page is accessible, so we target our access halfway up the top
 132      page.  Thanks Chris Metcalf for this idea.  */
 133   mem = allocate_and_test (stackaddr + pagesize / 2);
 134
 135   /* Before we celebrate, make sure we actually did test the same page.  */
 136   if (((uintptr_t) stackaddr & pagemask) != ((uintptr_t) mem & pagemask))
 137     {
 138       printf ("We successfully wrote into the wrong page.\n"
 139               "Expected %#" PRIxPTR ", but got %#" PRIxPTR "\n",
 140               (uintptr_t) stackaddr & pagemask, (uintptr_t) mem & pagemask);
 141
 142       return 1;
 143     }
 144
 145   puts ("Stack top tests done");
 146
 147   return 0;
 148 }
 149
 150 /* TODO: Similar check for thread stacks once the thread stack sizes are
 151    fixed.  */
 152 static int
 153 do_test (void)
 154 {
 155   pagesize = sysconf (_SC_PAGESIZE);
 156   return check_stack_top ();
 157 }
 158
 159
 160 #define TEST_FUNCTION do_test ()
 161 #include "../test-skeleton.c"