nptl/tst-pthread-getattr.c

   1 /* Make sure that the stackaddr returned by pthread_getattr_np is
   2    reachable.
   3
   4    Copyright (C) 2012-2022 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    <https://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 #include <support/support.h>
  32
  33 /* There is an obscure bug in the kernel due to which RLIMIT_STACK is sometimes
  34    returned as unlimited when it is not, which may cause this test to fail.
  35    There is also the other case where RLIMIT_STACK is intentionally set as
  36    unlimited or very high, which may result in a vma that is too large and again
  37    results in a test case failure.  To avoid these problems, we cap the stack
  38    size to one less than 8M.  See the following mailing list threads for more
  39    information about this problem:
  40    <https://sourceware.org/ml/libc-alpha/2012-06/msg00599.html>
  41    <https://sourceware.org/ml/libc-alpha/2012-06/msg00713.html>.  */
  42 #define MAX_STACK_SIZE (8192 * 1024 - 1)
  43
  44 static size_t pagesize;
  45
  46 /* Test that the page in which TARGET lies is accessible.  This will
  47    segfault if the write fails.  This function has only half a page
  48    of thread stack left and so should not do anything and immediately
  49    return the address to which the stack reached.  */
  50 static volatile uintptr_t
  51 allocate_and_test (char *target)
  52 {
  53   volatile char *mem = (char *) &mem;
  54   /* FIXME:  mem >= target for _STACK_GROWSUP.  */
  55   mem = alloca ((size_t) (mem - target));
  56
  57   *mem = 42;
  58   return (uintptr_t) mem;
  59 }
  60
  61 static int
  62 get_self_pthread_attr (const char *id, void **stackaddr, size_t *stacksize)
  63 {
  64   pthread_attr_t attr;
  65   int ret;
  66   pthread_t me = pthread_self ();
  67
  68   if ((ret = pthread_getattr_np (me, &attr)) < 0)
  69     {
  70       printf ("%s: pthread_getattr_np failed: %s\n", id, strerror (ret));
  71       return 1;
  72     }
  73
  74   if ((ret = pthread_attr_getstack (&attr, stackaddr, stacksize)) < 0)
  75     {
  76       printf ("%s: pthread_attr_getstack returned error: %s\n", id,
  77               strerror (ret));
  78       return 1;
  79     }
  80
  81   return 0;
  82 }
  83
  84 /* Verify that the stack size returned by pthread_getattr_np is usable when
  85    the returned value is subject to rlimit.  */
  86 static int
  87 check_stack_top (void)
  88 {
  89   struct rlimit stack_limit;
  90   void *stackaddr;
  91   size_t stacksize = 0;
  92   int ret;
  93   uintptr_t pagemask = ~(pagesize - 1);
  94
  95   puts ("Verifying that stack top is accessible");
  96
  97   ret = getrlimit (RLIMIT_STACK, &stack_limit);
  98   if (ret)
  99     {
 100       perror ("getrlimit failed");
 101       return 1;
 102     }
 103
 104   printf ("current rlimit_stack is %zu\n", (size_t) stack_limit.rlim_cur);
 105
 106   if (get_self_pthread_attr ("check_stack_top", &stackaddr, &stacksize))
 107     return 1;
 108
 109   /* Reduce the rlimit to a page less that what is currently being returned
 110      (subject to a maximum of MAX_STACK_SIZE) so that we ensure that
 111      pthread_getattr_np uses rlimit.  The figure is intentionally unaligned so
 112      to verify that pthread_getattr_np returns an aligned stacksize that
 113      correctly fits into the rlimit.  We don't bother about the case where the
 114      stack is limited by the vma below it and not by the rlimit because the
 115      stacksize returned in that case is computed from the end of that vma and is
 116      hence safe.  */
 117   stack_limit.rlim_cur = MIN (stacksize - pagesize + 1, MAX_STACK_SIZE);
 118   printf ("Adjusting RLIMIT_STACK to %zu\n", (size_t) stack_limit.rlim_cur);
 119   if ((ret = setrlimit (RLIMIT_STACK, &stack_limit)) < 0)
 120     {
 121       perror ("setrlimit failed");
 122       return 1;
 123     }
 124
 125   if (get_self_pthread_attr ("check_stack_top2", &stackaddr, &stacksize))
 126     return 1;
 127
 128   printf ("Adjusted rlimit: stacksize=%zu, stackaddr=%p\n", stacksize,
 129           stackaddr);
 130
 131   /* A lot of targets tend to write stuff on top of the user stack during
 132      context switches, so we cannot possibly safely go up to the very top of
 133      stack and test access there.  It is however sufficient to simply check if
 134      the top page is accessible, so we target our access halfway up the top
 135      page.  Thanks Chris Metcalf for this idea.  */
 136   uintptr_t mem = allocate_and_test (stackaddr + pagesize / 2);
 137
 138   /* Before we celebrate, make sure we actually did test the same page.  */
 139   if (((uintptr_t) stackaddr & pagemask) != (mem & pagemask))
 140     {
 141       printf ("We successfully wrote into the wrong page.\n"
 142               "Expected %#" PRIxPTR ", but got %#" PRIxPTR "\n",
 143               (uintptr_t) stackaddr & pagemask, mem & pagemask);
 144
 145       return 1;
 146     }
 147
 148   puts ("Stack top tests done");
 149
 150   return 0;
 151 }
 152
 153 /* TODO: Similar check for thread stacks once the thread stack sizes are
 154    fixed.  */
 155 static int
 156 do_test (void)
 157 {
 158   support_need_proc ("Reads /proc/self/maps to get stack size.");
 159
 160   pagesize = sysconf (_SC_PAGESIZE);
 161   return check_stack_top ();
 162 }
 163
 164
 165 #define TEST_FUNCTION do_test ()
 166 #include "../test-skeleton.c"