sysdeps/wordsize-64/tst-writev.c

   1 /* Copyright (C) 2011-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ryan S. Arnold <rsa@us.ibm.com>, 2011.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <fcntl.h>
  20 #include <limits.h>
  21 #include <paths.h>
  22 #include <stdio.h>
  23 #include <stdint.h>
  24 #include <stdlib.h>
  25 #include <unistd.h>
  26 #include <sys/uio.h>
  27
  28
  29 /* The purpose of this test is to verify that the INTERNAL_[V]SYSCALL_NCS
  30    macros on 64-bit platforms don't cast the return type to (int) which would
  31    erroneously sign extend the return value should the high bit of the bottom
  32    half of the word be '1'.  */
  33
  34 #if 0
  35 /* Used to test the non power-of-2 code path.  */
  36 #undef IOV_MAX
  37 #define IOV_MAX 1000
  38 #endif
  39
  40 /* writev() should report that it has written EXPECTED number of bytes.  */
  41 #define EXPECTED ((size_t) INT32_MAX + 1)
  42
  43 static int
  44 do_test (void)
  45 {
  46   struct iovec iv[IOV_MAX];
  47   /* POSIX doesn't guarantee that IOV_MAX is pow of 2 but we're optimistic.  */
  48   size_t bufsz = EXPECTED / IOV_MAX;
  49   size_t bufrem = EXPECTED % IOV_MAX;
  50
  51   /* If there's a remainder then IOV_MAX probably isn't a power of 2 and we
  52      need to make bufsz bigger so that the last iovec, iv[IOV_MAX-1], is free
  53      for the remainder.  */
  54   if (bufrem)
  55     {
  56       bufsz = bufsz + 1;
  57       bufrem = EXPECTED - (bufsz * (IOV_MAX - 1));
  58     }
  59
  60   /* We writev to /dev/null since we're just testing writev's return value.  */
  61   int fd = open (_PATH_DEVNULL, O_WRONLY);
  62   if (fd == -1)
  63     {
  64       printf ("Unable to open /dev/null for writing.\n");
  65       return -1;
  66     }
  67
  68   iv[0].iov_base = malloc (bufsz);
  69   if (iv[0].iov_base == NULL)
  70     {
  71       printf ("malloc (%zu) failed.\n", bufsz);
  72       close (fd);
  73       return -1;
  74     }
  75   iv[0].iov_len = bufsz;
  76
  77   /* We optimistically presume that there isn't a remainder and set all iovec
  78      instances to the same base and len as the first instance.  */
  79   for (int i = 1; i < IOV_MAX; i++)
  80     {
  81       /* We don't care what the data is so reuse the allocation from iv[0];  */
  82       iv[i].iov_base = iv[0].iov_base;
  83       iv[i].iov_len = iv[0].iov_len;
  84     }
  85
  86   /* If there is a remainder then we correct the last iov_len.  */
  87   if (bufrem)
  88     iv[IOV_MAX - 1].iov_len = bufrem;
  89
  90   /* Write junk to /dev/null with the writev syscall in order to get a return
  91      of INT32_MAX+1 bytes to verify that the INTERNAL_SYSCALL wrappers aren't
  92      mangling the result if the signbit of a 32-bit number is set.  */
  93   ssize_t ret = writev (fd, iv, IOV_MAX);
  94
  95   free (iv[0].iov_base);
  96   close (fd);
  97
  98   if (ret != (ssize_t) EXPECTED)
  99     {
 100 #ifdef ARTIFICIAL_LIMIT
 101       if (ret != (ssize_t) ARTIFICIAL_LIMIT)
 102 #endif
 103         {
 104           printf ("writev() return value: %zd != EXPECTED: %zd\n",
 105                   ret, EXPECTED);
 106           return 1;
 107         }
 108     }
 109
 110   return 0;
 111 }
 112
 113 /* Time enough for a large writev syscall to complete.  */
 114 #define TIMEOUT 20
 115
 116 #define TEST_FUNCTION do_test ()
 117 #include "../test-skeleton.c"