1  /* Copyright (C) 2011-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      12     Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public
      15     License along with the GNU C Library; if not, see
      16     <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <fcntl.h>
      19  #include <limits.h>
      20  #include <paths.h>
      21  #include <stdio.h>
      22  #include <stdint.h>
      23  #include <stdlib.h>
      24  #include <unistd.h>
      25  #include <sys/uio.h>
      26  
      27  /* GNU/Hurd does not define a IOV_MAX constraint.  */
      28  #ifndef IOV_MAX
      29  # define IOV_MAX 1024
      30  #endif
      31  
      32  
      33  /* The purpose of this test is to verify that the INTERNAL_[V]SYSCALL_NCS
      34     macros on 64-bit platforms don't cast the return type to (int) which would
      35     erroneously sign extend the return value should the high bit of the bottom
      36     half of the word be '1'.  */
      37  
      38  #if 0
      39  /* Used to test the non power-of-2 code path.  */
      40  #undef IOV_MAX
      41  #define IOV_MAX 1000
      42  #endif
      43  
      44  /* writev() should report that it has written EXPECTED number of bytes.  */
      45  #define EXPECTED ((size_t) INT32_MAX + 1)
      46  
      47  static int
      48  do_test (void)
      49  {
      50    struct iovec iv[IOV_MAX];
      51    /* POSIX doesn't guarantee that IOV_MAX is pow of 2 but we're optimistic.  */
      52    size_t bufsz = EXPECTED / IOV_MAX;
      53    size_t bufrem = EXPECTED % IOV_MAX;
      54  
      55    /* If there's a remainder then IOV_MAX probably isn't a power of 2 and we
      56       need to make bufsz bigger so that the last iovec, iv[IOV_MAX-1], is free
      57       for the remainder.  */
      58    if (bufrem)
      59      {
      60        bufsz = bufsz + 1;
      61        bufrem = EXPECTED - (bufsz * (IOV_MAX - 1));
      62      }
      63  
      64    /* We writev to /dev/null since we're just testing writev's return value.  */
      65    int fd = open (_PATH_DEVNULL, O_WRONLY);
      66    if (fd == -1)
      67      {
      68        printf ("Unable to open /dev/null for writing.\n");
      69        return -1;
      70      }
      71  
      72    iv[0].iov_base = malloc (bufsz);
      73    if (iv[0].iov_base == NULL)
      74      {
      75        printf ("malloc (%zu) failed.\n", bufsz);
      76        close (fd);
      77        return -1;
      78      }
      79    iv[0].iov_len = bufsz;
      80  
      81    /* We optimistically presume that there isn't a remainder and set all iovec
      82       instances to the same base and len as the first instance.  */
      83    for (int i = 1; i < IOV_MAX; i++)
      84      {
      85        /* We don't care what the data is so reuse the allocation from iv[0];  */
      86        iv[i].iov_base = iv[0].iov_base;
      87        iv[i].iov_len = iv[0].iov_len;
      88      }
      89  
      90    /* If there is a remainder then we correct the last iov_len.  */
      91    if (bufrem)
      92      iv[IOV_MAX - 1].iov_len = bufrem;
      93  
      94    /* Write junk to /dev/null with the writev syscall in order to get a return
      95       of INT32_MAX+1 bytes to verify that the INTERNAL_SYSCALL wrappers aren't
      96       mangling the result if the signbit of a 32-bit number is set.  */
      97    ssize_t ret = writev (fd, iv, IOV_MAX);
      98  
      99    free (iv[0].iov_base);
     100    close (fd);
     101  
     102    if (ret != (ssize_t) EXPECTED)
     103      {
     104  #ifdef ARTIFICIAL_LIMIT
     105        if (ret != (ssize_t) ARTIFICIAL_LIMIT)
     106  #endif
     107  	{
     108  	  printf ("writev() return value: %zd != EXPECTED: %zd\n",
     109  		  ret, EXPECTED);
     110  	  return 1;
     111  	}
     112      }
     113  
     114    return 0;
     115  }
     116  
     117  #define TEST_FUNCTION do_test ()
     118  #include "../test-skeleton.c"