gdb/testsuite/gdb.base/dcache-line-read-error.c

   1 /* This testcase is part of GDB, the GNU debugger.
   2
   3    Copyright 2012-2019 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #include <stdlib.h>
  19 #include <stdio.h>
  20 #include <sys/mman.h>
  21 #include <unistd.h>
  22 #include <string.h>
  23
  24 size_t pg_size;
  25 void *first_mapped_page;
  26 void *last_mapped_page;
  27
  28 void
  29 breakpt (void)
  30 {
  31   /* Nothing. */
  32 }
  33
  34 int
  35 main (void)
  36 {
  37   void *p;
  38   int pg_count;
  39   size_t i;
  40
  41   /* Map 6 contiguous pages, and then unmap all second first, and
  42      second last.
  43
  44      From GDB we will disassemble each of the _mapped_ pages, with a
  45      code-cache (dcache) line size bigger than the page size (twice
  46      bigger).  This makes GDB try to read one page before the mapped
  47      page once, and the page after another time.  GDB should give no
  48      error in either case.
  49
  50      That is, depending on where the kernel aligns the pages, we get
  51      either:
  52
  53       .---.---.---.---.---.---.
  54       | U | M | U | U | M | U |
  55       '---'---'---'---'---'---.
  56       |       |       |       |  <- line alignment
  57        ^^^^^^^         ^^^^^^^
  58           |               |
  59           + line1         + line2
  60
  61      Or:
  62
  63       .---.---.---.---.---.---.
  64       | U | M | U | U | M | U |
  65       '---'---'---'---'---'---.
  66           |       |       |      <- line alignment
  67            ^^^^^^^ ^^^^^^^
  68               |       |
  69         line1 +       + line2
  70
  71     Note we really want to test that dcache behaves correctly when
  72     reading a cache line fails.  We're just using unmapped memory as
  73     proxy for any kind of error.  */
  74
  75   pg_size = getpagesize ();
  76   pg_count = 6;
  77
  78   p = mmap (0, pg_count * pg_size, PROT_READ|PROT_WRITE,
  79             MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
  80   if (p == MAP_FAILED)
  81     {
  82       perror ("mmap");
  83       return EXIT_FAILURE;
  84     }
  85
  86   /* Leave memory zero-initialized.  Disassembling 0s should behave on
  87      all targets.  */
  88
  89   for (i = 0; i < pg_count; i++)
  90     {
  91       if (i == 1 || i == 4)
  92         continue;
  93
  94       if (munmap (p + (i * pg_size), pg_size) == -1)
  95         {
  96           perror ("munmap");
  97           return EXIT_FAILURE;
  98         }
  99     }
 100
 101   first_mapped_page = p + 1 * pg_size;;
 102   last_mapped_page = p + 4 * pg_size;
 103
 104   breakpt ();
 105
 106   return EXIT_SUCCESS;
 107 }