tests/zfs-tests/cmd/get_diff.c

   1 /*
   2  * This file and its contents are supplied under the terms of the
   3  * Common Development and Distribution License ("CDDL"), version 1.0.
   4  * You may only use this file in accordance with the terms of version
   5  * 1.0 of the CDDL.
   6  *
   7  * A full copy of the text of the CDDL should have accompanied this
   8  * source.  A copy of the CDDL is also available via the Internet at
   9  * http://www.illumos.org/license/CDDL.
  10  */
  11
  12 /*
  13  * Copyright (c) 2018 by Delphix. All rights reserved.
  14  */
  15
  16 #include <stdio.h>
  17 #include <fcntl.h>
  18 #include <unistd.h>
  19 #include <stdlib.h>
  20 #include <string.h>
  21 #include <assert.h>
  22 #include <sys/param.h>
  23 #include <sys/types.h>
  24 #include <sys/stat.h>
  25 #include <errno.h>
  26
  27 static void
  28 usage(const char *msg, int exit_value)
  29 {
  30         (void) fprintf(stderr, "usage: get_diff file redacted_file\n%s\n", msg);
  31         exit(exit_value);
  32 }
  33
  34 /*
  35  * This utility compares two files, an original and its redacted counterpart
  36  * (in that order). It compares the files 512 bytes at a time, printing out
  37  * any ranges (as offset and length) where the redacted file does not match
  38  * the original. This output is used to verify that the expected ranges of
  39  * a redacted file do not contain the original data.
  40  */
  41 int
  42 main(int argc, char *argv[])
  43 {
  44         off_t           diff_off = 0, diff_len = 0, off = 0;
  45         int             fd1, fd2;
  46         char            *fname1, *fname2;
  47         char            buf1[DEV_BSIZE], buf2[DEV_BSIZE];
  48         ssize_t         bytes;
  49
  50         if (argc != 3)
  51                 usage("Incorrect number of arguments.", 1);
  52
  53         if ((fname1 = argv[1]) == NULL)
  54                 usage("Filename missing.", 1);
  55         if ((fd1 = open(fname1, O_LARGEFILE | O_RDONLY)) < 0) {
  56                 perror("open1 failed");
  57                 exit(1);
  58         }
  59
  60         if ((fname2 = argv[2]) == NULL)
  61                 usage("Redacted filename missing.", 1);
  62         if ((fd2 = open(fname2, O_LARGEFILE | O_RDONLY)) < 0) {
  63                 perror("open2 failed");
  64                 exit(1);
  65         }
  66
  67         while ((bytes = pread(fd1, buf1, DEV_BSIZE, off)) > 0) {
  68                 if (pread(fd2, buf2, DEV_BSIZE, off) < 0) {
  69                         if (errno == EIO) {
  70                                 /*
  71                                  * A read in a redacted section of a file will
  72                                  * fail with EIO. If we get EIO, continue on
  73                                  * but ensure that a comparison of buf1 and
  74                                  * buf2 will fail, indicating a redacted block.
  75                                  */
  76                                 buf2[0] = ~buf1[0];
  77                         } else {
  78                                 perror("pread failed");
  79                                 exit(1);
  80                         }
  81                 }
  82                 if (memcmp(buf1, buf2, bytes) == 0) {
  83                         if (diff_len != 0) {
  84                                 (void) fprintf(stdout, "%lld,%lld\n",
  85                                     (long long)diff_off, (long long)diff_len);
  86                                 assert(off == diff_off + diff_len);
  87                                 diff_len = 0;
  88                         }
  89                         diff_off = 0;
  90                 } else {
  91                         if (diff_len == 0)
  92                                 diff_off = off;
  93                         assert(off == diff_off + diff_len);
  94                         diff_len += bytes;
  95                 }
  96                 off += bytes;
  97         }
  98
  99         if (diff_len != 0) {
 100                 (void) fprintf(stdout, "%lld,%lld\n", (long long)diff_off,
 101                     (long long)diff_len);
 102         }
 103
 104         (void) close(fd1);
 105         (void) close(fd2);
 106
 107         return (0);
 108 }