block/partitions/cmdline.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2013 HUAWEI
   4  * Author: Cai Zhiyong <caizhiyong@huawei.com>
   5  *
   6  * Read block device partition table from the command line.
   7  * Typically used for fixed block (eMMC) embedded devices.
   8  * It has no MBR, so saves storage space. Bootloader can be easily accessed
   9  * by absolute address of data on the block device.
  10  * Users can easily change the partition.
  11  *
  12  * The format for the command line is just like mtdparts.
  13  *
  14  * For further information, see "Documentation/block/cmdline-partition.rst"
  15  *
  16  */
  17
  18 #include <linux/cmdline-parser.h>
  19
  20 #include "check.h"
  21
  22 static char *cmdline;
  23 static struct cmdline_parts *bdev_parts;
  24
  25 static int add_part(int slot, struct cmdline_subpart *subpart, void *param)
  26 {
  27         int label_min;
  28         struct partition_meta_info *info;
  29         char tmp[sizeof(info->volname) + 4];
  30         struct parsed_partitions *state = (struct parsed_partitions *)param;
  31
  32         if (slot >= state->limit)
  33                 return 1;
  34
  35         put_partition(state, slot, subpart->from >> 9,
  36                       subpart->size >> 9);
  37
  38         info = &state->parts[slot].info;
  39
  40         label_min = min_t(int, sizeof(info->volname) - 1,
  41                           sizeof(subpart->name));
  42         strncpy(info->volname, subpart->name, label_min);
  43         info->volname[label_min] = '\0';
  44
  45         snprintf(tmp, sizeof(tmp), "(%s)", info->volname);
  46         strlcat(state->pp_buf, tmp, PAGE_SIZE);
  47
  48         state->parts[slot].has_info = true;
  49
  50         return 0;
  51 }
  52
  53 static int __init cmdline_parts_setup(char *s)
  54 {
  55         cmdline = s;
  56         return 1;
  57 }
  58 __setup("blkdevparts=", cmdline_parts_setup);
  59
  60 static bool has_overlaps(sector_t from, sector_t size,
  61                          sector_t from2, sector_t size2)
  62 {
  63         sector_t end = from + size;
  64         sector_t end2 = from2 + size2;
  65
  66         if (from >= from2 && from < end2)
  67                 return true;
  68
  69         if (end > from2 && end <= end2)
  70                 return true;
  71
  72         if (from2 >= from && from2 < end)
  73                 return true;
  74
  75         if (end2 > from && end2 <= end)
  76                 return true;
  77
  78         return false;
  79 }
  80
  81 static inline void overlaps_warns_header(void)
  82 {
  83         pr_warn("Overlapping partitions are used in command line partitions.");
  84         pr_warn("Don't use filesystems on overlapping partitions:");
  85 }
  86
  87 static void cmdline_parts_verifier(int slot, struct parsed_partitions *state)
  88 {
  89         int i;
  90         bool header = true;
  91
  92         for (; slot < state->limit && state->parts[slot].has_info; slot++) {
  93                 for (i = slot+1; i < state->limit && state->parts[i].has_info;
  94                      i++) {
  95                         if (has_overlaps(state->parts[slot].from,
  96                                          state->parts[slot].size,
  97                                          state->parts[i].from,
  98                                          state->parts[i].size)) {
  99                                 if (header) {
 100                                         header = false;
 101                                         overlaps_warns_header();
 102                                 }
 103                                 pr_warn("%s[%llu,%llu] overlaps with "
 104                                         "%s[%llu,%llu].",
 105                                         state->parts[slot].info.volname,
 106                                         (u64)state->parts[slot].from << 9,
 107                                         (u64)state->parts[slot].size << 9,
 108                                         state->parts[i].info.volname,
 109                                         (u64)state->parts[i].from << 9,
 110                                         (u64)state->parts[i].size << 9);
 111                         }
 112                 }
 113         }
 114 }
 115
 116 /*
 117  * Purpose: allocate cmdline partitions.
 118  * Returns:
 119  * -1 if unable to read the partition table
 120  *  0 if this isn't our partition table
 121  *  1 if successful
 122  */
 123 int cmdline_partition(struct parsed_partitions *state)
 124 {
 125         sector_t disk_size;
 126         char bdev[BDEVNAME_SIZE];
 127         struct cmdline_parts *parts;
 128
 129         if (cmdline) {
 130                 if (bdev_parts)
 131                         cmdline_parts_free(&bdev_parts);
 132
 133                 if (cmdline_parts_parse(&bdev_parts, cmdline)) {
 134                         cmdline = NULL;
 135                         return -1;
 136                 }
 137                 cmdline = NULL;
 138         }
 139
 140         if (!bdev_parts)
 141                 return 0;
 142
 143         bdevname(state->bdev, bdev);
 144         parts = cmdline_parts_find(bdev_parts, bdev);
 145         if (!parts)
 146                 return 0;
 147
 148         disk_size = get_capacity(state->bdev->bd_disk) << 9;
 149
 150         cmdline_parts_set(parts, disk_size, 1, add_part, (void *)state);
 151         cmdline_parts_verifier(1, state);
 152
 153         strlcat(state->pp_buf, "\n", PAGE_SIZE);
 154
 155         return 1;
 156 }