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 #include "cmdline.h"
  22
  23 static char *cmdline;
  24 static struct cmdline_parts *bdev_parts;
  25
  26 static int add_part(int slot, struct cmdline_subpart *subpart, void *param)
  27 {
  28         int label_min;
  29         struct partition_meta_info *info;
  30         char tmp[sizeof(info->volname) + 4];
  31         struct parsed_partitions *state = (struct parsed_partitions *)param;
  32
  33         if (slot >= state->limit)
  34                 return 1;
  35
  36         put_partition(state, slot, subpart->from >> 9,
  37                       subpart->size >> 9);
  38
  39         info = &state->parts[slot].info;
  40
  41         label_min = min_t(int, sizeof(info->volname) - 1,
  42                           sizeof(subpart->name));
  43         strncpy(info->volname, subpart->name, label_min);
  44         info->volname[label_min] = '\0';
  45
  46         snprintf(tmp, sizeof(tmp), "(%s)", info->volname);
  47         strlcat(state->pp_buf, tmp, PAGE_SIZE);
  48
  49         state->parts[slot].has_info = true;
  50
  51         return 0;
  52 }
  53
  54 static int __init cmdline_parts_setup(char *s)
  55 {
  56         cmdline = s;
  57         return 1;
  58 }
  59 __setup("blkdevparts=", cmdline_parts_setup);
  60
  61 static bool has_overlaps(sector_t from, sector_t size,
  62                          sector_t from2, sector_t size2)
  63 {
  64         sector_t end = from + size;
  65         sector_t end2 = from2 + size2;
  66
  67         if (from >= from2 && from < end2)
  68                 return true;
  69
  70         if (end > from2 && end <= end2)
  71                 return true;
  72
  73         if (from2 >= from && from2 < end)
  74                 return true;
  75
  76         if (end2 > from && end2 <= end)
  77                 return true;
  78
  79         return false;
  80 }
  81
  82 static inline void overlaps_warns_header(void)
  83 {
  84         pr_warn("Overlapping partitions are used in command line partitions.");
  85         pr_warn("Don't use filesystems on overlapping partitions:");
  86 }
  87
  88 static void cmdline_parts_verifier(int slot, struct parsed_partitions *state)
  89 {
  90         int i;
  91         bool header = true;
  92
  93         for (; slot < state->limit && state->parts[slot].has_info; slot++) {
  94                 for (i = slot+1; i < state->limit && state->parts[i].has_info;
  95                      i++) {
  96                         if (has_overlaps(state->parts[slot].from,
  97                                          state->parts[slot].size,
  98                                          state->parts[i].from,
  99                                          state->parts[i].size)) {
 100                                 if (header) {
 101                                         header = false;
 102                                         overlaps_warns_header();
 103                                 }
 104                                 pr_warn("%s[%llu,%llu] overlaps with "
 105                                         "%s[%llu,%llu].",
 106                                         state->parts[slot].info.volname,
 107                                         (u64)state->parts[slot].from << 9,
 108                                         (u64)state->parts[slot].size << 9,
 109                                         state->parts[i].info.volname,
 110                                         (u64)state->parts[i].from << 9,
 111                                         (u64)state->parts[i].size << 9);
 112                         }
 113                 }
 114         }
 115 }
 116
 117 /*
 118  * Purpose: allocate cmdline partitions.
 119  * Returns:
 120  * -1 if unable to read the partition table
 121  *  0 if this isn't our partition table
 122  *  1 if successful
 123  */
 124 int cmdline_partition(struct parsed_partitions *state)
 125 {
 126         sector_t disk_size;
 127         char bdev[BDEVNAME_SIZE];
 128         struct cmdline_parts *parts;
 129
 130         if (cmdline) {
 131                 if (bdev_parts)
 132                         cmdline_parts_free(&bdev_parts);
 133
 134                 if (cmdline_parts_parse(&bdev_parts, cmdline)) {
 135                         cmdline = NULL;
 136                         return -1;
 137                 }
 138                 cmdline = NULL;
 139         }
 140
 141         if (!bdev_parts)
 142                 return 0;
 143
 144         bdevname(state->bdev, bdev);
 145         parts = cmdline_parts_find(bdev_parts, bdev);
 146         if (!parts)
 147                 return 0;
 148
 149         disk_size = get_capacity(state->bdev->bd_disk) << 9;
 150
 151         cmdline_parts_set(parts, disk_size, 1, add_part, (void *)state);
 152         cmdline_parts_verifier(1, state);
 153
 154         strlcat(state->pp_buf, "\n", PAGE_SIZE);
 155
 156         return 1;
 157 }