target/linux/generic/files/drivers/platform/mikrotik/rb_softconfig.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Driver for MikroTik RouterBoot soft config.
   4  *
   5  * Copyright (C) 2020 Thibaut VARÈNE <hacks+kernel@slashdirt.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License version 2 as published
   9  * by the Free Software Foundation.
  10  *
  11  * This driver exposes the data encoded in the "soft_config" flash segment of
  12  * MikroTik RouterBOARDs devices. It presents the data in a sysfs folder
  13  * named "soft_config". The data is presented in a user/machine-friendly way
  14  * with just as much parsing as can be generalized across mikrotik platforms
  15  * (as inferred from reverse-engineering).
  16  *
  17  * The known soft_config tags are presented in the "soft_config" sysfs folder,
  18  * with the addition of one specific file named "commit", which is only
  19  * available if the driver supports writes to the mtd device: no modifications
  20  * made to any of the other attributes are actually written back to flash media
  21  * until a true value is input into this file (e.g. [Yy1]). This is to avoid
  22  * unnecessary flash wear, and to permit to revert all changes by issuing a
  23  * false value ([Nn0]). Reading the content of this file shows the current
  24  * status of the driver: if the data in sysfs matches the content of the
  25  * soft_config partition, the file will read "clean". Otherwise, it will read
  26  * "dirty".
  27  *
  28  * The writeable sysfs files presented by this driver will accept only inputs
  29  * which are in a valid range for the given tag. As a design choice, the driver
  30  * will not assess whether the inputs are identical to the existing data.
  31  *
  32  * Note: PAGE_SIZE is assumed to be >= 4K, hence the device attribute show
  33  * routines need not check for output overflow.
  34  *
  35  * Some constant defines extracted from rbcfg.h by Gabor Juhos
  36  * <juhosg@openwrt.org>
  37  */
  38
  39 #include <linux/types.h>
  40 #include <linux/init.h>
  41 #include <linux/kernel.h>
  42 #include <linux/slab.h>
  43 #include <linux/errno.h>
  44 #include <linux/kobject.h>
  45 #include <linux/string.h>
  46 #include <linux/mtd/mtd.h>
  47 #include <linux/sysfs.h>
  48 #include <linux/version.h>
  49 #include <linux/capability.h>
  50 #include <linux/spinlock.h>
  51 #include <linux/crc32.h>
  52
  53 #include "routerboot.h"
  54
  55 #define RB_SOFTCONFIG_VER               "0.01"
  56 #define RB_SC_PR_PFX                    "[rb_softconfig] "
  57
  58 /*
  59  * mtd operations before 4.17 are asynchronous, not handled by this code
  60  * Also make the driver act read-only if 4K_SECTORS are not enabled, since they
  61  * are require to handle partial erasing of the small soft_config partition.
  62  */
  63 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(4, 17, 0)) && defined(CONFIG_MTD_SPI_NOR_USE_4K_SECTORS)
  64  #define RB_SC_HAS_WRITE_SUPPORT        true
  65  #define RB_SC_WMODE                    S_IWUSR
  66  #define RB_SC_RMODE                    S_IRUSR
  67 #else
  68  #define RB_SC_HAS_WRITE_SUPPORT        false
  69  #define RB_SC_WMODE                    0
  70  #define RB_SC_RMODE                    S_IRUSR
  71 #endif
  72
  73 /* ID values for software settings */
  74 #define RB_SCID_UART_SPEED              0x01    // u32*1
  75 #define RB_SCID_BOOT_DELAY              0x02    // u32*1
  76 #define RB_SCID_BOOT_DEVICE             0x03    // u32*1
  77 #define RB_SCID_BOOT_KEY                0x04    // u32*1
  78 #define RB_SCID_CPU_MODE                0x05    // u32*1
  79 #define RB_SCID_BIOS_VERSION            0x06    // str
  80 #define RB_SCID_BOOT_PROTOCOL           0x09    // u32*1
  81 #define RB_SCID_CPU_FREQ_IDX            0x0C    // u32*1
  82 #define RB_SCID_BOOTER                  0x0D    // u32*1
  83 #define RB_SCID_SILENT_BOOT             0x0F    // u32*1
  84 /*
  85  * protected_routerboot seems to use tag 0x1F. It only works in combination with
  86  * RouterOS, resulting in a wiped board otherwise, so it's not implemented here.
  87  * The tag values are as follows:
  88  * - off: 0x0
  89  * - on: the lower halfword encodes the max value in s for the reset feature,
  90  *       the higher halfword encodes the min value in s for the reset feature.
  91  * Default value when on: 0x00140258: 0x14 = 20s / 0x258= 600s
  92  * See details here: https://wiki.mikrotik.com/wiki/Manual:RouterBOARD_settings#Protected_bootloader
  93  */
  94
  95 /* Tag values */
  96
  97 #define RB_UART_SPEED_115200            0
  98 #define RB_UART_SPEED_57600             1
  99 #define RB_UART_SPEED_38400             2
 100 #define RB_UART_SPEED_19200             3
 101 #define RB_UART_SPEED_9600              4
 102 #define RB_UART_SPEED_4800              5
 103 #define RB_UART_SPEED_2400              6
 104 #define RB_UART_SPEED_1200              7
 105 #define RB_UART_SPEED_OFF               8
 106
 107 /* valid boot delay: 1 - 9s in 1s increment */
 108 #define RB_BOOT_DELAY_MIN               1
 109 #define RB_BOOT_DELAY_MAX               9
 110
 111 #define RB_BOOT_DEVICE_ETHER            0       // "boot over Ethernet"
 112 #define RB_BOOT_DEVICE_NANDETH          1       // "boot from NAND, if fail then Ethernet"
 113 #define RB_BOOT_DEVICE_CFCARD           2       // (not available in rbcfg)
 114 #define RB_BOOT_DEVICE_ETHONCE          3       // "boot Ethernet once, then NAND"
 115 #define RB_BOOT_DEVICE_NANDONLY         5       // "boot from NAND only"
 116 #define RB_BOOT_DEVICE_FLASHCFG         7       // "boot in flash configuration mode"
 117 #define RB_BOOT_DEVICE_FLSHONCE         8       // "boot in flash configuration mode once, then NAND"
 118
 119 /*
 120  * ATH79 CPU frequency indices.
 121  * It is unknown if they apply to all ATH79 RBs, and some do not seem to feature
 122  * the up levels (QCA955x), while U3 is presumably AR9344-only.
 123  */
 124 #define RB_CPU_FREQ_IDX_ATH79_D2        (0 << 3)
 125 #define RB_CPU_FREQ_IDX_ATH79_D1        (1 << 3)        // 0x8
 126 #define RB_CPU_FREQ_IDX_ATH79_N0        (2 << 3)        // 0x10 - factory freq for many devices
 127 #define RB_CPU_FREQ_IDX_ATH79_U1        (3 << 3)        // 0x18
 128 #define RB_CPU_FREQ_IDX_ATH79_U2        (4 << 3)        // 0x20
 129 #define RB_CPU_FREQ_IDX_ATH79_U3        (5 << 3)        // 0x28
 130
 131 #define RB_SC_CRC32_OFFSET              4       // located right after magic
 132
 133 static struct kobject *sc_kobj;
 134 static u8 *sc_buf;
 135 static size_t sc_buflen;
 136 static rwlock_t sc_bufrwl;              // rw lock to sc_buf
 137
 138 /* MUST be used with lock held */
 139 #define RB_SC_CLRCRC()          *(u32 *)(sc_buf + RB_SC_CRC32_OFFSET) = 0
 140 #define RB_SC_GETCRC()          *(u32 *)(sc_buf + RB_SC_CRC32_OFFSET)
 141 #define RB_SC_SETCRC(_crc)      *(u32 *)(sc_buf + RB_SC_CRC32_OFFSET) = (_crc)
 142
 143 struct sc_u32tvs {
 144         const u32 val;
 145         const char *str;
 146 };
 147
 148 #define RB_SC_TVS(_val, _str) {         \
 149         .val = (_val),                  \
 150         .str = (_str),                  \
 151 }
 152
 153 static ssize_t sc_tag_show_u32tvs(const u8 *pld, u16 pld_len, char *buf,
 154                                   const struct sc_u32tvs tvs[], const int tvselmts)
 155 {
 156         const char *fmt;
 157         char *out = buf;
 158         u32 data;       // cpu-endian
 159         int i;
 160
 161         if (sizeof(data) != pld_len)
 162                 return -EINVAL;
 163
 164         read_lock(&sc_bufrwl);
 165         data = *(u32 *)pld;             // pld aliases sc_buf
 166         read_unlock(&sc_bufrwl);
 167
 168         for (i = 0; i < tvselmts; i++) {
 169                 fmt = (tvs[i].val == data) ? "[%s] " : "%s ";
 170                 out += sprintf(out, fmt, tvs[i].str);
 171         }
 172
 173         out += sprintf(out, "\n");
 174         return out - buf;
 175 }
 176
 177 static ssize_t sc_tag_store_u32tvs(const u8 *pld, u16 pld_len, const char *buf, size_t count,
 178                                    const struct sc_u32tvs tvs[], const int tvselmts)
 179 {
 180         int i;
 181
 182         if (sizeof(u32) != pld_len)
 183                 return -EINVAL;
 184
 185         for (i = 0; i < tvselmts; i++) {
 186                 if (sysfs_streq(buf, tvs[i].str)) {
 187                         write_lock(&sc_bufrwl);
 188                         *(u32 *)pld = tvs[i].val;       // pld aliases sc_buf
 189                         RB_SC_CLRCRC();
 190                         write_unlock(&sc_bufrwl);
 191                         return count;
 192                 }
 193         }
 194
 195         return -EINVAL;
 196 }
 197
 198 struct sc_boolts {
 199         const char *strfalse;
 200         const char *strtrue;
 201 };
 202
 203 static ssize_t sc_tag_show_boolts(const u8 *pld, u16 pld_len, char *buf,
 204                                   const struct sc_boolts *bts)
 205 {
 206         const char *fmt;
 207         char *out = buf;
 208         u32 data;       // cpu-endian
 209
 210         if (sizeof(data) != pld_len)
 211                 return -EINVAL;
 212
 213         read_lock(&sc_bufrwl);
 214         data = *(u32 *)pld;             // pld aliases sc_buf
 215         read_unlock(&sc_bufrwl);
 216
 217         fmt = (data) ? "%s [%s]\n" : "[%s] %s\n";
 218         out += sprintf(out, fmt, bts->strfalse, bts->strtrue);
 219
 220         return out - buf;
 221 }
 222
 223 static ssize_t sc_tag_store_boolts(const u8 *pld, u16 pld_len, const char *buf, size_t count,
 224                                    const struct sc_boolts *bts)
 225 {
 226         u32 data;       // cpu-endian
 227
 228         if (sizeof(data) != pld_len)
 229                 return -EINVAL;
 230
 231         if (sysfs_streq(buf, bts->strfalse))
 232                 data = 0;
 233         else if (sysfs_streq(buf, bts->strtrue))
 234                 data = 1;
 235         else
 236                 return -EINVAL;
 237
 238         write_lock(&sc_bufrwl);
 239         *(u32 *)pld = data;             // pld aliases sc_buf
 240         RB_SC_CLRCRC();
 241         write_unlock(&sc_bufrwl);
 242
 243         return count;
 244 }
 245 static struct sc_u32tvs const sc_uartspeeds[] = {
 246         RB_SC_TVS(RB_UART_SPEED_OFF,    "off"),
 247         RB_SC_TVS(RB_UART_SPEED_1200,   "1200"),
 248         RB_SC_TVS(RB_UART_SPEED_2400,   "2400"),
 249         RB_SC_TVS(RB_UART_SPEED_4800,   "4800"),
 250         RB_SC_TVS(RB_UART_SPEED_9600,   "9600"),
 251         RB_SC_TVS(RB_UART_SPEED_19200,  "19200"),
 252         RB_SC_TVS(RB_UART_SPEED_38400,  "38400"),
 253         RB_SC_TVS(RB_UART_SPEED_57600,  "57600"),
 254         RB_SC_TVS(RB_UART_SPEED_115200, "115200"),
 255 };
 256
 257 /*
 258  * While the defines are carried over from rbcfg, use strings that more clearly
 259  * show the actual setting purpose (especially since the NAND* settings apply
 260  * to both nand- and nor-based devices). "cfcard" was disabled in rbcfg: disable
 261  * it here too.
 262  */
 263 static struct sc_u32tvs const sc_bootdevices[] = {
 264         RB_SC_TVS(RB_BOOT_DEVICE_ETHER,         "eth"),
 265         RB_SC_TVS(RB_BOOT_DEVICE_NANDETH,       "flasheth"),
 266         //RB_SC_TVS(RB_BOOT_DEVICE_CFCARD,      "cfcard"),
 267         RB_SC_TVS(RB_BOOT_DEVICE_ETHONCE,       "ethonce"),
 268         RB_SC_TVS(RB_BOOT_DEVICE_NANDONLY,      "flash"),
 269         RB_SC_TVS(RB_BOOT_DEVICE_FLASHCFG,      "cfg"),
 270         RB_SC_TVS(RB_BOOT_DEVICE_FLSHONCE,      "cfgonce"),
 271 };
 272
 273 static struct sc_boolts const sc_bootkey = {
 274         .strfalse = "any",
 275         .strtrue = "del",
 276 };
 277
 278 static struct sc_boolts const sc_cpumode = {
 279         .strfalse = "powersave",
 280         .strtrue = "regular",
 281 };
 282
 283 static struct sc_boolts const sc_bootproto = {
 284         .strfalse = "bootp",
 285         .strtrue = "dhcp",
 286 };
 287
 288 static struct sc_boolts const sc_booter = {
 289         .strfalse = "regular",
 290         .strtrue = "backup",
 291 };
 292
 293 static struct sc_boolts const sc_silent_boot = {
 294         .strfalse = "off",
 295         .strtrue = "on",
 296 };
 297
 298 #define SC_TAG_SHOW_STORE_U32TVS_FUNCS(_name)           \
 299 static ssize_t sc_tag_show_##_name(const u8 *pld, u16 pld_len, char *buf)       \
 300 {                                                                               \
 301         return sc_tag_show_u32tvs(pld, pld_len, buf, sc_##_name, ARRAY_SIZE(sc_##_name));       \
 302 }                                                                               \
 303 static ssize_t sc_tag_store_##_name(const u8 *pld, u16 pld_len, const char *buf, size_t count)  \
 304 {                                                                               \
 305         return sc_tag_store_u32tvs(pld, pld_len, buf, count, sc_##_name, ARRAY_SIZE(sc_##_name));       \
 306 }
 307
 308 #define SC_TAG_SHOW_STORE_BOOLTS_FUNCS(_name)           \
 309 static ssize_t sc_tag_show_##_name(const u8 *pld, u16 pld_len, char *buf)       \
 310 {                                                                               \
 311         return sc_tag_show_boolts(pld, pld_len, buf, &sc_##_name);      \
 312 }                                                                               \
 313 static ssize_t sc_tag_store_##_name(const u8 *pld, u16 pld_len, const char *buf, size_t count)  \
 314 {                                                                               \
 315         return sc_tag_store_boolts(pld, pld_len, buf, count, &sc_##_name);      \
 316 }
 317
 318 SC_TAG_SHOW_STORE_U32TVS_FUNCS(uartspeeds)
 319 SC_TAG_SHOW_STORE_U32TVS_FUNCS(bootdevices)
 320 SC_TAG_SHOW_STORE_BOOLTS_FUNCS(bootkey)
 321 SC_TAG_SHOW_STORE_BOOLTS_FUNCS(cpumode)
 322 SC_TAG_SHOW_STORE_BOOLTS_FUNCS(bootproto)
 323 SC_TAG_SHOW_STORE_BOOLTS_FUNCS(booter)
 324 SC_TAG_SHOW_STORE_BOOLTS_FUNCS(silent_boot)
 325
 326 static ssize_t sc_tag_show_bootdelays(const u8 *pld, u16 pld_len, char *buf)
 327 {
 328         const char *fmt;
 329         char *out = buf;
 330         u32 data;       // cpu-endian
 331         int i;
 332
 333         if (sizeof(data) != pld_len)
 334                 return -EINVAL;
 335
 336         read_lock(&sc_bufrwl);
 337         data = *(u32 *)pld;             // pld aliases sc_buf
 338         read_unlock(&sc_bufrwl);
 339
 340         for (i = RB_BOOT_DELAY_MIN; i <= RB_BOOT_DELAY_MAX; i++) {
 341                 fmt = (i == data) ? "[%d] " : "%d ";
 342                 out += sprintf(out, fmt, i);
 343         }
 344
 345         out += sprintf(out, "\n");
 346         return out - buf;
 347 }
 348
 349 static ssize_t sc_tag_store_bootdelays(const u8 *pld, u16 pld_len, const char *buf, size_t count)
 350 {
 351         u32 data;       // cpu-endian
 352         int ret;
 353
 354         if (sizeof(data) != pld_len)
 355                 return -EINVAL;
 356
 357         ret = kstrtou32(buf, 10, &data);
 358         if (ret)
 359                 return ret;
 360
 361         if ((data < RB_BOOT_DELAY_MIN) || (RB_BOOT_DELAY_MAX < data))
 362                 return -EINVAL;
 363
 364         write_lock(&sc_bufrwl);
 365         *(u32 *)pld = data;             // pld aliases sc_buf
 366         RB_SC_CLRCRC();
 367         write_unlock(&sc_bufrwl);
 368
 369         return count;
 370 }
 371
 372 static ssize_t sc_attr_show(struct kobject *kobj, struct kobj_attribute *attr,
 373                             char *buf);
 374 static ssize_t sc_attr_store(struct kobject *kobj, struct kobj_attribute *attr,
 375                              const char *buf, size_t count);
 376
 377 /* Array of known tags to publish in sysfs */
 378 static struct sc_attr {
 379         const u16 tag_id;
 380         /* sysfs tag show attribute. Must lock sc_buf when dereferencing pld */
 381         ssize_t (* const tshow)(const u8 *pld, u16 pld_len, char *buf);
 382         /* sysfs tag store attribute. Must lock sc_buf when dereferencing pld */
 383         ssize_t (* const tstore)(const u8 *pld, u16 pld_len, const char *buf, size_t count);
 384         struct kobj_attribute kattr;
 385         u16 pld_ofs;
 386         u16 pld_len;
 387 } sc_attrs[] = {
 388         {
 389                 .tag_id = RB_SCID_UART_SPEED,
 390                 .tshow = sc_tag_show_uartspeeds,
 391                 .tstore = sc_tag_store_uartspeeds,
 392                 .kattr = __ATTR(uart_speed, RB_SC_RMODE|RB_SC_WMODE, sc_attr_show, sc_attr_store),
 393         }, {
 394                 .tag_id = RB_SCID_BOOT_DELAY,
 395                 .tshow = sc_tag_show_bootdelays,
 396                 .tstore = sc_tag_store_bootdelays,
 397                 .kattr = __ATTR(boot_delay, RB_SC_RMODE|RB_SC_WMODE, sc_attr_show, sc_attr_store),
 398         }, {
 399                 .tag_id = RB_SCID_BOOT_DEVICE,
 400                 .tshow = sc_tag_show_bootdevices,
 401                 .tstore = sc_tag_store_bootdevices,
 402                 .kattr = __ATTR(boot_device, RB_SC_RMODE|RB_SC_WMODE, sc_attr_show, sc_attr_store),
 403         }, {
 404                 .tag_id = RB_SCID_BOOT_KEY,
 405                 .tshow = sc_tag_show_bootkey,
 406                 .tstore = sc_tag_store_bootkey,
 407                 .kattr = __ATTR(boot_key, RB_SC_RMODE|RB_SC_WMODE, sc_attr_show, sc_attr_store),
 408         }, {
 409                 .tag_id = RB_SCID_CPU_MODE,
 410                 .tshow = sc_tag_show_cpumode,
 411                 .tstore = sc_tag_store_cpumode,
 412                 .kattr = __ATTR(cpu_mode, RB_SC_RMODE|RB_SC_WMODE, sc_attr_show, sc_attr_store),
 413         }, {
 414                 .tag_id = RB_SCID_BIOS_VERSION,
 415                 .tshow = routerboot_tag_show_string,
 416                 .tstore = NULL,
 417                 .kattr = __ATTR(bios_version, RB_SC_RMODE, sc_attr_show, NULL),
 418         }, {
 419                 .tag_id = RB_SCID_BOOT_PROTOCOL,
 420                 .tshow = sc_tag_show_bootproto,
 421                 .tstore = sc_tag_store_bootproto,
 422                 .kattr = __ATTR(boot_proto, RB_SC_RMODE|RB_SC_WMODE, sc_attr_show, sc_attr_store),
 423         }, {
 424                 .tag_id = RB_SCID_BOOTER,
 425                 .tshow = sc_tag_show_booter,
 426                 .tstore = sc_tag_store_booter,
 427                 .kattr = __ATTR(booter, RB_SC_RMODE|RB_SC_WMODE, sc_attr_show, sc_attr_store),
 428         }, {
 429                 .tag_id = RB_SCID_SILENT_BOOT,
 430                 .tshow = sc_tag_show_silent_boot,
 431                 .tstore = sc_tag_store_silent_boot,
 432                 .kattr = __ATTR(silent_boot, RB_SC_RMODE|RB_SC_WMODE, sc_attr_show, sc_attr_store),
 433         },
 434         // TODO CPU_FREQ
 435 };
 436
 437 static ssize_t sc_attr_show(struct kobject *kobj, struct kobj_attribute *attr,
 438                             char *buf)
 439 {
 440         const struct sc_attr *sc_attr;
 441         const u8 *pld;
 442         u16 pld_len;
 443
 444         sc_attr = container_of(attr, typeof(*sc_attr), kattr);
 445
 446         if (!sc_attr->pld_len)
 447                 return -ENOENT;
 448
 449         pld = sc_buf + sc_attr->pld_ofs;        // pld aliases sc_buf -> lock!
 450         pld_len = sc_attr->pld_len;
 451
 452         return sc_attr->tshow(pld, pld_len, buf);
 453 }
 454
 455 static ssize_t sc_attr_store(struct kobject *kobj, struct kobj_attribute *attr,
 456                              const char *buf, size_t count)
 457 {
 458         const struct sc_attr *sc_attr;
 459         const u8 *pld;
 460         u16 pld_len;
 461
 462         if (!RB_SC_HAS_WRITE_SUPPORT)
 463                 return -EOPNOTSUPP;
 464
 465         if (!capable(CAP_SYS_ADMIN))
 466                 return -EACCES;
 467
 468         sc_attr = container_of(attr, typeof(*sc_attr), kattr);
 469
 470         if (!sc_attr->tstore)
 471                 return -EOPNOTSUPP;
 472
 473         if (!sc_attr->pld_len)
 474                 return -ENOENT;
 475
 476         pld = sc_buf + sc_attr->pld_ofs;        // pld aliases sc_buf -> lock!
 477         pld_len = sc_attr->pld_len;
 478
 479         return sc_attr->tstore(pld, pld_len, buf, count);
 480 }
 481
 482 /*
 483  * Shows the current buffer status:
 484  * "clean": the buffer is in sync with the mtd data
 485  * "dirty": the buffer is out of sync with the mtd data
 486  */
 487 static ssize_t sc_commit_show(struct kobject *kobj, struct kobj_attribute *attr,
 488                               char *buf)
 489 {
 490         const char *str;
 491         char *out = buf;
 492         u32 crc;
 493
 494         read_lock(&sc_bufrwl);
 495         crc = RB_SC_GETCRC();
 496         read_unlock(&sc_bufrwl);
 497
 498         str = (crc) ? "clean" : "dirty";
 499         out += sprintf(out, "%s\n", str);
 500
 501         return out - buf;
 502 }
 503
 504 /*
 505  * Performs buffer flushing:
 506  * This routine expects an input compatible with kstrtobool().
 507  * - a "false" input discards the current changes and reads data back from mtd.
 508  * - a "true" input commits the current changes to mtd.
 509  * If there is no pending changes, this routine is a no-op.
 510  * Handling failures is left as an exercise to userspace.
 511  */
 512 static ssize_t sc_commit_store(struct kobject *kobj, struct kobj_attribute *attr,
 513                               const char *buf, size_t count)
 514 {
 515         struct mtd_info *mtd;
 516         struct erase_info ei;
 517         size_t bytes_rw, ret = count;
 518         bool flush;
 519         u32 crc;
 520
 521         if (!RB_SC_HAS_WRITE_SUPPORT)
 522                 return -EOPNOTSUPP;
 523
 524         read_lock(&sc_bufrwl);
 525         crc = RB_SC_GETCRC();
 526         read_unlock(&sc_bufrwl);
 527
 528         if (crc)
 529                 return count;   // NO-OP
 530
 531         ret = kstrtobool(buf, &flush);
 532         if (ret)
 533                 return ret;
 534
 535         mtd = get_mtd_device_nm(RB_MTD_SOFT_CONFIG);    // TODO allow override
 536         if (IS_ERR(mtd))
 537                 return -ENODEV;
 538
 539         write_lock(&sc_bufrwl);
 540         if (!flush)     // reread
 541                 ret = mtd_read(mtd, 0, mtd->size, &bytes_rw, sc_buf);
 542         else {  // crc32 + commit
 543                 /*
 544                  * CRC32 is computed on the entire buffer, excluding the CRC
 545                  * value itself. CRC is already null when we reach this point,
 546                  * so we can compute the CRC32 on the buffer as is.
 547                  * The expected CRC32 is Ethernet FCS style, meaning the seed is
 548                  * ~0 and the final result is also bitflipped.
 549                  */
 550
 551                 crc = ~crc32(~0, sc_buf, sc_buflen);
 552                 RB_SC_SETCRC(crc);
 553
 554                 /*
 555                  * The soft_config partition is assumed to be entirely contained
 556                  * in a single eraseblock.
 557                  */
 558
 559                 ei.addr = 0;
 560                 ei.len = mtd->size;
 561                 ret = mtd_erase(mtd, &ei);
 562                 if (!ret)
 563                         ret = mtd_write(mtd, 0, mtd->size, &bytes_rw, sc_buf);
 564
 565                 /*
 566                  * Handling mtd_write() failure here is a tricky situation. The
 567                  * proposed approach is to let userspace deal with retrying,
 568                  * with the caveat that it must try to flush the buffer again as
 569                  * rereading the mtd contents could potentially read garbage.
 570                  * The rationale is: even if we keep a shadow buffer of the
 571                  * original content, there is no guarantee that we will ever be
 572                  * able to write it anyway.
 573                  * Regardless, it appears that RouterBOOT will ignore an invalid
 574                  * soft_config (including a completely wiped segment) and will
 575                  * write back factory defaults when it happens.
 576                  */
 577         }
 578         write_unlock(&sc_bufrwl);
 579
 580         if (ret)
 581                 goto mtdfail;
 582
 583         if (bytes_rw != sc_buflen) {
 584                 ret = -EIO;
 585                 goto mtdfail;
 586         }
 587
 588         return count;
 589
 590 mtdfail:
 591         RB_SC_CLRCRC(); // mark buffer content as dirty/invalid
 592         return ret;
 593 }
 594
 595 static struct kobj_attribute sc_kattrcommit = __ATTR(commit, RB_SC_RMODE|RB_SC_WMODE, sc_commit_show, sc_commit_store);
 596
 597 int __init rb_softconfig_init(struct kobject *rb_kobj)
 598 {
 599         struct mtd_info *mtd;
 600         size_t bytes_read, buflen;
 601         const u8 *buf;
 602         int i, ret;
 603         u32 magic;
 604
 605         sc_buf = NULL;
 606         sc_kobj = NULL;
 607
 608         // TODO allow override
 609         mtd = get_mtd_device_nm(RB_MTD_SOFT_CONFIG);
 610         if (IS_ERR(mtd))
 611                 return -ENODEV;
 612
 613         sc_buflen = mtd->size;
 614         sc_buf = kmalloc(sc_buflen, GFP_KERNEL);
 615         if (!sc_buf)
 616                 return -ENOMEM;
 617
 618         ret = mtd_read(mtd, 0, sc_buflen, &bytes_read, sc_buf);
 619
 620         if (ret)
 621                 goto fail;
 622
 623         if (bytes_read != sc_buflen) {
 624                 ret = -EIO;
 625                 goto fail;
 626         }
 627
 628         /* Check we have what we expect */
 629         magic = *(const u32 *)sc_buf;
 630         if (RB_MAGIC_SOFT != magic) {
 631                 ret = -EINVAL;
 632                 goto fail;
 633         }
 634
 635         /* Skip magic and 32bit CRC located immediately after */
 636         buf = sc_buf + (sizeof(magic) + sizeof(u32));
 637         buflen = sc_buflen - (sizeof(magic) + sizeof(u32));
 638
 639         /* Populate sysfs */
 640         ret = -ENOMEM;
 641         sc_kobj = kobject_create_and_add(RB_MTD_SOFT_CONFIG, rb_kobj);
 642         if (!sc_kobj)
 643                 goto fail;
 644
 645         rwlock_init(&sc_bufrwl);
 646
 647         /* Locate and publish all known tags */
 648         for (i = 0; i < ARRAY_SIZE(sc_attrs); i++) {
 649                 ret = routerboot_tag_find(buf, buflen, sc_attrs[i].tag_id,
 650                                           &sc_attrs[i].pld_ofs, &sc_attrs[i].pld_len);
 651                 if (ret) {
 652                         sc_attrs[i].pld_ofs = sc_attrs[i].pld_len = 0;
 653                         continue;
 654                 }
 655
 656                 /* Account for skipped magic and crc32 */
 657                 sc_attrs[i].pld_ofs += sizeof(magic) + sizeof(u32);
 658
 659                 ret = sysfs_create_file(sc_kobj, &sc_attrs[i].kattr.attr);
 660                 if (ret)
 661                         pr_warn(RB_SC_PR_PFX "Could not create %s sysfs entry (%d)\n",
 662                                sc_attrs[i].kattr.attr.name, ret);
 663         }
 664
 665         /* Finally add the 'commit' attribute */
 666         if (RB_SC_HAS_WRITE_SUPPORT) {
 667                 ret = sysfs_create_file(sc_kobj, &sc_kattrcommit.attr);
 668                 if (ret) {
 669                         pr_err(RB_SC_PR_PFX "Could not create %s sysfs entry (%d), aborting!\n",
 670                                sc_kattrcommit.attr.name, ret);
 671                         goto sysfsfail; // required attribute
 672                 }
 673         }
 674
 675         pr_info("MikroTik RouterBOARD software configuration sysfs driver v" RB_SOFTCONFIG_VER "\n");
 676
 677         return 0;
 678
 679 sysfsfail:
 680         kobject_put(sc_kobj);
 681         sc_kobj = NULL;
 682 fail:
 683         kfree(sc_buf);
 684         sc_buf = NULL;
 685         return ret;
 686 }
 687
 688 void __exit rb_softconfig_exit(void)
 689 {
 690         kobject_put(sc_kobj);
 691         kfree(sc_buf);
 692 }