Googler | b48fa91 | 2023-03-17 12:40:29 +0530 | [diff] [blame^] | 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* |
| 3 | * Driver for MikroTik RouterBoot flash data. Common routines. |
| 4 | * |
| 5 | * Copyright (C) 2020 Thibaut VARĂˆNE <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 | |
| 12 | #include <linux/types.h> |
| 13 | #include <linux/module.h> |
| 14 | #include <linux/kernel.h> |
| 15 | #include <linux/sysfs.h> |
| 16 | |
| 17 | #include "routerboot.h" |
| 18 | |
| 19 | static struct kobject *rb_kobj; |
| 20 | |
| 21 | /** |
| 22 | * routerboot_tag_find() - Locate a given tag in routerboot config data. |
| 23 | * @bufhead: the buffer to look into. Must start with a tag node. |
| 24 | * @buflen: size of bufhead |
| 25 | * @tag_id: the tag identifier to look for |
| 26 | * @pld_ofs: will be updated with tag payload offset in bufhead, if tag found |
| 27 | * @pld_len: will be updated with tag payload size, if tag found |
| 28 | * |
| 29 | * This incarnation of tag_find() does only that: it finds a specific routerboot |
| 30 | * tag node in the input buffer. Routerboot tag nodes are u32 values: |
| 31 | * - The low nibble is the tag identification number, |
| 32 | * - The high nibble is the tag payload length (node excluded) in bytes. |
| 33 | * The payload immediately follows the tag node. Tag nodes are 32bit-aligned. |
| 34 | * The returned pld_ofs will always be aligned. pld_len may not end on 32bit |
| 35 | * boundary (the only known case is when parsing ERD data). |
| 36 | * The nodes are cpu-endian on the flash media. The payload is cpu-endian when |
| 37 | * applicable. Tag nodes are not ordered (by ID) on flash. |
| 38 | * |
| 39 | * Return: 0 on success (tag found) or errno |
| 40 | */ |
| 41 | int routerboot_tag_find(const u8 *bufhead, const size_t buflen, const u16 tag_id, |
| 42 | u16 *pld_ofs, u16 *pld_len) |
| 43 | { |
| 44 | const u32 *datum, *bufend; |
| 45 | u32 node; |
| 46 | u16 id, len; |
| 47 | int ret; |
| 48 | |
| 49 | if (!bufhead || !tag_id) |
| 50 | return -EINVAL; |
| 51 | |
| 52 | ret = -ENOENT; |
| 53 | datum = (const u32 *)bufhead; |
| 54 | bufend = (const u32 *)(bufhead + buflen); |
| 55 | |
| 56 | while (datum < bufend) { |
| 57 | node = *datum++; |
| 58 | |
| 59 | /* Tag list ends with null node */ |
| 60 | if (!node) |
| 61 | break; |
| 62 | |
| 63 | id = node & 0xFFFF; |
| 64 | len = node >> 16; |
| 65 | |
| 66 | if (tag_id == id) { |
| 67 | if (datum >= bufend) |
| 68 | break; |
| 69 | |
| 70 | if (pld_ofs) |
| 71 | *pld_ofs = (u16)((u8 *)datum - bufhead); |
| 72 | if (pld_len) |
| 73 | *pld_len = len; |
| 74 | |
| 75 | ret = 0; |
| 76 | break; |
| 77 | } |
| 78 | |
| 79 | /* |
| 80 | * The only known situation where len may not end on 32bit |
| 81 | * boundary is within ERD data. Since we're only extracting |
| 82 | * one tag (the first and only one) from that data, we should |
| 83 | * never need to forcefully ALIGN(). Do it anyway, this is not a |
| 84 | * performance path. |
| 85 | */ |
| 86 | len = ALIGN(len, sizeof(*datum)); |
| 87 | datum += len / sizeof(*datum); |
| 88 | } |
| 89 | |
| 90 | return ret; |
| 91 | } |
| 92 | |
| 93 | /** |
| 94 | * routerboot_rle_decode() - Simple RLE (MikroTik variant) decoding routine. |
| 95 | * @in: input buffer to decode |
| 96 | * @inlen: size of in |
| 97 | * @out: output buffer to write decoded data to |
| 98 | * @outlen: pointer to out size when function is called, will be updated with |
| 99 | * size of decoded output on return |
| 100 | * |
| 101 | * MikroTik's variant of RLE operates as follows, considering a signed run byte: |
| 102 | * - positive run => classic RLE |
| 103 | * - negative run => the next -<run> bytes must be copied verbatim |
| 104 | * The API is matched to the lzo1x routines for convenience. |
| 105 | * |
| 106 | * NB: The output buffer cannot overlap with the input buffer. |
| 107 | * |
| 108 | * Return: 0 on success or errno |
| 109 | */ |
| 110 | int routerboot_rle_decode(const u8 *in, size_t inlen, u8 *out, size_t *outlen) |
| 111 | { |
| 112 | int ret, run, nbytes; // use native types for speed |
| 113 | u8 byte; |
| 114 | |
| 115 | if (!in || (inlen < 2) || !out) |
| 116 | return -EINVAL; |
| 117 | |
| 118 | ret = -ENOSPC; |
| 119 | nbytes = 0; |
| 120 | while (inlen >= 2) { |
| 121 | run = *in++; |
| 122 | inlen--; |
| 123 | |
| 124 | /* Verbatim copies */ |
| 125 | if (run & 0x80) { |
| 126 | /* Invert run byte sign */ |
| 127 | run = ~run & 0xFF; |
| 128 | run++; |
| 129 | |
| 130 | if (run > inlen) |
| 131 | goto fail; |
| 132 | |
| 133 | inlen -= run; |
| 134 | |
| 135 | nbytes += run; |
| 136 | if (nbytes > *outlen) |
| 137 | goto fail; |
| 138 | |
| 139 | /* Basic memcpy */ |
| 140 | while (run-- > 0) |
| 141 | *out++ = *in++; |
| 142 | } |
| 143 | /* Stream of half-words RLE: <run><byte>. run == 0 is ignored */ |
| 144 | else { |
| 145 | byte = *in++; |
| 146 | inlen--; |
| 147 | |
| 148 | nbytes += run; |
| 149 | if (nbytes > *outlen) |
| 150 | goto fail; |
| 151 | |
| 152 | while (run-- > 0) |
| 153 | *out++ = byte; |
| 154 | } |
| 155 | } |
| 156 | |
| 157 | ret = 0; |
| 158 | fail: |
| 159 | *outlen = nbytes; |
| 160 | return ret; |
| 161 | } |
| 162 | |
| 163 | static int __init routerboot_init(void) |
| 164 | { |
| 165 | rb_kobj = kobject_create_and_add("mikrotik", firmware_kobj); |
| 166 | if (!rb_kobj) |
| 167 | return -ENOMEM; |
| 168 | |
| 169 | /* |
| 170 | * We ignore the following return values and always register. |
| 171 | * These init() routines are designed so that their failed state is |
| 172 | * always manageable by the corresponding exit() calls. |
| 173 | */ |
| 174 | rb_hardconfig_init(rb_kobj); |
| 175 | rb_softconfig_init(rb_kobj); |
| 176 | |
| 177 | return 0; |
| 178 | } |
| 179 | |
| 180 | static void __exit routerboot_exit(void) |
| 181 | { |
| 182 | rb_softconfig_exit(); |
| 183 | rb_hardconfig_exit(); |
| 184 | kobject_put(rb_kobj); // recursive afaict |
| 185 | } |
| 186 | |
| 187 | /* Common routines */ |
| 188 | |
| 189 | ssize_t routerboot_tag_show_string(const u8 *pld, u16 pld_len, char *buf) |
| 190 | { |
| 191 | return scnprintf(buf, pld_len+1, "%s\n", pld); |
| 192 | } |
| 193 | |
| 194 | ssize_t routerboot_tag_show_u32s(const u8 *pld, u16 pld_len, char *buf) |
| 195 | { |
| 196 | char *out = buf; |
| 197 | u32 *data; // cpu-endian |
| 198 | |
| 199 | /* Caller ensures pld_len > 0 */ |
| 200 | if (pld_len % sizeof(*data)) |
| 201 | return -EINVAL; |
| 202 | |
| 203 | data = (u32 *)pld; |
| 204 | |
| 205 | do { |
| 206 | out += sprintf(out, "0x%08x\n", *data); |
| 207 | data++; |
| 208 | } while ((pld_len -= sizeof(*data))); |
| 209 | |
| 210 | return out - buf; |
| 211 | } |
| 212 | |
| 213 | module_init(routerboot_init); |
| 214 | module_exit(routerboot_exit); |
| 215 | |
| 216 | MODULE_LICENSE("GPL v2"); |
| 217 | MODULE_DESCRIPTION("MikroTik RouterBoot sysfs support"); |
| 218 | MODULE_AUTHOR("Thibaut VARENE"); |