1 // SPDX-License-Identifier: GPL-2.0-only 2 /*====================================================================== 3 4 This driver provides a method to access memory not used by the kernel 5 itself (i.e. if the kernel commandline mem=xxx is used). To actually 6 use slram at least mtdblock or mtdchar is required (for block or 7 character device access). 8 9 Usage: 10 11 if compiled as loadable module: 12 modprobe slram map=<name>,<start>,<end/offset> 13 if statically linked into the kernel use the following kernel cmd.line 14 slram=<name>,<start>,<end/offset> 15 16 <name>: name of the device that will be listed in /proc/mtd 17 <start>: start of the memory region, decimal or hex (0xabcdef) 18 <end/offset>: end of the memory region. It's possible to use +0x1234 19 to specify the offset instead of the absolute address 20 21 NOTE: 22 With slram it's only possible to map a contiguous memory region. Therefore 23 if there's a device mapped somewhere in the region specified slram will 24 fail to load (see kernel log if modprobe fails). 25 26 - 27 28 Jochen Schaeuble <psionic@psionic.de> 29 30 ======================================================================*/ 31 32 33 #include <linux/module.h> 34 #include <linux/uaccess.h> 35 #include <linux/types.h> 36 #include <linux/kernel.h> 37 #include <linux/ptrace.h> 38 #include <linux/slab.h> 39 #include <linux/string.h> 40 #include <linux/timer.h> 41 #include <linux/major.h> 42 #include <linux/fs.h> 43 #include <linux/ioctl.h> 44 #include <linux/init.h> 45 #include <linux/io.h> 46 47 #include <linux/mtd/mtd.h> 48 49 #define SLRAM_MAX_DEVICES_PARAMS 6 /* 3 parameters / device */ 50 #define SLRAM_BLK_SZ 0x4000 51 52 #define T(fmt, args...) printk(KERN_DEBUG fmt, ## args) 53 #define E(fmt, args...) printk(KERN_NOTICE fmt, ## args) 54 55 typedef struct slram_priv { 56 u_char *start; 57 u_char *end; 58 } slram_priv_t; 59 60 typedef struct slram_mtd_list { 61 struct mtd_info *mtdinfo; 62 struct slram_mtd_list *next; 63 } slram_mtd_list_t; 64 65 #ifdef MODULE 66 static char *map[SLRAM_MAX_DEVICES_PARAMS]; 67 68 module_param_array(map, charp, NULL, 0); 69 MODULE_PARM_DESC(map, "List of memory regions to map. \"map=<name>, <start>, <length / end>\""); 70 #else 71 static char *map; 72 #endif 73 74 static slram_mtd_list_t *slram_mtdlist = NULL; 75 76 static int slram_erase(struct mtd_info *, struct erase_info *); 77 static int slram_point(struct mtd_info *, loff_t, size_t, size_t *, void **, 78 resource_size_t *); 79 static int slram_unpoint(struct mtd_info *, loff_t, size_t); 80 static int slram_read(struct mtd_info *, loff_t, size_t, size_t *, u_char *); 81 static int slram_write(struct mtd_info *, loff_t, size_t, size_t *, const u_char *); 82 83 static int slram_erase(struct mtd_info *mtd, struct erase_info *instr) 84 { 85 slram_priv_t *priv = mtd->priv; 86 87 memset(priv->start + instr->addr, 0xff, instr->len); 88 89 return(0); 90 } 91 92 static int slram_point(struct mtd_info *mtd, loff_t from, size_t len, 93 size_t *retlen, void **virt, resource_size_t *phys) 94 { 95 slram_priv_t *priv = mtd->priv; 96 97 *virt = priv->start + from; 98 *retlen = len; 99 return(0); 100 } 101 102 static int slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len) 103 { 104 return 0; 105 } 106 107 static int slram_read(struct mtd_info *mtd, loff_t from, size_t len, 108 size_t *retlen, u_char *buf) 109 { 110 slram_priv_t *priv = mtd->priv; 111 112 memcpy(buf, priv->start + from, len); 113 *retlen = len; 114 return(0); 115 } 116 117 static int slram_write(struct mtd_info *mtd, loff_t to, size_t len, 118 size_t *retlen, const u_char *buf) 119 { 120 slram_priv_t *priv = mtd->priv; 121 122 memcpy(priv->start + to, buf, len); 123 *retlen = len; 124 return(0); 125 } 126 127 /*====================================================================*/ 128 129 static int register_device(char *name, unsigned long start, unsigned long length) 130 { 131 slram_mtd_list_t **curmtd; 132 slram_mtd_list_t *new_mtd; 133 struct mtd_info *mtdinfo; 134 slram_priv_t *priv; 135 int ret = -ENOMEM; 136 137 curmtd = &slram_mtdlist; 138 while (*curmtd) { 139 curmtd = &(*curmtd)->next; 140 } 141 142 new_mtd = kmalloc_obj(slram_mtd_list_t); 143 if (!new_mtd) { 144 E("slram: Cannot allocate new MTD device.\n"); 145 return(-ENOMEM); 146 } 147 new_mtd->next = NULL; 148 149 mtdinfo = kzalloc_obj(struct mtd_info); 150 if (!mtdinfo) { 151 E("slram: Cannot allocate new MTD device.\n"); 152 goto err_free_list; 153 } 154 new_mtd->mtdinfo = mtdinfo; 155 156 priv = kzalloc_obj(slram_priv_t); 157 if (!priv) { 158 E("slram: Cannot allocate new MTD device.\n"); 159 goto err_free_mtdinfo; 160 } 161 mtdinfo->priv = priv; 162 163 priv->start = memremap(start, length, 164 MEMREMAP_WB | MEMREMAP_WT | MEMREMAP_WC); 165 if (!priv->start) { 166 E("slram: memremap failed\n"); 167 ret = -EIO; 168 goto err_free_priv; 169 } 170 priv->end = priv->start + length; 171 172 mtdinfo->name = name; 173 mtdinfo->size = length; 174 mtdinfo->flags = MTD_CAP_RAM; 175 mtdinfo->_erase = slram_erase; 176 mtdinfo->_point = slram_point; 177 mtdinfo->_unpoint = slram_unpoint; 178 mtdinfo->_read = slram_read; 179 mtdinfo->_write = slram_write; 180 mtdinfo->owner = THIS_MODULE; 181 mtdinfo->type = MTD_RAM; 182 mtdinfo->erasesize = SLRAM_BLK_SZ; 183 mtdinfo->writesize = 1; 184 185 if (mtd_device_register(mtdinfo, NULL, 0)) { 186 E("slram: Failed to register new device\n"); 187 ret = -EAGAIN; 188 goto err_unmap; 189 } 190 *curmtd = new_mtd; 191 T("slram: Registered device %s from %luKiB to %luKiB\n", name, 192 (start / 1024), ((start + length) / 1024)); 193 T("slram: Mapped from 0x%p to 0x%p\n", priv->start, priv->end); 194 return 0; 195 196 err_unmap: 197 memunmap(priv->start); 198 err_free_priv: 199 kfree(priv); 200 err_free_mtdinfo: 201 kfree(mtdinfo); 202 err_free_list: 203 kfree(new_mtd); 204 return ret; 205 } 206 207 static void unregister_devices(void) 208 { 209 slram_mtd_list_t *nextitem; 210 211 while (slram_mtdlist) { 212 nextitem = slram_mtdlist->next; 213 mtd_device_unregister(slram_mtdlist->mtdinfo); 214 memunmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start); 215 kfree(slram_mtdlist->mtdinfo->priv); 216 kfree(slram_mtdlist->mtdinfo); 217 kfree(slram_mtdlist); 218 slram_mtdlist = nextitem; 219 } 220 } 221 222 static unsigned long handle_unit(unsigned long value, char *unit) 223 { 224 if ((*unit == 'M') || (*unit == 'm')) { 225 return(value * 1024 * 1024); 226 } else if ((*unit == 'K') || (*unit == 'k')) { 227 return(value * 1024); 228 } 229 return(value); 230 } 231 232 static int parse_cmdline(char *devname, char *szstart, char *szlength) 233 { 234 char *buffer; 235 unsigned long devstart; 236 unsigned long devlength; 237 238 if ((!devname) || (!szstart) || (!szlength)) { 239 unregister_devices(); 240 return(-EINVAL); 241 } 242 243 devstart = simple_strtoul(szstart, &buffer, 0); 244 devstart = handle_unit(devstart, buffer); 245 246 if (*(szlength) != '+') { 247 devlength = simple_strtoul(szlength, &buffer, 0); 248 devlength = handle_unit(devlength, buffer); 249 if (devlength < devstart) 250 goto err_out; 251 252 devlength -= devstart; 253 } else { 254 devlength = simple_strtoul(szlength + 1, &buffer, 0); 255 devlength = handle_unit(devlength, buffer); 256 } 257 T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx\n", 258 devname, devstart, devlength); 259 if (devlength % SLRAM_BLK_SZ != 0) 260 goto err_out; 261 262 if ((devstart = register_device(devname, devstart, devlength))){ 263 unregister_devices(); 264 return((int)devstart); 265 } 266 return(0); 267 268 err_out: 269 E("slram: Illegal length parameter.\n"); 270 return(-EINVAL); 271 } 272 273 #ifndef MODULE 274 275 static int __init mtd_slram_setup(char *str) 276 { 277 map = str; 278 return(1); 279 } 280 281 __setup("slram=", mtd_slram_setup); 282 283 #endif 284 285 static int __init init_slram(void) 286 { 287 char *devname; 288 289 #ifndef MODULE 290 char *devstart; 291 char *devlength; 292 293 if (!map) { 294 E("slram: not enough parameters.\n"); 295 return(-EINVAL); 296 } 297 while (map) { 298 devname = devstart = devlength = NULL; 299 300 if (!(devname = strsep(&map, ","))) { 301 E("slram: No devicename specified.\n"); 302 break; 303 } 304 T("slram: devname = %s\n", devname); 305 if ((!map) || (!(devstart = strsep(&map, ",")))) { 306 E("slram: No devicestart specified.\n"); 307 break; 308 } 309 T("slram: devstart = %s\n", devstart); 310 if ((!map) || (!(devlength = strsep(&map, ",")))) { 311 E("slram: No devicelength / -end specified.\n"); 312 break; 313 } 314 T("slram: devlength = %s\n", devlength); 315 if (parse_cmdline(devname, devstart, devlength) != 0) { 316 return(-EINVAL); 317 } 318 } 319 #else 320 int count; 321 int i; 322 323 for (count = 0; count < SLRAM_MAX_DEVICES_PARAMS && map[count]; 324 count++) { 325 } 326 327 if ((count % 3 != 0) || (count == 0)) { 328 E("slram: not enough parameters.\n"); 329 return(-EINVAL); 330 } 331 for (i = 0; i < (count / 3); i++) { 332 devname = map[i * 3]; 333 334 if (parse_cmdline(devname, map[i * 3 + 1], map[i * 3 + 2])!=0) { 335 return(-EINVAL); 336 } 337 338 } 339 #endif /* !MODULE */ 340 341 return(0); 342 } 343 344 static void __exit cleanup_slram(void) 345 { 346 unregister_devices(); 347 } 348 349 module_init(init_slram); 350 module_exit(cleanup_slram); 351 352 MODULE_LICENSE("GPL"); 353 MODULE_AUTHOR("Jochen Schaeuble <psionic@psionic.de>"); 354 MODULE_DESCRIPTION("MTD driver for uncached system RAM"); 355