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; 132 133 curmtd = &slram_mtdlist; 134 while (*curmtd) { 135 curmtd = &(*curmtd)->next; 136 } 137 138 *curmtd = kmalloc(sizeof(slram_mtd_list_t), GFP_KERNEL); 139 if (!(*curmtd)) { 140 E("slram: Cannot allocate new MTD device.\n"); 141 return(-ENOMEM); 142 } 143 (*curmtd)->mtdinfo = kzalloc(sizeof(struct mtd_info), GFP_KERNEL); 144 (*curmtd)->next = NULL; 145 146 if ((*curmtd)->mtdinfo) { 147 (*curmtd)->mtdinfo->priv = 148 kzalloc(sizeof(slram_priv_t), GFP_KERNEL); 149 150 if (!(*curmtd)->mtdinfo->priv) { 151 kfree((*curmtd)->mtdinfo); 152 (*curmtd)->mtdinfo = NULL; 153 } 154 } 155 156 if (!(*curmtd)->mtdinfo) { 157 E("slram: Cannot allocate new MTD device.\n"); 158 return(-ENOMEM); 159 } 160 161 if (!(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start = 162 memremap(start, length, 163 MEMREMAP_WB | MEMREMAP_WT | MEMREMAP_WC))) { 164 E("slram: memremap failed\n"); 165 return -EIO; 166 } 167 ((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end = 168 ((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start + length; 169 170 171 (*curmtd)->mtdinfo->name = name; 172 (*curmtd)->mtdinfo->size = length; 173 (*curmtd)->mtdinfo->flags = MTD_CAP_RAM; 174 (*curmtd)->mtdinfo->_erase = slram_erase; 175 (*curmtd)->mtdinfo->_point = slram_point; 176 (*curmtd)->mtdinfo->_unpoint = slram_unpoint; 177 (*curmtd)->mtdinfo->_read = slram_read; 178 (*curmtd)->mtdinfo->_write = slram_write; 179 (*curmtd)->mtdinfo->owner = THIS_MODULE; 180 (*curmtd)->mtdinfo->type = MTD_RAM; 181 (*curmtd)->mtdinfo->erasesize = SLRAM_BLK_SZ; 182 (*curmtd)->mtdinfo->writesize = 1; 183 184 if (mtd_device_register((*curmtd)->mtdinfo, NULL, 0)) { 185 E("slram: Failed to register new device\n"); 186 memunmap(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start); 187 kfree((*curmtd)->mtdinfo->priv); 188 kfree((*curmtd)->mtdinfo); 189 return(-EAGAIN); 190 } 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", 194 ((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start, 195 ((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end); 196 return(0); 197 } 198 199 static void unregister_devices(void) 200 { 201 slram_mtd_list_t *nextitem; 202 203 while (slram_mtdlist) { 204 nextitem = slram_mtdlist->next; 205 mtd_device_unregister(slram_mtdlist->mtdinfo); 206 memunmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start); 207 kfree(slram_mtdlist->mtdinfo->priv); 208 kfree(slram_mtdlist->mtdinfo); 209 kfree(slram_mtdlist); 210 slram_mtdlist = nextitem; 211 } 212 } 213 214 static unsigned long handle_unit(unsigned long value, char *unit) 215 { 216 if ((*unit == 'M') || (*unit == 'm')) { 217 return(value * 1024 * 1024); 218 } else if ((*unit == 'K') || (*unit == 'k')) { 219 return(value * 1024); 220 } 221 return(value); 222 } 223 224 static int parse_cmdline(char *devname, char *szstart, char *szlength) 225 { 226 char *buffer; 227 unsigned long devstart; 228 unsigned long devlength; 229 230 if ((!devname) || (!szstart) || (!szlength)) { 231 unregister_devices(); 232 return(-EINVAL); 233 } 234 235 devstart = simple_strtoul(szstart, &buffer, 0); 236 devstart = handle_unit(devstart, buffer); 237 238 if (*(szlength) != '+') { 239 devlength = simple_strtoul(szlength, &buffer, 0); 240 devlength = handle_unit(devlength, buffer); 241 if (devlength < devstart) 242 goto err_out; 243 244 devlength -= devstart; 245 } else { 246 devlength = simple_strtoul(szlength + 1, &buffer, 0); 247 devlength = handle_unit(devlength, buffer); 248 } 249 T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx\n", 250 devname, devstart, devlength); 251 if (devlength % SLRAM_BLK_SZ != 0) 252 goto err_out; 253 254 if ((devstart = register_device(devname, devstart, devlength))){ 255 unregister_devices(); 256 return((int)devstart); 257 } 258 return(0); 259 260 err_out: 261 E("slram: Illegal length parameter.\n"); 262 return(-EINVAL); 263 } 264 265 #ifndef MODULE 266 267 static int __init mtd_slram_setup(char *str) 268 { 269 map = str; 270 return(1); 271 } 272 273 __setup("slram=", mtd_slram_setup); 274 275 #endif 276 277 static int __init init_slram(void) 278 { 279 char *devname; 280 281 #ifndef MODULE 282 char *devstart; 283 char *devlength; 284 285 if (!map) { 286 E("slram: not enough parameters.\n"); 287 return(-EINVAL); 288 } 289 while (map) { 290 devname = devstart = devlength = NULL; 291 292 if (!(devname = strsep(&map, ","))) { 293 E("slram: No devicename specified.\n"); 294 break; 295 } 296 T("slram: devname = %s\n", devname); 297 if ((!map) || (!(devstart = strsep(&map, ",")))) { 298 E("slram: No devicestart specified.\n"); 299 break; 300 } 301 T("slram: devstart = %s\n", devstart); 302 if ((!map) || (!(devlength = strsep(&map, ",")))) { 303 E("slram: No devicelength / -end specified.\n"); 304 break; 305 } 306 T("slram: devlength = %s\n", devlength); 307 if (parse_cmdline(devname, devstart, devlength) != 0) { 308 return(-EINVAL); 309 } 310 } 311 #else 312 int count; 313 int i; 314 315 for (count = 0; count < SLRAM_MAX_DEVICES_PARAMS && map[count]; 316 count++) { 317 } 318 319 if ((count % 3 != 0) || (count == 0)) { 320 E("slram: not enough parameters.\n"); 321 return(-EINVAL); 322 } 323 for (i = 0; i < (count / 3); i++) { 324 devname = map[i * 3]; 325 326 if (parse_cmdline(devname, map[i * 3 + 1], map[i * 3 + 2])!=0) { 327 return(-EINVAL); 328 } 329 330 } 331 #endif /* !MODULE */ 332 333 return(0); 334 } 335 336 static void __exit cleanup_slram(void) 337 { 338 unregister_devices(); 339 } 340 341 module_init(init_slram); 342 module_exit(cleanup_slram); 343 344 MODULE_LICENSE("GPL"); 345 MODULE_AUTHOR("Jochen Schaeuble <psionic@psionic.de>"); 346 MODULE_DESCRIPTION("MTD driver for uncached system RAM"); 347