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1// SPDX-License-Identifier: GPL-2.0-only2/*======================================================================3 4 This driver provides a method to access memory not used by the kernel5 itself (i.e. if the kernel commandline mem=xxx is used). To actually6 use slram at least mtdblock or mtdchar is required (for block or7 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.line14 slram=<name>,<start>,<end/offset>15 16 <name>: name of the device that will be listed in /proc/mtd17 <start>: start of the memory region, decimal or hex (0xabcdef)18 <end/offset>: end of the memory region. It's possible to use +0x123419 to specify the offset instead of the absolute address20 21 NOTE:22 With slram it's only possible to map a contiguous memory region. Therefore23 if there's a device mapped somewhere in the region specified slram will24 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 0x400051 52#define T(fmt, args...) printk(KERN_DEBUG fmt, ## args)53#define E(fmt, args...) printk(KERN_NOTICE fmt, ## args)54 55typedef struct slram_priv {56 u_char *start;57 u_char *end;58} slram_priv_t;59 60typedef struct slram_mtd_list {61 struct mtd_info *mtdinfo;62 struct slram_mtd_list *next;63} slram_mtd_list_t;64 65#ifdef MODULE66static char *map[SLRAM_MAX_DEVICES_PARAMS];67 68module_param_array(map, charp, NULL, 0);69MODULE_PARM_DESC(map, "List of memory regions to map. \"map=<name>, <start>, <length / end>\"");70#else71static char *map;72#endif73 74static slram_mtd_list_t *slram_mtdlist = NULL;75 76static int slram_erase(struct mtd_info *, struct erase_info *);77static int slram_point(struct mtd_info *, loff_t, size_t, size_t *, void **,78 resource_size_t *);79static int slram_unpoint(struct mtd_info *, loff_t, size_t);80static int slram_read(struct mtd_info *, loff_t, size_t, size_t *, u_char *);81static int slram_write(struct mtd_info *, loff_t, size_t, size_t *, const u_char *);82 83static 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 92static 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 102static int slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)103{104 return 0;105}106 107static 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 117static 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 129static 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 199static 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 214static 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 224static 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 260err_out:261 E("slram: Illegal length parameter.\n");262 return(-EINVAL);263}264 265#ifndef MODULE266 267static int __init mtd_slram_setup(char *str)268{269 map = str;270 return(1);271}272 273__setup("slram=", mtd_slram_setup);274 275#endif276 277static int __init init_slram(void)278{279 char *devname;280 281#ifndef MODULE282 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#else312 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 336static void __exit cleanup_slram(void)337{338 unregister_devices();339}340 341module_init(init_slram);342module_exit(cleanup_slram);343 344MODULE_LICENSE("GPL");345MODULE_AUTHOR("Jochen Schaeuble <psionic@psionic.de>");346MODULE_DESCRIPTION("MTD driver for uncached system RAM");347