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
slram_erase(struct mtd_info * mtd,struct erase_info * instr)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
slram_point(struct mtd_info * mtd,loff_t from,size_t len,size_t * retlen,void ** virt,resource_size_t * phys)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
slram_unpoint(struct mtd_info * mtd,loff_t from,size_t len)102 static int slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
103 {
104 return 0;
105 }
106
slram_read(struct mtd_info * mtd,loff_t from,size_t len,size_t * retlen,u_char * buf)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
slram_write(struct mtd_info * mtd,loff_t to,size_t len,size_t * retlen,const u_char * buf)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
register_device(char * name,unsigned long start,unsigned long length)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
unregister_devices(void)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
handle_unit(unsigned long value,char * unit)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
parse_cmdline(char * devname,char * szstart,char * szlength)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
mtd_slram_setup(char * str)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
init_slram(void)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
cleanup_slram(void)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