1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 1995, 1996 Gero Kuhlmann <gero@gkminix.han.de>
4 *
5 * Allow an NFS filesystem to be mounted as root. The way this works is:
6 * (1) Use the IP autoconfig mechanism to set local IP addresses and routes.
7 * (2) Construct the device string and the options string using DHCP
8 * option 17 and/or kernel command line options.
9 * (3) When mount_root() sets up the root file system, pass these strings
10 * to the NFS client's regular mount interface via sys_mount().
11 *
12 *
13 * Changes:
14 *
15 * Alan Cox : Removed get_address name clash with FPU.
16 * Alan Cox : Reformatted a bit.
17 * Gero Kuhlmann : Code cleanup
18 * Michael Rausch : Fixed recognition of an incoming RARP answer.
19 * Martin Mares : (2.0) Auto-configuration via BOOTP supported.
20 * Martin Mares : Manual selection of interface & BOOTP/RARP.
21 * Martin Mares : Using network routes instead of host routes,
22 * allowing the default configuration to be used
23 * for normal operation of the host.
24 * Martin Mares : Randomized timer with exponential backoff
25 * installed to minimize network congestion.
26 * Martin Mares : Code cleanup.
27 * Martin Mares : (2.1) BOOTP and RARP made configuration options.
28 * Martin Mares : Server hostname generation fixed.
29 * Gerd Knorr : Fixed wired inode handling
30 * Martin Mares : (2.2) "0.0.0.0" addresses from command line ignored.
31 * Martin Mares : RARP replies not tested for server address.
32 * Gero Kuhlmann : (2.3) Some bug fixes and code cleanup again (please
33 * send me your new patches _before_ bothering
34 * Linus so that I don' always have to cleanup
35 * _afterwards_ - thanks)
36 * Gero Kuhlmann : Last changes of Martin Mares undone.
37 * Gero Kuhlmann : RARP replies are tested for specified server
38 * again. However, it's now possible to have
39 * different RARP and NFS servers.
40 * Gero Kuhlmann : "0.0.0.0" addresses from command line are
41 * now mapped to INADDR_NONE.
42 * Gero Kuhlmann : Fixed a bug which prevented BOOTP path name
43 * from being used (thanks to Leo Spiekman)
44 * Andy Walker : Allow to specify the NFS server in nfs_root
45 * without giving a path name
46 * Swen Thümmler : Allow to specify the NFS options in nfs_root
47 * without giving a path name. Fix BOOTP request
48 * for domainname (domainname is NIS domain, not
49 * DNS domain!). Skip dummy devices for BOOTP.
50 * Jacek Zapala : Fixed a bug which prevented server-ip address
51 * from nfsroot parameter from being used.
52 * Olaf Kirch : Adapted to new NFS code.
53 * Jakub Jelinek : Free used code segment.
54 * Marko Kohtala : Fixed some bugs.
55 * Martin Mares : Debug message cleanup
56 * Martin Mares : Changed to use the new generic IP layer autoconfig
57 * code. BOOTP and RARP moved there.
58 * Martin Mares : Default path now contains host name instead of
59 * host IP address (but host name defaults to IP
60 * address anyway).
61 * Martin Mares : Use root_server_addr appropriately during setup.
62 * Martin Mares : Rewrote parameter parsing, now hopefully giving
63 * correct overriding.
64 * Trond Myklebust : Add in preliminary support for NFSv3 and TCP.
65 * Fix bug in root_nfs_addr(). nfs_data.namlen
66 * is NOT for the length of the hostname.
67 * Hua Qin : Support for mounting root file system via
68 * NFS over TCP.
69 * Fabian Frederick: Option parser rebuilt (using parser lib)
70 * Chuck Lever : Use super.c's text-based mount option parsing
71 * Chuck Lever : Add "nfsrootdebug".
72 */
73
74 #include <linux/types.h>
75 #include <linux/string.h>
76 #include <linux/init.h>
77 #include <linux/nfs.h>
78 #include <linux/nfs_fs.h>
79 #include <linux/utsname.h>
80 #include <linux/root_dev.h>
81 #include <net/ipconfig.h>
82
83 #include "internal.h"
84
85 #define NFSDBG_FACILITY NFSDBG_ROOT
86
87 /* Default path we try to mount. "%s" gets replaced by our IP address */
88 #define NFS_ROOT "/tftpboot/%s"
89
90 /* Default NFSROOT mount options. */
91 #if defined(CONFIG_NFS_V2)
92 #define NFS_DEF_OPTIONS "vers=2,tcp,rsize=4096,wsize=4096"
93 #elif defined(CONFIG_NFS_V3)
94 #define NFS_DEF_OPTIONS "vers=3,tcp,rsize=4096,wsize=4096"
95 #else
96 #define NFS_DEF_OPTIONS "vers=4,tcp,rsize=4096,wsize=4096"
97 #endif
98
99 /* Parameters passed from the kernel command line */
100 static char nfs_root_parms[NFS_MAXPATHLEN + 1] __initdata = "";
101
102 /* Text-based mount options passed to super.c */
103 static char nfs_root_options[256] __initdata = NFS_DEF_OPTIONS;
104
105 /* Address of NFS server */
106 static __be32 servaddr __initdata = htonl(INADDR_NONE);
107
108 /* Name of directory to mount */
109 static char nfs_export_path[NFS_MAXPATHLEN + 1] __initdata = "";
110
111 /* server:export path string passed to super.c */
112 static char nfs_root_device[NFS_MAXPATHLEN + 1] __initdata = "";
113
114 #ifdef NFS_DEBUG
115 /*
116 * When the "nfsrootdebug" kernel command line option is specified,
117 * enable debugging messages for NFSROOT.
118 */
nfs_root_debug(char * __unused)119 static int __init nfs_root_debug(char *__unused)
120 {
121 nfs_debug |= NFSDBG_ROOT | NFSDBG_MOUNT;
122 return 1;
123 }
124
125 __setup("nfsrootdebug", nfs_root_debug);
126 #endif
127
128 /*
129 * Parse NFS server and directory information passed on the kernel
130 * command line.
131 *
132 * nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>]
133 *
134 * If there is a "%s" token in the <root-dir> string, it is replaced
135 * by the ASCII-representation of the client's IP address.
136 */
nfs_root_setup(char * line)137 static int __init nfs_root_setup(char *line)
138 {
139 ROOT_DEV = Root_NFS;
140
141 if (line[0] == '/' || line[0] == ',' || (line[0] >= '0' && line[0] <= '9')) {
142 strscpy(nfs_root_parms, line, sizeof(nfs_root_parms));
143 } else {
144 size_t n = strlen(line) + sizeof(NFS_ROOT) - 1;
145 if (n >= sizeof(nfs_root_parms))
146 line[sizeof(nfs_root_parms) - sizeof(NFS_ROOT) - 2] = '\0';
147 sprintf(nfs_root_parms, NFS_ROOT, line);
148 }
149
150 /*
151 * Extract the IP address of the NFS server containing our
152 * root file system, if one was specified.
153 *
154 * Note: root_nfs_parse_addr() removes the server-ip from
155 * nfs_root_parms, if it exists.
156 */
157 root_server_addr = root_nfs_parse_addr(nfs_root_parms);
158
159 return 1;
160 }
161
162 __setup("nfsroot=", nfs_root_setup);
163
root_nfs_copy(char * dest,const char * src,const size_t destlen)164 static int __init root_nfs_copy(char *dest, const char *src,
165 const size_t destlen)
166 {
167 if (strscpy(dest, src, destlen) == -E2BIG)
168 return -1;
169 return 0;
170 }
171
root_nfs_cat(char * dest,const char * src,const size_t destlen)172 static int __init root_nfs_cat(char *dest, const char *src,
173 const size_t destlen)
174 {
175 size_t len = strlen(dest);
176
177 if (len && dest[len - 1] != ',')
178 if (strlcat(dest, ",", destlen) >= destlen)
179 return -1;
180
181 if (strlcat(dest, src, destlen) >= destlen)
182 return -1;
183 return 0;
184 }
185
186 /*
187 * Parse out root export path and mount options from
188 * passed-in string @incoming.
189 *
190 * Copy the export path into @exppath.
191 */
root_nfs_parse_options(char * incoming,char * exppath,const size_t exppathlen)192 static int __init root_nfs_parse_options(char *incoming, char *exppath,
193 const size_t exppathlen)
194 {
195 char *p;
196
197 /*
198 * Set the NFS remote path
199 */
200 p = strsep(&incoming, ",");
201 if (*p != '\0' && strcmp(p, "default") != 0)
202 if (root_nfs_copy(exppath, p, exppathlen))
203 return -1;
204
205 /*
206 * @incoming now points to the rest of the string; if it
207 * contains something, append it to our root options buffer
208 */
209 if (incoming != NULL && *incoming != '\0')
210 if (root_nfs_cat(nfs_root_options, incoming,
211 sizeof(nfs_root_options)))
212 return -1;
213 return 0;
214 }
215
216 /*
217 * Decode the export directory path name and NFS options from
218 * the kernel command line. This has to be done late in order to
219 * use a dynamically acquired client IP address for the remote
220 * root directory path.
221 *
222 * Returns zero if successful; otherwise -1 is returned.
223 */
root_nfs_data(char * cmdline)224 static int __init root_nfs_data(char *cmdline)
225 {
226 char mand_options[sizeof("nolock,addr=") + INET_ADDRSTRLEN + 1];
227 int len, retval = -1;
228 char *tmp = NULL;
229 const size_t tmplen = sizeof(nfs_export_path);
230
231 tmp = kzalloc(tmplen, GFP_KERNEL);
232 if (tmp == NULL)
233 goto out_nomem;
234 strcpy(tmp, NFS_ROOT);
235
236 if (root_server_path[0] != '\0') {
237 dprintk("Root-NFS: DHCPv4 option 17: %s\n",
238 root_server_path);
239 if (root_nfs_parse_options(root_server_path, tmp, tmplen))
240 goto out_optionstoolong;
241 }
242
243 if (cmdline[0] != '\0') {
244 dprintk("Root-NFS: nfsroot=%s\n", cmdline);
245 if (root_nfs_parse_options(cmdline, tmp, tmplen))
246 goto out_optionstoolong;
247 }
248
249 /*
250 * Append mandatory options for nfsroot so they override
251 * what has come before
252 */
253 snprintf(mand_options, sizeof(mand_options), "nolock,addr=%pI4",
254 &servaddr);
255 if (root_nfs_cat(nfs_root_options, mand_options,
256 sizeof(nfs_root_options)))
257 goto out_optionstoolong;
258
259 /*
260 * Set up nfs_root_device. For NFS mounts, this looks like
261 *
262 * server:/path
263 *
264 * At this point, utsname()->nodename contains our local
265 * IP address or hostname, set by ipconfig. If "%s" exists
266 * in tmp, substitute the nodename, then shovel the whole
267 * mess into nfs_root_device.
268 */
269 len = snprintf(nfs_export_path, sizeof(nfs_export_path),
270 tmp, utsname()->nodename);
271 if (len >= (int)sizeof(nfs_export_path))
272 goto out_devnametoolong;
273 len = snprintf(nfs_root_device, sizeof(nfs_root_device),
274 "%pI4:%s", &servaddr, nfs_export_path);
275 if (len >= (int)sizeof(nfs_root_device))
276 goto out_devnametoolong;
277
278 retval = 0;
279
280 out:
281 kfree(tmp);
282 return retval;
283 out_nomem:
284 printk(KERN_ERR "Root-NFS: could not allocate memory\n");
285 goto out;
286 out_optionstoolong:
287 printk(KERN_ERR "Root-NFS: mount options string too long\n");
288 goto out;
289 out_devnametoolong:
290 printk(KERN_ERR "Root-NFS: root device name too long.\n");
291 goto out;
292 }
293
294 /**
295 * nfs_root_data - Return prepared 'data' for NFSROOT mount
296 * @root_device: OUT: address of string containing NFSROOT device
297 * @root_data: OUT: address of string containing NFSROOT mount options
298 *
299 * Returns zero and sets @root_device and @root_data if successful,
300 * otherwise -1 is returned.
301 */
nfs_root_data(char ** root_device,char ** root_data)302 int __init nfs_root_data(char **root_device, char **root_data)
303 {
304 servaddr = root_server_addr;
305 if (servaddr == htonl(INADDR_NONE)) {
306 printk(KERN_ERR "Root-NFS: no NFS server address\n");
307 return -1;
308 }
309
310 if (root_nfs_data(nfs_root_parms) < 0)
311 return -1;
312
313 *root_device = nfs_root_device;
314 *root_data = nfs_root_options;
315 return 0;
316 }
317