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 #define NFS_DEF_OPTIONS		"vers=2,udp,rsize=4096,wsize=4096"
92 
93 /* Parameters passed from the kernel command line */
94 static char nfs_root_parms[NFS_MAXPATHLEN + 1] __initdata = "";
95 
96 /* Text-based mount options passed to super.c */
97 static char nfs_root_options[256] __initdata = NFS_DEF_OPTIONS;
98 
99 /* Address of NFS server */
100 static __be32 servaddr __initdata = htonl(INADDR_NONE);
101 
102 /* Name of directory to mount */
103 static char nfs_export_path[NFS_MAXPATHLEN + 1] __initdata = "";
104 
105 /* server:export path string passed to super.c */
106 static char nfs_root_device[NFS_MAXPATHLEN + 1] __initdata = "";
107 
108 #ifdef NFS_DEBUG
109 /*
110  * When the "nfsrootdebug" kernel command line option is specified,
111  * enable debugging messages for NFSROOT.
112  */
nfs_root_debug(char * __unused)113 static int __init nfs_root_debug(char *__unused)
114 {
115 	nfs_debug |= NFSDBG_ROOT | NFSDBG_MOUNT;
116 	return 1;
117 }
118 
119 __setup("nfsrootdebug", nfs_root_debug);
120 #endif
121 
122 /*
123  *  Parse NFS server and directory information passed on the kernel
124  *  command line.
125  *
126  *  nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>]
127  *
128  *  If there is a "%s" token in the <root-dir> string, it is replaced
129  *  by the ASCII-representation of the client's IP address.
130  */
nfs_root_setup(char * line)131 static int __init nfs_root_setup(char *line)
132 {
133 	ROOT_DEV = Root_NFS;
134 
135 	if (line[0] == '/' || line[0] == ',' || (line[0] >= '0' && line[0] <= '9')) {
136 		strlcpy(nfs_root_parms, line, sizeof(nfs_root_parms));
137 	} else {
138 		size_t n = strlen(line) + sizeof(NFS_ROOT) - 1;
139 		if (n >= sizeof(nfs_root_parms))
140 			line[sizeof(nfs_root_parms) - sizeof(NFS_ROOT) - 2] = '\0';
141 		sprintf(nfs_root_parms, NFS_ROOT, line);
142 	}
143 
144 	/*
145 	 * Extract the IP address of the NFS server containing our
146 	 * root file system, if one was specified.
147 	 *
148 	 * Note: root_nfs_parse_addr() removes the server-ip from
149 	 *	 nfs_root_parms, if it exists.
150 	 */
151 	root_server_addr = root_nfs_parse_addr(nfs_root_parms);
152 
153 	return 1;
154 }
155 
156 __setup("nfsroot=", nfs_root_setup);
157 
root_nfs_copy(char * dest,const char * src,const size_t destlen)158 static int __init root_nfs_copy(char *dest, const char *src,
159 				     const size_t destlen)
160 {
161 	if (strlcpy(dest, src, destlen) > destlen)
162 		return -1;
163 	return 0;
164 }
165 
root_nfs_cat(char * dest,const char * src,const size_t destlen)166 static int __init root_nfs_cat(char *dest, const char *src,
167 			       const size_t destlen)
168 {
169 	size_t len = strlen(dest);
170 
171 	if (len && dest[len - 1] != ',')
172 		if (strlcat(dest, ",", destlen) > destlen)
173 			return -1;
174 
175 	if (strlcat(dest, src, destlen) > destlen)
176 		return -1;
177 	return 0;
178 }
179 
180 /*
181  * Parse out root export path and mount options from
182  * passed-in string @incoming.
183  *
184  * Copy the export path into @exppath.
185  */
root_nfs_parse_options(char * incoming,char * exppath,const size_t exppathlen)186 static int __init root_nfs_parse_options(char *incoming, char *exppath,
187 					 const size_t exppathlen)
188 {
189 	char *p;
190 
191 	/*
192 	 * Set the NFS remote path
193 	 */
194 	p = strsep(&incoming, ",");
195 	if (*p != '\0' && strcmp(p, "default") != 0)
196 		if (root_nfs_copy(exppath, p, exppathlen))
197 			return -1;
198 
199 	/*
200 	 * @incoming now points to the rest of the string; if it
201 	 * contains something, append it to our root options buffer
202 	 */
203 	if (incoming != NULL && *incoming != '\0')
204 		if (root_nfs_cat(nfs_root_options, incoming,
205 						sizeof(nfs_root_options)))
206 			return -1;
207 	return 0;
208 }
209 
210 /*
211  *  Decode the export directory path name and NFS options from
212  *  the kernel command line.  This has to be done late in order to
213  *  use a dynamically acquired client IP address for the remote
214  *  root directory path.
215  *
216  *  Returns zero if successful; otherwise -1 is returned.
217  */
root_nfs_data(char * cmdline)218 static int __init root_nfs_data(char *cmdline)
219 {
220 	char mand_options[sizeof("nolock,addr=") + INET_ADDRSTRLEN + 1];
221 	int len, retval = -1;
222 	char *tmp = NULL;
223 	const size_t tmplen = sizeof(nfs_export_path);
224 
225 	tmp = kzalloc(tmplen, GFP_KERNEL);
226 	if (tmp == NULL)
227 		goto out_nomem;
228 	strcpy(tmp, NFS_ROOT);
229 
230 	if (root_server_path[0] != '\0') {
231 		dprintk("Root-NFS: DHCPv4 option 17: %s\n",
232 			root_server_path);
233 		if (root_nfs_parse_options(root_server_path, tmp, tmplen))
234 			goto out_optionstoolong;
235 	}
236 
237 	if (cmdline[0] != '\0') {
238 		dprintk("Root-NFS: nfsroot=%s\n", cmdline);
239 		if (root_nfs_parse_options(cmdline, tmp, tmplen))
240 			goto out_optionstoolong;
241 	}
242 
243 	/*
244 	 * Append mandatory options for nfsroot so they override
245 	 * what has come before
246 	 */
247 	snprintf(mand_options, sizeof(mand_options), "nolock,addr=%pI4",
248 			&servaddr);
249 	if (root_nfs_cat(nfs_root_options, mand_options,
250 						sizeof(nfs_root_options)))
251 		goto out_optionstoolong;
252 
253 	/*
254 	 * Set up nfs_root_device.  For NFS mounts, this looks like
255 	 *
256 	 *	server:/path
257 	 *
258 	 * At this point, utsname()->nodename contains our local
259 	 * IP address or hostname, set by ipconfig.  If "%s" exists
260 	 * in tmp, substitute the nodename, then shovel the whole
261 	 * mess into nfs_root_device.
262 	 */
263 	len = snprintf(nfs_export_path, sizeof(nfs_export_path),
264 				tmp, utsname()->nodename);
265 	if (len >= (int)sizeof(nfs_export_path))
266 		goto out_devnametoolong;
267 	len = snprintf(nfs_root_device, sizeof(nfs_root_device),
268 				"%pI4:%s", &servaddr, nfs_export_path);
269 	if (len >= (int)sizeof(nfs_root_device))
270 		goto out_devnametoolong;
271 
272 	retval = 0;
273 
274 out:
275 	kfree(tmp);
276 	return retval;
277 out_nomem:
278 	printk(KERN_ERR "Root-NFS: could not allocate memory\n");
279 	goto out;
280 out_optionstoolong:
281 	printk(KERN_ERR "Root-NFS: mount options string too long\n");
282 	goto out;
283 out_devnametoolong:
284 	printk(KERN_ERR "Root-NFS: root device name too long.\n");
285 	goto out;
286 }
287 
288 /**
289  * nfs_root_data - Return prepared 'data' for NFSROOT mount
290  * @root_device: OUT: address of string containing NFSROOT device
291  * @root_data: OUT: address of string containing NFSROOT mount options
292  *
293  * Returns zero and sets @root_device and @root_data if successful,
294  * otherwise -1 is returned.
295  */
nfs_root_data(char ** root_device,char ** root_data)296 int __init nfs_root_data(char **root_device, char **root_data)
297 {
298 	servaddr = root_server_addr;
299 	if (servaddr == htonl(INADDR_NONE)) {
300 		printk(KERN_ERR "Root-NFS: no NFS server address\n");
301 		return -1;
302 	}
303 
304 	if (root_nfs_data(nfs_root_parms) < 0)
305 		return -1;
306 
307 	*root_device = nfs_root_device;
308 	*root_data = nfs_root_options;
309 	return 0;
310 }
311