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Linux/fs/nfs/nfsroot.c

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  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 Th├╝mmler  :       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  */
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  */
131 static int __init nfs_root_setup(char *line)
132 {
133         ROOT_DEV = Root_NFS;
134 
135         if (line[0] == '/' || line[0] == ',' || (line[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 
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 
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  */
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  */
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  */
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 

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