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Linux/fs/nfs/nfsroot.c

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

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