fs/nfs/nfsroot.c

   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 Thümmler  :       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[256] __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] >= '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 }