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 /* Parameters passed from the kernel command line */
  90 static char nfs_root_parms[256] __initdata = "";
  91
  92 /* Text-based mount options passed to super.c */
  93 static char nfs_root_options[256] __initdata = "";
  94
  95 /* Address of NFS server */
  96 static __be32 servaddr __initdata = htonl(INADDR_NONE);
  97
  98 /* Name of directory to mount */
  99 static char nfs_export_path[NFS_MAXPATHLEN + 1] __initdata = "";
 100
 101 /* server:export path string passed to super.c */
 102 static char nfs_root_device[NFS_MAXPATHLEN + 1] __initdata = "";
 103
 104 /*
 105  * When the "nfsrootdebug" kernel command line option is specified,
 106  * enable debugging messages for NFSROOT.
 107  */
 108 static int __init nfs_root_debug(char *__unused)
 109 {
 110         nfs_debug |= NFSDBG_ROOT | NFSDBG_MOUNT;
 111         return 1;
 112 }
 113
 114 __setup("nfsrootdebug", nfs_root_debug);
 115
 116 /*
 117  *  Parse NFS server and directory information passed on the kernel
 118  *  command line.
 119  *
 120  *  nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>]
 121  *
 122  *  If there is a "%s" token in the <root-dir> string, it is replaced
 123  *  by the ASCII-representation of the client's IP address.
 124  */
 125 static int __init nfs_root_setup(char *line)
 126 {
 127         ROOT_DEV = Root_NFS;
 128
 129         if (line[0] == '/' || line[0] == ',' || (line[0] >= '0' && line[0] <= '9')) {
 130                 strlcpy(nfs_root_parms, line, sizeof(nfs_root_parms));
 131         } else {
 132                 size_t n = strlen(line) + sizeof(NFS_ROOT) - 1;
 133                 if (n >= sizeof(nfs_root_parms))
 134                         line[sizeof(nfs_root_parms) - sizeof(NFS_ROOT) - 2] = '\0';
 135                 sprintf(nfs_root_parms, NFS_ROOT, line);
 136         }
 137
 138         /*
 139          * Extract the IP address of the NFS server containing our
 140          * root file system, if one was specified.
 141          *
 142          * Note: root_nfs_parse_addr() removes the server-ip from
 143          *       nfs_root_parms, if it exists.
 144          */
 145         root_server_addr = root_nfs_parse_addr(nfs_root_parms);
 146
 147         return 1;
 148 }
 149
 150 __setup("nfsroot=", nfs_root_setup);
 151
 152 static int __init root_nfs_copy(char *dest, const char *src,
 153                                      const size_t destlen)
 154 {
 155         if (strlcpy(dest, src, destlen) > destlen)
 156                 return -1;
 157         return 0;
 158 }
 159
 160 static int __init root_nfs_cat(char *dest, const char *src,
 161                                   const size_t destlen)
 162 {
 163         if (strlcat(dest, src, destlen) > destlen)
 164                 return -1;
 165         return 0;
 166 }
 167
 168 /*
 169  * Parse out root export path and mount options from
 170  * passed-in string @incoming.
 171  *
 172  * Copy the export path into @exppath.
 173  */
 174 static int __init root_nfs_parse_options(char *incoming, char *exppath,
 175                                          const size_t exppathlen)
 176 {
 177         char *p;
 178
 179         /*
 180          * Set the NFS remote path
 181          */
 182         p = strsep(&incoming, ",");
 183         if (*p != '\0' && strcmp(p, "default") != 0)
 184                 if (root_nfs_copy(exppath, p, exppathlen))
 185                         return -1;
 186
 187         /*
 188          * @incoming now points to the rest of the string; if it
 189          * contains something, append it to our root options buffer
 190          */
 191         if (incoming != NULL && *incoming != '\0')
 192                 if (root_nfs_cat(nfs_root_options, incoming,
 193                                                 sizeof(nfs_root_options)))
 194                         return -1;
 195
 196         /*
 197          * Possibly prepare for more options to be appended
 198          */
 199         if (nfs_root_options[0] != '\0' &&
 200             nfs_root_options[strlen(nfs_root_options)] != ',')
 201                 if (root_nfs_cat(nfs_root_options, ",",
 202                                                 sizeof(nfs_root_options)))
 203                         return -1;
 204
 205         return 0;
 206 }
 207
 208 /*
 209  *  Decode the export directory path name and NFS options from
 210  *  the kernel command line.  This has to be done late in order to
 211  *  use a dynamically acquired client IP address for the remote
 212  *  root directory path.
 213  *
 214  *  Returns zero if successful; otherwise -1 is returned.
 215  */
 216 static int __init root_nfs_data(char *cmdline)
 217 {
 218         char addr_option[sizeof("nolock,addr=") + INET_ADDRSTRLEN + 1];
 219         int len, retval = -1;
 220         char *tmp = NULL;
 221         const size_t tmplen = sizeof(nfs_export_path);
 222
 223         tmp = kzalloc(tmplen, GFP_KERNEL);
 224         if (tmp == NULL)
 225                 goto out_nomem;
 226         strcpy(tmp, NFS_ROOT);
 227
 228         if (root_server_path[0] != '\0') {
 229                 dprintk("Root-NFS: DHCPv4 option 17: %s\n",
 230                         root_server_path);
 231                 if (root_nfs_parse_options(root_server_path, tmp, tmplen))
 232                         goto out_optionstoolong;
 233         }
 234
 235         if (cmdline[0] != '\0') {
 236                 dprintk("Root-NFS: nfsroot=%s\n", cmdline);
 237                 if (root_nfs_parse_options(cmdline, tmp, tmplen))
 238                         goto out_optionstoolong;
 239         }
 240
 241         /*
 242          * Append mandatory options for nfsroot so they override
 243          * what has come before
 244          */
 245         snprintf(addr_option, sizeof(addr_option), "nolock,addr=%pI4",
 246                         &servaddr);
 247         if (root_nfs_cat(nfs_root_options, addr_option,
 248                                                 sizeof(nfs_root_options)))
 249                 goto out_optionstoolong;
 250
 251         /*
 252          * Set up nfs_root_device.  For NFS mounts, this looks like
 253          *
 254          *      server:/path
 255          *
 256          * At this point, utsname()->nodename contains our local
 257          * IP address or hostname, set by ipconfig.  If "%s" exists
 258          * in tmp, substitute the nodename, then shovel the whole
 259          * mess into nfs_root_device.
 260          */
 261         len = snprintf(nfs_export_path, sizeof(nfs_export_path),
 262                                 tmp, utsname()->nodename);
 263         if (len > (int)sizeof(nfs_export_path))
 264                 goto out_devnametoolong;
 265         len = snprintf(nfs_root_device, sizeof(nfs_root_device),
 266                                 "%pI4:%s", &servaddr, nfs_export_path);
 267         if (len > (int)sizeof(nfs_root_device))
 268                 goto out_devnametoolong;
 269
 270         retval = 0;
 271
 272 out:
 273         kfree(tmp);
 274         return retval;
 275 out_nomem:
 276         printk(KERN_ERR "Root-NFS: could not allocate memory\n");
 277         goto out;
 278 out_optionstoolong:
 279         printk(KERN_ERR "Root-NFS: mount options string too long\n");
 280         goto out;
 281 out_devnametoolong:
 282         printk(KERN_ERR "Root-NFS: root device name too long.\n");
 283         goto out;
 284 }
 285
 286 /**
 287  * nfs_root_data - Return prepared 'data' for NFSROOT mount
 288  * @root_device: OUT: address of string containing NFSROOT device
 289  * @root_data: OUT: address of string containing NFSROOT mount options
 290  *
 291  * Returns zero and sets @root_device and @root_data if successful,
 292  * otherwise -1 is returned.
 293  */
 294 int __init nfs_root_data(char **root_device, char **root_data)
 295 {
 296         servaddr = root_server_addr;
 297         if (servaddr == htonl(INADDR_NONE)) {
 298                 printk(KERN_ERR "Root-NFS: no NFS server address\n");
 299                 return -1;
 300         }
 301
 302         if (root_nfs_data(nfs_root_parms) < 0)
 303                 return -1;
 304
 305         *root_device = nfs_root_device;
 306         *root_data = nfs_root_options;
 307         return 0;
 308 }