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 #if defined(CONFIG_NFS_V2) 92 #define NFS_DEF_OPTIONS "vers=2,tcp,rsize=4096,wsize=4096" 93 #elif defined(CONFIG_NFS_V3) 94 #define NFS_DEF_OPTIONS "vers=3,tcp,rsize=4096,wsize=4096" 95 #else 96 #define NFS_DEF_OPTIONS "vers=4,tcp,rsize=4096,wsize=4096" 97 #endif 98 99 /* Parameters passed from the kernel command line */ 100 static char nfs_root_parms[NFS_MAXPATHLEN + 1] __initdata = ""; 101 102 /* Text-based mount options passed to super.c */ 103 static char nfs_root_options[256] __initdata = NFS_DEF_OPTIONS; 104 105 /* Address of NFS server */ 106 static __be32 servaddr __initdata = htonl(INADDR_NONE); 107 108 /* Name of directory to mount */ 109 static char nfs_export_path[NFS_MAXPATHLEN + 1] __initdata = ""; 110 111 /* server:export path string passed to super.c */ 112 static char nfs_root_device[NFS_MAXPATHLEN + 1] __initdata = ""; 113 114 #ifdef NFS_DEBUG 115 /* 116 * When the "nfsrootdebug" kernel command line option is specified, 117 * enable debugging messages for NFSROOT. 118 */ 119 static int __init nfs_root_debug(char *__unused) 120 { 121 nfs_debug |= NFSDBG_ROOT | NFSDBG_MOUNT; 122 return 1; 123 } 124 125 __setup("nfsrootdebug", nfs_root_debug); 126 #endif 127 128 /* 129 * Parse NFS server and directory information passed on the kernel 130 * command line. 131 * 132 * nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>] 133 * 134 * If there is a "%s" token in the <root-dir> string, it is replaced 135 * by the ASCII-representation of the client's IP address. 136 */ 137 static int __init nfs_root_setup(char *line) 138 { 139 ROOT_DEV = Root_NFS; 140 141 if (line[0] == '/' || line[0] == ',' || (line[0] >= '0' && line[0] <= '9')) { 142 strscpy(nfs_root_parms, line, sizeof(nfs_root_parms)); 143 } else { 144 size_t n = strlen(line) + sizeof(NFS_ROOT) - 1; 145 if (n >= sizeof(nfs_root_parms)) 146 line[sizeof(nfs_root_parms) - sizeof(NFS_ROOT) - 2] = '\0'; 147 sprintf(nfs_root_parms, NFS_ROOT, line); 148 } 149 150 /* 151 * Extract the IP address of the NFS server containing our 152 * root file system, if one was specified. 153 * 154 * Note: root_nfs_parse_addr() removes the server-ip from 155 * nfs_root_parms, if it exists. 156 */ 157 root_server_addr = root_nfs_parse_addr(nfs_root_parms); 158 159 return 1; 160 } 161 162 __setup("nfsroot=", nfs_root_setup); 163 164 static int __init root_nfs_copy(char *dest, const char *src, 165 const size_t destlen) 166 { 167 if (strscpy(dest, src, destlen) == -E2BIG) 168 return -1; 169 return 0; 170 } 171 172 static int __init root_nfs_cat(char *dest, const char *src, 173 const size_t destlen) 174 { 175 size_t len = strlen(dest); 176 177 if (len && dest[len - 1] != ',') 178 if (strlcat(dest, ",", destlen) >= destlen) 179 return -1; 180 181 if (strlcat(dest, src, destlen) >= destlen) 182 return -1; 183 return 0; 184 } 185 186 /* 187 * Parse out root export path and mount options from 188 * passed-in string @incoming. 189 * 190 * Copy the export path into @exppath. 191 */ 192 static int __init root_nfs_parse_options(char *incoming, char *exppath, 193 const size_t exppathlen) 194 { 195 char *p; 196 197 /* 198 * Set the NFS remote path 199 */ 200 p = strsep(&incoming, ","); 201 if (*p != '\0' && strcmp(p, "default") != 0) 202 if (root_nfs_copy(exppath, p, exppathlen)) 203 return -1; 204 205 /* 206 * @incoming now points to the rest of the string; if it 207 * contains something, append it to our root options buffer 208 */ 209 if (incoming != NULL && *incoming != '\0') 210 if (root_nfs_cat(nfs_root_options, incoming, 211 sizeof(nfs_root_options))) 212 return -1; 213 return 0; 214 } 215 216 /* 217 * Decode the export directory path name and NFS options from 218 * the kernel command line. This has to be done late in order to 219 * use a dynamically acquired client IP address for the remote 220 * root directory path. 221 * 222 * Returns zero if successful; otherwise -1 is returned. 223 */ 224 static int __init root_nfs_data(char *cmdline) 225 { 226 char mand_options[sizeof("nolock,addr=") + INET_ADDRSTRLEN + 1]; 227 int len, retval = -1; 228 char *tmp = NULL; 229 const size_t tmplen = sizeof(nfs_export_path); 230 231 tmp = kzalloc(tmplen, GFP_KERNEL); 232 if (tmp == NULL) 233 goto out_nomem; 234 strcpy(tmp, NFS_ROOT); 235 236 if (root_server_path[0] != '\0') { 237 dprintk("Root-NFS: DHCPv4 option 17: %s\n", 238 root_server_path); 239 if (root_nfs_parse_options(root_server_path, tmp, tmplen)) 240 goto out_optionstoolong; 241 } 242 243 if (cmdline[0] != '\0') { 244 dprintk("Root-NFS: nfsroot=%s\n", cmdline); 245 if (root_nfs_parse_options(cmdline, tmp, tmplen)) 246 goto out_optionstoolong; 247 } 248 249 /* 250 * Append mandatory options for nfsroot so they override 251 * what has come before 252 */ 253 snprintf(mand_options, sizeof(mand_options), "nolock,addr=%pI4", 254 &servaddr); 255 if (root_nfs_cat(nfs_root_options, mand_options, 256 sizeof(nfs_root_options))) 257 goto out_optionstoolong; 258 259 /* 260 * Set up nfs_root_device. For NFS mounts, this looks like 261 * 262 * server:/path 263 * 264 * At this point, utsname()->nodename contains our local 265 * IP address or hostname, set by ipconfig. If "%s" exists 266 * in tmp, substitute the nodename, then shovel the whole 267 * mess into nfs_root_device. 268 */ 269 len = snprintf(nfs_export_path, sizeof(nfs_export_path), 270 tmp, utsname()->nodename); 271 if (len >= (int)sizeof(nfs_export_path)) 272 goto out_devnametoolong; 273 len = snprintf(nfs_root_device, sizeof(nfs_root_device), 274 "%pI4:%s", &servaddr, nfs_export_path); 275 if (len >= (int)sizeof(nfs_root_device)) 276 goto out_devnametoolong; 277 278 retval = 0; 279 280 out: 281 kfree(tmp); 282 return retval; 283 out_nomem: 284 printk(KERN_ERR "Root-NFS: could not allocate memory\n"); 285 goto out; 286 out_optionstoolong: 287 printk(KERN_ERR "Root-NFS: mount options string too long\n"); 288 goto out; 289 out_devnametoolong: 290 printk(KERN_ERR "Root-NFS: root device name too long.\n"); 291 goto out; 292 } 293 294 /** 295 * nfs_root_data - Return prepared 'data' for NFSROOT mount 296 * @root_device: OUT: address of string containing NFSROOT device 297 * @root_data: OUT: address of string containing NFSROOT mount options 298 * 299 * Returns zero and sets @root_device and @root_data if successful, 300 * otherwise -1 is returned. 301 */ 302 int __init nfs_root_data(char **root_device, char **root_data) 303 { 304 servaddr = root_server_addr; 305 if (servaddr == htonl(INADDR_NONE)) { 306 printk(KERN_ERR "Root-NFS: no NFS server address\n"); 307 return -1; 308 } 309 310 if (root_nfs_data(nfs_root_parms) < 0) 311 return -1; 312 313 *root_device = nfs_root_device; 314 *root_data = nfs_root_options; 315 return 0; 316 } 317