fs/cifs/cifsroot.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * SMB root file system support
0004  *
0005  * Copyright (c) 2019 Paulo Alcantara <palcantara@suse.de>
0006  */
0007 #include <linux/init.h>
0008 #include <linux/fs.h>
0009 #include <linux/types.h>
0010 #include <linux/ctype.h>
0011 #include <linux/string.h>
0012 #include <linux/root_dev.h>
0013 #include <linux/kernel.h>
0014 #include <linux/in.h>
0015 #include <linux/inet.h>
0016 #include <net/ipconfig.h>
0017
0018 #define DEFAULT_MNT_OPTS \
0019     "vers=1.0,cifsacl,mfsymlinks,rsize=1048576,wsize=65536,uid=0,gid=0," \
0020     "hard,rootfs"
0021
0022 static char root_dev[2048] __initdata = "";
0023 static char root_opts[1024] __initdata = DEFAULT_MNT_OPTS;
0024
0025 static __be32 __init parse_srvaddr(char *start, char *end)
0026 {
0027     /* TODO: ipv6 support */
0028     char addr[sizeof("aaa.bbb.ccc.ddd")];
0029     int i = 0;
0030
0031     while (start < end && i < sizeof(addr) - 1) {
0032         if (isdigit(*start) || *start == '.')
0033             addr[i++] = *start;
0034         start++;
0035     }
0036     addr[i] = '\0';
0037     return in_aton(addr);
0038 }
0039
0040 /* cifsroot=//<server-ip>/<share>[,options] */
0041 static int __init cifs_root_setup(char *line)
0042 {
0043     char *s;
0044     int len;
0045     __be32 srvaddr = htonl(INADDR_NONE);
0046
0047     ROOT_DEV = Root_CIFS;
0048
0049     if (strlen(line) > 3 && line[0] == '/' && line[1] == '/') {
0050         s = strchr(&line[2], '/');
0051         if (!s || s[1] == '\0')
0052             return 1;
0053
0054         /* make s point to ',' or '\0' at end of line */
0055         s = strchrnul(s, ',');
0056         /* len is strlen(unc) + '\0' */
0057         len = s - line + 1;
0058         if (len > sizeof(root_dev)) {
0059             pr_err("Root-CIFS: UNC path too long\n");
0060             return 1;
0061         }
0062         strscpy(root_dev, line, len);
0063         srvaddr = parse_srvaddr(&line[2], s);
0064         if (*s) {
0065             int n = snprintf(root_opts,
0066                      sizeof(root_opts), "%s,%s",
0067                      DEFAULT_MNT_OPTS, s + 1);
0068             if (n >= sizeof(root_opts)) {
0069                 pr_err("Root-CIFS: mount options string too long\n");
0070                 root_opts[sizeof(root_opts)-1] = '\0';
0071                 return 1;
0072             }
0073         }
0074     }
0075
0076     root_server_addr = srvaddr;
0077
0078     return 1;
0079 }
0080
0081 __setup("cifsroot=", cifs_root_setup);
0082
0083 int __init cifs_root_data(char **dev, char **opts)
0084 {
0085     if (!root_dev[0] || root_server_addr == htonl(INADDR_NONE)) {
0086         pr_err("Root-CIFS: no SMB server address\n");
0087         return -1;
0088     }
0089
0090     *dev = root_dev;
0091     *opts = root_opts;
0092
0093     return 0;
0094 }