// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 1995, 1996 Gero Kuhlmann <gero@gkminix.han.de>
*
* Allow an NFS filesystem to be mounted as root. The way this works is:
* (1) Use the IP autoconfig mechanism to set local IP addresses and routes.
* (2) Construct the device string and the options string using DHCP
* option 17 and/or kernel command line options.
* (3) When mount_root() sets up the root file system, pass these strings
* to the NFS client's regular mount interface via sys_mount().
*
*
* Changes:
*
* Alan Cox : Removed get_address name clash with FPU.
* Alan Cox : Reformatted a bit.
* Gero Kuhlmann : Code cleanup
* Michael Rausch : Fixed recognition of an incoming RARP answer.
* Martin Mares : (2.0) Auto-configuration via BOOTP supported.
* Martin Mares : Manual selection of interface & BOOTP/RARP.
* Martin Mares : Using network routes instead of host routes,
* allowing the default configuration to be used
* for normal operation of the host.
* Martin Mares : Randomized timer with exponential backoff
* installed to minimize network congestion.
* Martin Mares : Code cleanup.
* Martin Mares : (2.1) BOOTP and RARP made configuration options.
* Martin Mares : Server hostname generation fixed.
* Gerd Knorr : Fixed wired inode handling
* Martin Mares : (2.2) "0.0.0.0" addresses from command line ignored.
* Martin Mares : RARP replies not tested for server address.
* Gero Kuhlmann : (2.3) Some bug fixes and code cleanup again (please
* send me your new patches _before_ bothering
* Linus so that I don' always have to cleanup
* _afterwards_ - thanks)
* Gero Kuhlmann : Last changes of Martin Mares undone.
* Gero Kuhlmann : RARP replies are tested for specified server
* again. However, it's now possible to have
* different RARP and NFS servers.
* Gero Kuhlmann : "0.0.0.0" addresses from command line are
* now mapped to INADDR_NONE.
* Gero Kuhlmann : Fixed a bug which prevented BOOTP path name
* from being used (thanks to Leo Spiekman)
* Andy Walker : Allow to specify the NFS server in nfs_root
* without giving a path name
* Swen Thümmler : Allow to specify the NFS options in nfs_root
* without giving a path name. Fix BOOTP request
* for domainname (domainname is NIS domain, not
* DNS domain!). Skip dummy devices for BOOTP.
* Jacek Zapala : Fixed a bug which prevented server-ip address
* from nfsroot parameter from being used.
* Olaf Kirch : Adapted to new NFS code.
* Jakub Jelinek : Free used code segment.
* Marko Kohtala : Fixed some bugs.
* Martin Mares : Debug message cleanup
* Martin Mares : Changed to use the new generic IP layer autoconfig
* code. BOOTP and RARP moved there.
* Martin Mares : Default path now contains host name instead of
* host IP address (but host name defaults to IP
* address anyway).
* Martin Mares : Use root_server_addr appropriately during setup.
* Martin Mares : Rewrote parameter parsing, now hopefully giving
* correct overriding.
* Trond Myklebust : Add in preliminary support for NFSv3 and TCP.
* Fix bug in root_nfs_addr(). nfs_data.namlen
* is NOT for the length of the hostname.
* Hua Qin : Support for mounting root file system via
* NFS over TCP.
* Fabian Frederick: Option parser rebuilt (using parser lib)
* Chuck Lever : Use super.c's text-based mount option parsing
* Chuck Lever : Add "nfsrootdebug".
*/
#include <linux/types.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/nfs.h>
#include <linux/nfs_fs.h>
#include <linux/utsname.h>
#include <linux/root_dev.h>
#include <net/ipconfig.h>
#include "internal.h"
#define NFSDBG_FACILITY NFSDBG_ROOT
/* Default path we try to mount. "%s" gets replaced by our IP address */
#define NFS_ROOT "/tftpboot/%s"
/* Default NFSROOT mount options. */
#if defined(CONFIG_NFS_V2)
#define NFS_DEF_OPTIONS "vers=2,tcp,rsize=4096,wsize=4096"
#elif defined(CONFIG_NFS_V3)
#define NFS_DEF_OPTIONS "vers=3,tcp,rsize=4096,wsize=4096"
#else
#define NFS_DEF_OPTIONS "vers=4,tcp,rsize=4096,wsize=4096"
#endif
/* Parameters passed from the kernel command line */
static char nfs_root_parms[NFS_MAXPATHLEN + 1] __initdata = "";
/* Text-based mount options passed to super.c */
static char nfs_root_options[256] __initdata = NFS_DEF_OPTIONS;
/* Address of NFS server */
static __be32 servaddr __initdata = htonl(INADDR_NONE);
/* Name of directory to mount */
static char nfs_export_path[NFS_MAXPATHLEN + 1] __initdata = "";
/* server:export path string passed to super.c */
static char nfs_root_device[NFS_MAXPATHLEN + 1] __initdata = "";
#ifdef NFS_DEBUG
/*
* When the "nfsrootdebug" kernel command line option is specified,
* enable debugging messages for NFSROOT.
*/
static int __init nfs_root_debug(char *__unused)
{
nfs_debug |= NFSDBG_ROOT | NFSDBG_MOUNT;
return 1;
}
__setup("nfsrootdebug", nfs_root_debug);
#endif
/*
* Parse NFS server and directory information passed on the kernel
* command line.
*
* nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>]
*
* If there is a "%s" token in the <root-dir> string, it is replaced
* by the ASCII-representation of the client's IP address.
*/
static int __init nfs_root_setup(char *line)
{
ROOT_DEV = Root_NFS;
if (line[0] == '/' || line[0] == ',' || (line[0] >= '0' && line[0] <= '9')) {
strscpy(nfs_root_parms, line, sizeof(nfs_root_parms));
} else {
size_t n = strlen(line) + sizeof(NFS_ROOT) - 1;
if (n >= sizeof(nfs_root_parms))
line[sizeof(nfs_root_parms) - sizeof(NFS_ROOT) - 2] = '\0';
sprintf(nfs_root_parms, NFS_ROOT, line);
}
/*
* Extract the IP address of the NFS server containing our
* root file system, if one was specified.
*
* Note: root_nfs_parse_addr() removes the server-ip from
* nfs_root_parms, if it exists.
*/
root_server_addr = root_nfs_parse_addr(nfs_root_parms);
return 1;
}
__setup("nfsroot=", nfs_root_setup);
static int __init root_nfs_copy(char *dest, const char *src,
const size_t destlen)
{
if (strscpy(dest, src, destlen) == -E2BIG)
return -1;
return 0;
}
static int __init root_nfs_cat(char *dest, const char *src,
const size_t destlen)
{
size_t len = strlen(dest);
if (len && dest[len - 1] != ',')
if (strlcat(dest, ",", destlen) > destlen)
return -1;
if (strlcat(dest, src, destlen) > destlen)
return -1;
return 0;
}
/*
* Parse out root export path and mount options from
* passed-in string @incoming.
*
* Copy the export path into @exppath.
*/
static int __init root_nfs_parse_options(char *incoming, char *exppath,
const size_t exppathlen)
{
char *p;
/*
* Set the NFS remote path
*/
p = strsep(&incoming, ",");
if (*p != '\0' && strcmp(p, "default") != 0)
if (root_nfs_copy(exppath, p, exppathlen))
return -1;
/*
* @incoming now points to the rest of the string; if it
* contains something, append it to our root options buffer
*/
if (incoming != NULL && *incoming != '\0')
if (root_nfs_cat(nfs_root_options, incoming,
sizeof(nfs_root_options)))
return -1;
return 0;
}
/*
* Decode the export directory path name and NFS options from
* the kernel command line. This has to be done late in order to
* use a dynamically acquired client IP address for the remote
* root directory path.
*
* Returns zero if successful; otherwise -1 is returned.
*/
static int __init root_nfs_data(char *cmdline)
{
char mand_options[sizeof("nolock,addr=") + INET_ADDRSTRLEN + 1];
int len, retval = -1;
char *tmp = NULL;
const size_t tmplen = sizeof(nfs_export_path);
tmp = kzalloc(tmplen, GFP_KERNEL);
if (tmp == NULL)
goto out_nomem;
strcpy(tmp, NFS_ROOT);
if (root_server_path[0] != '\0') {
dprintk("Root-NFS: DHCPv4 option 17: %s\n",
root_server_path);
if (root_nfs_parse_options(root_server_path, tmp, tmplen))
goto out_optionstoolong;
}
if (cmdline[0] != '\0') {
dprintk("Root-NFS: nfsroot=%s\n", cmdline);
if (root_nfs_parse_options(cmdline, tmp, tmplen))
goto out_optionstoolong;
}
/*
* Append mandatory options for nfsroot so they override
* what has come before
*/
snprintf(mand_options, sizeof(mand_options), "nolock,addr=%pI4",
&servaddr);
if (root_nfs_cat(nfs_root_options, mand_options,
sizeof(nfs_root_options)))
goto out_optionstoolong;
/*
* Set up nfs_root_device. For NFS mounts, this looks like
*
* server:/path
*
* At this point, utsname()->nodename contains our local
* IP address or hostname, set by ipconfig. If "%s" exists
* in tmp, substitute the nodename, then shovel the whole
* mess into nfs_root_device.
*/
len = snprintf(nfs_export_path, sizeof(nfs_export_path),
tmp, utsname()->nodename);
if (len >= (int)sizeof(nfs_export_path))
goto out_devnametoolong;
len = snprintf(nfs_root_device, sizeof(nfs_root_device),
"%pI4:%s", &servaddr, nfs_export_path);
if (len >= (int)sizeof(nfs_root_device))
goto out_devnametoolong;
retval = 0;
out:
kfree(tmp);
return retval;
out_nomem:
printk(KERN_ERR "Root-NFS: could not allocate memory\n");
goto out;
out_optionstoolong:
printk(KERN_ERR "Root-NFS: mount options string too long\n");
goto out;
out_devnametoolong:
printk(KERN_ERR "Root-NFS: root device name too long.\n");
goto out;
}
/**
* nfs_root_data - Return prepared 'data' for NFSROOT mount
* @root_device: OUT: address of string containing NFSROOT device
* @root_data: OUT: address of string containing NFSROOT mount options
*
* Returns zero and sets @root_device and @root_data if successful,
* otherwise -1 is returned.
*/
int __init nfs_root_data(char **root_device, char **root_data)
{
servaddr = root_server_addr;
if (servaddr == htonl(INADDR_NONE)) {
printk(KERN_ERR "Root-NFS: no NFS server address\n");
return -1;
}
if (root_nfs_data(nfs_root_parms) < 0)
return -1;
*root_device = nfs_root_device;
*root_data = nfs_root_options;
return 0;
}