v4.19.13 snapshot.
diff --git a/fs/nfs/nfsroot.c b/fs/nfs/nfsroot.c
new file mode 100644
index 0000000..effaa42
--- /dev/null
+++ b/fs/nfs/nfsroot.c
@@ -0,0 +1,310 @@
+// 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. */
+#define NFS_DEF_OPTIONS "vers=2,udp,rsize=4096,wsize=4096"
+
+/* 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')) {
+ strlcpy(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 (strlcpy(dest, src, destlen) > destlen)
+ 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;
+}