ASR_BASE
Change-Id: Icf3719cc0afe3eeb3edc7fa80a2eb5199ca9dda1
diff --git a/marvell/linux/fs/binfmt_misc.c b/marvell/linux/fs/binfmt_misc.c
new file mode 100644
index 0000000..7557fb4
--- /dev/null
+++ b/marvell/linux/fs/binfmt_misc.c
@@ -0,0 +1,1003 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * binfmt_misc.c
+ *
+ * Copyright (C) 1997 Richard Günther
+ *
+ * binfmt_misc detects binaries via a magic or filename extension and invokes
+ * a specified wrapper. See Documentation/admin-guide/binfmt-misc.rst for more details.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched/mm.h>
+#include <linux/magic.h>
+#include <linux/binfmts.h>
+#include <linux/slab.h>
+#include <linux/ctype.h>
+#include <linux/string_helpers.h>
+#include <linux/file.h>
+#include <linux/pagemap.h>
+#include <linux/namei.h>
+#include <linux/mount.h>
+#include <linux/fs_context.h>
+#include <linux/syscalls.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+
+#include "internal.h"
+
+#ifdef DEBUG
+# define USE_DEBUG 1
+#else
+# define USE_DEBUG 0
+#endif
+
+enum {
+ VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
+};
+
+static LIST_HEAD(entries);
+static int enabled = 1;
+
+enum {Enabled, Magic};
+#define MISC_FMT_PRESERVE_ARGV0 (1UL << 31)
+#define MISC_FMT_OPEN_BINARY (1UL << 30)
+#define MISC_FMT_CREDENTIALS (1UL << 29)
+#define MISC_FMT_OPEN_FILE (1UL << 28)
+
+typedef struct {
+ struct list_head list;
+ unsigned long flags; /* type, status, etc. */
+ int offset; /* offset of magic */
+ int size; /* size of magic/mask */
+ char *magic; /* magic or filename extension */
+ char *mask; /* mask, NULL for exact match */
+ const char *interpreter; /* filename of interpreter */
+ char *name;
+ struct dentry *dentry;
+ struct file *interp_file;
+ refcount_t users; /* sync removal with load_misc_binary() */
+} Node;
+
+static DEFINE_RWLOCK(entries_lock);
+static struct file_system_type bm_fs_type;
+
+/*
+ * Max length of the register string. Determined by:
+ * - 7 delimiters
+ * - name: ~50 bytes
+ * - type: 1 byte
+ * - offset: 3 bytes (has to be smaller than BINPRM_BUF_SIZE)
+ * - magic: 128 bytes (512 in escaped form)
+ * - mask: 128 bytes (512 in escaped form)
+ * - interp: ~50 bytes
+ * - flags: 5 bytes
+ * Round that up a bit, and then back off to hold the internal data
+ * (like struct Node).
+ */
+#define MAX_REGISTER_LENGTH 1920
+
+/**
+ * search_binfmt_handler - search for a binary handler for @bprm
+ * @misc: handle to binfmt_misc instance
+ * @bprm: binary for which we are looking for a handler
+ *
+ * Search for a binary type handler for @bprm in the list of registered binary
+ * type handlers.
+ *
+ * Return: binary type list entry on success, NULL on failure
+ */
+static Node *search_binfmt_handler(struct linux_binprm *bprm)
+{
+ char *p = strrchr(bprm->interp, '.');
+ Node *e;
+
+ /* Walk all the registered handlers. */
+ list_for_each_entry(e, &entries, list) {
+ char *s;
+ int j;
+
+ /* Make sure this one is currently enabled. */
+ if (!test_bit(Enabled, &e->flags))
+ continue;
+
+ /* Do matching based on extension if applicable. */
+ if (!test_bit(Magic, &e->flags)) {
+ if (p && !strcmp(e->magic, p + 1))
+ return e;
+ continue;
+ }
+
+ /* Do matching based on magic & mask. */
+ s = bprm->buf + e->offset;
+ if (e->mask) {
+ for (j = 0; j < e->size; j++)
+ if ((*s++ ^ e->magic[j]) & e->mask[j])
+ break;
+ } else {
+ for (j = 0; j < e->size; j++)
+ if ((*s++ ^ e->magic[j]))
+ break;
+ }
+ if (j == e->size)
+ return e;
+ }
+
+ return NULL;
+}
+
+/**
+ * get_binfmt_handler - try to find a binary type handler
+ * @misc: handle to binfmt_misc instance
+ * @bprm: binary for which we are looking for a handler
+ *
+ * Try to find a binfmt handler for the binary type. If one is found take a
+ * reference to protect against removal via bm_{entry,status}_write().
+ *
+ * Return: binary type list entry on success, NULL on failure
+ */
+static Node *get_binfmt_handler(struct linux_binprm *bprm)
+{
+ Node *e;
+
+ read_lock(&entries_lock);
+ e = search_binfmt_handler(bprm);
+ if (e)
+ refcount_inc(&e->users);
+ read_unlock(&entries_lock);
+ return e;
+}
+
+/**
+ * put_binfmt_handler - put binary handler node
+ * @e: node to put
+ *
+ * Free node syncing with load_misc_binary() and defer final free to
+ * load_misc_binary() in case it is using the binary type handler we were
+ * requested to remove.
+ */
+static void put_binfmt_handler(Node *e)
+{
+ if (refcount_dec_and_test(&e->users)) {
+ if (e->flags & MISC_FMT_OPEN_FILE)
+ filp_close(e->interp_file, NULL);
+ kfree(e);
+ }
+}
+
+/*
+ * the loader itself
+ */
+static int load_misc_binary(struct linux_binprm *bprm)
+{
+ Node *fmt;
+ struct file *interp_file = NULL;
+ int retval;
+ int fd_binary = -1;
+
+ retval = -ENOEXEC;
+ if (!enabled)
+ return retval;
+
+ fmt = get_binfmt_handler(bprm);
+ if (!fmt)
+ return retval;
+
+ /* Need to be able to load the file after exec */
+ retval = -ENOENT;
+ if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
+ goto ret;
+
+ if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
+ retval = remove_arg_zero(bprm);
+ if (retval)
+ goto ret;
+ }
+
+ if (fmt->flags & MISC_FMT_OPEN_BINARY) {
+
+ /* if the binary should be opened on behalf of the
+ * interpreter than keep it open and assign descriptor
+ * to it
+ */
+ fd_binary = get_unused_fd_flags(0);
+ if (fd_binary < 0) {
+ retval = fd_binary;
+ goto ret;
+ }
+ fd_install(fd_binary, bprm->file);
+
+ /* if the binary is not readable than enforce mm->dumpable=0
+ regardless of the interpreter's permissions */
+ would_dump(bprm, bprm->file);
+
+ allow_write_access(bprm->file);
+ bprm->file = NULL;
+
+ /* mark the bprm that fd should be passed to interp */
+ bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
+ bprm->interp_data = fd_binary;
+
+ } else {
+ allow_write_access(bprm->file);
+ fput(bprm->file);
+ bprm->file = NULL;
+ }
+ /* make argv[1] be the path to the binary */
+ retval = copy_strings_kernel(1, &bprm->interp, bprm);
+ if (retval < 0)
+ goto error;
+ bprm->argc++;
+
+ /* add the interp as argv[0] */
+ retval = copy_strings_kernel(1, &fmt->interpreter, bprm);
+ if (retval < 0)
+ goto error;
+ bprm->argc++;
+
+ /* Update interp in case binfmt_script needs it. */
+ retval = bprm_change_interp(fmt->interpreter, bprm);
+ if (retval < 0)
+ goto error;
+
+ if (fmt->flags & MISC_FMT_OPEN_FILE) {
+ interp_file = file_clone_open(fmt->interp_file);
+ if (!IS_ERR(interp_file))
+ deny_write_access(interp_file);
+ } else {
+ interp_file = open_exec(fmt->interpreter);
+ }
+ retval = PTR_ERR(interp_file);
+ if (IS_ERR(interp_file))
+ goto error;
+
+ bprm->file = interp_file;
+ if (fmt->flags & MISC_FMT_CREDENTIALS) {
+ loff_t pos = 0;
+
+ /*
+ * No need to call prepare_binprm(), it's already been
+ * done. bprm->buf is stale, update from interp_file.
+ */
+ memset(bprm->buf, 0, BINPRM_BUF_SIZE);
+ retval = kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE,
+ &pos);
+ } else
+ retval = prepare_binprm(bprm);
+
+ if (retval < 0)
+ goto error;
+
+ retval = search_binary_handler(bprm);
+ if (retval < 0)
+ goto error;
+
+ret:
+
+ /*
+ * If we actually put the node here all concurrent calls to
+ * load_misc_binary() will have finished. We also know
+ * that for the refcount to be zero ->evict_inode() must have removed
+ * the node to be deleted from the list. All that is left for us is to
+ * close and free.
+ */
+ put_binfmt_handler(fmt);
+
+ return retval;
+error:
+ if (fd_binary > 0)
+ ksys_close(fd_binary);
+ bprm->interp_flags = 0;
+ bprm->interp_data = 0;
+ goto ret;
+}
+
+/* Command parsers */
+
+/*
+ * parses and copies one argument enclosed in del from *sp to *dp,
+ * recognising the \x special.
+ * returns pointer to the copied argument or NULL in case of an
+ * error (and sets err) or null argument length.
+ */
+static char *scanarg(char *s, char del)
+{
+ char c;
+
+ while ((c = *s++) != del) {
+ if (c == '\\' && *s == 'x') {
+ s++;
+ if (!isxdigit(*s++))
+ return NULL;
+ if (!isxdigit(*s++))
+ return NULL;
+ }
+ }
+ s[-1] ='\0';
+ return s;
+}
+
+static char *check_special_flags(char *sfs, Node *e)
+{
+ char *p = sfs;
+ int cont = 1;
+
+ /* special flags */
+ while (cont) {
+ switch (*p) {
+ case 'P':
+ pr_debug("register: flag: P (preserve argv0)\n");
+ p++;
+ e->flags |= MISC_FMT_PRESERVE_ARGV0;
+ break;
+ case 'O':
+ pr_debug("register: flag: O (open binary)\n");
+ p++;
+ e->flags |= MISC_FMT_OPEN_BINARY;
+ break;
+ case 'C':
+ pr_debug("register: flag: C (preserve creds)\n");
+ p++;
+ /* this flags also implies the
+ open-binary flag */
+ e->flags |= (MISC_FMT_CREDENTIALS |
+ MISC_FMT_OPEN_BINARY);
+ break;
+ case 'F':
+ pr_debug("register: flag: F: open interpreter file now\n");
+ p++;
+ e->flags |= MISC_FMT_OPEN_FILE;
+ break;
+ default:
+ cont = 0;
+ }
+ }
+
+ return p;
+}
+
+/*
+ * This registers a new binary format, it recognises the syntax
+ * ':name:type:offset:magic:mask:interpreter:flags'
+ * where the ':' is the IFS, that can be chosen with the first char
+ */
+static Node *create_entry(const char __user *buffer, size_t count)
+{
+ Node *e;
+ int memsize, err;
+ char *buf, *p;
+ char del;
+
+ pr_debug("register: received %zu bytes\n", count);
+
+ /* some sanity checks */
+ err = -EINVAL;
+ if ((count < 11) || (count > MAX_REGISTER_LENGTH))
+ goto out;
+
+ err = -ENOMEM;
+ memsize = sizeof(Node) + count + 8;
+ e = kmalloc(memsize, GFP_KERNEL);
+ if (!e)
+ goto out;
+
+ p = buf = (char *)e + sizeof(Node);
+
+ memset(e, 0, sizeof(Node));
+ if (copy_from_user(buf, buffer, count))
+ goto efault;
+
+ del = *p++; /* delimeter */
+
+ pr_debug("register: delim: %#x {%c}\n", del, del);
+
+ /* Pad the buffer with the delim to simplify parsing below. */
+ memset(buf + count, del, 8);
+
+ /* Parse the 'name' field. */
+ e->name = p;
+ p = strchr(p, del);
+ if (!p)
+ goto einval;
+ *p++ = '\0';
+ if (!e->name[0] ||
+ !strcmp(e->name, ".") ||
+ !strcmp(e->name, "..") ||
+ strchr(e->name, '/'))
+ goto einval;
+
+ pr_debug("register: name: {%s}\n", e->name);
+
+ /* Parse the 'type' field. */
+ switch (*p++) {
+ case 'E':
+ pr_debug("register: type: E (extension)\n");
+ e->flags = 1 << Enabled;
+ break;
+ case 'M':
+ pr_debug("register: type: M (magic)\n");
+ e->flags = (1 << Enabled) | (1 << Magic);
+ break;
+ default:
+ goto einval;
+ }
+ if (*p++ != del)
+ goto einval;
+
+ if (test_bit(Magic, &e->flags)) {
+ /* Handle the 'M' (magic) format. */
+ char *s;
+
+ /* Parse the 'offset' field. */
+ s = strchr(p, del);
+ if (!s)
+ goto einval;
+ *s = '\0';
+ if (p != s) {
+ int r = kstrtoint(p, 10, &e->offset);
+ if (r != 0 || e->offset < 0)
+ goto einval;
+ }
+ p = s;
+ if (*p++)
+ goto einval;
+ pr_debug("register: offset: %#x\n", e->offset);
+
+ /* Parse the 'magic' field. */
+ e->magic = p;
+ p = scanarg(p, del);
+ if (!p)
+ goto einval;
+ if (!e->magic[0])
+ goto einval;
+ if (USE_DEBUG)
+ print_hex_dump_bytes(
+ KBUILD_MODNAME ": register: magic[raw]: ",
+ DUMP_PREFIX_NONE, e->magic, p - e->magic);
+
+ /* Parse the 'mask' field. */
+ e->mask = p;
+ p = scanarg(p, del);
+ if (!p)
+ goto einval;
+ if (!e->mask[0]) {
+ e->mask = NULL;
+ pr_debug("register: mask[raw]: none\n");
+ } else if (USE_DEBUG)
+ print_hex_dump_bytes(
+ KBUILD_MODNAME ": register: mask[raw]: ",
+ DUMP_PREFIX_NONE, e->mask, p - e->mask);
+
+ /*
+ * Decode the magic & mask fields.
+ * Note: while we might have accepted embedded NUL bytes from
+ * above, the unescape helpers here will stop at the first one
+ * it encounters.
+ */
+ e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX);
+ if (e->mask &&
+ string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size)
+ goto einval;
+ if (e->size > BINPRM_BUF_SIZE ||
+ BINPRM_BUF_SIZE - e->size < e->offset)
+ goto einval;
+ pr_debug("register: magic/mask length: %i\n", e->size);
+ if (USE_DEBUG) {
+ print_hex_dump_bytes(
+ KBUILD_MODNAME ": register: magic[decoded]: ",
+ DUMP_PREFIX_NONE, e->magic, e->size);
+
+ if (e->mask) {
+ int i;
+ char *masked = kmalloc(e->size, GFP_KERNEL);
+
+ print_hex_dump_bytes(
+ KBUILD_MODNAME ": register: mask[decoded]: ",
+ DUMP_PREFIX_NONE, e->mask, e->size);
+
+ if (masked) {
+ for (i = 0; i < e->size; ++i)
+ masked[i] = e->magic[i] & e->mask[i];
+ print_hex_dump_bytes(
+ KBUILD_MODNAME ": register: magic[masked]: ",
+ DUMP_PREFIX_NONE, masked, e->size);
+
+ kfree(masked);
+ }
+ }
+ }
+ } else {
+ /* Handle the 'E' (extension) format. */
+
+ /* Skip the 'offset' field. */
+ p = strchr(p, del);
+ if (!p)
+ goto einval;
+ *p++ = '\0';
+
+ /* Parse the 'magic' field. */
+ e->magic = p;
+ p = strchr(p, del);
+ if (!p)
+ goto einval;
+ *p++ = '\0';
+ if (!e->magic[0] || strchr(e->magic, '/'))
+ goto einval;
+ pr_debug("register: extension: {%s}\n", e->magic);
+
+ /* Skip the 'mask' field. */
+ p = strchr(p, del);
+ if (!p)
+ goto einval;
+ *p++ = '\0';
+ }
+
+ /* Parse the 'interpreter' field. */
+ e->interpreter = p;
+ p = strchr(p, del);
+ if (!p)
+ goto einval;
+ *p++ = '\0';
+ if (!e->interpreter[0])
+ goto einval;
+ pr_debug("register: interpreter: {%s}\n", e->interpreter);
+
+ /* Parse the 'flags' field. */
+ p = check_special_flags(p, e);
+ if (*p == '\n')
+ p++;
+ if (p != buf + count)
+ goto einval;
+
+ return e;
+
+out:
+ return ERR_PTR(err);
+
+efault:
+ kfree(e);
+ return ERR_PTR(-EFAULT);
+einval:
+ kfree(e);
+ return ERR_PTR(-EINVAL);
+}
+
+/*
+ * Set status of entry/binfmt_misc:
+ * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
+ */
+static int parse_command(const char __user *buffer, size_t count)
+{
+ char s[4];
+
+ if (count > 3)
+ return -EINVAL;
+ if (copy_from_user(s, buffer, count))
+ return -EFAULT;
+ if (!count)
+ return 0;
+ if (s[count - 1] == '\n')
+ count--;
+ if (count == 1 && s[0] == '0')
+ return 1;
+ if (count == 1 && s[0] == '1')
+ return 2;
+ if (count == 2 && s[0] == '-' && s[1] == '1')
+ return 3;
+ return -EINVAL;
+}
+
+/* generic stuff */
+
+static void entry_status(Node *e, char *page)
+{
+ char *dp = page;
+ const char *status = "disabled";
+
+ if (test_bit(Enabled, &e->flags))
+ status = "enabled";
+
+ if (!VERBOSE_STATUS) {
+ sprintf(page, "%s\n", status);
+ return;
+ }
+
+ dp += sprintf(dp, "%s\ninterpreter %s\n", status, e->interpreter);
+
+ /* print the special flags */
+ dp += sprintf(dp, "flags: ");
+ if (e->flags & MISC_FMT_PRESERVE_ARGV0)
+ *dp++ = 'P';
+ if (e->flags & MISC_FMT_OPEN_BINARY)
+ *dp++ = 'O';
+ if (e->flags & MISC_FMT_CREDENTIALS)
+ *dp++ = 'C';
+ if (e->flags & MISC_FMT_OPEN_FILE)
+ *dp++ = 'F';
+ *dp++ = '\n';
+
+ if (!test_bit(Magic, &e->flags)) {
+ sprintf(dp, "extension .%s\n", e->magic);
+ } else {
+ dp += sprintf(dp, "offset %i\nmagic ", e->offset);
+ dp = bin2hex(dp, e->magic, e->size);
+ if (e->mask) {
+ dp += sprintf(dp, "\nmask ");
+ dp = bin2hex(dp, e->mask, e->size);
+ }
+ *dp++ = '\n';
+ *dp = '\0';
+ }
+}
+
+static struct inode *bm_get_inode(struct super_block *sb, int mode)
+{
+ struct inode *inode = new_inode(sb);
+
+ if (inode) {
+ inode->i_ino = get_next_ino();
+ inode->i_mode = mode;
+ inode->i_atime = inode->i_mtime = inode->i_ctime =
+ current_time(inode);
+ }
+ return inode;
+}
+
+/**
+ * bm_evict_inode - cleanup data associated with @inode
+ * @inode: inode to which the data is attached
+ *
+ * Cleanup the binary type handler data associated with @inode if a binary type
+ * entry is removed or the filesystem is unmounted and the super block is
+ * shutdown.
+ *
+ * If the ->evict call was not caused by a super block shutdown but by a write
+ * to remove the entry or all entries via bm_{entry,status}_write() the entry
+ * will have already been removed from the list. We keep the list_empty() check
+ * to make that explicit.
+*/
+static void bm_evict_inode(struct inode *inode)
+{
+ Node *e = inode->i_private;
+
+ clear_inode(inode);
+
+ if (e) {
+ write_lock(&entries_lock);
+ if (!list_empty(&e->list))
+ list_del_init(&e->list);
+ write_unlock(&entries_lock);
+ put_binfmt_handler(e);
+ }
+}
+
+/**
+ * unlink_binfmt_dentry - remove the dentry for the binary type handler
+ * @dentry: dentry associated with the binary type handler
+ *
+ * Do the actual filesystem work to remove a dentry for a registered binary
+ * type handler. Since binfmt_misc only allows simple files to be created
+ * directly under the root dentry of the filesystem we ensure that we are
+ * indeed passed a dentry directly beneath the root dentry, that the inode
+ * associated with the root dentry is locked, and that it is a regular file we
+ * are asked to remove.
+ */
+static void unlink_binfmt_dentry(struct dentry *dentry)
+{
+ struct dentry *parent = dentry->d_parent;
+ struct inode *inode, *parent_inode;
+
+ /* All entries are immediate descendants of the root dentry. */
+ if (WARN_ON_ONCE(dentry->d_sb->s_root != parent))
+ return;
+
+ /* We only expect to be called on regular files. */
+ inode = d_inode(dentry);
+ if (WARN_ON_ONCE(!S_ISREG(inode->i_mode)))
+ return;
+
+ /* The parent inode must be locked. */
+ parent_inode = d_inode(parent);
+ if (WARN_ON_ONCE(!inode_is_locked(parent_inode)))
+ return;
+
+ if (simple_positive(dentry)) {
+ dget(dentry);
+ simple_unlink(parent_inode, dentry);
+ d_delete(dentry);
+ dput(dentry);
+ }
+}
+
+/**
+ * remove_binfmt_handler - remove a binary type handler
+ * @misc: handle to binfmt_misc instance
+ * @e: binary type handler to remove
+ *
+ * Remove a binary type handler from the list of binary type handlers and
+ * remove its associated dentry. This is called from
+ * binfmt_{entry,status}_write(). In the future, we might want to think about
+ * adding a proper ->unlink() method to binfmt_misc instead of forcing caller's
+ * to use writes to files in order to delete binary type handlers. But it has
+ * worked for so long that it's not a pressing issue.
+ */
+static void remove_binfmt_handler(Node *e)
+{
+ write_lock(&entries_lock);
+ list_del_init(&e->list);
+ write_unlock(&entries_lock);
+ unlink_binfmt_dentry(e->dentry);
+}
+
+/* /<entry> */
+
+static ssize_t
+bm_entry_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+{
+ Node *e = file_inode(file)->i_private;
+ ssize_t res;
+ char *page;
+
+ page = (char *) __get_free_page(GFP_KERNEL);
+ if (!page)
+ return -ENOMEM;
+
+ entry_status(e, page);
+
+ res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
+
+ free_page((unsigned long) page);
+ return res;
+}
+
+static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ struct inode *inode = file_inode(file);
+ Node *e = inode->i_private;
+ int res = parse_command(buffer, count);
+
+ switch (res) {
+ case 1:
+ /* Disable this handler. */
+ clear_bit(Enabled, &e->flags);
+ break;
+ case 2:
+ /* Enable this handler. */
+ set_bit(Enabled, &e->flags);
+ break;
+ case 3:
+ /* Delete this handler. */
+ inode = d_inode(inode->i_sb->s_root);
+ inode_lock(inode);
+
+ /*
+ * In order to add new element or remove elements from the list
+ * via bm_{entry,register,status}_write() inode_lock() on the
+ * root inode must be held.
+ * The lock is exclusive ensuring that the list can't be
+ * modified. Only load_misc_binary() can access but does so
+ * read-only. So we only need to take the write lock when we
+ * actually remove the entry from the list.
+ */
+ if (!list_empty(&e->list))
+ remove_binfmt_handler(e);
+
+ inode_unlock(inode);
+ break;
+ default:
+ return res;
+ }
+
+ return count;
+}
+
+static const struct file_operations bm_entry_operations = {
+ .read = bm_entry_read,
+ .write = bm_entry_write,
+ .llseek = default_llseek,
+};
+
+/* /register */
+
+static ssize_t bm_register_write(struct file *file, const char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ Node *e;
+ struct inode *inode;
+ struct super_block *sb = file_inode(file)->i_sb;
+ struct dentry *root = sb->s_root, *dentry;
+ int err = 0;
+ struct file *f = NULL;
+
+ e = create_entry(buffer, count);
+
+ if (IS_ERR(e))
+ return PTR_ERR(e);
+
+ if (e->flags & MISC_FMT_OPEN_FILE) {
+ f = open_exec(e->interpreter);
+ if (IS_ERR(f)) {
+ pr_notice("register: failed to install interpreter file %s\n",
+ e->interpreter);
+ kfree(e);
+ return PTR_ERR(f);
+ }
+ e->interp_file = f;
+ }
+
+ inode_lock(d_inode(root));
+ dentry = lookup_one_len(e->name, root, strlen(e->name));
+ err = PTR_ERR(dentry);
+ if (IS_ERR(dentry))
+ goto out;
+
+ err = -EEXIST;
+ if (d_really_is_positive(dentry))
+ goto out2;
+
+ inode = bm_get_inode(sb, S_IFREG | 0644);
+
+ err = -ENOMEM;
+ if (!inode)
+ goto out2;
+
+ refcount_set(&e->users, 1);
+ e->dentry = dget(dentry);
+ inode->i_private = e;
+ inode->i_fop = &bm_entry_operations;
+
+ d_instantiate(dentry, inode);
+ write_lock(&entries_lock);
+ list_add(&e->list, &entries);
+ write_unlock(&entries_lock);
+
+ err = 0;
+out2:
+ dput(dentry);
+out:
+ inode_unlock(d_inode(root));
+
+ if (err) {
+ if (f)
+ filp_close(f, NULL);
+ kfree(e);
+ return err;
+ }
+ return count;
+}
+
+static const struct file_operations bm_register_operations = {
+ .write = bm_register_write,
+ .llseek = noop_llseek,
+};
+
+/* /status */
+
+static ssize_t
+bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+{
+ char *s = enabled ? "enabled\n" : "disabled\n";
+
+ return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
+}
+
+static ssize_t bm_status_write(struct file *file, const char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ int res = parse_command(buffer, count);
+ Node *e, *next;
+ struct inode *inode;
+
+ switch (res) {
+ case 1:
+ /* Disable all handlers. */
+ enabled = 0;
+ break;
+ case 2:
+ /* Enable all handlers. */
+ enabled = 1;
+ break;
+ case 3:
+ /* Delete all handlers. */
+ inode = d_inode(file_inode(file)->i_sb->s_root);
+ inode_lock(inode);
+
+ /*
+ * In order to add new element or remove elements from the list
+ * via bm_{entry,register,status}_write() inode_lock() on the
+ * root inode must be held.
+ * The lock is exclusive ensuring that the list can't be
+ * modified. Only load_misc_binary() can access but does so
+ * read-only. So we only need to take the write lock when we
+ * actually remove the entry from the list.
+ */
+ list_for_each_entry_safe(e, next, &entries, list)
+ remove_binfmt_handler(e);
+
+ inode_unlock(inode);
+ break;
+ default:
+ return res;
+ }
+
+ return count;
+}
+
+static const struct file_operations bm_status_operations = {
+ .read = bm_status_read,
+ .write = bm_status_write,
+ .llseek = default_llseek,
+};
+
+/* Superblock handling */
+
+static const struct super_operations s_ops = {
+ .statfs = simple_statfs,
+ .evict_inode = bm_evict_inode,
+};
+
+static int bm_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+ int err;
+ static const struct tree_descr bm_files[] = {
+ [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
+ [3] = {"register", &bm_register_operations, S_IWUSR},
+ /* last one */ {""}
+ };
+
+ err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
+ if (!err)
+ sb->s_op = &s_ops;
+ return err;
+}
+
+static int bm_get_tree(struct fs_context *fc)
+{
+ return get_tree_single(fc, bm_fill_super);
+}
+
+static const struct fs_context_operations bm_context_ops = {
+ .get_tree = bm_get_tree,
+};
+
+static int bm_init_fs_context(struct fs_context *fc)
+{
+ fc->ops = &bm_context_ops;
+ return 0;
+}
+
+static struct linux_binfmt misc_format = {
+ .module = THIS_MODULE,
+ .load_binary = load_misc_binary,
+};
+
+static struct file_system_type bm_fs_type = {
+ .owner = THIS_MODULE,
+ .name = "binfmt_misc",
+ .init_fs_context = bm_init_fs_context,
+ .kill_sb = kill_litter_super,
+};
+MODULE_ALIAS_FS("binfmt_misc");
+
+static int __init init_misc_binfmt(void)
+{
+ int err = register_filesystem(&bm_fs_type);
+ if (!err)
+ insert_binfmt(&misc_format);
+ return err;
+}
+
+static void __exit exit_misc_binfmt(void)
+{
+ unregister_binfmt(&misc_format);
+ unregister_filesystem(&bm_fs_type);
+}
+
+core_initcall(init_misc_binfmt);
+module_exit(exit_misc_binfmt);
+MODULE_LICENSE("GPL");