/*
   *  This code exports profiling data as debugfs files to userspace.
   *
   *    Copyright IBM Corp. 2009
   *    Author(s): Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
   *
   *    Uses gcc-internal data definitions.
   *    Based on the gcov-kernel patch by:
   *		 Hubertus Franke <frankeh@us.ibm.com>
   *		 Nigel Hinds <nhinds@us.ibm.com>
   *		 Rajan Ravindran <rajancr@us.ibm.com>
   *		 Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
   *		 Paul Larson
   *		 Yi CDL Yang
   */
  
  #define pr_fmt(fmt)	"gcov: " fmt
  
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/debugfs.h>
  #include <linux/fs.h>
  #include <linux/list.h>
  #include <linux/string.h>
  #include <linux/slab.h>
  #include <linux/mutex.h>
  #include <linux/seq_file.h>
  #include "gcov.h"
  
  /**
   * struct gcov_node - represents a debugfs entry
   * @list: list head for child node list
   * @children: child nodes
   * @all: list head for list of all nodes
   * @parent: parent node

   * @loaded_info: array of pointers to profiling data sets for loaded object
   *   files.
   * @num_loaded: number of profiling data sets for loaded object files.
   * @unloaded_info: accumulated copy of profiling data sets for unloaded
   *   object files. Used only when gcov_persist=1.

   * @dentry: main debugfs entry, either a directory or data file
   * @links: associated symbolic links
   * @name: data file basename
   *
   * struct gcov_node represents an entity within the gcov/ subdirectory
   * of debugfs. There are directory and data file nodes. The latter represent
   * the actual synthesized data file plus any associated symbolic links which
   * are needed by the gcov tool to work correctly.
   */
  struct gcov_node {
  	struct list_head list;
  	struct list_head children;
  	struct list_head all;
  	struct gcov_node *parent;

  	struct gcov_info **loaded_info;
  	struct gcov_info *unloaded_info;

  	struct dentry *dentry;
  	struct dentry **links;

  	int num_loaded;

  	char name[0];
  };
  
  static const char objtree[] = OBJTREE;
  static const char srctree[] = SRCTREE;
  static struct gcov_node root_node;
  static struct dentry *reset_dentry;
  static LIST_HEAD(all_head);
  static DEFINE_MUTEX(node_lock);
  
  /* If non-zero, keep copies of profiling data for unloaded modules. */
  static int gcov_persist = 1;
  
  static int __init gcov_persist_setup(char *str)
  {
  	unsigned long val;
  
  	if (strict_strtoul(str, 0, &val)) {
  		pr_warning("invalid gcov_persist parameter '%s'
  ", str);
  		return 0;
  	}
  	gcov_persist = val;
  	pr_info("setting gcov_persist to %d
  ", gcov_persist);
  
  	return 1;
  }
  __setup("gcov_persist=", gcov_persist_setup);
  
  /*
   * seq_file.start() implementation for gcov data files. Note that the
   * gcov_iterator interface is designed to be more restrictive than seq_file
   * (no start from arbitrary position, etc.), to simplify the iterator
   * implementation.
   */
  static void *gcov_seq_start(struct seq_file *seq, loff_t *pos)
  {
  	loff_t i;
  
  	gcov_iter_start(seq->private);
  	for (i = 0; i < *pos; i++) {
  		if (gcov_iter_next(seq->private))
  			return NULL;
  	}
  	return seq->private;
  }
  
  /* seq_file.next() implementation for gcov data files. */
  static void *gcov_seq_next(struct seq_file *seq, void *data, loff_t *pos)
  {
  	struct gcov_iterator *iter = data;
  
  	if (gcov_iter_next(iter))
  		return NULL;
  	(*pos)++;
  
  	return iter;
  }
  
  /* seq_file.show() implementation for gcov data files. */
  static int gcov_seq_show(struct seq_file *seq, void *data)
  {
  	struct gcov_iterator *iter = data;
  
  	if (gcov_iter_write(iter, seq))
  		return -EINVAL;
  	return 0;
  }
  
  static void gcov_seq_stop(struct seq_file *seq, void *data)
  {
  	/* Unused. */
  }
  
  static const struct seq_operations gcov_seq_ops = {
  	.start	= gcov_seq_start,
  	.next	= gcov_seq_next,
  	.show	= gcov_seq_show,
  	.stop	= gcov_seq_stop,
  };
  
  /*

   * Return a profiling data set associated with the given node. This is
   * either a data set for a loaded object file or a data set copy in case
   * all associated object files have been unloaded.

   */
  static struct gcov_info *get_node_info(struct gcov_node *node)
  {

  	if (node->num_loaded > 0)
  		return node->loaded_info[0];

  	return node->unloaded_info;
  }
  
  /*
   * Return a newly allocated profiling data set which contains the sum of
   * all profiling data associated with the given node.
   */
  static struct gcov_info *get_accumulated_info(struct gcov_node *node)
  {
  	struct gcov_info *info;
  	int i = 0;
  
  	if (node->unloaded_info)
  		info = gcov_info_dup(node->unloaded_info);
  	else
  		info = gcov_info_dup(node->loaded_info[i++]);
  	if (!info)
  		return NULL;
  	for (; i < node->num_loaded; i++)
  		gcov_info_add(info, node->loaded_info[i]);
  
  	return info;

  }
  
  /*
   * open() implementation for gcov data files. Create a copy of the profiling
   * data set and initialize the iterator and seq_file interface.
   */
  static int gcov_seq_open(struct inode *inode, struct file *file)
  {
  	struct gcov_node *node = inode->i_private;
  	struct gcov_iterator *iter;
  	struct seq_file *seq;
  	struct gcov_info *info;
  	int rc = -ENOMEM;
  
  	mutex_lock(&node_lock);
  	/*
  	 * Read from a profiling data copy to minimize reference tracking

  	 * complexity and concurrent access and to keep accumulating multiple
  	 * profiling data sets associated with one node simple.

  	 */

  	info = get_accumulated_info(node);

  	if (!info)
  		goto out_unlock;
  	iter = gcov_iter_new(info);
  	if (!iter)
  		goto err_free_info;
  	rc = seq_open(file, &gcov_seq_ops);
  	if (rc)
  		goto err_free_iter_info;
  	seq = file->private_data;
  	seq->private = iter;
  out_unlock:
  	mutex_unlock(&node_lock);
  	return rc;
  
  err_free_iter_info:
  	gcov_iter_free(iter);
  err_free_info:
  	gcov_info_free(info);
  	goto out_unlock;
  }
  
  /*
   * release() implementation for gcov data files. Release resources allocated
   * by open().
   */
  static int gcov_seq_release(struct inode *inode, struct file *file)
  {
  	struct gcov_iterator *iter;
  	struct gcov_info *info;
  	struct seq_file *seq;
  
  	seq = file->private_data;
  	iter = seq->private;
  	info = gcov_iter_get_info(iter);
  	gcov_iter_free(iter);
  	gcov_info_free(info);
  	seq_release(inode, file);
  
  	return 0;
  }
  
  /*
   * Find a node by the associated data file name. Needs to be called with
   * node_lock held.
   */
  static struct gcov_node *get_node_by_name(const char *name)
  {
  	struct gcov_node *node;
  	struct gcov_info *info;
  
  	list_for_each_entry(node, &all_head, all) {
  		info = get_node_info(node);
  		if (info && (strcmp(info->filename, name) == 0))
  			return node;
  	}
  
  	return NULL;
  }

  /*
   * Reset all profiling data associated with the specified node.
   */
  static void reset_node(struct gcov_node *node)
  {
  	int i;
  
  	if (node->unloaded_info)
  		gcov_info_reset(node->unloaded_info);
  	for (i = 0; i < node->num_loaded; i++)
  		gcov_info_reset(node->loaded_info[i]);
  }

  static void remove_node(struct gcov_node *node);
  
  /*
   * write() implementation for gcov data files. Reset profiling data for the

   * corresponding file. If all associated object files have been unloaded,
   * remove the debug fs node as well.

   */
  static ssize_t gcov_seq_write(struct file *file, const char __user *addr,
  			      size_t len, loff_t *pos)
  {
  	struct seq_file *seq;
  	struct gcov_info *info;
  	struct gcov_node *node;
  
  	seq = file->private_data;
  	info = gcov_iter_get_info(seq->private);
  	mutex_lock(&node_lock);
  	node = get_node_by_name(info->filename);
  	if (node) {
  		/* Reset counts or remove node for unloaded modules. */

  		if (node->num_loaded == 0)

  			remove_node(node);
  		else

  			reset_node(node);

  	}
  	/* Reset counts for open file. */
  	gcov_info_reset(info);
  	mutex_unlock(&node_lock);
  
  	return len;
  }
  
  /*
   * Given a string <path> representing a file path of format:
   *   path/to/file.gcda
   * construct and return a new string:
   *   <dir/>path/to/file.<ext>
   */
  static char *link_target(const char *dir, const char *path, const char *ext)
  {
  	char *target;
  	char *old_ext;
  	char *copy;
  
  	copy = kstrdup(path, GFP_KERNEL);
  	if (!copy)
  		return NULL;
  	old_ext = strrchr(copy, '.');
  	if (old_ext)
  		*old_ext = '\0';
  	if (dir)
  		target = kasprintf(GFP_KERNEL, "%s/%s.%s", dir, copy, ext);
  	else
  		target = kasprintf(GFP_KERNEL, "%s.%s", copy, ext);
  	kfree(copy);
  
  	return target;
  }
  
  /*
   * Construct a string representing the symbolic link target for the given
   * gcov data file name and link type. Depending on the link type and the
   * location of the data file, the link target can either point to a
   * subdirectory of srctree, objtree or in an external location.
   */
  static char *get_link_target(const char *filename, const struct gcov_link *ext)
  {
  	const char *rel;
  	char *result;
  
  	if (strncmp(filename, objtree, strlen(objtree)) == 0) {
  		rel = filename + strlen(objtree) + 1;
  		if (ext->dir == SRC_TREE)
  			result = link_target(srctree, rel, ext->ext);
  		else
  			result = link_target(objtree, rel, ext->ext);
  	} else {
  		/* External compilation. */
  		result = link_target(NULL, filename, ext->ext);
  	}
  
  	return result;
  }
  
  #define SKEW_PREFIX	".tmp_"
  
  /*
   * For a filename .tmp_filename.ext return filename.ext. Needed to compensate
   * for filename skewing caused by the mod-versioning mechanism.
   */
  static const char *deskew(const char *basename)
  {
  	if (strncmp(basename, SKEW_PREFIX, sizeof(SKEW_PREFIX) - 1) == 0)
  		return basename + sizeof(SKEW_PREFIX) - 1;
  	return basename;
  }
  
  /*
   * Create links to additional files (usually .c and .gcno files) which the
   * gcov tool expects to find in the same directory as the gcov data file.
   */
  static void add_links(struct gcov_node *node, struct dentry *parent)
  {
  	char *basename;
  	char *target;
  	int num;
  	int i;
  
  	for (num = 0; gcov_link[num].ext; num++)
  		/* Nothing. */;
  	node->links = kcalloc(num, sizeof(struct dentry *), GFP_KERNEL);
  	if (!node->links)
  		return;
  	for (i = 0; i < num; i++) {
  		target = get_link_target(get_node_info(node)->filename,
  					 &gcov_link[i]);
  		if (!target)
  			goto out_err;
  		basename = strrchr(target, '/');
  		if (!basename)
  			goto out_err;
  		basename++;
  		node->links[i] = debugfs_create_symlink(deskew(basename),
  							parent,	target);
  		if (!node->links[i])
  			goto out_err;
  		kfree(target);
  	}
  
  	return;
  out_err:
  	kfree(target);
  	while (i-- > 0)
  		debugfs_remove(node->links[i]);
  	kfree(node->links);
  	node->links = NULL;
  }
  
  static const struct file_operations gcov_data_fops = {
  	.open		= gcov_seq_open,
  	.release	= gcov_seq_release,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.write		= gcov_seq_write,
  };
  
  /* Basic initialization of a new node. */
  static void init_node(struct gcov_node *node, struct gcov_info *info,
  		      const char *name, struct gcov_node *parent)
  {
  	INIT_LIST_HEAD(&node->list);
  	INIT_LIST_HEAD(&node->children);
  	INIT_LIST_HEAD(&node->all);

  	if (node->loaded_info) {
  		node->loaded_info[0] = info;
  		node->num_loaded = 1;
  	}

  	node->parent = parent;
  	if (name)
  		strcpy(node->name, name);
  }
  
  /*
   * Create a new node and associated debugfs entry. Needs to be called with
   * node_lock held.
   */
  static struct gcov_node *new_node(struct gcov_node *parent,
  				  struct gcov_info *info, const char *name)
  {
  	struct gcov_node *node;
  
  	node = kzalloc(sizeof(struct gcov_node) + strlen(name) + 1, GFP_KERNEL);

  	if (!node)
  		goto err_nomem;
  	if (info) {
  		node->loaded_info = kcalloc(1, sizeof(struct gcov_info *),
  					   GFP_KERNEL);
  		if (!node->loaded_info)
  			goto err_nomem;

  	}
  	init_node(node, info, name, parent);
  	/* Differentiate between gcov data file nodes and directory nodes. */
  	if (info) {
  		node->dentry = debugfs_create_file(deskew(node->name), 0600,
  					parent->dentry, node, &gcov_data_fops);
  	} else
  		node->dentry = debugfs_create_dir(node->name, parent->dentry);
  	if (!node->dentry) {
  		pr_warning("could not create file
  ");
  		kfree(node);
  		return NULL;
  	}
  	if (info)
  		add_links(node, parent->dentry);
  	list_add(&node->list, &parent->children);
  	list_add(&node->all, &all_head);
  
  	return node;

  
  err_nomem:
  	kfree(node);
  	pr_warning("out of memory
  ");
  	return NULL;

  }
  
  /* Remove symbolic links associated with node. */
  static void remove_links(struct gcov_node *node)
  {
  	int i;
  
  	if (!node->links)
  		return;
  	for (i = 0; gcov_link[i].ext; i++)
  		debugfs_remove(node->links[i]);
  	kfree(node->links);
  	node->links = NULL;
  }
  
  /*
   * Remove node from all lists and debugfs and release associated resources.
   * Needs to be called with node_lock held.
   */
  static void release_node(struct gcov_node *node)
  {
  	list_del(&node->list);
  	list_del(&node->all);
  	debugfs_remove(node->dentry);
  	remove_links(node);

  	kfree(node->loaded_info);
  	if (node->unloaded_info)
  		gcov_info_free(node->unloaded_info);

  	kfree(node);
  }
  
  /* Release node and empty parents. Needs to be called with node_lock held. */
  static void remove_node(struct gcov_node *node)
  {
  	struct gcov_node *parent;
  
  	while ((node != &root_node) && list_empty(&node->children)) {
  		parent = node->parent;
  		release_node(node);
  		node = parent;
  	}
  }
  
  /*
   * Find child node with given basename. Needs to be called with node_lock
   * held.
   */
  static struct gcov_node *get_child_by_name(struct gcov_node *parent,
  					   const char *name)
  {
  	struct gcov_node *node;
  
  	list_for_each_entry(node, &parent->children, list) {
  		if (strcmp(node->name, name) == 0)
  			return node;
  	}
  
  	return NULL;
  }
  
  /*
   * write() implementation for reset file. Reset all profiling data to zero

   * and remove nodes for which all associated object files are unloaded.

   */
  static ssize_t reset_write(struct file *file, const char __user *addr,
  			   size_t len, loff_t *pos)
  {
  	struct gcov_node *node;
  
  	mutex_lock(&node_lock);
  restart:
  	list_for_each_entry(node, &all_head, all) {

  		if (node->num_loaded > 0)
  			reset_node(node);

  		else if (list_empty(&node->children)) {
  			remove_node(node);
  			/* Several nodes may have gone - restart loop. */
  			goto restart;
  		}
  	}
  	mutex_unlock(&node_lock);
  
  	return len;
  }
  
  /* read() implementation for reset file. Unused. */
  static ssize_t reset_read(struct file *file, char __user *addr, size_t len,
  			  loff_t *pos)
  {
  	/* Allow read operation so that a recursive copy won't fail. */
  	return 0;
  }
  
  static const struct file_operations gcov_reset_fops = {
  	.write	= reset_write,
  	.read	= reset_read,

  	.llseek = noop_llseek,

  };
  
  /*
   * Create a node for a given profiling data set and add it to all lists and
   * debugfs. Needs to be called with node_lock held.
   */
  static void add_node(struct gcov_info *info)
  {
  	char *filename;
  	char *curr;
  	char *next;
  	struct gcov_node *parent;
  	struct gcov_node *node;
  
  	filename = kstrdup(info->filename, GFP_KERNEL);
  	if (!filename)
  		return;
  	parent = &root_node;
  	/* Create directory nodes along the path. */
  	for (curr = filename; (next = strchr(curr, '/')); curr = next + 1) {
  		if (curr == next)
  			continue;
  		*next = 0;
  		if (strcmp(curr, ".") == 0)
  			continue;
  		if (strcmp(curr, "..") == 0) {
  			if (!parent->parent)
  				goto err_remove;
  			parent = parent->parent;
  			continue;
  		}
  		node = get_child_by_name(parent, curr);
  		if (!node) {
  			node = new_node(parent, NULL, curr);
  			if (!node)
  				goto err_remove;
  		}
  		parent = node;
  	}
  	/* Create file node. */
  	node = new_node(parent, info, curr);
  	if (!node)
  		goto err_remove;
  out:
  	kfree(filename);
  	return;
  
  err_remove:
  	remove_node(parent);
  	goto out;
  }
  
  /*

   * Associate a profiling data set with an existing node. Needs to be called
   * with node_lock held.

   */

  static void add_info(struct gcov_node *node, struct gcov_info *info)

  {

  	struct gcov_info **loaded_info;
  	int num = node->num_loaded;
  
  	/*
  	 * Prepare new array. This is done first to simplify cleanup in
  	 * case the new data set is incompatible, the node only contains
  	 * unloaded data sets and there's not enough memory for the array.
  	 */
  	loaded_info = kcalloc(num + 1, sizeof(struct gcov_info *), GFP_KERNEL);
  	if (!loaded_info) {
  		pr_warning("could not add '%s' (out of memory)
  ",
  			   info->filename);
  		return;
  	}
  	memcpy(loaded_info, node->loaded_info,
  	       num * sizeof(struct gcov_info *));
  	loaded_info[num] = info;
  	/* Check if the new data set is compatible. */
  	if (num == 0) {
  		/*
  		 * A module was unloaded, modified and reloaded. The new
  		 * data set replaces the copy of the last one.
  		 */
  		if (!gcov_info_is_compatible(node->unloaded_info, info)) {
  			pr_warning("discarding saved data for %s "
  				   "(incompatible version)
  ", info->filename);
  			gcov_info_free(node->unloaded_info);
  			node->unloaded_info = NULL;
  		}
  	} else {
  		/*
  		 * Two different versions of the same object file are loaded.
  		 * The initial one takes precedence.
  		 */
  		if (!gcov_info_is_compatible(node->loaded_info[0], info)) {
  			pr_warning("could not add '%s' (incompatible "
  				   "version)
  ", info->filename);
  			kfree(loaded_info);
  			return;
  		}

  	}

  	/* Overwrite previous array. */
  	kfree(node->loaded_info);
  	node->loaded_info = loaded_info;
  	node->num_loaded = num + 1;
  }

  /*
   * Return the index of a profiling data set associated with a node.
   */
  static int get_info_index(struct gcov_node *node, struct gcov_info *info)
  {
  	int i;
  
  	for (i = 0; i < node->num_loaded; i++) {
  		if (node->loaded_info[i] == info)
  			return i;
  	}
  	return -ENOENT;

  }
  
  /*

   * Save the data of a profiling data set which is being unloaded.

   */

  static void save_info(struct gcov_node *node, struct gcov_info *info)

  {

  	if (node->unloaded_info)
  		gcov_info_add(node->unloaded_info, info);

  	else {

  		node->unloaded_info = gcov_info_dup(info);
  		if (!node->unloaded_info) {
  			pr_warning("could not save data for '%s' "
  				   "(out of memory)
  ", info->filename);
  		}
  	}
  }
  
  /*
   * Disassociate a profiling data set from a node. Needs to be called with
   * node_lock held.
   */
  static void remove_info(struct gcov_node *node, struct gcov_info *info)
  {
  	int i;
  
  	i = get_info_index(node, info);
  	if (i < 0) {
  		pr_warning("could not remove '%s' (not found)
  ",

  			   info->filename);

  		return;

  	}

  	if (gcov_persist)
  		save_info(node, info);
  	/* Shrink array. */
  	node->loaded_info[i] = node->loaded_info[node->num_loaded - 1];
  	node->num_loaded--;
  	if (node->num_loaded > 0)
  		return;
  	/* Last loaded data set was removed. */
  	kfree(node->loaded_info);
  	node->loaded_info = NULL;
  	node->num_loaded = 0;
  	if (!node->unloaded_info)
  		remove_node(node);

  }
  
  /*
   * Callback to create/remove profiling files when code compiled with
   * -fprofile-arcs is loaded/unloaded.
   */
  void gcov_event(enum gcov_action action, struct gcov_info *info)
  {
  	struct gcov_node *node;
  
  	mutex_lock(&node_lock);
  	node = get_node_by_name(info->filename);
  	switch (action) {
  	case GCOV_ADD:

  		if (node)
  			add_info(node, info);
  		else

  			add_node(info);

  		break;
  	case GCOV_REMOVE:

  		if (node)
  			remove_info(node, info);
  		else {

  			pr_warning("could not remove '%s' (not found)
  ",
  				   info->filename);

  		}

  		break;
  	}
  	mutex_unlock(&node_lock);
  }
  
  /* Create debugfs entries. */
  static __init int gcov_fs_init(void)
  {
  	int rc = -EIO;
  
  	init_node(&root_node, NULL, NULL, NULL);
  	/*
  	 * /sys/kernel/debug/gcov will be parent for the reset control file
  	 * and all profiling files.
  	 */
  	root_node.dentry = debugfs_create_dir("gcov", NULL);
  	if (!root_node.dentry)
  		goto err_remove;
  	/*
  	 * Create reset file which resets all profiling counts when written
  	 * to.
  	 */
  	reset_dentry = debugfs_create_file("reset", 0600, root_node.dentry,
  					   NULL, &gcov_reset_fops);
  	if (!reset_dentry)
  		goto err_remove;
  	/* Replay previous events to get our fs hierarchy up-to-date. */
  	gcov_enable_events();
  	return 0;
  
  err_remove:
  	pr_err("init failed
  ");
  	if (root_node.dentry)
  		debugfs_remove(root_node.dentry);
  
  	return rc;
  }
  device_initcall(gcov_fs_init);