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 // SPDX-License-Identifier: GPL-2.0
 /*
  *  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 <linux/mm.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[];
 };
 
 static const char objtree[] = OBJTREE;
 static const char srctree[] = SRCTREE;
 static struct gcov_node root_node;
 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 (kstrtoul(str, 0, &val)) {
         pr_warn("invalid gcov_persist parameter '%s'\n", str);
         return 0;
     }
     gcov_persist = val;
     pr_info("setting gcov_persist to %d\n", gcov_persist);
 
     return 1;
 }
 __setup("gcov_persist=", gcov_persist_setup);
 
 #define ITER_STRIDE PAGE_SIZE
 
 /**
  * struct gcov_iterator - specifies current file position in logical records
  * @info: associated profiling data
  * @buffer: buffer containing file data
  * @size: size of buffer
  * @pos: current position in file
  */
 struct gcov_iterator {
     struct gcov_info *info;
     size_t size;
     loff_t pos;
     char buffer[];
 };
 
 /**
  * gcov_iter_new - allocate and initialize profiling data iterator
  * @info: profiling data set to be iterated
  *
  * Return file iterator on success, %NULL otherwise.
  */
 static struct gcov_iterator *gcov_iter_new(struct gcov_info *info)
 {
     struct gcov_iterator *iter;
     size_t size;
 
     /* Dry-run to get the actual buffer size. */
     size = convert_to_gcda(NULL, info);
 
     iter = kvmalloc(struct_size(iter, buffer, size), GFP_KERNEL);
     if (!iter)
         return NULL;
 
     iter->info = info;
     iter->size = size;
     convert_to_gcda(iter->buffer, info);
 
     return iter;
 }
 
 
 /**
  * gcov_iter_free - free iterator data
  * @iter: file iterator
  */
 static void gcov_iter_free(struct gcov_iterator *iter)
 {
     kvfree(iter);
 }
 
 /**
  * gcov_iter_get_info - return profiling data set for given file iterator
  * @iter: file iterator
  */
 static struct gcov_info *gcov_iter_get_info(struct gcov_iterator *iter)
 {
     return iter->info;
 }
 
 /**
  * gcov_iter_start - reset file iterator to starting position
  * @iter: file iterator
  */
 static void gcov_iter_start(struct gcov_iterator *iter)
 {
     iter->pos = 0;
 }
 
 /**
  * gcov_iter_next - advance file iterator to next logical record
  * @iter: file iterator
  *
  * Return zero if new position is valid, non-zero if iterator has reached end.
  */
 static int gcov_iter_next(struct gcov_iterator *iter)
 {
     if (iter->pos < iter->size)
         iter->pos += ITER_STRIDE;
 
     if (iter->pos >= iter->size)
         return -EINVAL;
 
     return 0;
 }
 
 /**
  * gcov_iter_write - write data for current pos to seq_file
  * @iter: file iterator
  * @seq: seq_file handle
  *
  * Return zero on success, non-zero otherwise.
  */
 static int gcov_iter_write(struct gcov_iterator *iter, struct seq_file *seq)
 {
     size_t len;
 
     if (iter->pos >= iter->size)
         return -EINVAL;
 
     len = ITER_STRIDE;
     if (iter->pos + len > iter->size)
         len = iter->size - iter->pos;
 
     seq_write(seq, iter->buffer + iter->pos, len);
 
     return 0;
 }
 
 /*
  * 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;
 
     (*pos)++;
     if (gcov_iter_next(iter))
         return NULL;
 
     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(gcov_info_filename(info), 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(gcov_info_filename(info));
     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)
 {
     const 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(
                 gcov_info_filename(get_node_info(node)),
                 &gcov_link[i]);
         if (!target)
             goto out_err;
         basename = kbasename(target);
         if (basename == target)
             goto out_err;
         node->links[i] = debugfs_create_symlink(deskew(basename),
                             parent, target);
         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 (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_warn("out of memory\n");
     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(gcov_info_filename(info), 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_warn("could not add '%s' (out of memory)\n",
             gcov_info_filename(info));
         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_warn("discarding saved data for %s "
                 "(incompatible version)\n",
                 gcov_info_filename(info));
             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_warn("could not add '%s' (incompatible "
                 "version)\n", gcov_info_filename(info));
             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_warn("could not save data for '%s' "
                 "(out of memory)\n",
                 gcov_info_filename(info));
         }
     }
 }
 
 /*
  * 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_warn("could not remove '%s' (not found)\n",
             gcov_info_filename(info));
         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(gcov_info_filename(info));
     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_warn("could not remove '%s' (not found)\n",
                 gcov_info_filename(info));
         }
         break;
     }
     mutex_unlock(&node_lock);
 }
 
 /* Create debugfs entries. */
 static __init int gcov_fs_init(void)
 {
     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);
     /*
      * Create reset file which resets all profiling counts when written
      * to.
      */
     debugfs_create_file("reset", 0600, root_node.dentry, NULL,
                 &gcov_reset_fops);
     /* Replay previous events to get our fs hierarchy up-to-date. */
     gcov_enable_events();
     return 0;
 }
 device_initcall(gcov_fs_init);

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