cregit-Linux how code gets into the kernel

Release 4.15 kernel/gcov/fs.c

Directory: kernel/gcov
// 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 "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 (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; }

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Peter Oberparleiter5196.23%133.33%
Andrew Morton11.89%133.33%
Jingoo Han11.89%133.33%
Total53100.00%3100.00%

__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; }

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Peter Oberparleiter59100.00%1100.00%
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/* 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; }

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Peter Oberparleiter46100.00%1100.00%
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/* 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; }

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static void gcov_seq_stop(struct seq_file *seq, void *data) { /* Unused. */ }

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Peter Oberparleiter16100.00%1100.00%
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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; }

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Peter Oberparleiter34100.00%2100.00%
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/* * 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; }

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Peter Oberparleiter87100.00%2100.00%
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/* * 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; }

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Peter Oberparleiter140100.00%2100.00%
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/* * 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; }

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Peter Oberparleiter70100.00%1100.00%
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/* * 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; }

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Peter Oberparleiter6195.31%150.00%
Frantisek Hrbata34.69%150.00%
Total64100.00%2100.00%

/* * 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]); }

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Peter Oberparleiter52100.00%1100.00%
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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; }

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Peter Oberparleiter10897.30%266.67%
Frantisek Hrbata32.70%133.33%
Total111100.00%3100.00%

/* * 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; }

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Peter Oberparleiter110100.00%1100.00%
Total110100.00%1100.00%

/* * 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; }

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Peter Oberparleiter111100.00%1100.00%
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#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; }

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Peter Oberparleiter44100.00%1100.00%
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/* * 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); 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; }

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Peter Oberparleiter20196.63%133.33%
Andy Shevchenko41.92%133.33%
Frantisek Hrbata31.44%133.33%
Total208100.00%3100.00%

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); }

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Peter Oberparleiter92100.00%2100.00%
Total92100.00%2100.00%

/* * 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_warn("could not create file\n"); 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_warn("out of memory\n"); return NULL; }

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Peter Oberparleiter22499.12%266.67%
Andrew Morton20.88%133.33%
Total226100.00%3100.00%

/* 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; }

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Peter Oberparleiter61100.00%1100.00%
Total61100.00%1100.00%

/* * 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); }

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Peter Oberparleiter64100.00%2100.00%
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/* 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; } }

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Peter Oberparleiter50100.00%1100.00%
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/* * 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; }

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Peter Oberparleiter52100.00%1100.00%
Total52100.00%1100.00%

/* * 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; }

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Peter Oberparleiter91100.00%2100.00%
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/* 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; }

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Peter Oberparleiter27100.00%1100.00%
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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; }

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Peter Oberparleiter21098.59%150.00%
Frantisek Hrbata31.41%150.00%
Total213100.00%2100.00%

/* * 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; }

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Peter Oberparleiter18793.97%250.00%
Frantisek Hrbata94.52%125.00%
Andrew Morton31.51%125.00%
Total199100.00%4100.00%

/* * 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; }

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Peter Oberparleiter54100.00%2100.00%
Total54100.00%2100.00%

/* * 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)); } } }

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Peter Oberparleiter5993.65%250.00%
Frantisek Hrbata34.76%125.00%
Andrew Morton11.59%125.00%
Total63100.00%4100.00%

/* * 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); }

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Peter Oberparleiter11996.75%250.00%
Frantisek Hrbata32.44%125.00%
Andrew Morton10.81%125.00%
Total123100.00%4100.00%

/* * 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); }

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Peter Oberparleiter8992.71%250.00%
Frantisek Hrbata66.25%125.00%
Andrew Morton11.04%125.00%
Total96100.00%4100.00%

/* 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\n"); debugfs_remove(root_node.dentry); return rc; }

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Peter Oberparleiter100100.00%1100.00%
Total100100.00%1100.00%

device_initcall(gcov_fs_init);

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Peter Oberparleiter297998.25%225.00%
Frantisek Hrbata331.09%112.50%
Andrew Morton90.30%112.50%
Arnd Bergmann50.16%112.50%
Andy Shevchenko40.13%112.50%
Greg Kroah-Hartman10.03%112.50%
Jingoo Han10.03%112.50%
Total3032100.00%8100.00%
Directory: kernel/gcov
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