// SPDX-License-Identifier: GPL-2.0
/*
* This code exports profiling data as debugfs files to userspace.
*
* Copyright IBM Corp. 2009
* Author(s): Peter Oberparleiter <[email protected]>
*
* Uses gcc-internal data definitions.
* Based on the gcov-kernel patch by:
* Hubertus Franke <[email protected]>
* Nigel Hinds <[email protected]>
* Rajan Ravindran <[email protected]>
* Peter Oberparleiter <[email protected]>
* 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[] __counted_by(size);
};
/**
* 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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