linux/kernel/gcov/fs.c
Peter Oberparleiter 85a0fdfd0f gcov: fix null-pointer dereference for certain module types
The gcov-kernel infrastructure expects that each object file is loaded
only once.  This may not be true, e.g.  when loading multiple kernel
modules which are linked to the same object file.  As a result, loading
such kernel modules will result in incorrect gcov results while unloading
will cause a null-pointer dereference.

This patch fixes these problems by changing the gcov-kernel infrastructure
so that multiple profiling data sets can be associated with one debugfs
entry.  It applies to 2.6.36-rc1.

Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Reported-by: Werner Spies <werner.spies@thalesgroup.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-09-09 18:57:23 -07:00

789 lines
19 KiB
C

/*
* 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'\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);
/*
* 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\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_warning("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,
};
/*
* 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)\n",
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)\n", 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)\n", 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)\n", 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)\n",
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)\n",
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\n");
if (root_node.dentry)
debugfs_remove(root_node.dentry);
return rc;
}
device_initcall(gcov_fs_init);