/*
* Copyright (C) 2007 Mathieu Desnoyers
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/types.h>
#include <linux/jhash.h>
#include <linux/list.h>
#include <linux/rcupdate.h>
#include <linux/marker.h>
#include <linux/err.h>
extern struct marker __start___markers[];
extern struct marker __stop___markers[];
/*
* markers_mutex nests inside module_mutex. Markers mutex protects the builtin
* and module markers, the hash table and deferred_sync.
*/
static DEFINE_MUTEX(markers_mutex);
/*
* Marker deferred synchronization.
* Upon marker probe_unregister, we delay call to synchronize_sched() to
* accelerate mass unregistration (only when there is no more reference to a
* given module do we call synchronize_sched()). However, we need to make sure
* every critical region has ended before we re-arm a marker that has been
* unregistered and then registered back with a different probe data.
*/
static int deferred_sync;
/*
* Marker hash table, containing the active markers.
* Protected by module_mutex.
*/
#define MARKER_HASH_BITS 6
#define MARKER_TABLE_SIZE (1 << MARKER_HASH_BITS)
struct marker_entry {
struct hlist_node hlist;
char *format;
marker_probe_func *probe;
void *private;
int refcount; /* Number of times armed. 0 if disarmed. */
char name[0]; /* Contains name'\0'format'\0' */
};
static struct hlist_head marker_table[MARKER_TABLE_SIZE];
/**
* __mark_empty_function - Empty probe callback
* @mdata: pointer of type const struct marker
* @fmt: format string
* @...: variable argument list
*
* Empty callback provided as a probe to the markers. By providing this to a
* disabled marker, we make sure the execution flow is always valid even
* though the function pointer change and the marker enabling are two distinct
* operations that modifies the execution flow of preemptible code.
*/
void __mark_empty_function(const struct marker *mdata, void *private,
const char *fmt, ...)
{
}
EXPORT_SYMBOL_GPL(__mark_empty_function);
/*
* Get marker if the marker is present in the marker hash table.
* Must be called with markers_mutex held.
* Returns NULL if not present.
*/
static struct marker_entry *get_marker(const char *name)
{
struct hlist_head *head;
struct hlist_node *node;
struct marker_entry *e;
u32 hash = jhash(name, strlen(name), 0);
head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
hlist_for_each_entry(e, node, head, hlist) {
if (!strcmp(name, e->name))
return e;
}
return NULL;
}
/*
* Add the marker to the marker hash table. Must be called with markers_mutex
* held.
*/
static int add_marker(const char *name, const char *format,
marker_probe_func *probe, void *private)
{
struct hlist_head *head;
struct hlist_node *node;
struct marker_entry *e;
size_t name_len = strlen(name) + 1;
size_t format_len = 0;
u32 hash = jhash(name, name_len-1, 0);
if (format)
format_len = strlen(format) + 1;
head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
hlist_for_each_entry(e, node, head, hlist) {
if (!strcmp(name, e->name)) {
printk(KERN_NOTICE
"Marker %s busy, probe %p already installed\n",
name, e->probe);
return -EBUSY; /* Already there */
}
}
/*
* Using kmalloc here to allocate a variable length element. Could
* cause some memory fragmentation if overused.
*/
e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
GFP_KERNEL);
if (!e)
return -ENOMEM;
memcpy(&e->name[0], name, name_len);
if (format) {
e->format = &e->name[name_len];
memcpy(e->format, format, format_len);
trace_mark(core_marker_format, "name %s format %s",
e->name, e->format);
} else
e->format = NULL;
e->probe = probe;
e->private = private;
e->refcount = 0;
hlist_add_head(&e->hlist, head);
return 0;
}
/*
* Remove the marker from the marker hash table. Must be called with mutex_lock
* held.
*/
static void *remove_marker(const char *name)
{
struct hlist_head *head;
struct hlist_node *node;
struct marker_entry *e;
int found = 0;
size_t len = strlen(name) + 1;
void *private = NULL;
u32 hash = jhash(name, len-1, 0);
head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
hlist_for_each_entry(e, node, head, hlist) {
if (!strcmp(name, e->name)) {
found = 1;
break;
}
}
if (found) {
private = e->private;
hlist_del(&e->hlist);
kfree(e);
}
return private;
}
/*
* Set the mark_entry format to the format found in the element.
*/
static int marker_set_format(struct marker_entry **entry, const char *format)
{
struct marker_entry *e;
size_t name_len = strlen((*entry)->name) + 1;
size_t format_len = strlen(format) + 1;
e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
GFP_KERNEL);
if (!e)
return -ENOMEM;
memcpy(&e->name[0], (*entry)->name, name_len);
e->format = &e->name[name_len];
memcpy(e->format, format, format_len);
e->probe = (*entry)->probe;
e->private = (*entry)->private;
e->refcount = (*entry)->refcount;
hlist_add_before(&e->hlist, &(*entry)->hlist);
hlist_del(&(*entry)->hlist);
kfree(*entry);
*entry = e;
trace_mark(core_marker_format, "name %s format %s",
e->name, e->format);
return 0;
}
/*
* Sets the probe callback corresponding to one marker.
*/
static int set_marker(struct marker_entry **entry, struct marker *elem)
{
int ret;
WARN_ON(strcmp((*entry)->name, elem->name) != 0);
if ((*entry)->format) {
if (strcmp((*entry)->format, elem->format) != 0) {
printk(KERN_NOTICE
"Format mismatch for probe %s "
"(%s), marker (%s)\n",
(*entry)->name,
(*entry)->format,
elem->format);
return -EPERM;
}
} else {
ret = marker_set_format(entry, elem->format);
if (ret)
return ret;
}
elem->call = (*entry)->probe;
elem->private = (*entry)->private;
elem->state = 1;
return 0;
}
/*
* Disable a marker and its probe callback.
* Note: only after a synchronize_sched() issued after setting elem->call to the
* empty function insures that the original callback is not used anymore. This
* insured by preemption disabling around the call site.
*/
static void disable_marker(struct marker *elem)
{
elem->state = 0;
elem->call = __mark_empty_function;
/*
* Leave the private data and id there, because removal is racy and
* should be done only after a synchronize_sched(). These are never used
* until the next initialization anyway.
*/
}
/**
* marker_update_probe_range - Update a probe range
* @begin: beginning of the range
* @end: end of the range
* @probe_module: module address of the probe being updated
* @refcount: number of references left to the given probe_module (out)
*
* Updates the probe callback corresponding to a range of markers.
*/
void marker_update_probe_range(struct marker *begin,
struct marker *end, struct module *probe_module,
int *refcount)
{
struct marker *iter;
struct marker_entry *mark_entry;
mutex_lock(&markers_mutex);
for (iter = begin; iter < end; iter++) {
mark_entry = get_marker(iter->name);
if (mark_entry && mark_entry->refcount) {
set_marker(&mark_entry, iter);
/*
* ignore error, continue
*/
if (probe_module)
if (probe_module ==
__module_text_address((unsigned long)mark_entry->probe))
(*refcount)++;
} else {
disable_marker(iter);
}
}
mutex_unlock(&markers_mutex);
}
/*
* Update probes, removing the faulty probes.
* Issues a synchronize_sched() when no reference to the module passed
* as parameter is found in the probes so the probe module can be
* safely unloaded from now on.
*/
static void marker_update_probes(struct module *probe_module)
{
int refcount = 0;
/* Core kernel markers */
marker_update_probe_range(__start___markers,
__stop___markers, probe_module, &refcount);
/* Markers in modules. */
module_update_markers(probe_module, &refcount);
if (probe_module && refcount == 0) {
synchronize_sched();
deferred_sync = 0;
}
}
/**
* marker_probe_register - Connect a probe to a marker
* @name: marker name
* @format: format string
* @probe: probe handler
* @private: probe private data
*
* private data must be a valid allocated memory address, or NULL.
* Returns 0 if ok, error value on error.
*/
int marker_probe_register(const char *name, const char *format,
marker_probe_func *probe, void *private)
{
struct marker_entry *entry;
int ret = 0;
mutex_lock(&markers_mutex);
entry = get_marker(name);
if (entry && entry->refcount) {
ret = -EBUSY;
goto end;
}
if (deferred_sync) {
synchronize_sched();
deferred_sync = 0;
}
ret = add_marker(name, format, probe, private);
if (ret)
goto end;
mutex_unlock(&markers_mutex);
marker_update_probes(NULL);
return ret;
end:
mutex_unlock(&markers_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(marker_probe_register);
/**
* marker_probe_unregister - Disconnect a probe from a marker
* @name: marker name
*
* Returns the private data given to marker_probe_register, or an ERR_PTR().
*/
void *marker_probe_unregister(const char *name)
{
struct module *probe_module;
struct marker_entry *entry;
void *private;
mutex_lock(&markers_mutex);
entry = get_marker(name);
if (!entry) {
private = ERR_PTR(-ENOENT);
goto end;
}
entry->refcount = 0;
/* In what module is the probe handler ? */
probe_module = __module_text_address((unsigned long)entry->probe);
private = remove_marker(name);
deferred_sync = 1;
mutex_unlock(&markers_mutex);
marker_update_probes(probe_module);
return private;
end:
mutex_unlock(&markers_mutex);
return private;
}
EXPORT_SYMBOL_GPL(marker_probe_unregister);
/**
* marker_probe_unregister_private_data - Disconnect a probe from a marker
* @private: probe private data
*
* Unregister a marker by providing the registered private data.
* Returns the private data given to marker_probe_register, or an ERR_PTR().
*/
void *marker_probe_unregister_private_data(void *private)
{
struct module *probe_module;
struct hlist_head *head;
struct hlist_node *node;
struct marker_entry *entry;
int found = 0;
unsigned int i;
mutex_lock(&markers_mutex);
for (i = 0; i < MARKER_TABLE_SIZE; i++) {
head = &marker_table[i];
hlist_for_each_entry(entry, node, head, hlist) {
if (entry->private == private) {
found = 1;
goto iter_end;
}
}
}
iter_end:
if (!found) {
private = ERR_PTR(-ENOENT);
goto end;
}
entry->refcount = 0;
/* In what module is the probe handler ? */
probe_module = __module_text_address((unsigned long)entry->probe);
private = remove_marker(entry->name);
deferred_sync = 1;
mutex_unlock(&markers_mutex);
marker_update_probes(probe_module);
return private;
end:
mutex_unlock(&markers_mutex);
return private;
}
EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
/**
* marker_arm - Arm a marker
* @name: marker name
*
* Activate a marker. It keeps a reference count of the number of
* arming/disarming done.
* Returns 0 if ok, error value on error.
*/
int marker_arm(const char *name)
{
struct marker_entry *entry;
int ret = 0;
mutex_lock(&markers_mutex);
entry = get_marker(name);
if (!entry) {
ret = -ENOENT;
goto end;
}
/*
* Only need to update probes when refcount passes from 0 to 1.
*/
if (entry->refcount++)
goto end;
end:
mutex_unlock(&markers_mutex);
marker_update_probes(NULL);
return ret;
}
EXPORT_SYMBOL_GPL(marker_arm);
/**
* marker_disarm - Disarm a marker
* @name: marker name
*
* Disarm a marker. It keeps a reference count of the number of arming/disarming
* done.
* Returns 0 if ok, error value on error.
*/
int marker_disarm(const char *name)
{
struct marker_entry *entry;
int ret = 0;
mutex_lock(&markers_mutex);
entry = get_marker(name);
if (!entry) {
ret = -ENOENT;
goto end;
}
/*
* Only permit decrement refcount if higher than 0.
* Do probe update only on 1 -> 0 transition.
*/
if (entry->refcount) {
if (--entry->refcount)
goto end;
} else {
ret = -EPERM;
goto end;
}
end:
mutex_unlock(&markers_mutex);
marker_update_probes(NULL);
return ret;
}
EXPORT_SYMBOL_GPL(marker_disarm);
/**
* marker_get_private_data - Get a marker's probe private data
* @name: marker name
*
* Returns the private data pointer, or an ERR_PTR.
* The private data pointer should _only_ be dereferenced if the caller is the
* owner of the data, or its content could vanish. This is mostly used to
* confirm that a caller is the owner of a registered probe.
*/
void *marker_get_private_data(const char *name)
{
struct hlist_head *head;
struct hlist_node *node;
struct marker_entry *e;
size_t name_len = strlen(name) + 1;
u32 hash = jhash(name, name_len-1, 0);
int found = 0;
head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
hlist_for_each_entry(e, node, head, hlist) {
if (!strcmp(name, e->name)) {
found = 1;
return e->private;
}
}
return ERR_PTR(-ENOENT);
}
EXPORT_SYMBOL_GPL(marker_get_private_data);
