android_kernel_xiaomi_sm8350/kernel/marker.c
Mathieu Desnoyers 5def9a3a22 markers: fix markers read barrier for multiple probes
Paul pointed out two incorrect read barriers in the marker handler code in
the path where multiple probes are connected.  Those are ordering reads of
"ptype" (single or multi probe marker), "multi" array pointer, and "multi"
array data access.

It should be ordered like this :

read ptype
smp_rmb()
read multi array pointer
smp_read_barrier_depends()
access data referenced by multi array pointer

The code with a single probe connected (optimized case, does not have to
allocate an array) has correct memory ordering.

It applies to kernel 2.6.26.x, 2.6.25.x and linux-next.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: <stable@kernel.org>		[2.6.25.x, 2.6.26.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-07-30 09:41:45 -07:00

857 lines
24 KiB
C

/*
* 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>
#include <linux/slab.h>
extern struct marker __start___markers[];
extern struct marker __stop___markers[];
/* Set to 1 to enable marker debug output */
static const int marker_debug;
/*
* markers_mutex nests inside module_mutex. Markers mutex protects the builtin
* and module markers and the hash table.
*/
static DEFINE_MUTEX(markers_mutex);
/*
* Marker hash table, containing the active markers.
* Protected by module_mutex.
*/
#define MARKER_HASH_BITS 6
#define MARKER_TABLE_SIZE (1 << MARKER_HASH_BITS)
/*
* Note about RCU :
* It is used to make sure every handler has finished using its private data
* between two consecutive operation (add or remove) on a given marker. It is
* also used to delay the free of multiple probes array until a quiescent state
* is reached.
* marker entries modifications are protected by the markers_mutex.
*/
struct marker_entry {
struct hlist_node hlist;
char *format;
/* Probe wrapper */
void (*call)(const struct marker *mdata, void *call_private, ...);
struct marker_probe_closure single;
struct marker_probe_closure *multi;
int refcount; /* Number of times armed. 0 if disarmed. */
struct rcu_head rcu;
void *oldptr;
unsigned char rcu_pending:1;
unsigned char ptype:1;
char name[0]; /* Contains name'\0'format'\0' */
};
static struct hlist_head marker_table[MARKER_TABLE_SIZE];
/**
* __mark_empty_function - Empty probe callback
* @probe_private: probe private data
* @call_private: call site private data
* @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(void *probe_private, void *call_private,
const char *fmt, va_list *args)
{
}
EXPORT_SYMBOL_GPL(__mark_empty_function);
/*
* marker_probe_cb Callback that prepares the variable argument list for probes.
* @mdata: pointer of type struct marker
* @call_private: caller site private data
* @...: Variable argument list.
*
* Since we do not use "typical" pointer based RCU in the 1 argument case, we
* need to put a full smp_rmb() in this branch. This is why we do not use
* rcu_dereference() for the pointer read.
*/
void marker_probe_cb(const struct marker *mdata, void *call_private, ...)
{
va_list args;
char ptype;
/*
* preempt_disable does two things : disabling preemption to make sure
* the teardown of the callbacks can be done correctly when they are in
* modules and they insure RCU read coherency.
*/
preempt_disable();
ptype = mdata->ptype;
if (likely(!ptype)) {
marker_probe_func *func;
/* Must read the ptype before ptr. They are not data dependant,
* so we put an explicit smp_rmb() here. */
smp_rmb();
func = mdata->single.func;
/* Must read the ptr before private data. They are not data
* dependant, so we put an explicit smp_rmb() here. */
smp_rmb();
va_start(args, call_private);
func(mdata->single.probe_private, call_private, mdata->format,
&args);
va_end(args);
} else {
struct marker_probe_closure *multi;
int i;
/*
* Read mdata->ptype before mdata->multi.
*/
smp_rmb();
multi = mdata->multi;
/*
* multi points to an array, therefore accessing the array
* depends on reading multi. However, even in this case,
* we must insure that the pointer is read _before_ the array
* data. Same as rcu_dereference, but we need a full smp_rmb()
* in the fast path, so put the explicit barrier here.
*/
smp_read_barrier_depends();
for (i = 0; multi[i].func; i++) {
va_start(args, call_private);
multi[i].func(multi[i].probe_private, call_private,
mdata->format, &args);
va_end(args);
}
}
preempt_enable();
}
EXPORT_SYMBOL_GPL(marker_probe_cb);
/*
* marker_probe_cb Callback that does not prepare the variable argument list.
* @mdata: pointer of type struct marker
* @call_private: caller site private data
* @...: Variable argument list.
*
* Should be connected to markers "MARK_NOARGS".
*/
void marker_probe_cb_noarg(const struct marker *mdata, void *call_private, ...)
{
va_list args; /* not initialized */
char ptype;
preempt_disable();
ptype = mdata->ptype;
if (likely(!ptype)) {
marker_probe_func *func;
/* Must read the ptype before ptr. They are not data dependant,
* so we put an explicit smp_rmb() here. */
smp_rmb();
func = mdata->single.func;
/* Must read the ptr before private data. They are not data
* dependant, so we put an explicit smp_rmb() here. */
smp_rmb();
func(mdata->single.probe_private, call_private, mdata->format,
&args);
} else {
struct marker_probe_closure *multi;
int i;
/*
* Read mdata->ptype before mdata->multi.
*/
smp_rmb();
multi = mdata->multi;
/*
* multi points to an array, therefore accessing the array
* depends on reading multi. However, even in this case,
* we must insure that the pointer is read _before_ the array
* data. Same as rcu_dereference, but we need a full smp_rmb()
* in the fast path, so put the explicit barrier here.
*/
smp_read_barrier_depends();
for (i = 0; multi[i].func; i++)
multi[i].func(multi[i].probe_private, call_private,
mdata->format, &args);
}
preempt_enable();
}
EXPORT_SYMBOL_GPL(marker_probe_cb_noarg);
static void free_old_closure(struct rcu_head *head)
{
struct marker_entry *entry = container_of(head,
struct marker_entry, rcu);
kfree(entry->oldptr);
/* Make sure we free the data before setting the pending flag to 0 */
smp_wmb();
entry->rcu_pending = 0;
}
static void debug_print_probes(struct marker_entry *entry)
{
int i;
if (!marker_debug)
return;
if (!entry->ptype) {
printk(KERN_DEBUG "Single probe : %p %p\n",
entry->single.func,
entry->single.probe_private);
} else {
for (i = 0; entry->multi[i].func; i++)
printk(KERN_DEBUG "Multi probe %d : %p %p\n", i,
entry->multi[i].func,
entry->multi[i].probe_private);
}
}
static struct marker_probe_closure *
marker_entry_add_probe(struct marker_entry *entry,
marker_probe_func *probe, void *probe_private)
{
int nr_probes = 0;
struct marker_probe_closure *old, *new;
WARN_ON(!probe);
debug_print_probes(entry);
old = entry->multi;
if (!entry->ptype) {
if (entry->single.func == probe &&
entry->single.probe_private == probe_private)
return ERR_PTR(-EBUSY);
if (entry->single.func == __mark_empty_function) {
/* 0 -> 1 probes */
entry->single.func = probe;
entry->single.probe_private = probe_private;
entry->refcount = 1;
entry->ptype = 0;
debug_print_probes(entry);
return NULL;
} else {
/* 1 -> 2 probes */
nr_probes = 1;
old = NULL;
}
} else {
/* (N -> N+1), (N != 0, 1) probes */
for (nr_probes = 0; old[nr_probes].func; nr_probes++)
if (old[nr_probes].func == probe
&& old[nr_probes].probe_private
== probe_private)
return ERR_PTR(-EBUSY);
}
/* + 2 : one for new probe, one for NULL func */
new = kzalloc((nr_probes + 2) * sizeof(struct marker_probe_closure),
GFP_KERNEL);
if (new == NULL)
return ERR_PTR(-ENOMEM);
if (!old)
new[0] = entry->single;
else
memcpy(new, old,
nr_probes * sizeof(struct marker_probe_closure));
new[nr_probes].func = probe;
new[nr_probes].probe_private = probe_private;
entry->refcount = nr_probes + 1;
entry->multi = new;
entry->ptype = 1;
debug_print_probes(entry);
return old;
}
static struct marker_probe_closure *
marker_entry_remove_probe(struct marker_entry *entry,
marker_probe_func *probe, void *probe_private)
{
int nr_probes = 0, nr_del = 0, i;
struct marker_probe_closure *old, *new;
old = entry->multi;
debug_print_probes(entry);
if (!entry->ptype) {
/* 0 -> N is an error */
WARN_ON(entry->single.func == __mark_empty_function);
/* 1 -> 0 probes */
WARN_ON(probe && entry->single.func != probe);
WARN_ON(entry->single.probe_private != probe_private);
entry->single.func = __mark_empty_function;
entry->refcount = 0;
entry->ptype = 0;
debug_print_probes(entry);
return NULL;
} else {
/* (N -> M), (N > 1, M >= 0) probes */
for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
if ((!probe || old[nr_probes].func == probe)
&& old[nr_probes].probe_private
== probe_private)
nr_del++;
}
}
if (nr_probes - nr_del == 0) {
/* N -> 0, (N > 1) */
entry->single.func = __mark_empty_function;
entry->refcount = 0;
entry->ptype = 0;
} else if (nr_probes - nr_del == 1) {
/* N -> 1, (N > 1) */
for (i = 0; old[i].func; i++)
if ((probe && old[i].func != probe) ||
old[i].probe_private != probe_private)
entry->single = old[i];
entry->refcount = 1;
entry->ptype = 0;
} else {
int j = 0;
/* N -> M, (N > 1, M > 1) */
/* + 1 for NULL */
new = kzalloc((nr_probes - nr_del + 1)
* sizeof(struct marker_probe_closure), GFP_KERNEL);
if (new == NULL)
return ERR_PTR(-ENOMEM);
for (i = 0; old[i].func; i++)
if ((probe && old[i].func != probe) ||
old[i].probe_private != probe_private)
new[j++] = old[i];
entry->refcount = nr_probes - nr_del;
entry->ptype = 1;
entry->multi = new;
}
debug_print_probes(entry);
return old;
}
/*
* 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 struct marker_entry *add_marker(const char *name, const char *format)
{
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\n", name);
return ERR_PTR(-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 ERR_PTR(-ENOMEM);
memcpy(&e->name[0], name, name_len);
if (format) {
e->format = &e->name[name_len];
memcpy(e->format, format, format_len);
if (strcmp(e->format, MARK_NOARGS) == 0)
e->call = marker_probe_cb_noarg;
else
e->call = marker_probe_cb;
trace_mark(core_marker_format, "name %s format %s",
e->name, e->format);
} else {
e->format = NULL;
e->call = marker_probe_cb;
}
e->single.func = __mark_empty_function;
e->single.probe_private = NULL;
e->multi = NULL;
e->ptype = 0;
e->refcount = 0;
e->rcu_pending = 0;
hlist_add_head(&e->hlist, head);
return e;
}
/*
* Remove the marker from the marker hash table. Must be called with mutex_lock
* held.
*/
static int 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;
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)
return -ENOENT;
if (e->single.func != __mark_empty_function)
return -EBUSY;
hlist_del(&e->hlist);
/* Make sure the call_rcu has been executed */
if (e->rcu_pending)
rcu_barrier_sched();
kfree(e);
return 0;
}
/*
* 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);
if (strcmp(e->format, MARK_NOARGS) == 0)
e->call = marker_probe_cb_noarg;
else
e->call = marker_probe_cb;
e->single = (*entry)->single;
e->multi = (*entry)->multi;
e->ptype = (*entry)->ptype;
e->refcount = (*entry)->refcount;
e->rcu_pending = 0;
hlist_add_before(&e->hlist, &(*entry)->hlist);
hlist_del(&(*entry)->hlist);
/* Make sure the call_rcu has been executed */
if ((*entry)->rcu_pending)
rcu_barrier_sched();
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 active)
{
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;
}
/*
* probe_cb setup (statically known) is done here. It is
* asynchronous with the rest of execution, therefore we only
* pass from a "safe" callback (with argument) to an "unsafe"
* callback (does not set arguments).
*/
elem->call = (*entry)->call;
/*
* Sanity check :
* We only update the single probe private data when the ptr is
* set to a _non_ single probe! (0 -> 1 and N -> 1, N != 1)
*/
WARN_ON(elem->single.func != __mark_empty_function
&& elem->single.probe_private
!= (*entry)->single.probe_private &&
!elem->ptype);
elem->single.probe_private = (*entry)->single.probe_private;
/*
* Make sure the private data is valid when we update the
* single probe ptr.
*/
smp_wmb();
elem->single.func = (*entry)->single.func;
/*
* We also make sure that the new probe callbacks array is consistent
* before setting a pointer to it.
*/
rcu_assign_pointer(elem->multi, (*entry)->multi);
/*
* Update the function or multi probe array pointer before setting the
* ptype.
*/
smp_wmb();
elem->ptype = (*entry)->ptype;
elem->state = active;
return 0;
}
/*
* Disable a marker and its probe callback.
* Note: only waiting an RCU period after setting elem->call to the empty
* function insures that the original callback is not used anymore. This insured
* by preempt_disable around the call site.
*/
static void disable_marker(struct marker *elem)
{
/* leave "call" as is. It is known statically. */
elem->state = 0;
elem->single.func = __mark_empty_function;
/* Update the function before setting the ptype */
smp_wmb();
elem->ptype = 0; /* single probe */
/*
* Leave the private data and id there, because removal is racy and
* should be done only after an RCU period. 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
*
* Updates the probe callback corresponding to a range of markers.
*/
void marker_update_probe_range(struct marker *begin,
struct marker *end)
{
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) {
set_marker(&mark_entry, iter,
!!mark_entry->refcount);
/*
* ignore error, continue
*/
} else {
disable_marker(iter);
}
}
mutex_unlock(&markers_mutex);
}
/*
* Update probes, removing the faulty probes.
*
* Internal callback only changed before the first probe is connected to it.
* Single probe private data can only be changed on 0 -> 1 and 2 -> 1
* transitions. All other transitions will leave the old private data valid.
* This makes the non-atomicity of the callback/private data updates valid.
*
* "special case" updates :
* 0 -> 1 callback
* 1 -> 0 callback
* 1 -> 2 callbacks
* 2 -> 1 callbacks
* Other updates all behave the same, just like the 2 -> 3 or 3 -> 2 updates.
* Site effect : marker_set_format may delete the marker entry (creating a
* replacement).
*/
static void marker_update_probes(void)
{
/* Core kernel markers */
marker_update_probe_range(__start___markers, __stop___markers);
/* Markers in modules. */
module_update_markers();
}
/**
* marker_probe_register - Connect a probe to a marker
* @name: marker name
* @format: format string
* @probe: probe handler
* @probe_private: probe private data
*
* private data must be a valid allocated memory address, or NULL.
* Returns 0 if ok, error value on error.
* The probe address must at least be aligned on the architecture pointer size.
*/
int marker_probe_register(const char *name, const char *format,
marker_probe_func *probe, void *probe_private)
{
struct marker_entry *entry;
int ret = 0;
struct marker_probe_closure *old;
mutex_lock(&markers_mutex);
entry = get_marker(name);
if (!entry) {
entry = add_marker(name, format);
if (IS_ERR(entry)) {
ret = PTR_ERR(entry);
goto end;
}
}
/*
* If we detect that a call_rcu is pending for this marker,
* make sure it's executed now.
*/
if (entry->rcu_pending)
rcu_barrier_sched();
old = marker_entry_add_probe(entry, probe, probe_private);
if (IS_ERR(old)) {
ret = PTR_ERR(old);
goto end;
}
mutex_unlock(&markers_mutex);
marker_update_probes(); /* may update entry */
mutex_lock(&markers_mutex);
entry = get_marker(name);
WARN_ON(!entry);
entry->oldptr = old;
entry->rcu_pending = 1;
/* write rcu_pending before calling the RCU callback */
smp_wmb();
call_rcu_sched(&entry->rcu, free_old_closure);
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
* @probe: probe function pointer
* @probe_private: probe private data
*
* Returns the private data given to marker_probe_register, or an ERR_PTR().
* We do not need to call a synchronize_sched to make sure the probes have
* finished running before doing a module unload, because the module unload
* itself uses stop_machine(), which insures that every preempt disabled section
* have finished.
*/
int marker_probe_unregister(const char *name,
marker_probe_func *probe, void *probe_private)
{
struct marker_entry *entry;
struct marker_probe_closure *old;
int ret = -ENOENT;
mutex_lock(&markers_mutex);
entry = get_marker(name);
if (!entry)
goto end;
if (entry->rcu_pending)
rcu_barrier_sched();
old = marker_entry_remove_probe(entry, probe, probe_private);
mutex_unlock(&markers_mutex);
marker_update_probes(); /* may update entry */
mutex_lock(&markers_mutex);
entry = get_marker(name);
if (!entry)
goto end;
entry->oldptr = old;
entry->rcu_pending = 1;
/* write rcu_pending before calling the RCU callback */
smp_wmb();
call_rcu_sched(&entry->rcu, free_old_closure);
remove_marker(name); /* Ignore busy error message */
ret = 0;
end:
mutex_unlock(&markers_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(marker_probe_unregister);
static struct marker_entry *
get_marker_from_private_data(marker_probe_func *probe, void *probe_private)
{
struct marker_entry *entry;
unsigned int i;
struct hlist_head *head;
struct hlist_node *node;
for (i = 0; i < MARKER_TABLE_SIZE; i++) {
head = &marker_table[i];
hlist_for_each_entry(entry, node, head, hlist) {
if (!entry->ptype) {
if (entry->single.func == probe
&& entry->single.probe_private
== probe_private)
return entry;
} else {
struct marker_probe_closure *closure;
closure = entry->multi;
for (i = 0; closure[i].func; i++) {
if (closure[i].func == probe &&
closure[i].probe_private
== probe_private)
return entry;
}
}
}
}
return NULL;
}
/**
* marker_probe_unregister_private_data - Disconnect a probe from a marker
* @probe: probe function
* @probe_private: probe private data
*
* Unregister a probe by providing the registered private data.
* Only removes the first marker found in hash table.
* Return 0 on success or error value.
* We do not need to call a synchronize_sched to make sure the probes have
* finished running before doing a module unload, because the module unload
* itself uses stop_machine(), which insures that every preempt disabled section
* have finished.
*/
int marker_probe_unregister_private_data(marker_probe_func *probe,
void *probe_private)
{
struct marker_entry *entry;
int ret = 0;
struct marker_probe_closure *old;
mutex_lock(&markers_mutex);
entry = get_marker_from_private_data(probe, probe_private);
if (!entry) {
ret = -ENOENT;
goto end;
}
if (entry->rcu_pending)
rcu_barrier_sched();
old = marker_entry_remove_probe(entry, NULL, probe_private);
mutex_unlock(&markers_mutex);
marker_update_probes(); /* may update entry */
mutex_lock(&markers_mutex);
entry = get_marker_from_private_data(probe, probe_private);
WARN_ON(!entry);
entry->oldptr = old;
entry->rcu_pending = 1;
/* write rcu_pending before calling the RCU callback */
smp_wmb();
call_rcu_sched(&entry->rcu, free_old_closure);
remove_marker(entry->name); /* Ignore busy error message */
end:
mutex_unlock(&markers_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
/**
* marker_get_private_data - Get a marker's probe private data
* @name: marker name
* @probe: probe to match
* @num: get the nth matching probe's private data
*
* Returns the nth private data pointer (starting from 0) matching, or an
* ERR_PTR.
* 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, marker_probe_func *probe,
int num)
{
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 i;
head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
hlist_for_each_entry(e, node, head, hlist) {
if (!strcmp(name, e->name)) {
if (!e->ptype) {
if (num == 0 && e->single.func == probe)
return e->single.probe_private;
else
break;
} else {
struct marker_probe_closure *closure;
int match = 0;
closure = e->multi;
for (i = 0; closure[i].func; i++) {
if (closure[i].func != probe)
continue;
if (match++ == num)
return closure[i].probe_private;
}
}
}
}
return ERR_PTR(-ENOENT);
}
EXPORT_SYMBOL_GPL(marker_get_private_data);