- data[] - storage for shadow data
It is important to note that the klp_shadow_alloc() and
-klp_shadow_get_or_alloc() calls, described below, store a *copy* of the
-data that the functions are provided. Callers should provide whatever
-mutual exclusion is required of the shadow data.
+klp_shadow_get_or_alloc() are zeroing the variable by default.
+They also allow to call a custom constructor function when a non-zero
+value is needed. Callers should provide whatever mutual exclusion
+is required.
+
+Note that the constructor is called under klp_shadow_lock spinlock. It allows
+to do actions that can be done only once when a new variable is allocated.
* klp_shadow_get() - retrieve a shadow variable data pointer
- search hashtable for <obj, id> pair
- WARN and return NULL
- if <obj, id> doesn't already exist
- allocate a new shadow variable
- - copy data into the new shadow variable
+ - initialize the variable using a custom constructor and data when provided
- add <obj, id> to the global hashtable
* klp_shadow_get_or_alloc() - get existing or alloc a new shadow variable
- return existing shadow variable
- if <obj, id> doesn't already exist
- allocate a new shadow variable
- - copy data into the new shadow variable
+ - initialize the variable using a custom constructor and data when provided
- add <obj, id> pair to the global hashtable
* klp_shadow_free() - detach and free a <obj, id> shadow variable
- find and remove a <obj, id> reference from global hashtable
- - if found, free shadow variable
+ - if found
+ - call destructor function if defined
+ - free shadow variable
* klp_shadow_free_all() - detach and free all <*, id> shadow variables
- find and remove any <*, id> references from global hashtable
- - if found, free shadow variable
+ - if found
+ - call destructor function if defined
+ - free shadow variable
2. Use cases
sta = kzalloc(sizeof(*sta) + hw->sta_data_size, gfp);
/* Attach a corresponding shadow variable, then initialize it */
- ps_lock = klp_shadow_alloc(sta, PS_LOCK, NULL, sizeof(*ps_lock), gfp);
+ ps_lock = klp_shadow_alloc(sta, PS_LOCK, sizeof(*ps_lock), gfp,
+ NULL, NULL);
if (!ps_lock)
goto shadow_fail;
spin_lock_init(ps_lock);
void sta_info_free(struct ieee80211_local *local, struct sta_info *sta)
{
- klp_shadow_free(sta, PS_LOCK);
+ klp_shadow_free(sta, PS_LOCK, NULL);
kfree(sta);
...
For commit 1d147bfa6429, a good spot to allocate a shadow spinlock is
inside ieee80211_sta_ps_deliver_wakeup():
+int ps_lock_shadow_ctor(void *obj, void *shadow_data, void *ctor_data)
+{
+ spinlock_t *lock = shadow_data;
+
+ spin_lock_init(lock);
+ return 0;
+}
+
#define PS_LOCK 1
void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta)
{
- DEFINE_SPINLOCK(ps_lock_fallback);
spinlock_t *ps_lock;
/* sync with ieee80211_tx_h_unicast_ps_buf */
ps_lock = klp_shadow_get_or_alloc(sta, PS_LOCK,
- &ps_lock_fallback, sizeof(ps_lock_fallback),
- GFP_ATOMIC);
+ sizeof(*ps_lock), GFP_ATOMIC,
+ ps_lock_shadow_ctor, NULL);
+
if (ps_lock)
spin_lock(ps_lock);
...
IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
}
+typedef int (*klp_shadow_ctor_t)(void *obj,
+ void *shadow_data,
+ void *ctor_data);
+typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data);
+
void *klp_shadow_get(void *obj, unsigned long id);
-void *klp_shadow_alloc(void *obj, unsigned long id, void *data,
- size_t size, gfp_t gfp_flags);
-void *klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
- size_t size, gfp_t gfp_flags);
-void klp_shadow_free(void *obj, unsigned long id);
-void klp_shadow_free_all(unsigned long id);
+void *klp_shadow_alloc(void *obj, unsigned long id,
+ size_t size, gfp_t gfp_flags,
+ klp_shadow_ctor_t ctor, void *ctor_data);
+void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
+ size_t size, gfp_t gfp_flags,
+ klp_shadow_ctor_t ctor, void *ctor_data);
+void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor);
+void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor);
#else /* !CONFIG_LIVEPATCH */
}
EXPORT_SYMBOL_GPL(klp_shadow_get);
-static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
- size_t size, gfp_t gfp_flags, bool warn_on_exist)
+static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id,
+ size_t size, gfp_t gfp_flags,
+ klp_shadow_ctor_t ctor, void *ctor_data,
+ bool warn_on_exist)
{
struct klp_shadow *new_shadow;
void *shadow_data;
if (shadow_data)
goto exists;
- /* Allocate a new shadow variable for use inside the lock below */
+ /*
+ * Allocate a new shadow variable. Fill it with zeroes by default.
+ * More complex setting can be done by @ctor function. But it is
+ * called only when the buffer is really used (under klp_shadow_lock).
+ */
new_shadow = kzalloc(size + sizeof(*new_shadow), gfp_flags);
if (!new_shadow)
return NULL;
- new_shadow->obj = obj;
- new_shadow->id = id;
-
- /* Initialize the shadow variable if data provided */
- if (data)
- memcpy(new_shadow->data, data, size);
-
/* Look for <obj, id> again under the lock */
spin_lock_irqsave(&klp_shadow_lock, flags);
shadow_data = klp_shadow_get(obj, id);
goto exists;
}
+ new_shadow->obj = obj;
+ new_shadow->id = id;
+
+ if (ctor) {
+ int err;
+
+ err = ctor(obj, new_shadow->data, ctor_data);
+ if (err) {
+ spin_unlock_irqrestore(&klp_shadow_lock, flags);
+ kfree(new_shadow);
+ pr_err("Failed to construct shadow variable <%p, %lx> (%d)\n",
+ obj, id, err);
+ return NULL;
+ }
+ }
+
/* No <obj, id> found, so attach the newly allocated one */
hash_add_rcu(klp_shadow_hash, &new_shadow->node,
(unsigned long)new_shadow->obj);
* klp_shadow_alloc() - allocate and add a new shadow variable
* @obj: pointer to parent object
* @id: data identifier
- * @data: pointer to data to attach to parent
* @size: size of attached data
* @gfp_flags: GFP mask for allocation
+ * @ctor: custom constructor to initialize the shadow data (optional)
+ * @ctor_data: pointer to any data needed by @ctor (optional)
+ *
+ * Allocates @size bytes for new shadow variable data using @gfp_flags.
+ * The data are zeroed by default. They are further initialized by @ctor
+ * function if it is not NULL. The new shadow variable is then added
+ * to the global hashtable.
*
- * Allocates @size bytes for new shadow variable data using @gfp_flags
- * and copies @size bytes from @data into the new shadow variable's own
- * data space. If @data is NULL, @size bytes are still allocated, but
- * no copy is performed. The new shadow variable is then added to the
- * global hashtable.
+ * If an existing <obj, id> shadow variable can be found, this routine will
+ * issue a WARN, exit early and return NULL.
*
- * If an existing <obj, id> shadow variable can be found, this routine
- * will issue a WARN, exit early and return NULL.
+ * This function guarantees that the constructor function is called only when
+ * the variable did not exist before. The cost is that @ctor is called
+ * in atomic context under a spin lock.
*
* Return: the shadow variable data element, NULL on duplicate or
* failure.
*/
-void *klp_shadow_alloc(void *obj, unsigned long id, void *data,
- size_t size, gfp_t gfp_flags)
+void *klp_shadow_alloc(void *obj, unsigned long id,
+ size_t size, gfp_t gfp_flags,
+ klp_shadow_ctor_t ctor, void *ctor_data)
{
- return __klp_shadow_get_or_alloc(obj, id, data, size, gfp_flags, true);
+ return __klp_shadow_get_or_alloc(obj, id, size, gfp_flags,
+ ctor, ctor_data, true);
}
EXPORT_SYMBOL_GPL(klp_shadow_alloc);
* klp_shadow_get_or_alloc() - get existing or allocate a new shadow variable
* @obj: pointer to parent object
* @id: data identifier
- * @data: pointer to data to attach to parent
* @size: size of attached data
* @gfp_flags: GFP mask for allocation
+ * @ctor: custom constructor to initialize the shadow data (optional)
+ * @ctor_data: pointer to any data needed by @ctor (optional)
*
* Returns a pointer to existing shadow data if an <obj, id> shadow
* variable is already present. Otherwise, it creates a new shadow
* variable like klp_shadow_alloc().
*
- * This function guarantees that only one shadow variable exists with
- * the given @id for the given @obj. It also guarantees that the shadow
- * variable will be initialized by the given @data only when it did not
- * exist before.
+ * This function guarantees that only one shadow variable exists with the given
+ * @id for the given @obj. It also guarantees that the constructor function
+ * will be called only when the variable did not exist before. The cost is
+ * that @ctor is called in atomic context under a spin lock.
*
* Return: the shadow variable data element, NULL on failure.
*/
-void *klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
- size_t size, gfp_t gfp_flags)
+void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
+ size_t size, gfp_t gfp_flags,
+ klp_shadow_ctor_t ctor, void *ctor_data)
{
- return __klp_shadow_get_or_alloc(obj, id, data, size, gfp_flags, false);
+ return __klp_shadow_get_or_alloc(obj, id, size, gfp_flags,
+ ctor, ctor_data, false);
}
EXPORT_SYMBOL_GPL(klp_shadow_get_or_alloc);
+static void klp_shadow_free_struct(struct klp_shadow *shadow,
+ klp_shadow_dtor_t dtor)
+{
+ hash_del_rcu(&shadow->node);
+ if (dtor)
+ dtor(shadow->obj, shadow->data);
+ kfree_rcu(shadow, rcu_head);
+}
+
/**
* klp_shadow_free() - detach and free a <obj, id> shadow variable
* @obj: pointer to parent object
* @id: data identifier
+ * @dtor: custom callback that can be used to unregister the variable
+ * and/or free data that the shadow variable points to (optional)
*
* This function releases the memory for this <obj, id> shadow variable
* instance, callers should stop referencing it accordingly.
*/
-void klp_shadow_free(void *obj, unsigned long id)
+void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor)
{
struct klp_shadow *shadow;
unsigned long flags;
(unsigned long)obj) {
if (klp_shadow_match(shadow, obj, id)) {
- hash_del_rcu(&shadow->node);
- kfree_rcu(shadow, rcu_head);
+ klp_shadow_free_struct(shadow, dtor);
break;
}
}
/**
* klp_shadow_free_all() - detach and free all <*, id> shadow variables
* @id: data identifier
+ * @dtor: custom callback that can be used to unregister the variable
+ * and/or free data that the shadow variable points to (optional)
*
* This function releases the memory for all <*, id> shadow variable
* instances, callers should stop referencing them accordingly.
*/
-void klp_shadow_free_all(unsigned long id)
+void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor)
{
struct klp_shadow *shadow;
unsigned long flags;
/* Delete all <*, id> from hash */
hash_for_each(klp_shadow_hash, i, shadow, node) {
- if (klp_shadow_match(shadow, shadow->obj, id)) {
- hash_del_rcu(&shadow->node);
- kfree_rcu(shadow, rcu_head);
- }
+ if (klp_shadow_match(shadow, shadow->obj, id))
+ klp_shadow_free_struct(shadow, dtor);
}
spin_unlock_irqrestore(&klp_shadow_lock, flags);
unsigned long jiffies_expire;
};
+/*
+ * The constructor makes more sense together with klp_shadow_get_or_alloc().
+ * In this example, it would be safe to assign the pointer also to the shadow
+ * variable returned by klp_shadow_alloc(). But we wanted to show the more
+ * complicated use of the API.
+ */
+static int shadow_leak_ctor(void *obj, void *shadow_data, void *ctor_data)
+{
+ void **shadow_leak = shadow_data;
+ void *leak = ctor_data;
+
+ *shadow_leak = leak;
+ return 0;
+}
+
struct dummy *livepatch_fix1_dummy_alloc(void)
{
struct dummy *d;
* pointer to handle resource release.
*/
leak = kzalloc(sizeof(int), GFP_KERNEL);
- klp_shadow_alloc(d, SV_LEAK, &leak, sizeof(leak), GFP_KERNEL);
+ klp_shadow_alloc(d, SV_LEAK, sizeof(leak), GFP_KERNEL,
+ shadow_leak_ctor, leak);
pr_info("%s: dummy @ %p, expires @ %lx\n",
__func__, d, d->jiffies_expire);
return d;
}
+static void livepatch_fix1_dummy_leak_dtor(void *obj, void *shadow_data)
+{
+ void *d = obj;
+ void **shadow_leak = shadow_data;
+
+ kfree(*shadow_leak);
+ pr_info("%s: dummy @ %p, prevented leak @ %p\n",
+ __func__, d, *shadow_leak);
+}
+
void livepatch_fix1_dummy_free(struct dummy *d)
{
- void **shadow_leak, *leak;
+ void **shadow_leak;
/*
* Patch: fetch the saved SV_LEAK shadow variable, detach and
* was loaded.)
*/
shadow_leak = klp_shadow_get(d, SV_LEAK);
- if (shadow_leak) {
- leak = *shadow_leak;
- klp_shadow_free(d, SV_LEAK);
- kfree(leak);
- pr_info("%s: dummy @ %p, prevented leak @ %p\n",
- __func__, d, leak);
- } else {
+ if (shadow_leak)
+ klp_shadow_free(d, SV_LEAK, livepatch_fix1_dummy_leak_dtor);
+ else
pr_info("%s: dummy @ %p leaked!\n", __func__, d);
- }
kfree(d);
}
static void livepatch_shadow_fix1_exit(void)
{
/* Cleanup any existing SV_LEAK shadow variables */
- klp_shadow_free_all(SV_LEAK);
+ klp_shadow_free_all(SV_LEAK, livepatch_fix1_dummy_leak_dtor);
WARN_ON(klp_unregister_patch(&patch));
}
bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
{
int *shadow_count;
- int count;
/*
* Patch: handle in-flight dummy structures, if they do not
* already have a SV_COUNTER shadow variable, then attach a
* new one.
*/
- count = 0;
shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
- &count, sizeof(count),
- GFP_NOWAIT);
+ sizeof(*shadow_count), GFP_NOWAIT,
+ NULL, NULL);
if (shadow_count)
*shadow_count += 1;
return time_after(jiffies, d->jiffies_expire);
}
+static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data)
+{
+ void *d = obj;
+ void **shadow_leak = shadow_data;
+
+ kfree(*shadow_leak);
+ pr_info("%s: dummy @ %p, prevented leak @ %p\n",
+ __func__, d, *shadow_leak);
+}
+
void livepatch_fix2_dummy_free(struct dummy *d)
{
- void **shadow_leak, *leak;
+ void **shadow_leak;
int *shadow_count;
/* Patch: copy the memory leak patch from the fix1 module. */
shadow_leak = klp_shadow_get(d, SV_LEAK);
- if (shadow_leak) {
- leak = *shadow_leak;
- klp_shadow_free(d, SV_LEAK);
- kfree(leak);
- pr_info("%s: dummy @ %p, prevented leak @ %p\n",
- __func__, d, leak);
- } else {
+ if (shadow_leak)
+ klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor);
+ else
pr_info("%s: dummy @ %p leaked!\n", __func__, d);
- }
/*
* Patch: fetch the SV_COUNTER shadow variable and display
if (shadow_count) {
pr_info("%s: dummy @ %p, check counter = %d\n",
__func__, d, *shadow_count);
- klp_shadow_free(d, SV_COUNTER);
+ klp_shadow_free(d, SV_COUNTER, NULL);
}
kfree(d);
static void livepatch_shadow_fix2_exit(void)
{
/* Cleanup any existing SV_COUNTER shadow variables */
- klp_shadow_free_all(SV_COUNTER);
+ klp_shadow_free_all(SV_COUNTER, NULL);
WARN_ON(klp_unregister_patch(&patch));
}
git.samba.org / sfrench / cifs-2.6.git / commitdiff