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tracing/user_events: Move pages/locks into groups to prepare for namespaces

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In order to enable namespaces or any sort of isolation within
user_events the register lock and pages need to be broken up into
groups. Each event and file now has a group pointer which stores the
actual pages to map, lookup data and synchronization objects.

This only enables a single group that maps to init_user_ns, as IMA
namespace has done. This enables user_events to start the work of
supporting namespaces by walking the namespaces up to the init_user_ns.
Future patches will address other user namespaces and will align to the
approaches the IMA namespace uses.

Link: https://lore.kernel.org/linux-kernel/20220915193221.1728029-15-stefanb@linux.ibm.com/#t
Link: https://lkml.kernel.org/r/20221001001016.2832-2-beaub@linux.microsoft.com

Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Beau Belgrave 2022-09-30 17:10:16 -07:00 committed by Steven Rostedt (Google)
parent 5d8d2bb946
commit e5d271812e
1 changed files with 274 additions and 72 deletions
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346
kernel/trace/trace_events_user.c
View File

@ -74,11 +74,25 @@
#define EVENT_STATUS_PERF BIT(1) #define EVENT_STATUS_PERF BIT(1)
#define EVENT_STATUS_OTHER BIT(7) #define EVENT_STATUS_OTHER BIT(7)
static char *register_page_data; /*
* Stores the pages, tables, and locks for a group of events.
* Each logical grouping of events has its own group, with a
* matching page for status checks within user programs. This
* allows for isolation of events to user programs by various
* means.
*/
struct user_event_group {
struct page *pages;
char *register_page_data;
char *system_name;
struct hlist_node node;
struct mutex reg_mutex;
DECLARE_HASHTABLE(register_table, 8);
DECLARE_BITMAP(page_bitmap, MAX_EVENTS);
};
static DEFINE_MUTEX(reg_mutex); /* Group for init_user_ns mapping, top-most group */
static DEFINE_HASHTABLE(register_table, 8); static struct user_event_group *init_group;
static DECLARE_BITMAP(page_bitmap, MAX_EVENTS);
/* /*
* Stores per-event properties, as users register events * Stores per-event properties, as users register events
@ -88,6 +102,7 @@ static DECLARE_BITMAP(page_bitmap, MAX_EVENTS);
* refcnt reaches one. * refcnt reaches one.
*/ */
struct user_event { struct user_event {
struct user_event_group *group;
struct tracepoint tracepoint; struct tracepoint tracepoint;
struct trace_event_call call; struct trace_event_call call;
struct trace_event_class class; struct trace_event_class class;
@ -114,6 +129,11 @@ struct user_event_refs {
struct user_event *events[]; struct user_event *events[];
}; };
struct user_event_file_info {
struct user_event_group *group;
struct user_event_refs *refs;
};
#define VALIDATOR_ENSURE_NULL (1 << 0) #define VALIDATOR_ENSURE_NULL (1 << 0)
#define VALIDATOR_REL (1 << 1) #define VALIDATOR_REL (1 << 1)
@ -126,7 +146,8 @@ struct user_event_validator {
typedef void (*user_event_func_t) (struct user_event *user, struct iov_iter *i, typedef void (*user_event_func_t) (struct user_event *user, struct iov_iter *i,
void *tpdata, bool *faulted); void *tpdata, bool *faulted);
static int user_event_parse(char *name, char *args, char *flags, static int user_event_parse(struct user_event_group *group, char *name,
char *args, char *flags,
struct user_event **newuser); struct user_event **newuser);
static u32 user_event_key(char *name) static u32 user_event_key(char *name)
@ -134,12 +155,128 @@ static u32 user_event_key(char *name)
return jhash(name, strlen(name), 0); return jhash(name, strlen(name), 0);
} }
static void set_page_reservations(char *pages, bool set)
{
int page;
for (page = 0; page < MAX_PAGES; ++page) {
void *addr = pages + (PAGE_SIZE * page);
if (set)
SetPageReserved(virt_to_page(addr));
else
ClearPageReserved(virt_to_page(addr));
}
}
static void user_event_group_destroy(struct user_event_group *group)
{
if (group->register_page_data)
set_page_reservations(group->register_page_data, false);
if (group->pages)
__free_pages(group->pages, MAX_PAGE_ORDER);
kfree(group->system_name);
kfree(group);
}
static char *user_event_group_system_name(struct user_namespace *user_ns)
{
char *system_name;
int len = sizeof(USER_EVENTS_SYSTEM) + 1;
if (user_ns != &init_user_ns) {
/*
* Unexpected at this point:
* We only currently support init_user_ns.
* When we enable more, this will trigger a failure so log.
*/
pr_warn("user_events: Namespace other than init_user_ns!\n");
return NULL;
}
system_name = kmalloc(len, GFP_KERNEL);
if (!system_name)
return NULL;
snprintf(system_name, len, "%s", USER_EVENTS_SYSTEM);
return system_name;
}
static inline struct user_event_group
*user_event_group_from_user_ns(struct user_namespace *user_ns)
{
if (user_ns == &init_user_ns)
return init_group;
return NULL;
}
static struct user_event_group *current_user_event_group(void)
{
struct user_namespace *user_ns = current_user_ns();
struct user_event_group *group = NULL;
while (user_ns) {
group = user_event_group_from_user_ns(user_ns);
if (group)
break;
user_ns = user_ns->parent;
}
return group;
}
static struct user_event_group
*user_event_group_create(struct user_namespace *user_ns)
{
struct user_event_group *group;
group = kzalloc(sizeof(*group), GFP_KERNEL);
if (!group)
return NULL;
group->system_name = user_event_group_system_name(user_ns);
if (!group->system_name)
goto error;
group->pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, MAX_PAGE_ORDER);
if (!group->pages)
goto error;
group->register_page_data = page_address(group->pages);
set_page_reservations(group->register_page_data, true);
/* Zero all bits beside 0 (which is reserved for failures) */
bitmap_zero(group->page_bitmap, MAX_EVENTS);
set_bit(0, group->page_bitmap);
mutex_init(&group->reg_mutex);
hash_init(group->register_table);
return group;
error:
if (group)
user_event_group_destroy(group);
return NULL;
};
static __always_inline static __always_inline
void user_event_register_set(struct user_event *user) void user_event_register_set(struct user_event *user)
{ {
int i = user->index; int i = user->index;
register_page_data[MAP_STATUS_BYTE(i)] |= MAP_STATUS_MASK(i); user->group->register_page_data[MAP_STATUS_BYTE(i)] |= MAP_STATUS_MASK(i);
} }
static __always_inline static __always_inline
@ -147,7 +284,7 @@ void user_event_register_clear(struct user_event *user)
{ {
int i = user->index; int i = user->index;
register_page_data[MAP_STATUS_BYTE(i)] &= ~MAP_STATUS_MASK(i); user->group->register_page_data[MAP_STATUS_BYTE(i)] &= ~MAP_STATUS_MASK(i);
} }
static __always_inline __must_check static __always_inline __must_check
@ -191,7 +328,8 @@ static struct list_head *user_event_get_fields(struct trace_event_call *call)
* *
* Upon success user_event has its ref count increased by 1. * Upon success user_event has its ref count increased by 1.
*/ */
static int user_event_parse_cmd(char *raw_command, struct user_event **newuser) static int user_event_parse_cmd(struct user_event_group *group,
char *raw_command, struct user_event **newuser)
{ {
char *name = raw_command; char *name = raw_command;
char *args = strpbrk(name, " "); char *args = strpbrk(name, " ");
@ -205,7 +343,7 @@ static int user_event_parse_cmd(char *raw_command, struct user_event **newuser)
if (flags) if (flags)
*flags++ = '\0'; *flags++ = '\0';
return user_event_parse(name, args, flags, newuser); return user_event_parse(group, name, args, flags, newuser);
} }
static int user_field_array_size(const char *type) static int user_field_array_size(const char *type)
@ -693,7 +831,7 @@ static int destroy_user_event(struct user_event *user)
dyn_event_remove(&user->devent); dyn_event_remove(&user->devent);
user_event_register_clear(user); user_event_register_clear(user);
clear_bit(user->index, page_bitmap); clear_bit(user->index, user->group->page_bitmap);
hash_del(&user->node); hash_del(&user->node);
user_event_destroy_validators(user); user_event_destroy_validators(user);
@ -704,14 +842,15 @@ static int destroy_user_event(struct user_event *user)
return ret; return ret;
} }
static struct user_event *find_user_event(char *name, u32 *outkey) static struct user_event *find_user_event(struct user_event_group *group,
char *name, u32 *outkey)
{ {
struct user_event *user; struct user_event *user;
u32 key = user_event_key(name); u32 key = user_event_key(name);
*outkey = key; *outkey = key;
hash_for_each_possible(register_table, user, node, key) hash_for_each_possible(group->register_table, user, node, key)
if (!strcmp(EVENT_NAME(user), name)) { if (!strcmp(EVENT_NAME(user), name)) {
refcount_inc(&user->refcnt); refcount_inc(&user->refcnt);
return user; return user;
@ -943,6 +1082,7 @@ dec:
static int user_event_create(const char *raw_command) static int user_event_create(const char *raw_command)
{ {
struct user_event_group *group;
struct user_event *user; struct user_event *user;
char *name; char *name;
int ret; int ret;
@ -958,14 +1098,19 @@ static int user_event_create(const char *raw_command)
if (!name) if (!name)
return -ENOMEM; return -ENOMEM;
mutex_lock(&reg_mutex); group = current_user_event_group();
ret = user_event_parse_cmd(name, &user); if (!group)
return -ENOENT;
mutex_lock(&group->reg_mutex);
ret = user_event_parse_cmd(group, name, &user);
if (!ret) if (!ret)
refcount_dec(&user->refcnt); refcount_dec(&user->refcnt);
mutex_unlock(&reg_mutex); mutex_unlock(&group->reg_mutex);
if (ret) if (ret)
kfree(name); kfree(name);
@ -1119,7 +1264,8 @@ static int user_event_trace_register(struct user_event *user)
* The name buffer lifetime is owned by this method for success cases only. * The name buffer lifetime is owned by this method for success cases only.
* Upon success the returned user_event has its ref count increased by 1. * Upon success the returned user_event has its ref count increased by 1.
*/ */
static int user_event_parse(char *name, char *args, char *flags, static int user_event_parse(struct user_event_group *group, char *name,
char *args, char *flags,
struct user_event **newuser) struct user_event **newuser)
{ {
int ret; int ret;
@ -1129,7 +1275,7 @@ static int user_event_parse(char *name, char *args, char *flags,
/* Prevent dyn_event from racing */ /* Prevent dyn_event from racing */
mutex_lock(&event_mutex); mutex_lock(&event_mutex);
user = find_user_event(name, &key); user = find_user_event(group, name, &key);
mutex_unlock(&event_mutex); mutex_unlock(&event_mutex);
if (user) { if (user) {
@ -1142,7 +1288,7 @@ static int user_event_parse(char *name, char *args, char *flags,
return 0; return 0;
} }
index = find_first_zero_bit(page_bitmap, MAX_EVENTS); index = find_first_zero_bit(group->page_bitmap, MAX_EVENTS);
if (index == MAX_EVENTS) if (index == MAX_EVENTS)
return -EMFILE; return -EMFILE;
@ -1156,6 +1302,7 @@ static int user_event_parse(char *name, char *args, char *flags,
INIT_LIST_HEAD(&user->fields); INIT_LIST_HEAD(&user->fields);
INIT_LIST_HEAD(&user->validators); INIT_LIST_HEAD(&user->validators);
user->group = group;
user->tracepoint.name = name; user->tracepoint.name = name;
ret = user_event_parse_fields(user, args); ret = user_event_parse_fields(user, args);
@ -1174,8 +1321,8 @@ static int user_event_parse(char *name, char *args, char *flags,
user->call.flags = TRACE_EVENT_FL_TRACEPOINT; user->call.flags = TRACE_EVENT_FL_TRACEPOINT;
user->call.tp = &user->tracepoint; user->call.tp = &user->tracepoint;
user->call.event.funcs = &user_event_funcs; user->call.event.funcs = &user_event_funcs;
user->class.system = group->system_name;
user->class.system = USER_EVENTS_SYSTEM;
user->class.fields_array = user_event_fields_array; user->class.fields_array = user_event_fields_array;
user->class.get_fields = user_event_get_fields; user->class.get_fields = user_event_get_fields;
user->class.reg = user_event_reg; user->class.reg = user_event_reg;
@ -1198,8 +1345,8 @@ static int user_event_parse(char *name, char *args, char *flags,
dyn_event_init(&user->devent, &user_event_dops); dyn_event_init(&user->devent, &user_event_dops);
dyn_event_add(&user->devent, &user->call); dyn_event_add(&user->devent, &user->call);
set_bit(user->index, page_bitmap); set_bit(user->index, group->page_bitmap);
hash_add(register_table, &user->node, key); hash_add(group->register_table, &user->node, key);
mutex_unlock(&event_mutex); mutex_unlock(&event_mutex);
@ -1217,10 +1364,10 @@ put_user:
/* /*
* Deletes a previously created event if it is no longer being used. * Deletes a previously created event if it is no longer being used.
*/ */
static int delete_user_event(char *name) static int delete_user_event(struct user_event_group *group, char *name)
{ {
u32 key; u32 key;
struct user_event *user = find_user_event(name, &key); struct user_event *user = find_user_event(group, name, &key);
if (!user) if (!user)
return -ENOENT; return -ENOENT;
@ -1238,6 +1385,7 @@ static int delete_user_event(char *name)
*/ */
static ssize_t user_events_write_core(struct file *file, struct iov_iter *i) static ssize_t user_events_write_core(struct file *file, struct iov_iter *i)
{ {
struct user_event_file_info *info = file->private_data;
struct user_event_refs *refs; struct user_event_refs *refs;
struct user_event *user = NULL; struct user_event *user = NULL;
struct tracepoint *tp; struct tracepoint *tp;
@ -1249,7 +1397,7 @@ static ssize_t user_events_write_core(struct file *file, struct iov_iter *i)
rcu_read_lock_sched(); rcu_read_lock_sched();
refs = rcu_dereference_sched(file->private_data); refs = rcu_dereference_sched(info->refs);
/* /*
* The refs->events array is protected by RCU, and new items may be * The refs->events array is protected by RCU, and new items may be
@ -1307,6 +1455,28 @@ static ssize_t user_events_write_core(struct file *file, struct iov_iter *i)
return ret; return ret;
} }
static int user_events_open(struct inode *node, struct file *file)
{
struct user_event_group *group;
struct user_event_file_info *info;
group = current_user_event_group();
if (!group)
return -ENOENT;
info = kzalloc(sizeof(*info), GFP_KERNEL);
if (!info)
return -ENOMEM;
info->group = group;
file->private_data = info;
return 0;
}
static ssize_t user_events_write(struct file *file, const char __user *ubuf, static ssize_t user_events_write(struct file *file, const char __user *ubuf,
size_t count, loff_t *ppos) size_t count, loff_t *ppos)
{ {
@ -1328,13 +1498,15 @@ static ssize_t user_events_write_iter(struct kiocb *kp, struct iov_iter *i)
return user_events_write_core(kp->ki_filp, i); return user_events_write_core(kp->ki_filp, i);
} }
static int user_events_ref_add(struct file *file, struct user_event *user) static int user_events_ref_add(struct user_event_file_info *info,
struct user_event *user)
{ {
struct user_event_group *group = info->group;
struct user_event_refs *refs, *new_refs; struct user_event_refs *refs, *new_refs;
int i, size, count = 0; int i, size, count = 0;
refs = rcu_dereference_protected(file->private_data, refs = rcu_dereference_protected(info->refs,
lockdep_is_held(&reg_mutex)); lockdep_is_held(&group->reg_mutex));
if (refs) { if (refs) {
count = refs->count; count = refs->count;
@ -1360,7 +1532,7 @@ static int user_events_ref_add(struct file *file, struct user_event *user)
refcount_inc(&user->refcnt); refcount_inc(&user->refcnt);
rcu_assign_pointer(file->private_data, new_refs); rcu_assign_pointer(info->refs, new_refs);
if (refs) if (refs)
kfree_rcu(refs, rcu); kfree_rcu(refs, rcu);
@ -1397,7 +1569,8 @@ static long user_reg_get(struct user_reg __user *ureg, struct user_reg *kreg)
/* /*
* Registers a user_event on behalf of a user process. * Registers a user_event on behalf of a user process.
*/ */
static long user_events_ioctl_reg(struct file *file, unsigned long uarg) static long user_events_ioctl_reg(struct user_event_file_info *info,
unsigned long uarg)
{ {
struct user_reg __user *ureg = (struct user_reg __user *)uarg; struct user_reg __user *ureg = (struct user_reg __user *)uarg;
struct user_reg reg; struct user_reg reg;
@ -1418,14 +1591,14 @@ static long user_events_ioctl_reg(struct file *file, unsigned long uarg)
return ret; return ret;
} }
ret = user_event_parse_cmd(name, &user); ret = user_event_parse_cmd(info->group, name, &user);
if (ret) { if (ret) {
kfree(name); kfree(name);
return ret; return ret;
} }
ret = user_events_ref_add(file, user); ret = user_events_ref_add(info, user);
/* No longer need parse ref, ref_add either worked or not */ /* No longer need parse ref, ref_add either worked or not */
refcount_dec(&user->refcnt); refcount_dec(&user->refcnt);
@ -1443,7 +1616,8 @@ static long user_events_ioctl_reg(struct file *file, unsigned long uarg)
/* /*
* Deletes a user_event on behalf of a user process. * Deletes a user_event on behalf of a user process.
*/ */
static long user_events_ioctl_del(struct file *file, unsigned long uarg) static long user_events_ioctl_del(struct user_event_file_info *info,
unsigned long uarg)
{ {
void __user *ubuf = (void __user *)uarg; void __user *ubuf = (void __user *)uarg;
char *name; char *name;
@ -1456,7 +1630,7 @@ static long user_events_ioctl_del(struct file *file, unsigned long uarg)
/* event_mutex prevents dyn_event from racing */ /* event_mutex prevents dyn_event from racing */
mutex_lock(&event_mutex); mutex_lock(&event_mutex);
ret = delete_user_event(name); ret = delete_user_event(info->group, name);
mutex_unlock(&event_mutex); mutex_unlock(&event_mutex);
kfree(name); kfree(name);
@ -1470,19 +1644,21 @@ static long user_events_ioctl_del(struct file *file, unsigned long uarg)
static long user_events_ioctl(struct file *file, unsigned int cmd, static long user_events_ioctl(struct file *file, unsigned int cmd,
unsigned long uarg) unsigned long uarg)
{ {
struct user_event_file_info *info = file->private_data;
struct user_event_group *group = info->group;
long ret = -ENOTTY; long ret = -ENOTTY;
switch (cmd) { switch (cmd) {
case DIAG_IOCSREG: case DIAG_IOCSREG:
mutex_lock(&reg_mutex); mutex_lock(&group->reg_mutex);
ret = user_events_ioctl_reg(file, uarg); ret = user_events_ioctl_reg(info, uarg);
mutex_unlock(&reg_mutex); mutex_unlock(&group->reg_mutex);
break; break;
case DIAG_IOCSDEL: case DIAG_IOCSDEL:
mutex_lock(&reg_mutex); mutex_lock(&group->reg_mutex);
ret = user_events_ioctl_del(file, uarg); ret = user_events_ioctl_del(info, uarg);
mutex_unlock(&reg_mutex); mutex_unlock(&group->reg_mutex);
break; break;
} }
@ -1494,17 +1670,24 @@ static long user_events_ioctl(struct file *file, unsigned int cmd,
*/ */
static int user_events_release(struct inode *node, struct file *file) static int user_events_release(struct inode *node, struct file *file)
{ {
struct user_event_file_info *info = file->private_data;
struct user_event_group *group;
struct user_event_refs *refs; struct user_event_refs *refs;
struct user_event *user; struct user_event *user;
int i; int i;
if (!info)
return -EINVAL;
group = info->group;
/* /*
* Ensure refs cannot change under any situation by taking the * Ensure refs cannot change under any situation by taking the
* register mutex during the final freeing of the references. * register mutex during the final freeing of the references.
*/ */
mutex_lock(&reg_mutex); mutex_lock(&group->reg_mutex);
refs = file->private_data; refs = info->refs;
if (!refs) if (!refs)
goto out; goto out;
@ -1523,32 +1706,51 @@ static int user_events_release(struct inode *node, struct file *file)
out: out:
file->private_data = NULL; file->private_data = NULL;
mutex_unlock(&reg_mutex); mutex_unlock(&group->reg_mutex);
kfree(refs); kfree(refs);
kfree(info);
return 0; return 0;
} }
static const struct file_operations user_data_fops = { static const struct file_operations user_data_fops = {
.open = user_events_open,
.write = user_events_write, .write = user_events_write,
.write_iter = user_events_write_iter, .write_iter = user_events_write_iter,
.unlocked_ioctl = user_events_ioctl, .unlocked_ioctl = user_events_ioctl,
.release = user_events_release, .release = user_events_release,
}; };
static struct user_event_group *user_status_group(struct file *file)
{
struct seq_file *m = file->private_data;
if (!m)
return NULL;
return m->private;
}
/* /*
* Maps the shared page into the user process for checking if event is enabled. * Maps the shared page into the user process for checking if event is enabled.
*/ */
static int user_status_mmap(struct file *file, struct vm_area_struct *vma) static int user_status_mmap(struct file *file, struct vm_area_struct *vma)
{ {
char *pages;
struct user_event_group *group = user_status_group(file);
unsigned long size = vma->vm_end - vma->vm_start; unsigned long size = vma->vm_end - vma->vm_start;
if (size != MAX_BYTES) if (size != MAX_BYTES)
return -EINVAL; return -EINVAL;
if (!group)
return -EINVAL;
pages = group->register_page_data;
return remap_pfn_range(vma, vma->vm_start, return remap_pfn_range(vma, vma->vm_start,
virt_to_phys(register_page_data) >> PAGE_SHIFT, virt_to_phys(pages) >> PAGE_SHIFT,
size, vm_get_page_prot(VM_READ)); size, vm_get_page_prot(VM_READ));
} }
@ -1572,13 +1774,17 @@ static void user_seq_stop(struct seq_file *m, void *p)
static int user_seq_show(struct seq_file *m, void *p) static int user_seq_show(struct seq_file *m, void *p)
{ {
struct user_event_group *group = m->private;
struct user_event *user; struct user_event *user;
char status; char status;
int i, active = 0, busy = 0, flags; int i, active = 0, busy = 0, flags;
mutex_lock(&reg_mutex); if (!group)
return -EINVAL;
hash_for_each(register_table, i, user, node) { mutex_lock(&group->reg_mutex);
hash_for_each(group->register_table, i, user, node) {
status = user->status; status = user->status;
flags = user->flags; flags = user->flags;
@ -1602,7 +1808,7 @@ static int user_seq_show(struct seq_file *m, void *p)
active++; active++;
} }
mutex_unlock(&reg_mutex); mutex_unlock(&group->reg_mutex);
seq_puts(m, "\n"); seq_puts(m, "\n");
seq_printf(m, "Active: %d\n", active); seq_printf(m, "Active: %d\n", active);
@ -1621,7 +1827,24 @@ static const struct seq_operations user_seq_ops = {
static int user_status_open(struct inode *node, struct file *file) static int user_status_open(struct inode *node, struct file *file)
{ {
return seq_open(file, &user_seq_ops); struct user_event_group *group;
int ret;
group = current_user_event_group();
if (!group)
return -ENOENT;
ret = seq_open(file, &user_seq_ops);
if (!ret) {
/* Chain group to seq_file */
struct seq_file *m = file->private_data;
m->private = group;
}
return ret;
} }
static const struct file_operations user_status_fops = { static const struct file_operations user_status_fops = {
@ -1662,42 +1885,21 @@ err:
return -ENODEV; return -ENODEV;
} }
static void set_page_reservations(bool set)
{
int page;
for (page = 0; page < MAX_PAGES; ++page) {
void *addr = register_page_data + (PAGE_SIZE * page);
if (set)
SetPageReserved(virt_to_page(addr));
else
ClearPageReserved(virt_to_page(addr));
}
}
static int __init trace_events_user_init(void) static int __init trace_events_user_init(void)
{ {
struct page *pages;
int ret; int ret;
/* Zero all bits beside 0 (which is reserved for failures) */ init_group = user_event_group_create(&init_user_ns);
bitmap_zero(page_bitmap, MAX_EVENTS);
set_bit(0, page_bitmap);
pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, MAX_PAGE_ORDER); if (!init_group)
if (!pages)
return -ENOMEM; return -ENOMEM;
register_page_data = page_address(pages);
set_page_reservations(true);
ret = create_user_tracefs(); ret = create_user_tracefs();
if (ret) { if (ret) {
pr_warn("user_events could not register with tracefs\n"); pr_warn("user_events could not register with tracefs\n");
set_page_reservations(false); user_event_group_destroy(init_group);
__free_pages(pages, MAX_PAGE_ORDER); init_group = NULL;
return ret; return ret;
} }