Commit 21b3ddd3 authored by Sylvain Chouleur's avatar Sylvain Chouleur Committed by Matt Fleming
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efi: Don't use spinlocks for efi vars



All efivars operations are protected by a spinlock which prevents
interruptions and preemption. This is too restricted, we just need a
lock preventing concurrency.
The idea is to use a semaphore of count 1 and to have two ways of
locking, depending on the context:
- In interrupt context, we call down_trylock(), if it fails we return
  an error
- In normal context, we call down_interruptible()

We don't use a mutex here because the mutex_trylock() function must not
be called from interrupt context, whereas the down_trylock() can.
Signed-off-by: default avatarSylvain Chouleur <sylvain.chouleur@intel.com>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Sylvain Chouleur <sylvain.chouleur@gmail.com>
Signed-off-by: default avatarMatt Fleming <matt@codeblueprint.co.uk>
parent 217b27d4
......@@ -125,16 +125,19 @@ static void efi_pstore_scan_sysfs_enter(struct efivar_entry *pos,
* @entry: deleting entry
* @turn_off_scanning: Check if a scanning flag should be turned off
*/
static inline void __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
static inline int __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
bool turn_off_scanning)
{
if (entry->deleting) {
list_del(&entry->list);
efivar_entry_iter_end();
efivar_unregister(entry);
efivar_entry_iter_begin();
if (efivar_entry_iter_begin())
return -EINTR;
} else if (turn_off_scanning)
entry->scanning = false;
return 0;
}
/**
......@@ -144,13 +147,18 @@ static inline void __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
* @head: list head
* @stop: a flag checking if scanning will stop
*/
static void efi_pstore_scan_sysfs_exit(struct efivar_entry *pos,
static int efi_pstore_scan_sysfs_exit(struct efivar_entry *pos,
struct efivar_entry *next,
struct list_head *head, bool stop)
{
__efi_pstore_scan_sysfs_exit(pos, true);
int ret = __efi_pstore_scan_sysfs_exit(pos, true);
if (ret)
return ret;
if (stop)
__efi_pstore_scan_sysfs_exit(next, &next->list != head);
ret = __efi_pstore_scan_sysfs_exit(next, &next->list != head);
return ret;
}
/**
......@@ -172,13 +180,17 @@ static int efi_pstore_sysfs_entry_iter(void *data, struct efivar_entry **pos)
struct efivar_entry *entry, *n;
struct list_head *head = &efivar_sysfs_list;
int size = 0;
int ret;
if (!*pos) {
list_for_each_entry_safe(entry, n, head, list) {
efi_pstore_scan_sysfs_enter(entry, n, head);
size = efi_pstore_read_func(entry, data);
efi_pstore_scan_sysfs_exit(entry, n, head, size < 0);
ret = efi_pstore_scan_sysfs_exit(entry, n, head,
size < 0);
if (ret)
return ret;
if (size)
break;
}
......@@ -190,7 +202,9 @@ static int efi_pstore_sysfs_entry_iter(void *data, struct efivar_entry **pos)
efi_pstore_scan_sysfs_enter((*pos), n, head);
size = efi_pstore_read_func((*pos), data);
efi_pstore_scan_sysfs_exit((*pos), n, head, size < 0);
ret = efi_pstore_scan_sysfs_exit((*pos), n, head, size < 0);
if (ret)
return ret;
if (size)
break;
}
......@@ -232,7 +246,10 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
if (!*data.buf)
return -ENOMEM;
efivar_entry_iter_begin();
if (efivar_entry_iter_begin()) {
kfree(*data.buf);
return -EINTR;
}
size = efi_pstore_sysfs_entry_iter(&data,
(struct efivar_entry **)&psi->data);
efivar_entry_iter_end();
......@@ -347,7 +364,8 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
edata.time = time;
edata.name = efi_name;
efivar_entry_iter_begin();
if (efivar_entry_iter_begin())
return -EINTR;
found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list, &edata, &entry);
if (found && !entry->scanning) {
......
......@@ -510,7 +510,8 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
vendor = del_var->VendorGuid;
}
efivar_entry_iter_begin();
if (efivar_entry_iter_begin())
return -EINTR;
entry = efivar_entry_find(name, vendor, &efivar_sysfs_list, true);
if (!entry)
err = -EINVAL;
......@@ -575,7 +576,10 @@ efivar_create_sysfs_entry(struct efivar_entry *new_var)
return ret;
kobject_uevent(&new_var->kobj, KOBJ_ADD);
efivar_entry_add(new_var, &efivar_sysfs_list);
if (efivar_entry_add(new_var, &efivar_sysfs_list)) {
efivar_unregister(new_var);
return -EINTR;
}
return 0;
}
......@@ -690,7 +694,10 @@ static int efivars_sysfs_callback(efi_char16_t *name, efi_guid_t vendor,
static int efivar_sysfs_destroy(struct efivar_entry *entry, void *data)
{
efivar_entry_remove(entry);
int err = efivar_entry_remove(entry);
if (err)
return err;
efivar_unregister(entry);
return 0;
}
......@@ -698,7 +705,14 @@ static int efivar_sysfs_destroy(struct efivar_entry *entry, void *data)
static void efivars_sysfs_exit(void)
{
/* Remove all entries and destroy */
__efivar_entry_iter(efivar_sysfs_destroy, &efivar_sysfs_list, NULL, NULL);
int err;
err = __efivar_entry_iter(efivar_sysfs_destroy, &efivar_sysfs_list,
NULL, NULL);
if (err) {
pr_err("efivars: Failed to destroy sysfs entries\n");
return;
}
if (efivars_new_var)
sysfs_remove_bin_file(&efivars_kset->kobj, efivars_new_var);
......
......@@ -43,7 +43,7 @@ static struct efivars *__efivars;
* 2) ->ops calls
* 3) (un)registration of __efivars
*/
static DEFINE_SPINLOCK(efivars_lock);
static DEFINE_SEMAPHORE(efivars_lock);
static bool efivar_wq_enabled = true;
DECLARE_WORK(efivar_work, NULL);
......@@ -442,7 +442,10 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
return -ENOMEM;
}
spin_lock_irq(&efivars_lock);
if (down_interruptible(&efivars_lock)) {
err = -EINTR;
goto free;
}
/*
* Per EFI spec, the maximum storage allocated for both
......@@ -458,7 +461,7 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
switch (status) {
case EFI_SUCCESS:
if (duplicates)
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
variable_name_size = var_name_strnsize(variable_name,
variable_name_size);
......@@ -484,8 +487,12 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
status = EFI_NOT_FOUND;
}
if (duplicates)
spin_lock_irq(&efivars_lock);
if (duplicates) {
if (down_interruptible(&efivars_lock)) {
err = -EINTR;
goto free;
}
}
break;
case EFI_NOT_FOUND:
......@@ -499,8 +506,8 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
} while (status != EFI_NOT_FOUND);
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
free:
kfree(variable_name);
return err;
......@@ -511,24 +518,34 @@ EXPORT_SYMBOL_GPL(efivar_init);
* efivar_entry_add - add entry to variable list
* @entry: entry to add to list
* @head: list head
*
* Returns 0 on success, or a kernel error code on failure.
*/
void efivar_entry_add(struct efivar_entry *entry, struct list_head *head)
int efivar_entry_add(struct efivar_entry *entry, struct list_head *head)
{
spin_lock_irq(&efivars_lock);
if (down_interruptible(&efivars_lock))
return -EINTR;
list_add(&entry->list, head);
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
return 0;
}
EXPORT_SYMBOL_GPL(efivar_entry_add);
/**
* efivar_entry_remove - remove entry from variable list
* @entry: entry to remove from list
*
* Returns 0 on success, or a kernel error code on failure.
*/
void efivar_entry_remove(struct efivar_entry *entry)
int efivar_entry_remove(struct efivar_entry *entry)
{
spin_lock_irq(&efivars_lock);
if (down_interruptible(&efivars_lock))
return -EINTR;
list_del(&entry->list);
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
return 0;
}
EXPORT_SYMBOL_GPL(efivar_entry_remove);
......@@ -545,10 +562,8 @@ EXPORT_SYMBOL_GPL(efivar_entry_remove);
*/
static void efivar_entry_list_del_unlock(struct efivar_entry *entry)
{
lockdep_assert_held(&efivars_lock);
list_del(&entry->list);
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
}
/**
......@@ -571,8 +586,6 @@ int __efivar_entry_delete(struct efivar_entry *entry)
const struct efivar_operations *ops = __efivars->ops;
efi_status_t status;
lockdep_assert_held(&efivars_lock);
status = ops->set_variable(entry->var.VariableName,
&entry->var.VendorGuid,
0, 0, NULL);
......@@ -589,20 +602,22 @@ EXPORT_SYMBOL_GPL(__efivar_entry_delete);
* variable list. It is the caller's responsibility to free @entry
* once we return.
*
* Returns 0 on success, or a converted EFI status code if
* set_variable() fails.
* Returns 0 on success, -EINTR if we can't grab the semaphore,
* converted EFI status code if set_variable() fails.
*/
int efivar_entry_delete(struct efivar_entry *entry)
{
const struct efivar_operations *ops = __efivars->ops;
efi_status_t status;
spin_lock_irq(&efivars_lock);
if (down_interruptible(&efivars_lock))
return -EINTR;
status = ops->set_variable(entry->var.VariableName,
&entry->var.VendorGuid,
0, 0, NULL);
if (!(status == EFI_SUCCESS || status == EFI_NOT_FOUND)) {
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
return efi_status_to_err(status);
}
......@@ -628,9 +643,9 @@ EXPORT_SYMBOL_GPL(efivar_entry_delete);
* If @head is not NULL a lookup is performed to determine whether
* the entry is already on the list.
*
* Returns 0 on success, -EEXIST if a lookup is performed and the entry
* already exists on the list, or a converted EFI status code if
* set_variable() fails.
* Returns 0 on success, -EINTR if we can't grab the semaphore,
* -EEXIST if a lookup is performed and the entry already exists on
* the list, or a converted EFI status code if set_variable() fails.
*/
int efivar_entry_set(struct efivar_entry *entry, u32 attributes,
unsigned long size, void *data, struct list_head *head)
......@@ -640,10 +655,10 @@ int efivar_entry_set(struct efivar_entry *entry, u32 attributes,
efi_char16_t *name = entry->var.VariableName;
efi_guid_t vendor = entry->var.VendorGuid;
spin_lock_irq(&efivars_lock);
if (down_interruptible(&efivars_lock))
return -EINTR;
if (head && efivar_entry_find(name, vendor, head, false)) {
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
return -EEXIST;
}
......@@ -652,7 +667,7 @@ int efivar_entry_set(struct efivar_entry *entry, u32 attributes,
status = ops->set_variable(name, &vendor,
attributes, size, data);
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
return efi_status_to_err(status);
......@@ -673,23 +688,22 @@ efivar_entry_set_nonblocking(efi_char16_t *name, efi_guid_t vendor,
u32 attributes, unsigned long size, void *data)
{
const struct efivar_operations *ops = __efivars->ops;
unsigned long flags;
efi_status_t status;
if (!spin_trylock_irqsave(&efivars_lock, flags))
if (down_trylock(&efivars_lock))
return -EBUSY;
status = check_var_size_nonblocking(attributes,
size + ucs2_strsize(name, 1024));
if (status != EFI_SUCCESS) {
spin_unlock_irqrestore(&efivars_lock, flags);
up(&efivars_lock);
return -ENOSPC;
}
status = ops->set_variable_nonblocking(name, &vendor, attributes,
size, data);
spin_unlock_irqrestore(&efivars_lock, flags);
up(&efivars_lock);
return efi_status_to_err(status);
}
......@@ -714,7 +728,6 @@ int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
bool block, unsigned long size, void *data)
{
const struct efivar_operations *ops = __efivars->ops;
unsigned long flags;
efi_status_t status;
if (!ops->query_variable_store)
......@@ -735,21 +748,22 @@ int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
size, data);
if (!block) {
if (!spin_trylock_irqsave(&efivars_lock, flags))
if (down_trylock(&efivars_lock))
return -EBUSY;
} else {
spin_lock_irqsave(&efivars_lock, flags);
if (down_interruptible(&efivars_lock))
return -EINTR;
}
status = check_var_size(attributes, size + ucs2_strsize(name, 1024));
if (status != EFI_SUCCESS) {
spin_unlock_irqrestore(&efivars_lock, flags);
up(&efivars_lock);
return -ENOSPC;
}
status = ops->set_variable(name, &vendor, attributes, size, data);
spin_unlock_irqrestore(&efivars_lock, flags);
up(&efivars_lock);
return efi_status_to_err(status);
}
......@@ -779,8 +793,6 @@ struct efivar_entry *efivar_entry_find(efi_char16_t *name, efi_guid_t guid,
int strsize1, strsize2;
bool found = false;
lockdep_assert_held(&efivars_lock);
list_for_each_entry_safe(entry, n, head, list) {
strsize1 = ucs2_strsize(name, 1024);
strsize2 = ucs2_strsize(entry->var.VariableName, 1024);
......@@ -822,10 +834,11 @@ int efivar_entry_size(struct efivar_entry *entry, unsigned long *size)
*size = 0;
spin_lock_irq(&efivars_lock);
if (down_interruptible(&efivars_lock))
return -EINTR;
status = ops->get_variable(entry->var.VariableName,
&entry->var.VendorGuid, NULL, size, NULL);
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
if (status != EFI_BUFFER_TOO_SMALL)
return efi_status_to_err(status);
......@@ -851,8 +864,6 @@ int __efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
const struct efivar_operations *ops = __efivars->ops;
efi_status_t status;
lockdep_assert_held(&efivars_lock);
status = ops->get_variable(entry->var.VariableName,
&entry->var.VendorGuid,
attributes, size, data);
......@@ -874,11 +885,12 @@ int efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
const struct efivar_operations *ops = __efivars->ops;
efi_status_t status;
spin_lock_irq(&efivars_lock);
if (down_interruptible(&efivars_lock))
return -EINTR;
status = ops->get_variable(entry->var.VariableName,
&entry->var.VendorGuid,
attributes, size, data);
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
return efi_status_to_err(status);
}
......@@ -925,7 +937,8 @@ int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
* set_variable call, and removal of the variable from the efivars
* list (in the case of an authenticated delete).
*/
spin_lock_irq(&efivars_lock);
if (down_interruptible(&efivars_lock))
return -EINTR;
/*
* Ensure that the available space hasn't shrunk below the safe level
......@@ -965,7 +978,7 @@ int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
if (status == EFI_NOT_FOUND)
efivar_entry_list_del_unlock(entry);
else
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
if (status && status != EFI_BUFFER_TOO_SMALL)
return efi_status_to_err(status);
......@@ -973,7 +986,7 @@ int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
return 0;
out:
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
return err;
}
......@@ -986,9 +999,9 @@ EXPORT_SYMBOL_GPL(efivar_entry_set_get_size);
* efivar_entry_iter_end() is called. This function is usually used in
* conjunction with __efivar_entry_iter() or efivar_entry_iter().
*/
void efivar_entry_iter_begin(void)
int efivar_entry_iter_begin(void)
{
spin_lock_irq(&efivars_lock);
return down_interruptible(&efivars_lock);
}
EXPORT_SYMBOL_GPL(efivar_entry_iter_begin);
......@@ -999,7 +1012,7 @@ EXPORT_SYMBOL_GPL(efivar_entry_iter_begin);
*/
void efivar_entry_iter_end(void)
{
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
}
EXPORT_SYMBOL_GPL(efivar_entry_iter_end);
......@@ -1075,7 +1088,9 @@ int efivar_entry_iter(int (*func)(struct efivar_entry *, void *),
{
int err = 0;
efivar_entry_iter_begin();
err = efivar_entry_iter_begin();
if (err)
return err;
err = __efivar_entry_iter(func, head, data, NULL);
efivar_entry_iter_end();
......@@ -1120,12 +1135,17 @@ int efivars_register(struct efivars *efivars,
const struct efivar_operations *ops,
struct kobject *kobject)
{
spin_lock_irq(&efivars_lock);
if (down_interruptible(&efivars_lock))
return -EINTR;
efivars->ops = ops;
efivars->kobject = kobject;
__efivars = efivars;
spin_unlock_irq(&efivars_lock);
pr_info("Registered efivars operations\n");
up(&efivars_lock);
return 0;
}
......@@ -1142,7 +1162,9 @@ int efivars_unregister(struct efivars *efivars)
{
int rv;
spin_lock_irq(&efivars_lock);
if (down_interruptible(&efivars_lock))
return -EINTR;
if (!__efivars) {
printk(KERN_ERR "efivars not registered\n");
rv = -EINVAL;
......@@ -1154,11 +1176,12 @@ int efivars_unregister(struct efivars *efivars)
goto out;
}
pr_info("Unregistered efivars operations\n");
__efivars = NULL;
rv = 0;
out:
spin_unlock_irq(&efivars_lock);
up(&efivars_lock);
return rv;
}
EXPORT_SYMBOL_GPL(efivars_unregister);
......@@ -105,7 +105,10 @@ static int efivarfs_create(struct inode *dir, struct dentry *dentry,
inode->i_private = var;
efivar_entry_add(var, &efivarfs_list);
err = efivar_entry_add(var, &efivarfs_list);
if (err)
goto out;
d_instantiate(dentry, inode);
dget(dentry);
out:
......
......@@ -161,7 +161,9 @@ static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
kfree(name);
efivar_entry_size(entry, &size);
efivar_entry_add(entry, &efivarfs_list);
err = efivar_entry_add(entry, &efivarfs_list);
if (err)
goto fail_inode;
inode_lock(inode);
inode->i_private = entry;
......@@ -182,7 +184,10 @@ static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
static int efivarfs_destroy(struct efivar_entry *entry, void *data)
{
efivar_entry_remove(entry);
int err = efivar_entry_remove(entry);
if (err)
return err;
kfree(entry);
return 0;
}
......
......@@ -1297,8 +1297,8 @@ struct kobject *efivars_kobject(void);
int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
void *data, bool duplicates, struct list_head *head);
void efivar_entry_add(struct efivar_entry *entry, struct list_head *head);
void efivar_entry_remove(struct efivar_entry *entry);
int efivar_entry_add(struct efivar_entry *entry, struct list_head *head);
int efivar_entry_remove(struct efivar_entry *entry);
int __efivar_entry_delete(struct efivar_entry *entry);
int efivar_entry_delete(struct efivar_entry *entry);
......@@ -1315,7 +1315,7 @@ int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
bool block, unsigned long size, void *data);
void efivar_entry_iter_begin(void);
int efivar_entry_iter_begin(void);
void efivar_entry_iter_end(void);
int __efivar_entry_iter(int (*func)(struct efivar_entry *, void *),
......
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