From 21b3ddd39feecd2f4d6c52bcd30f0a4fa14f125a Mon Sep 17 00:00:00 2001 From: Sylvain Chouleur Date: Fri, 15 Jul 2016 21:36:30 +0200 Subject: 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: Sylvain Chouleur Signed-off-by: Ard Biesheuvel Cc: Leif Lindholm Cc: Mark Rutland Cc: Sylvain Chouleur Signed-off-by: Matt Fleming --- drivers/firmware/efi/vars.c | 137 ++++++++++++++++++++++++++------------------ 1 file changed, 80 insertions(+), 57 deletions(-) (limited to 'drivers/firmware/efi/vars.c') diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c index d0d807e1287e..9336ffdf6e2c 100644 --- a/drivers/firmware/efi/vars.c +++ b/drivers/firmware/efi/vars.c @@ -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); -- cgit v1.2.3