linux/drivers/firmware/efi/runtime-wrappers.c

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/*
* runtime-wrappers.c - Runtime Services function call wrappers
*
* Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org>
*
* Split off from arch/x86/platform/efi/efi.c
*
* Copyright (C) 1999 VA Linux Systems
* Copyright (C) 1999 Walt Drummond <drummond@valinux.com>
* Copyright (C) 1999-2002 Hewlett-Packard Co.
* Copyright (C) 2005-2008 Intel Co.
* Copyright (C) 2013 SuSE Labs
*
* This file is released under the GPLv2.
*/
#include <linux/bug.h>
#include <linux/efi.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <asm/efi.h>
/*
* According to section 7.1 of the UEFI spec, Runtime Services are not fully
* reentrant, and there are particular combinations of calls that need to be
* serialized. (source: UEFI Specification v2.4A)
*
* Table 31. Rules for Reentry Into Runtime Services
* +------------------------------------+-------------------------------+
* | If previous call is busy in | Forbidden to call |
* +------------------------------------+-------------------------------+
* | Any | SetVirtualAddressMap() |
* +------------------------------------+-------------------------------+
* | ConvertPointer() | ConvertPointer() |
* +------------------------------------+-------------------------------+
* | SetVariable() | ResetSystem() |
* | UpdateCapsule() | |
* | SetTime() | |
* | SetWakeupTime() | |
* | GetNextHighMonotonicCount() | |
* +------------------------------------+-------------------------------+
* | GetVariable() | GetVariable() |
* | GetNextVariableName() | GetNextVariableName() |
* | SetVariable() | SetVariable() |
* | QueryVariableInfo() | QueryVariableInfo() |
* | UpdateCapsule() | UpdateCapsule() |
* | QueryCapsuleCapabilities() | QueryCapsuleCapabilities() |
* | GetNextHighMonotonicCount() | GetNextHighMonotonicCount() |
* +------------------------------------+-------------------------------+
* | GetTime() | GetTime() |
* | SetTime() | SetTime() |
* | GetWakeupTime() | GetWakeupTime() |
* | SetWakeupTime() | SetWakeupTime() |
* +------------------------------------+-------------------------------+
*
* Due to the fact that the EFI pstore may write to the variable store in
* interrupt context, we need to use a spinlock for at least the groups that
* contain SetVariable() and QueryVariableInfo(). That leaves little else, as
* none of the remaining functions are actually ever called at runtime.
* So let's just use a single spinlock to serialize all Runtime Services calls.
*/
static DEFINE_SPINLOCK(efi_runtime_lock);
/*
* Some runtime services calls can be reentrant under NMI, even if the table
* above says they are not. (source: UEFI Specification v2.4A)
*
* Table 32. Functions that may be called after Machine Check, INIT and NMI
* +----------------------------+------------------------------------------+
* | Function | Called after Machine Check, INIT and NMI |
* +----------------------------+------------------------------------------+
* | GetTime() | Yes, even if previously busy. |
* | GetVariable() | Yes, even if previously busy |
* | GetNextVariableName() | Yes, even if previously busy |
* | QueryVariableInfo() | Yes, even if previously busy |
* | SetVariable() | Yes, even if previously busy |
* | UpdateCapsule() | Yes, even if previously busy |
* | QueryCapsuleCapabilities() | Yes, even if previously busy |
* | ResetSystem() | Yes, even if previously busy |
* +----------------------------+------------------------------------------+
*
* In order to prevent deadlocks under NMI, the wrappers for these functions
* may only grab the efi_runtime_lock or rtc_lock spinlocks if !efi_in_nmi().
* However, not all of the services listed are reachable through NMI code paths,
* so the the special handling as suggested by the UEFI spec is only implemented
* for QueryVariableInfo() and SetVariable(), as these can be reached in NMI
* context through efi_pstore_write().
*/
/*
* As per commit ef68c8f87ed1 ("x86: Serialize EFI time accesses on rtc_lock"),
* the EFI specification requires that callers of the time related runtime
* functions serialize with other CMOS accesses in the kernel, as the EFI time
* functions may choose to also use the legacy CMOS RTC.
*/
__weak DEFINE_SPINLOCK(rtc_lock);
static efi_status_t virt_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
{
unsigned long flags;
efi_status_t status;
spin_lock_irqsave(&rtc_lock, flags);
spin_lock(&efi_runtime_lock);
status = efi_call_virt(get_time, tm, tc);
spin_unlock(&efi_runtime_lock);
spin_unlock_irqrestore(&rtc_lock, flags);
return status;
}
static efi_status_t virt_efi_set_time(efi_time_t *tm)
{
unsigned long flags;
efi_status_t status;
spin_lock_irqsave(&rtc_lock, flags);
spin_lock(&efi_runtime_lock);
status = efi_call_virt(set_time, tm);
spin_unlock(&efi_runtime_lock);
spin_unlock_irqrestore(&rtc_lock, flags);
return status;
}
static efi_status_t virt_efi_get_wakeup_time(efi_bool_t *enabled,
efi_bool_t *pending,
efi_time_t *tm)
{
unsigned long flags;
efi_status_t status;
spin_lock_irqsave(&rtc_lock, flags);
spin_lock(&efi_runtime_lock);
status = efi_call_virt(get_wakeup_time, enabled, pending, tm);
spin_unlock(&efi_runtime_lock);
spin_unlock_irqrestore(&rtc_lock, flags);
return status;
}
static efi_status_t virt_efi_set_wakeup_time(efi_bool_t enabled, efi_time_t *tm)
{
unsigned long flags;
efi_status_t status;
spin_lock_irqsave(&rtc_lock, flags);
spin_lock(&efi_runtime_lock);
status = efi_call_virt(set_wakeup_time, enabled, tm);
spin_unlock(&efi_runtime_lock);
spin_unlock_irqrestore(&rtc_lock, flags);
return status;
}
static efi_status_t virt_efi_get_variable(efi_char16_t *name,
efi_guid_t *vendor,
u32 *attr,
unsigned long *data_size,
void *data)
{
unsigned long flags;
efi_status_t status;
spin_lock_irqsave(&efi_runtime_lock, flags);
status = efi_call_virt(get_variable, name, vendor, attr, data_size,
data);
spin_unlock_irqrestore(&efi_runtime_lock, flags);
return status;
}
static efi_status_t virt_efi_get_next_variable(unsigned long *name_size,
efi_char16_t *name,
efi_guid_t *vendor)
{
unsigned long flags;
efi_status_t status;
spin_lock_irqsave(&efi_runtime_lock, flags);
status = efi_call_virt(get_next_variable, name_size, name, vendor);
spin_unlock_irqrestore(&efi_runtime_lock, flags);
return status;
}
static efi_status_t virt_efi_set_variable(efi_char16_t *name,
efi_guid_t *vendor,
u32 attr,
unsigned long data_size,
void *data)
{
unsigned long flags;
efi_status_t status;
spin_lock_irqsave(&efi_runtime_lock, flags);
status = efi_call_virt(set_variable, name, vendor, attr, data_size,
data);
spin_unlock_irqrestore(&efi_runtime_lock, flags);
return status;
}
static efi_status_t
virt_efi_set_variable_nonblocking(efi_char16_t *name, efi_guid_t *vendor,
u32 attr, unsigned long data_size,
void *data)
{
unsigned long flags;
efi_status_t status;
if (!spin_trylock_irqsave(&efi_runtime_lock, flags))
return EFI_NOT_READY;
status = efi_call_virt(set_variable, name, vendor, attr, data_size,
data);
spin_unlock_irqrestore(&efi_runtime_lock, flags);
return status;
}
static efi_status_t virt_efi_query_variable_info(u32 attr,
u64 *storage_space,
u64 *remaining_space,
u64 *max_variable_size)
{
unsigned long flags;
efi_status_t status;
if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
return EFI_UNSUPPORTED;
spin_lock_irqsave(&efi_runtime_lock, flags);
status = efi_call_virt(query_variable_info, attr, storage_space,
remaining_space, max_variable_size);
spin_unlock_irqrestore(&efi_runtime_lock, flags);
return status;
}
static efi_status_t virt_efi_get_next_high_mono_count(u32 *count)
{
unsigned long flags;
efi_status_t status;
spin_lock_irqsave(&efi_runtime_lock, flags);
status = efi_call_virt(get_next_high_mono_count, count);
spin_unlock_irqrestore(&efi_runtime_lock, flags);
return status;
}
static void virt_efi_reset_system(int reset_type,
efi_status_t status,
unsigned long data_size,
efi_char16_t *data)
{
unsigned long flags;
spin_lock_irqsave(&efi_runtime_lock, flags);
__efi_call_virt(reset_system, reset_type, status, data_size, data);
spin_unlock_irqrestore(&efi_runtime_lock, flags);
}
static efi_status_t virt_efi_update_capsule(efi_capsule_header_t **capsules,
unsigned long count,
unsigned long sg_list)
{
unsigned long flags;
efi_status_t status;
if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
return EFI_UNSUPPORTED;
spin_lock_irqsave(&efi_runtime_lock, flags);
status = efi_call_virt(update_capsule, capsules, count, sg_list);
spin_unlock_irqrestore(&efi_runtime_lock, flags);
return status;
}
static efi_status_t virt_efi_query_capsule_caps(efi_capsule_header_t **capsules,
unsigned long count,
u64 *max_size,
int *reset_type)
{
unsigned long flags;
efi_status_t status;
if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
return EFI_UNSUPPORTED;
spin_lock_irqsave(&efi_runtime_lock, flags);
status = efi_call_virt(query_capsule_caps, capsules, count, max_size,
reset_type);
spin_unlock_irqrestore(&efi_runtime_lock, flags);
return status;
}
void efi_native_runtime_setup(void)
{
efi.get_time = virt_efi_get_time;
efi.set_time = virt_efi_set_time;
efi.get_wakeup_time = virt_efi_get_wakeup_time;
efi.set_wakeup_time = virt_efi_set_wakeup_time;
efi.get_variable = virt_efi_get_variable;
efi.get_next_variable = virt_efi_get_next_variable;
efi.set_variable = virt_efi_set_variable;
efi.set_variable_nonblocking = virt_efi_set_variable_nonblocking;
efi.get_next_high_mono_count = virt_efi_get_next_high_mono_count;
efi.reset_system = virt_efi_reset_system;
efi.query_variable_info = virt_efi_query_variable_info;
efi.update_capsule = virt_efi_update_capsule;
efi.query_capsule_caps = virt_efi_query_capsule_caps;
}