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linux/drivers/firmware/efi/runtime-wrappers.c
Ard Biesheuvel dce48e351c efi: Replace runtime services spinlock with semaphore 
The purpose of the efi_runtime_lock is to prevent concurrent calls into
the firmware. There is no need to use spinlocks here, as long as we ensure
that runtime service invocations from an atomic context (i.e., EFI pstore)
cannot block.

So use a semaphore instead, and use down_trylock() in the nonblocking case.
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: Ard 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: Matt Fleming <matt@codeblueprint.co.uk>
2016-09-09 16:08:43 +01:00

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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.
*/
#define pr_fmt(fmt) "efi: " fmt
#include <linux/bug.h>
#include <linux/efi.h>
#include <linux/irqflags.h>
#include <linux/mutex.h>
#include <linux/semaphore.h>
#include <linux/stringify.h>
#include <asm/efi.h>
/*
* Wrap around the new efi_call_virt_generic() macros so that the
* code doesn't get too cluttered:
*/
#define efi_call_virt(f, args...) \
efi_call_virt_pointer(efi.systab->runtime, f, args)
#define __efi_call_virt(f, args...) \
__efi_call_virt_pointer(efi.systab->runtime, f, args)
void efi_call_virt_check_flags(unsigned long flags, const char *call)
{
unsigned long cur_flags, mismatch;
local_save_flags(cur_flags);
mismatch = flags ^ cur_flags;
if (!WARN_ON_ONCE(mismatch & ARCH_EFI_IRQ_FLAGS_MASK))
return;
add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_NOW_UNRELIABLE);
pr_err_ratelimited(FW_BUG "IRQ flags corrupted (0x%08lx=>0x%08lx) by EFI %s\n",
flags, cur_flags, call);
local_irq_restore(flags);
}
/*
* 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 lock 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 lock to serialize all Runtime Services calls.
*/
static DEFINE_SEMAPHORE(efi_runtime_lock);
static efi_status_t virt_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
{
efi_status_t status;
if (down_interruptible(&efi_runtime_lock))
return EFI_ABORTED;
status = efi_call_virt(get_time, tm, tc);
up(&efi_runtime_lock);
return status;
}
static efi_status_t virt_efi_set_time(efi_time_t *tm)
{
efi_status_t status;
if (down_interruptible(&efi_runtime_lock))
return EFI_ABORTED;
status = efi_call_virt(set_time, tm);
up(&efi_runtime_lock);
return status;
}
static efi_status_t virt_efi_get_wakeup_time(efi_bool_t *enabled,
efi_bool_t *pending,
efi_time_t *tm)
{
efi_status_t status;
if (down_interruptible(&efi_runtime_lock))
return EFI_ABORTED;
status = efi_call_virt(get_wakeup_time, enabled, pending, tm);
up(&efi_runtime_lock);
return status;
}
static efi_status_t virt_efi_set_wakeup_time(efi_bool_t enabled, efi_time_t *tm)
{
efi_status_t status;
if (down_interruptible(&efi_runtime_lock))
return EFI_ABORTED;
status = efi_call_virt(set_wakeup_time, enabled, tm);
up(&efi_runtime_lock);
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)
{
efi_status_t status;
if (down_interruptible(&efi_runtime_lock))
return EFI_ABORTED;
status = efi_call_virt(get_variable, name, vendor, attr, data_size,
data);
up(&efi_runtime_lock);
return status;
}
static efi_status_t virt_efi_get_next_variable(unsigned long *name_size,
efi_char16_t *name,
efi_guid_t *vendor)
{
efi_status_t status;
if (down_interruptible(&efi_runtime_lock))
return EFI_ABORTED;
status = efi_call_virt(get_next_variable, name_size, name, vendor);
up(&efi_runtime_lock);
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)
{
efi_status_t status;
if (down_interruptible(&efi_runtime_lock))
return EFI_ABORTED;
status = efi_call_virt(set_variable, name, vendor, attr, data_size,
data);
up(&efi_runtime_lock);
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)
{
efi_status_t status;
if (down_trylock(&efi_runtime_lock))
return EFI_NOT_READY;
status = efi_call_virt(set_variable, name, vendor, attr, data_size,
data);
up(&efi_runtime_lock);
return status;
}
static efi_status_t virt_efi_query_variable_info(u32 attr,
u64 *storage_space,
u64 *remaining_space,
u64 *max_variable_size)
{
efi_status_t status;
if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
return EFI_UNSUPPORTED;
if (down_interruptible(&efi_runtime_lock))
return EFI_ABORTED;
status = efi_call_virt(query_variable_info, attr, storage_space,
remaining_space, max_variable_size);
up(&efi_runtime_lock);
return status;
}
static efi_status_t
virt_efi_query_variable_info_nonblocking(u32 attr,
u64 *storage_space,
u64 *remaining_space,
u64 *max_variable_size)
{
efi_status_t status;
if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
return EFI_UNSUPPORTED;
if (down_trylock(&efi_runtime_lock))
return EFI_NOT_READY;
status = efi_call_virt(query_variable_info, attr, storage_space,
remaining_space, max_variable_size);
up(&efi_runtime_lock);
return status;
}
static efi_status_t virt_efi_get_next_high_mono_count(u32 *count)
{
efi_status_t status;
if (down_interruptible(&efi_runtime_lock))
return EFI_ABORTED;
status = efi_call_virt(get_next_high_mono_count, count);
up(&efi_runtime_lock);
return status;
}
static void virt_efi_reset_system(int reset_type,
efi_status_t status,
unsigned long data_size,
efi_char16_t *data)
{
if (down_interruptible(&efi_runtime_lock)) {
pr_warn("failed to invoke the reset_system() runtime service:\n"
"could not get exclusive access to the firmware\n");
return;
}
__efi_call_virt(reset_system, reset_type, status, data_size, data);
up(&efi_runtime_lock);
}
static efi_status_t virt_efi_update_capsule(efi_capsule_header_t **capsules,
unsigned long count,
unsigned long sg_list)
{
efi_status_t status;
if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
return EFI_UNSUPPORTED;
if (down_interruptible(&efi_runtime_lock))
return EFI_ABORTED;
status = efi_call_virt(update_capsule, capsules, count, sg_list);
up(&efi_runtime_lock);
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)
{
efi_status_t status;
if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
return EFI_UNSUPPORTED;
if (down_interruptible(&efi_runtime_lock))
return EFI_ABORTED;
status = efi_call_virt(query_capsule_caps, capsules, count, max_size,
reset_type);
up(&efi_runtime_lock);
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.query_variable_info_nonblocking = virt_efi_query_variable_info_nonblocking;
efi.update_capsule = virt_efi_update_capsule;
efi.query_capsule_caps = virt_efi_query_capsule_caps;
}
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