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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. Use a spinlock to serialize all Runtime Services with respect to all others, even if this is more than strictly needed. We've managed to get away without requiring a runtime services lock until now because most of the interactions with EFI involve EFI variables, and those operations are already serialised with __efivars->lock. Some of the assumptions underlying the decision whether locks are needed or not (e.g., SetVariable() against ResetSystem()) may not apply universally to all [new] architectures that implement UEFI. Rather than try to reason our way out of this, let's just implement at least what the spec requires in terms of locking. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Matt Fleming <matt.fleming@intel.com>
296 lines
9.6 KiB
C
296 lines
9.6 KiB
C
/*
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* runtime-wrappers.c - Runtime Services function call wrappers
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*
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* Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org>
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*
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* Split off from arch/x86/platform/efi/efi.c
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*
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* Copyright (C) 1999 VA Linux Systems
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* Copyright (C) 1999 Walt Drummond <drummond@valinux.com>
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* Copyright (C) 1999-2002 Hewlett-Packard Co.
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* Copyright (C) 2005-2008 Intel Co.
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* Copyright (C) 2013 SuSE Labs
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*
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* This file is released under the GPLv2.
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*/
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#include <linux/bug.h>
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#include <linux/efi.h>
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#include <linux/mutex.h>
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#include <linux/spinlock.h>
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#include <asm/efi.h>
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/*
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* According to section 7.1 of the UEFI spec, Runtime Services are not fully
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* reentrant, and there are particular combinations of calls that need to be
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* serialized. (source: UEFI Specification v2.4A)
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*
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* Table 31. Rules for Reentry Into Runtime Services
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* +------------------------------------+-------------------------------+
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* | If previous call is busy in | Forbidden to call |
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* +------------------------------------+-------------------------------+
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* | Any | SetVirtualAddressMap() |
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* +------------------------------------+-------------------------------+
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* | ConvertPointer() | ConvertPointer() |
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* +------------------------------------+-------------------------------+
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* | SetVariable() | ResetSystem() |
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* | UpdateCapsule() | |
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* | SetTime() | |
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* | SetWakeupTime() | |
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* | GetNextHighMonotonicCount() | |
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* +------------------------------------+-------------------------------+
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* | GetVariable() | GetVariable() |
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* | GetNextVariableName() | GetNextVariableName() |
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* | SetVariable() | SetVariable() |
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* | QueryVariableInfo() | QueryVariableInfo() |
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* | UpdateCapsule() | UpdateCapsule() |
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* | QueryCapsuleCapabilities() | QueryCapsuleCapabilities() |
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* | GetNextHighMonotonicCount() | GetNextHighMonotonicCount() |
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* +------------------------------------+-------------------------------+
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* | GetTime() | GetTime() |
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* | SetTime() | SetTime() |
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* | GetWakeupTime() | GetWakeupTime() |
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* | SetWakeupTime() | SetWakeupTime() |
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* +------------------------------------+-------------------------------+
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*
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* Due to the fact that the EFI pstore may write to the variable store in
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* interrupt context, we need to use a spinlock for at least the groups that
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* contain SetVariable() and QueryVariableInfo(). That leaves little else, as
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* none of the remaining functions are actually ever called at runtime.
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* So let's just use a single spinlock to serialize all Runtime Services calls.
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*/
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static DEFINE_SPINLOCK(efi_runtime_lock);
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/*
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* Some runtime services calls can be reentrant under NMI, even if the table
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* above says they are not. (source: UEFI Specification v2.4A)
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*
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* Table 32. Functions that may be called after Machine Check, INIT and NMI
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* +----------------------------+------------------------------------------+
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* | Function | Called after Machine Check, INIT and NMI |
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* +----------------------------+------------------------------------------+
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* | GetTime() | Yes, even if previously busy. |
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* | GetVariable() | Yes, even if previously busy |
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* | GetNextVariableName() | Yes, even if previously busy |
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* | QueryVariableInfo() | Yes, even if previously busy |
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* | SetVariable() | Yes, even if previously busy |
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* | UpdateCapsule() | Yes, even if previously busy |
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* | QueryCapsuleCapabilities() | Yes, even if previously busy |
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* | ResetSystem() | Yes, even if previously busy |
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* +----------------------------+------------------------------------------+
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*
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* In order to prevent deadlocks under NMI, the wrappers for these functions
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* may only grab the efi_runtime_lock or rtc_lock spinlocks if !efi_in_nmi().
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* However, not all of the services listed are reachable through NMI code paths,
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* so the the special handling as suggested by the UEFI spec is only implemented
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* for QueryVariableInfo() and SetVariable(), as these can be reached in NMI
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* context through efi_pstore_write().
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*/
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#ifndef efi_in_nmi
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#define efi_in_nmi() (0)
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#endif
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/*
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* As per commit ef68c8f87ed1 ("x86: Serialize EFI time accesses on rtc_lock"),
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* the EFI specification requires that callers of the time related runtime
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* functions serialize with other CMOS accesses in the kernel, as the EFI time
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* functions may choose to also use the legacy CMOS RTC.
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*/
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__weak DEFINE_SPINLOCK(rtc_lock);
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static efi_status_t virt_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
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{
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unsigned long flags;
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efi_status_t status;
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spin_lock_irqsave(&rtc_lock, flags);
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spin_lock(&efi_runtime_lock);
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status = efi_call_virt(get_time, tm, tc);
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spin_unlock(&efi_runtime_lock);
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spin_unlock_irqrestore(&rtc_lock, flags);
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return status;
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}
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static efi_status_t virt_efi_set_time(efi_time_t *tm)
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{
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unsigned long flags;
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efi_status_t status;
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spin_lock_irqsave(&rtc_lock, flags);
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spin_lock(&efi_runtime_lock);
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status = efi_call_virt(set_time, tm);
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spin_unlock(&efi_runtime_lock);
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spin_unlock_irqrestore(&rtc_lock, flags);
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return status;
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}
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static efi_status_t virt_efi_get_wakeup_time(efi_bool_t *enabled,
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efi_bool_t *pending,
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efi_time_t *tm)
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{
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unsigned long flags;
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efi_status_t status;
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spin_lock_irqsave(&rtc_lock, flags);
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spin_lock(&efi_runtime_lock);
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status = efi_call_virt(get_wakeup_time, enabled, pending, tm);
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spin_unlock(&efi_runtime_lock);
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spin_unlock_irqrestore(&rtc_lock, flags);
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return status;
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}
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static efi_status_t virt_efi_set_wakeup_time(efi_bool_t enabled, efi_time_t *tm)
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{
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unsigned long flags;
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efi_status_t status;
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spin_lock_irqsave(&rtc_lock, flags);
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spin_lock(&efi_runtime_lock);
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status = efi_call_virt(set_wakeup_time, enabled, tm);
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spin_unlock(&efi_runtime_lock);
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spin_unlock_irqrestore(&rtc_lock, flags);
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return status;
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}
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static efi_status_t virt_efi_get_variable(efi_char16_t *name,
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efi_guid_t *vendor,
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u32 *attr,
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unsigned long *data_size,
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void *data)
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{
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unsigned long flags;
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efi_status_t status;
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spin_lock_irqsave(&efi_runtime_lock, flags);
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status = efi_call_virt(get_variable, name, vendor, attr, data_size,
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data);
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spin_unlock_irqrestore(&efi_runtime_lock, flags);
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return status;
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}
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static efi_status_t virt_efi_get_next_variable(unsigned long *name_size,
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efi_char16_t *name,
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efi_guid_t *vendor)
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{
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unsigned long flags;
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efi_status_t status;
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spin_lock_irqsave(&efi_runtime_lock, flags);
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status = efi_call_virt(get_next_variable, name_size, name, vendor);
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spin_unlock_irqrestore(&efi_runtime_lock, flags);
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return status;
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}
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static efi_status_t virt_efi_set_variable(efi_char16_t *name,
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efi_guid_t *vendor,
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u32 attr,
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unsigned long data_size,
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void *data)
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{
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unsigned long flags;
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efi_status_t status;
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bool __in_nmi = efi_in_nmi();
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if (!__in_nmi)
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spin_lock_irqsave(&efi_runtime_lock, flags);
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status = efi_call_virt(set_variable, name, vendor, attr, data_size,
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data);
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if (!__in_nmi)
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spin_unlock_irqrestore(&efi_runtime_lock, flags);
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return status;
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}
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static efi_status_t virt_efi_query_variable_info(u32 attr,
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u64 *storage_space,
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u64 *remaining_space,
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u64 *max_variable_size)
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{
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unsigned long flags;
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efi_status_t status;
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bool __in_nmi = efi_in_nmi();
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if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
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return EFI_UNSUPPORTED;
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if (!__in_nmi)
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spin_lock_irqsave(&efi_runtime_lock, flags);
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status = efi_call_virt(query_variable_info, attr, storage_space,
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remaining_space, max_variable_size);
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if (!__in_nmi)
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spin_unlock_irqrestore(&efi_runtime_lock, flags);
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return status;
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}
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static efi_status_t virt_efi_get_next_high_mono_count(u32 *count)
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{
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unsigned long flags;
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efi_status_t status;
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spin_lock_irqsave(&efi_runtime_lock, flags);
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status = efi_call_virt(get_next_high_mono_count, count);
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spin_unlock_irqrestore(&efi_runtime_lock, flags);
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return status;
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}
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static void virt_efi_reset_system(int reset_type,
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efi_status_t status,
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unsigned long data_size,
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efi_char16_t *data)
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{
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unsigned long flags;
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spin_lock_irqsave(&efi_runtime_lock, flags);
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__efi_call_virt(reset_system, reset_type, status, data_size, data);
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spin_unlock_irqrestore(&efi_runtime_lock, flags);
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}
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static efi_status_t virt_efi_update_capsule(efi_capsule_header_t **capsules,
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unsigned long count,
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unsigned long sg_list)
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{
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unsigned long flags;
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efi_status_t status;
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if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
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return EFI_UNSUPPORTED;
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spin_lock_irqsave(&efi_runtime_lock, flags);
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status = efi_call_virt(update_capsule, capsules, count, sg_list);
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spin_unlock_irqrestore(&efi_runtime_lock, flags);
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return status;
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}
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static efi_status_t virt_efi_query_capsule_caps(efi_capsule_header_t **capsules,
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unsigned long count,
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u64 *max_size,
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int *reset_type)
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{
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unsigned long flags;
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efi_status_t status;
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if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
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return EFI_UNSUPPORTED;
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spin_lock_irqsave(&efi_runtime_lock, flags);
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status = efi_call_virt(query_capsule_caps, capsules, count, max_size,
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reset_type);
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spin_unlock_irqrestore(&efi_runtime_lock, flags);
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return status;
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}
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void efi_native_runtime_setup(void)
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{
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efi.get_time = virt_efi_get_time;
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efi.set_time = virt_efi_set_time;
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efi.get_wakeup_time = virt_efi_get_wakeup_time;
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efi.set_wakeup_time = virt_efi_set_wakeup_time;
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efi.get_variable = virt_efi_get_variable;
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efi.get_next_variable = virt_efi_get_next_variable;
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efi.set_variable = virt_efi_set_variable;
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efi.get_next_high_mono_count = virt_efi_get_next_high_mono_count;
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efi.reset_system = virt_efi_reset_system;
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efi.query_variable_info = virt_efi_query_variable_info;
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efi.update_capsule = virt_efi_update_capsule;
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efi.query_capsule_caps = virt_efi_query_capsule_caps;
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}
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