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efi: Implement mandatory locking for UEFI Runtime Services

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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>
This commit is contained in:
Ard Biesheuvel
2014-08-04 18:16:00 +02:00
committed by Matt Fleming
parent 7d1311b93e
commit 161485e827
2 changed files with 146 additions and 10 deletions
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arch/x86/include/asm/efi.h
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@@ -86,6 +86,8 @@ extern void __iomem *efi_ioremap(unsigned long addr, unsigned long size,
#endif /* CONFIG_X86_32 */
#define efi_in_nmi() in_nmi()
extern int add_efi_memmap;
extern struct efi_scratch efi_scratch;
extern void efi_set_executable(efi_memory_desc_t *md, bool executable);