From a6e4d5a03e9e3587e88aba687d8f225f4f04c792 Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Mon, 25 Mar 2013 09:14:30 +0000 Subject: x86, efivars: firmware bug workarounds should be in platform code Let's not burden ia64 with checks in the common efivars code that we're not writing too much data to the variable store. That kind of thing is an x86 firmware bug, plain and simple. efi_query_variable_store() provides platforms with a wrapper in which they can perform checks and workarounds for EFI variable storage bugs. Cc: H. Peter Anvin Cc: Matthew Garrett Signed-off-by: Matt Fleming --- arch/x86/platform/efi/efi.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) (limited to 'arch/x86') diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c index 5f2ecaf3f9d8..c89c245eff40 100644 --- a/arch/x86/platform/efi/efi.c +++ b/arch/x86/platform/efi/efi.c @@ -999,3 +999,28 @@ u64 efi_mem_attributes(unsigned long phys_addr) } return 0; } + +/* + * Some firmware has serious problems when using more than 50% of the EFI + * variable store, i.e. it triggers bugs that can brick machines. Ensure that + * we never use more than this safe limit. + * + * Return EFI_SUCCESS if it is safe to write 'size' bytes to the variable + * store. + */ +efi_status_t efi_query_variable_store(u32 attributes, unsigned long size) +{ + efi_status_t status; + u64 storage_size, remaining_size, max_size; + + status = efi.query_variable_info(attributes, &storage_size, + &remaining_size, &max_size); + if (status != EFI_SUCCESS) + return status; + + if (!storage_size || size > remaining_size || size > max_size || + (remaining_size - size) < (storage_size / 2)) + return EFI_OUT_OF_RESOURCES; + + return EFI_SUCCESS; +} -- cgit v1.2.3