xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

efi: Add nonblocking option to efi_query_variable_store()

Browse Source 
The function efi_query_variable_store() may be invoked by
efivar_entry_set_nonblocking(), which itself takes care to only
call a non-blocking version of the SetVariable() runtime
wrapper. However, efi_query_variable_store() may call the
SetVariable() wrapper directly, as well as the wrapper for
QueryVariableInfo(), both of which could deadlock in the same
way we are trying to prevent by calling
efivar_entry_set_nonblocking() in the first place.

So instead, modify efi_query_variable_store() to use the
non-blocking variants of QueryVariableInfo() (and give up rather
than free up space if the available space is below
EFI_MIN_RESERVE) if invoked with the 'nonblocking' argument set
to true.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1454364428-494-5-git-send-email-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ard Biesheuvel
2016-02-01 22:06:58 +00:00
committed by Ingo Molnar
parent d3cac1f83c
commit ca0e30dcaa
3 changed files with 55 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
arch/x86/platform/efi/quirks.c
View File

@@ -56,6 +56,33 @@ void efi_delete_dummy_variable(void)
0, NULL);
}
/*
* In the nonblocking case we do not attempt to perform garbage
* collection if we do not have enough free space. Rather, we do the
* bare minimum check and give up immediately if the available space
* is below EFI_MIN_RESERVE.
*
* This function is intended to be small and simple because it is
* invoked from crash handler paths.
*/
static efi_status_t
query_variable_store_nonblocking(u32 attributes, unsigned long size)
{
efi_status_t status;
u64 storage_size, remaining_size, max_size;
status = efi.query_variable_info_nonblocking(attributes, &storage_size,
&remaining_size,
&max_size);
if (status != EFI_SUCCESS)
return status;
if (remaining_size - size < EFI_MIN_RESERVE)
return EFI_OUT_OF_RESOURCES;
return EFI_SUCCESS;
}
/*
* Some firmware implementations refuse to boot if there's insufficient space
* in the variable store. Ensure that we never use more than a safe limit.
@@ -63,7 +90,8 @@ void efi_delete_dummy_variable(void)
* 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 efi_query_variable_store(u32 attributes, unsigned long size,
bool nonblocking)
{
efi_status_t status;
u64 storage_size, remaining_size, max_size;
@@ -71,6 +99,9 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
if (!(attributes & EFI_VARIABLE_NON_VOLATILE))
return 0;
if (nonblocking)
return query_variable_store_nonblocking(attributes, size);
status = efi.query_variable_info(attributes, &storage_size,
&remaining_size, &max_size);
if (status != EFI_SUCCESS)