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| author | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2018-03-08 08:00:13 +0000 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-03-09 08:58:22 +0100 |
| commit | 7e611e7dbb235938fca1dd359bad5e5f86ceabcb (patch) | |
| tree | 9ae6a27e4b8c8e5d4b3832cb9d5fad3405623917 /arch/arm64/kernel/efi-rt-wrapper.S | |
| parent | 1832e64162ffbbbdf7230401298550f2b624351b (diff) | |
| download | linux-7e611e7dbb235938fca1dd359bad5e5f86ceabcb.tar.gz | |
efi/arm64: Check whether x18 is preserved by runtime services calls
Whether or not we will ever decide to start using x18 as a platform
register in Linux is uncertain, but by that time, we will need to
ensure that UEFI runtime services calls don't corrupt it.
So let's start issuing warnings now for this, and increase the
likelihood that these firmware images have all been replaced by that time.
This has been fixed on the EDK2 side in commit:
6d73863b5464 ("BaseTools/tools_def AARCH64: mark register x18 as reserved")
dated July 13, 2017.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20180308080020.22828-6-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/arm64/kernel/efi-rt-wrapper.S')
| -rw-r--r-- | arch/arm64/kernel/efi-rt-wrapper.S | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/arch/arm64/kernel/efi-rt-wrapper.S b/arch/arm64/kernel/efi-rt-wrapper.S new file mode 100644 index 000000000000..05235ebb336d --- /dev/null +++ b/arch/arm64/kernel/efi-rt-wrapper.S @@ -0,0 +1,41 @@ +/* + * Copyright (C) 2018 Linaro Ltd <ard.biesheuvel@linaro.org> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include <linux/linkage.h> + +ENTRY(__efi_rt_asm_wrapper) + stp x29, x30, [sp, #-32]! + mov x29, sp + + /* + * Register x18 is designated as the 'platform' register by the AAPCS, + * which means firmware running at the same exception level as the OS + * (such as UEFI) should never touch it. + */ + stp x1, x18, [sp, #16] + + /* + * We are lucky enough that no EFI runtime services take more than + * 5 arguments, so all are passed in registers rather than via the + * stack. + */ + mov x8, x0 + mov x0, x2 + mov x1, x3 + mov x2, x4 + mov x3, x5 + mov x4, x6 + blr x8 + + ldp x1, x2, [sp, #16] + cmp x2, x18 + ldp x29, x30, [sp], #32 + b.ne 0f + ret +0: b efi_handle_corrupted_x18 // tail call +ENDPROC(__efi_rt_asm_wrapper) |