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Date: Fri, 9 Mar 2018 01:12:51 -0800
From: tip-bot for Ard Biesheuvel <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: peterz@...radead.org, linux-kernel@...r.kernel.org,
matt@...eblueprint.co.uk, will.deacon@....com, mingo@...nel.org,
tglx@...utronix.de, hpa@...or.com, ard.biesheuvel@...aro.org,
torvalds@...ux-foundation.org
Subject: [tip:efi/core] efi/arm64: Check whether x18 is preserved by runtime
services calls
Commit-ID: 7e611e7dbb235938fca1dd359bad5e5f86ceabcb
Gitweb: https://git.kernel.org/tip/7e611e7dbb235938fca1dd359bad5e5f86ceabcb
Author: Ard Biesheuvel <ard.biesheuvel@...aro.org>
AuthorDate: Thu, 8 Mar 2018 08:00:13 +0000
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 9 Mar 2018 08:58:22 +0100
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likelihood that these firmware images have all been replaced by that time.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@...aro.org>
Acked-by: Will Deacon <will.deacon@....com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Matt Fleming <matt@...eblueprint.co.uk>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-efi@...r.kernel.org
Link: http://lkml.kernel.org/r/20180308080020.22828-6-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
arch/arm64/include/asm/efi.h | 4 +++-
arch/arm64/kernel/Makefile | 3 ++-
arch/arm64/kernel/efi-rt-wrapper.S | 41 ++++++++++++++++++++++++++++++++++++++
arch/arm64/kernel/efi.c | 6 ++++++
4 files changed, 52 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index 8389050328bb..192d791f1103 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -31,7 +31,7 @@ int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
({ \
efi_##f##_t *__f; \
__f = p->f; \
- __f(args); \
+ __efi_rt_asm_wrapper(__f, #f, args); \
})
#define arch_efi_call_virt_teardown() \
@@ -40,6 +40,8 @@ int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
efi_virtmap_unload(); \
})
+efi_status_t __efi_rt_asm_wrapper(void *, const char *, ...);
+
#define ARCH_EFI_IRQ_FLAGS_MASK (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT)
/* arch specific definitions used by the stub code */
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index b87541360f43..6a4bd80c75bd 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -38,7 +38,8 @@ arm64-obj-$(CONFIG_CPU_PM) += sleep.o suspend.o
arm64-obj-$(CONFIG_CPU_IDLE) += cpuidle.o
arm64-obj-$(CONFIG_JUMP_LABEL) += jump_label.o
arm64-obj-$(CONFIG_KGDB) += kgdb.o
-arm64-obj-$(CONFIG_EFI) += efi.o efi-entry.stub.o
+arm64-obj-$(CONFIG_EFI) += efi.o efi-entry.stub.o \
+ efi-rt-wrapper.o
arm64-obj-$(CONFIG_PCI) += pci.o
arm64-obj-$(CONFIG_ARMV8_DEPRECATED) += armv8_deprecated.o
arm64-obj-$(CONFIG_ACPI) += acpi.o
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@...aro.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)
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index a8bf1c892b90..4f9acb5fbe97 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -126,3 +126,9 @@ bool efi_poweroff_required(void)
{
return efi_enabled(EFI_RUNTIME_SERVICES);
}
+
+asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
+{
+ pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
+ return s;
+}
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