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| author | Marc Zyngier <marc.zyngier@arm.com> | 2018-02-27 18:38:08 +0100 |
|---|---|---|
| committer | Marc Zyngier <marc.zyngier@arm.com> | 2018-03-19 14:06:01 +0100 |
| commit | 71dcb8be6d29cffff3f4a4463232f38786e97797 (patch) | |
| tree | bb065a9d3f86c74f0324e3deeaa2f12e301ed70e /arch/arm64/kernel | |
| parent | arm64: KVM: Reserve 4 additional instructions in the BPI template (diff) | |
| download | linux-71dcb8be6d29cffff3f4a4463232f38786e97797.tar.xz linux-71dcb8be6d29cffff3f4a4463232f38786e97797.zip | |
arm64: KVM: Allow far branches from vector slots to the main vectors
So far, the branch from the vector slots to the main vectors can at
most be 4GB from the main vectors (the reach of ADRP), and this
distance is known at compile time. If we were to remap the slots
to an unrelated VA, things would break badly.
A way to achieve VA independence would be to load the absolute
address of the vectors (__kvm_hyp_vector), either using a constant
pool or a series of movs, followed by an indirect branch.
This patches implements the latter solution, using another instance
of a patching callback. Note that since we have to save a register
pair on the stack, we branch to the *second* instruction in the
vectors in order to compensate for it. This also results in having
to adjust this balance in the invalid vector entry point.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Diffstat (limited to 'arch/arm64/kernel')
| -rw-r--r-- | arch/arm64/kernel/bpi.S | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/arch/arm64/kernel/bpi.S b/arch/arm64/kernel/bpi.S index ce1cfe3b24e6..dc51ef2ce98a 100644 --- a/arch/arm64/kernel/bpi.S +++ b/arch/arm64/kernel/bpi.S @@ -19,16 +19,37 @@ #include <linux/linkage.h> #include <linux/arm-smccc.h> +#include <asm/alternative.h> + .macro hyp_ventry .align 7 1: .rept 27 nop .endr +/* + * The default sequence is to directly branch to the KVM vectors, + * using the computed offset. This applies for VHE as well as + * !ARM64_HARDEN_EL2_VECTORS. + * + * For ARM64_HARDEN_EL2_VECTORS configurations, this gets replaced + * with: + * + * stp x0, x1, [sp, #-16]! + * movz x0, #(addr & 0xffff) + * movk x0, #((addr >> 16) & 0xffff), lsl #16 + * movk x0, #((addr >> 32) & 0xffff), lsl #32 + * br x0 + * + * Where addr = kern_hyp_va(__kvm_hyp_vector) + vector-offset + 4. + * See kvm_patch_vector_branch for details. + */ +alternative_cb kvm_patch_vector_branch b __kvm_hyp_vector + (1b - 0b) nop nop nop nop +alternative_cb_end .endm .macro generate_vectors |