linux/arch/arm64/kvm
Marc Zyngier ed57cac83e arm64: KVM: Introduce EL2 VA randomisation
The main idea behind randomising the EL2 VA is that we usually have
a few spare bits between the most significant bit of the VA mask
and the most significant bit of the linear mapping.

Those bits could be a bunch of zeroes, and could be useful
to move things around a bit. Of course, the more memory you have,
the less randomisation you get...

Alternatively, these bits could be the result of KASLR, in which
case they are already random. But it would be nice to have a
*different* randomization, just to make the job of a potential
attacker a bit more difficult.

Inserting these random bits is a bit involved. We don't have a spare
register (short of rewriting all the kern_hyp_va call sites), and
the immediate we want to insert is too random to be used with the
ORR instruction. The best option I could come up with is the following
sequence:

	and x0, x0, #va_mask
	ror x0, x0, #first_random_bit
	add x0, x0, #(random & 0xfff)
	add x0, x0, #(random >> 12), lsl #12
	ror x0, x0, #(63 - first_random_bit)

making it a fairly long sequence, but one that a decent CPU should
be able to execute without breaking a sweat. It is of course NOPed
out on VHE. The last 4 instructions can also be turned into NOPs
if it appears that there is no free bits to use.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
2018-03-19 13:05:22 +00:00
..
hyp KVM: arm/arm64: Keep GICv2 HYP VAs in kvm_vgic_global_state 2018-03-19 13:04:06 +00:00
debug.c KVM: arm64: Rewrite system register accessors to read/write functions 2018-03-19 10:53:16 +00:00
guest.c KVM: arm/arm64: Avoid vcpu_load for other vcpu ioctls than KVM_RUN 2018-03-19 10:53:09 +00:00
handle_exit.c arm/arm64: KVM: Advertise SMCCC v1.1 2018-02-06 22:54:01 +00:00
hyp-init.S arm64: assembler: Change order of macro arguments in phys_to_ttbr 2018-02-06 22:53:21 +00:00
hyp.S arm64: hyp-stub/KVM: Kill __hyp_get_vectors 2017-04-09 07:49:34 -07:00
inject_fault.c KVM: arm64: Prepare to handle deferred save/restore of ELR_EL1 2018-03-19 10:53:17 +00:00
irq.h KVM: arm/arm64: Enable irqchip routing 2016-07-22 18:52:01 +01:00
Kconfig GICv4 Support for KVM/ARM for v4.15 2017-11-17 13:20:01 +01:00
Makefile arm64: KVM: Dynamically patch the kernel/hyp VA mask 2018-03-19 13:03:29 +00:00
regmap.c KVM: arm64: Prepare to handle deferred save/restore of 32-bit registers 2018-03-19 10:53:18 +00:00
reset.c KVM: arm/arm64: Move timer IRQ default init to arch_timer.c 2017-06-08 16:59:56 +02:00
sys_regs_generic_v8.c KVM: arm64: Rewrite system register accessors to read/write functions 2018-03-19 10:53:16 +00:00
sys_regs.c KVM: arm64: Defer saving/restoring 32-bit sysregs to vcpu load/put 2018-03-19 10:53:18 +00:00
sys_regs.h KVM: arm64: Rewrite system register accessors to read/write functions 2018-03-19 10:53:16 +00:00
trace.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
va_layout.c arm64: KVM: Introduce EL2 VA randomisation 2018-03-19 13:05:22 +00:00
vgic-sys-reg-v3.c KVM: arm/arm64: Extract GICv3 max APRn index calculation 2017-09-05 17:33:39 +02:00