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KVM: arm64: Patch kimage_voffset instead of loading the EL1 value

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Directly using the kimage_voffset variable is fine for now, but
will become more problematic as we start distrusting EL1.

Instead, patch the kimage_voffset into the HYP text, ensuring
we don't have to load an untrusted value later on.

Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier 2020-10-24 16:33:38 +01:00
parent 7cd0aaafaa
commit 68b824e428
4 changed files with 30 additions and 7 deletions
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22
arch/arm64/include/asm/kvm_mmu.h
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@ -72,6 +72,28 @@ alternative_cb kvm_update_va_mask
alternative_cb_end
.endm
/*
* Convert a kernel image address to a PA
* reg: kernel address to be converted in place
* tmp: temporary register
*
* The actual code generation takes place in kvm_get_kimage_voffset, and
* the instructions below are only there to reserve the space and
* perform the register allocation (kvm_get_kimage_voffset uses the
* specific registers encoded in the instructions).
*/
.macro kimg_pa reg, tmp
alternative_cb kvm_get_kimage_voffset
movz \tmp, #0
movk \tmp, #0, lsl #16
movk \tmp, #0, lsl #32
movk \tmp, #0, lsl #48
alternative_cb_end
/* reg = __pa(reg) */
sub \reg, \reg, \tmp
.endm
#else
#include <linux/pgtable.h>

4
arch/arm64/kernel/image-vars.h
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@ -65,13 +65,11 @@ __efistub__ctype = _ctype;
KVM_NVHE_ALIAS(kvm_patch_vector_branch);
KVM_NVHE_ALIAS(kvm_update_va_mask);
KVM_NVHE_ALIAS(kvm_update_kimg_phys_offset);
KVM_NVHE_ALIAS(kvm_get_kimage_voffset);
/* Global kernel state accessed by nVHE hyp code. */
KVM_NVHE_ALIAS(kvm_vgic_global_state);
/* Kernel constant needed to compute idmap addresses. */
KVM_NVHE_ALIAS(kimage_voffset);
/* Kernel symbols used to call panic() from nVHE hyp code (via ERET). */
KVM_NVHE_ALIAS(__hyp_panic_string);
KVM_NVHE_ALIAS(panic);

5
arch/arm64/kvm/hyp/nvhe/host.S
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@ -115,10 +115,7 @@ SYM_FUNC_END(__hyp_do_panic)
* Preserve x0-x4, which may contain stub parameters.
*/
ldr x5, =__kvm_handle_stub_hvc
ldr_l x6, kimage_voffset
/* x5 = __pa(x5) */
sub x5, x5, x6
kimg_pa x5, x6
br x5
.L__vect_end\@:
.if ((.L__vect_end\@ - .L__vect_start\@) > 0x80)

6
arch/arm64/kvm/va_layout.c
View File

@ -251,3 +251,9 @@ void kvm_update_kimg_phys_offset(struct alt_instr *alt,
{
generate_mov_q(kimage_voffset + PHYS_OFFSET, origptr, updptr, nr_inst);
}
void kvm_get_kimage_voffset(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr, int nr_inst)
{
generate_mov_q(kimage_voffset, origptr, updptr, nr_inst);
}