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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2017 ARM Ltd.
* Author: Marc Zyngier <marc.zyngier@arm.com>
*/
#include <linux/kvm_host.h>
#include <linux/random.h>
#include <linux/memblock.h>
#include <asm/alternative.h>
#include <asm/debug-monitors.h>
#include <asm/insn.h>
#include <asm/kvm_mmu.h>
/*
* The LSB of the random hyp VA tag or 0 if no randomization is used.
*/
static u8 tag_lsb;
/*
* The random hyp VA tag value with the region bit if hyp randomization is used
*/
static u64 tag_val;
static u64 va_mask;
static void compute_layout(void)
{
phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start);
u64 hyp_va_msb;
int kva_msb;
/* Where is my RAM region? */
hyp_va_msb = idmap_addr & BIT(VA_BITS - 1);
hyp_va_msb ^= BIT(VA_BITS - 1);
kva_msb = fls64((u64)phys_to_virt(memblock_start_of_DRAM()) ^
(u64)(high_memory - 1));
if (kva_msb == (VA_BITS - 1)) {
/*
* No space in the address, let's compute the mask so
* that it covers (VA_BITS - 1) bits, and the region
* bit. The tag stays set to zero.
*/
va_mask = BIT(VA_BITS - 1) - 1;
va_mask |= hyp_va_msb;
} else {
/*
* We do have some free bits to insert a random tag.
* Hyp VAs are now created from kernel linear map VAs
* using the following formula (with V == VA_BITS):
*
* 63 ... V | V-1 | V-2 .. tag_lsb | tag_lsb - 1 .. 0
* ---------------------------------------------------------
* | 0000000 | hyp_va_msb | random tag | kern linear VA |
*/
tag_lsb = kva_msb;
va_mask = GENMASK_ULL(tag_lsb - 1, 0);
tag_val = get_random_long() & GENMASK_ULL(VA_BITS - 2, tag_lsb);
tag_val |= hyp_va_msb;
tag_val >>= tag_lsb;
}
}
static u32 compute_instruction(int n, u32 rd, u32 rn)
{
u32 insn = AARCH64_BREAK_FAULT;
switch (n) {
case 0:
insn = aarch64_insn_gen_logical_immediate(AARCH64_INSN_LOGIC_AND,
AARCH64_INSN_VARIANT_64BIT,
rn, rd, va_mask);
break;
case 1:
/* ROR is a variant of EXTR with Rm = Rn */
insn = aarch64_insn_gen_extr(AARCH64_INSN_VARIANT_64BIT,
rn, rn, rd,
tag_lsb);
break;
case 2:
insn = aarch64_insn_gen_add_sub_imm(rd, rn,
tag_val & GENMASK(11, 0),
AARCH64_INSN_VARIANT_64BIT,
AARCH64_INSN_ADSB_ADD);
break;
case 3:
insn = aarch64_insn_gen_add_sub_imm(rd, rn,
tag_val & GENMASK(23, 12),
AARCH64_INSN_VARIANT_64BIT,
AARCH64_INSN_ADSB_ADD);
break;
case 4:
/* ROR is a variant of EXTR with Rm = Rn */
insn = aarch64_insn_gen_extr(AARCH64_INSN_VARIANT_64BIT,
rn, rn, rd, 64 - tag_lsb);
break;
}
return insn;
}
void __init kvm_update_va_mask(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr, int nr_inst)
{
int i;
BUG_ON(nr_inst != 5);
if (!has_vhe() && !va_mask)
compute_layout();
for (i = 0; i < nr_inst; i++) {
u32 rd, rn, insn, oinsn;
/*
* VHE doesn't need any address translation, let's NOP
* everything.
*
* Alternatively, if we don't have any spare bits in
* the address, NOP everything after masking that
* kernel VA.
*/
if (has_vhe() || (!tag_lsb && i > 0)) {
updptr[i] = cpu_to_le32(aarch64_insn_gen_nop());
continue;
}
oinsn = le32_to_cpu(origptr[i]);
rd = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RD, oinsn);
rn = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RN, oinsn);
insn = compute_instruction(i, rd, rn);
BUG_ON(insn == AARCH64_BREAK_FAULT);
updptr[i] = cpu_to_le32(insn);
}
}
void *__kvm_bp_vect_base;
int __kvm_harden_el2_vector_slot;
void kvm_patch_vector_branch(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr, int nr_inst)
{
u64 addr;
u32 insn;
BUG_ON(nr_inst != 5);
if (has_vhe() || !cpus_have_const_cap(ARM64_HARDEN_EL2_VECTORS)) {
WARN_ON_ONCE(cpus_have_const_cap(ARM64_HARDEN_EL2_VECTORS));
return;
}
if (!va_mask)
compute_layout();
/*
* Compute HYP VA by using the same computation as kern_hyp_va()
*/
addr = (uintptr_t)kvm_ksym_ref(__kvm_hyp_vector);
addr &= va_mask;
addr |= tag_val << tag_lsb;
/* Use PC[10:7] to branch to the same vector in KVM */
addr |= ((u64)origptr & GENMASK_ULL(10, 7));
/*
* Branch to the second instruction in the vectors in order to
* avoid the initial store on the stack (which we already
* perform in the hardening vectors).
*/
addr += AARCH64_INSN_SIZE;
/* stp x0, x1, [sp, #-16]! */
insn = aarch64_insn_gen_load_store_pair(AARCH64_INSN_REG_0,
AARCH64_INSN_REG_1,
AARCH64_INSN_REG_SP,
-16,
AARCH64_INSN_VARIANT_64BIT,
AARCH64_INSN_LDST_STORE_PAIR_PRE_INDEX);
*updptr++ = cpu_to_le32(insn);
/* movz x0, #(addr & 0xffff) */
insn = aarch64_insn_gen_movewide(AARCH64_INSN_REG_0,
(u16)addr,
0,
AARCH64_INSN_VARIANT_64BIT,
AARCH64_INSN_MOVEWIDE_ZERO);
*updptr++ = cpu_to_le32(insn);
/* movk x0, #((addr >> 16) & 0xffff), lsl #16 */
insn = aarch64_insn_gen_movewide(AARCH64_INSN_REG_0,
(u16)(addr >> 16),
16,
AARCH64_INSN_VARIANT_64BIT,
AARCH64_INSN_MOVEWIDE_KEEP);
*updptr++ = cpu_to_le32(insn);
/* movk x0, #((addr >> 32) & 0xffff), lsl #32 */
insn = aarch64_insn_gen_movewide(AARCH64_INSN_REG_0,
(u16)(addr >> 32),
32,
AARCH64_INSN_VARIANT_64BIT,
AARCH64_INSN_MOVEWIDE_KEEP);
*updptr++ = cpu_to_le32(insn);
/* br x0 */
insn = aarch64_insn_gen_branch_reg(AARCH64_INSN_REG_0,
AARCH64_INSN_BRANCH_NOLINK);
*updptr++ = cpu_to_le32(insn);
}
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