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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>
#include <asm/memory.h>
/*
* The LSB of the HYP VA tag
*/
static u8 tag_lsb;
/*
* The HYP VA tag value with the region bit
*/
static u64 tag_val;
static u64 va_mask;
/*
* Compute HYP VA by using the same computation as kern_hyp_va().
*/
static u64 __early_kern_hyp_va(u64 addr)
{
addr &= va_mask;
addr |= tag_val << tag_lsb;
return addr;
}
/*
* Store a hyp VA <-> PA offset into a EL2-owned variable.
*/
static void init_hyp_physvirt_offset(void)
{
u64 kern_va, hyp_va;
/* Compute the offset from the hyp VA and PA of a random symbol. */
kern_va = (u64)lm_alias(__hyp_text_start);
hyp_va = __early_kern_hyp_va(kern_va);
hyp_physvirt_offset = (s64)__pa(kern_va) - (s64)hyp_va;
}
/*
* We want to generate a hyp VA with the following format (with V ==
* vabits_actual):
*
* 63 ... V | V-1 | V-2 .. tag_lsb | tag_lsb - 1 .. 0
* ---------------------------------------------------------
* | 0000000 | hyp_va_msb | random tag | kern linear VA |
* |--------- tag_val -----------|----- va_mask ---|
*
* which does not conflict with the idmap regions.
*/
__init void kvm_compute_layout(void)
{
phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start);
u64 hyp_va_msb;
/* Where is my RAM region? */
hyp_va_msb = idmap_addr & BIT(vabits_actual - 1);
hyp_va_msb ^= BIT(vabits_actual - 1);
tag_lsb = fls64((u64)phys_to_virt(memblock_start_of_DRAM()) ^
(u64)(high_memory - 1));
va_mask = GENMASK_ULL(tag_lsb - 1, 0);
tag_val = hyp_va_msb;
if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && tag_lsb != (vabits_actual - 1)) {
/* We have some free bits to insert a random tag. */
tag_val |= get_random_long() & GENMASK_ULL(vabits_actual - 2, tag_lsb);
}
tag_val >>= tag_lsb;
init_hyp_physvirt_offset();
}
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);
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 the tag is zero (because the layout
* dictates it and we don't have any spare bits in the
* address), NOP everything after masking the kernel VA.
*/
if (has_vhe() || (!tag_val && 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_patch_vector_branch(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr, int nr_inst)
{
u64 addr;
u32 insn;
BUG_ON(nr_inst != 4);
if (!cpus_have_const_cap(ARM64_SPECTRE_V3A) || WARN_ON_ONCE(has_vhe()))
return;
/*
* Compute HYP VA by using the same computation as kern_hyp_va()
*/
addr = __early_kern_hyp_va((u64)kvm_ksym_ref(__kvm_hyp_vector));
/* Use PC[10:7] to branch to the same vector in KVM */
addr |= ((u64)origptr & GENMASK_ULL(10, 7));
/*
* Branch over the preamble in order to avoid the initial store on
* the stack (which we already perform in the hardening vectors).
*/
addr += KVM_VECTOR_PREAMBLE;
/* 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);
}
static void generate_mov_q(u64 val, __le32 *origptr, __le32 *updptr, int nr_inst)
{
u32 insn, oinsn, rd;
BUG_ON(nr_inst != 4);
/* Compute target register */
oinsn = le32_to_cpu(*origptr);
rd = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RD, oinsn);
/* movz rd, #(val & 0xffff) */
insn = aarch64_insn_gen_movewide(rd,
(u16)val,
0,
AARCH64_INSN_VARIANT_64BIT,
AARCH64_INSN_MOVEWIDE_ZERO);
*updptr++ = cpu_to_le32(insn);
/* movk rd, #((val >> 16) & 0xffff), lsl #16 */
insn = aarch64_insn_gen_movewide(rd,
(u16)(val >> 16),
16,
AARCH64_INSN_VARIANT_64BIT,
AARCH64_INSN_MOVEWIDE_KEEP);
*updptr++ = cpu_to_le32(insn);
/* movk rd, #((val >> 32) & 0xffff), lsl #32 */
insn = aarch64_insn_gen_movewide(rd,
(u16)(val >> 32),
32,
AARCH64_INSN_VARIANT_64BIT,
AARCH64_INSN_MOVEWIDE_KEEP);
*updptr++ = cpu_to_le32(insn);
/* movk rd, #((val >> 48) & 0xffff), lsl #48 */
insn = aarch64_insn_gen_movewide(rd,
(u16)(val >> 48),
48,
AARCH64_INSN_VARIANT_64BIT,
AARCH64_INSN_MOVEWIDE_KEEP);
*updptr++ = cpu_to_le32(insn);
}
void kvm_update_kimg_phys_offset(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr, int nr_inst)
{
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);
}
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