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linux/arch/arm64/include/asm/kvm_asm.h
Quentin Perret fe41a7f8c0 KVM: arm64: Unmap 'kvm_arm_hyp_percpu_base' from the host 
When pKVM is enabled, the hypervisor at EL2 does not trust the host at
EL1 and must therefore prevent it from having unrestricted access to
internal hypervisor state.

The 'kvm_arm_hyp_percpu_base' array holds the offsets for hypervisor
per-cpu allocations, so move this this into the nVHE code where it
cannot be modified by the untrusted host at EL1.

Tested-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221110190259.26861-22-will@kernel.org
2022-11-11 17:19:35 +00:00

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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright (C) 2012,2013 - ARM Ltd
* Author: Marc Zyngier <marc.zyngier@arm.com>
*/
#ifndef __ARM_KVM_ASM_H__
#define __ARM_KVM_ASM_H__
#include <asm/hyp_image.h>
#include <asm/insn.h>
#include <asm/virt.h>
#define ARM_EXIT_WITH_SERROR_BIT 31
#define ARM_EXCEPTION_CODE(x) ((x) & ~(1U << ARM_EXIT_WITH_SERROR_BIT))
#define ARM_EXCEPTION_IS_TRAP(x) (ARM_EXCEPTION_CODE((x)) == ARM_EXCEPTION_TRAP)
#define ARM_SERROR_PENDING(x) !!((x) & (1U << ARM_EXIT_WITH_SERROR_BIT))
#define ARM_EXCEPTION_IRQ 0
#define ARM_EXCEPTION_EL1_SERROR 1
#define ARM_EXCEPTION_TRAP 2
#define ARM_EXCEPTION_IL 3
/* The hyp-stub will return this for any kvm_call_hyp() call */
#define ARM_EXCEPTION_HYP_GONE HVC_STUB_ERR
#define kvm_arm_exception_type \
{ARM_EXCEPTION_IRQ, "IRQ" }, \
{ARM_EXCEPTION_EL1_SERROR, "SERROR" }, \
{ARM_EXCEPTION_TRAP, "TRAP" }, \
{ARM_EXCEPTION_HYP_GONE, "HYP_GONE" }
/*
* Size of the HYP vectors preamble. kvm_patch_vector_branch() generates code
* that jumps over this.
*/
#define KVM_VECTOR_PREAMBLE (2 * AARCH64_INSN_SIZE)
#define KVM_HOST_SMCCC_ID(id) \
ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
ARM_SMCCC_SMC_64, \
ARM_SMCCC_OWNER_VENDOR_HYP, \
(id))
#define KVM_HOST_SMCCC_FUNC(name) KVM_HOST_SMCCC_ID(__KVM_HOST_SMCCC_FUNC_##name)
#define __KVM_HOST_SMCCC_FUNC___kvm_hyp_init 0
#ifndef __ASSEMBLY__
#include <linux/mm.h>
enum __kvm_host_smccc_func {
/* Hypercalls available only prior to pKVM finalisation */
/* __KVM_HOST_SMCCC_FUNC___kvm_hyp_init */
__KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2 = __KVM_HOST_SMCCC_FUNC___kvm_hyp_init + 1,
__KVM_HOST_SMCCC_FUNC___pkvm_init,
__KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping,
__KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector,
__KVM_HOST_SMCCC_FUNC___kvm_enable_ssbs,
__KVM_HOST_SMCCC_FUNC___vgic_v3_init_lrs,
__KVM_HOST_SMCCC_FUNC___vgic_v3_get_gic_config,
__KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize,
/* Hypercalls available after pKVM finalisation */
__KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp,
__KVM_HOST_SMCCC_FUNC___pkvm_host_unshare_hyp,
__KVM_HOST_SMCCC_FUNC___kvm_adjust_pc,
__KVM_HOST_SMCCC_FUNC___kvm_vcpu_run,
__KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context,
__KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa,
__KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid,
__KVM_HOST_SMCCC_FUNC___kvm_flush_cpu_context,
__KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff,
__KVM_HOST_SMCCC_FUNC___vgic_v3_read_vmcr,
__KVM_HOST_SMCCC_FUNC___vgic_v3_write_vmcr,
__KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs,
__KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs,
__KVM_HOST_SMCCC_FUNC___pkvm_vcpu_init_traps,
__KVM_HOST_SMCCC_FUNC___pkvm_init_vm,
__KVM_HOST_SMCCC_FUNC___pkvm_init_vcpu,
__KVM_HOST_SMCCC_FUNC___pkvm_teardown_vm,
};
#define DECLARE_KVM_VHE_SYM(sym) extern char sym[]
#define DECLARE_KVM_NVHE_SYM(sym) extern char kvm_nvhe_sym(sym)[]
/*
* Define a pair of symbols sharing the same name but one defined in
* VHE and the other in nVHE hyp implementations.
*/
#define DECLARE_KVM_HYP_SYM(sym) \
DECLARE_KVM_VHE_SYM(sym); \
DECLARE_KVM_NVHE_SYM(sym)
#define DECLARE_KVM_VHE_PER_CPU(type, sym) \
DECLARE_PER_CPU(type, sym)
#define DECLARE_KVM_NVHE_PER_CPU(type, sym) \
DECLARE_PER_CPU(type, kvm_nvhe_sym(sym))
#define DECLARE_KVM_HYP_PER_CPU(type, sym) \
DECLARE_KVM_VHE_PER_CPU(type, sym); \
DECLARE_KVM_NVHE_PER_CPU(type, sym)
/*
* Compute pointer to a symbol defined in nVHE percpu region.
* Returns NULL if percpu memory has not been allocated yet.
*/
#define this_cpu_ptr_nvhe_sym(sym) per_cpu_ptr_nvhe_sym(sym, smp_processor_id())
#define per_cpu_ptr_nvhe_sym(sym, cpu) \
({ \
unsigned long base, off; \
base = kvm_nvhe_sym(kvm_arm_hyp_percpu_base)[cpu]; \
off = (unsigned long)&CHOOSE_NVHE_SYM(sym) - \
(unsigned long)&CHOOSE_NVHE_SYM(__per_cpu_start); \
base ? (typeof(CHOOSE_NVHE_SYM(sym))*)(base + off) : NULL; \
})
#if defined(__KVM_NVHE_HYPERVISOR__)
#define CHOOSE_NVHE_SYM(sym) sym
#define CHOOSE_HYP_SYM(sym) CHOOSE_NVHE_SYM(sym)
/* The nVHE hypervisor shouldn't even try to access VHE symbols */
extern void *__nvhe_undefined_symbol;
#define CHOOSE_VHE_SYM(sym) __nvhe_undefined_symbol
#define this_cpu_ptr_hyp_sym(sym) (&__nvhe_undefined_symbol)
#define per_cpu_ptr_hyp_sym(sym, cpu) (&__nvhe_undefined_symbol)
#elif defined(__KVM_VHE_HYPERVISOR__)
#define CHOOSE_VHE_SYM(sym) sym
#define CHOOSE_HYP_SYM(sym) CHOOSE_VHE_SYM(sym)
/* The VHE hypervisor shouldn't even try to access nVHE symbols */
extern void *__vhe_undefined_symbol;
#define CHOOSE_NVHE_SYM(sym) __vhe_undefined_symbol
#define this_cpu_ptr_hyp_sym(sym) (&__vhe_undefined_symbol)
#define per_cpu_ptr_hyp_sym(sym, cpu) (&__vhe_undefined_symbol)
#else
/*
* BIG FAT WARNINGS:
*
* - Don't be tempted to change the following is_kernel_in_hyp_mode()
* to has_vhe(). has_vhe() is implemented as a *final* capability,
* while this is used early at boot time, when the capabilities are
* not final yet....
*
* - Don't let the nVHE hypervisor have access to this, as it will
* pick the *wrong* symbol (yes, it runs at EL2...).
*/
#define CHOOSE_HYP_SYM(sym) (is_kernel_in_hyp_mode() \
? CHOOSE_VHE_SYM(sym) \
: CHOOSE_NVHE_SYM(sym))
#define this_cpu_ptr_hyp_sym(sym) (is_kernel_in_hyp_mode() \
? this_cpu_ptr(&sym) \
: this_cpu_ptr_nvhe_sym(sym))
#define per_cpu_ptr_hyp_sym(sym, cpu) (is_kernel_in_hyp_mode() \
? per_cpu_ptr(&sym, cpu) \
: per_cpu_ptr_nvhe_sym(sym, cpu))
#define CHOOSE_VHE_SYM(sym) sym
#define CHOOSE_NVHE_SYM(sym) kvm_nvhe_sym(sym)
#endif
struct kvm_nvhe_init_params {
unsigned long mair_el2;
unsigned long tcr_el2;
unsigned long tpidr_el2;
unsigned long stack_hyp_va;
unsigned long stack_pa;
phys_addr_t pgd_pa;
unsigned long hcr_el2;
unsigned long vttbr;
unsigned long vtcr;
};
/*
* Used by the host in EL1 to dump the nVHE hypervisor backtrace on
* hyp_panic() in non-protected mode.
*
* @stack_base: hyp VA of the hyp_stack base.
* @overflow_stack_base: hyp VA of the hyp_overflow_stack base.
* @fp: hyp FP where the backtrace begins.
* @pc: hyp PC where the backtrace begins.
*/
struct kvm_nvhe_stacktrace_info {
unsigned long stack_base;
unsigned long overflow_stack_base;
unsigned long fp;
unsigned long pc;
};
/* Translate a kernel address @ptr into its equivalent linear mapping */
#define kvm_ksym_ref(ptr) \
({ \
void *val = (ptr); \
if (!is_kernel_in_hyp_mode()) \
val = lm_alias((ptr)); \
val; \
})
#define kvm_ksym_ref_nvhe(sym) kvm_ksym_ref(kvm_nvhe_sym(sym))
struct kvm;
struct kvm_vcpu;
struct kvm_s2_mmu;
DECLARE_KVM_NVHE_SYM(__kvm_hyp_init);
DECLARE_KVM_HYP_SYM(__kvm_hyp_vector);
#define __kvm_hyp_init CHOOSE_NVHE_SYM(__kvm_hyp_init)
#define __kvm_hyp_vector CHOOSE_HYP_SYM(__kvm_hyp_vector)
extern unsigned long kvm_nvhe_sym(kvm_arm_hyp_percpu_base)[];
DECLARE_KVM_NVHE_SYM(__per_cpu_start);
DECLARE_KVM_NVHE_SYM(__per_cpu_end);
DECLARE_KVM_HYP_SYM(__bp_harden_hyp_vecs);
#define __bp_harden_hyp_vecs CHOOSE_HYP_SYM(__bp_harden_hyp_vecs)
extern void __kvm_flush_vm_context(void);
extern void __kvm_flush_cpu_context(struct kvm_s2_mmu *mmu);
extern void __kvm_tlb_flush_vmid_ipa(struct kvm_s2_mmu *mmu, phys_addr_t ipa,
int level);
extern void __kvm_tlb_flush_vmid(struct kvm_s2_mmu *mmu);
extern void __kvm_timer_set_cntvoff(u64 cntvoff);
extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
extern void __kvm_adjust_pc(struct kvm_vcpu *vcpu);
extern u64 __vgic_v3_get_gic_config(void);
extern u64 __vgic_v3_read_vmcr(void);
extern void __vgic_v3_write_vmcr(u32 vmcr);
extern void __vgic_v3_init_lrs(void);
extern u64 __kvm_get_mdcr_el2(void);
#define __KVM_EXTABLE(from, to) \
" .pushsection __kvm_ex_table, \"a\"\n" \
" .align 3\n" \
" .long (" #from " - .), (" #to " - .)\n" \
" .popsection\n"
#define __kvm_at(at_op, addr) \
( { \
int __kvm_at_err = 0; \
u64 spsr, elr; \
asm volatile( \
" mrs %1, spsr_el2\n" \
" mrs %2, elr_el2\n" \
"1: at "at_op", %3\n" \
" isb\n" \
" b 9f\n" \
"2: msr spsr_el2, %1\n" \
" msr elr_el2, %2\n" \
" mov %w0, %4\n" \
"9:\n" \
__KVM_EXTABLE(1b, 2b) \
: "+r" (__kvm_at_err), "=&r" (spsr), "=&r" (elr) \
: "r" (addr), "i" (-EFAULT)); \
__kvm_at_err; \
} )
#else /* __ASSEMBLY__ */
.macro get_host_ctxt reg, tmp
adr_this_cpu \reg, kvm_host_data, \tmp
add \reg, \reg, #HOST_DATA_CONTEXT
.endm
.macro get_vcpu_ptr vcpu, ctxt
get_host_ctxt \ctxt, \vcpu
ldr \vcpu, [\ctxt, #HOST_CONTEXT_VCPU]
.endm
.macro get_loaded_vcpu vcpu, ctxt
adr_this_cpu \ctxt, kvm_hyp_ctxt, \vcpu
ldr \vcpu, [\ctxt, #HOST_CONTEXT_VCPU]
.endm
.macro set_loaded_vcpu vcpu, ctxt, tmp
adr_this_cpu \ctxt, kvm_hyp_ctxt, \tmp
str \vcpu, [\ctxt, #HOST_CONTEXT_VCPU]
.endm
/*
* KVM extable for unexpected exceptions.
* Create a struct kvm_exception_table_entry output to a section that can be
* mapped by EL2. The table is not sorted.
*
* The caller must ensure:
* x18 has the hypervisor value to allow any Shadow-Call-Stack instrumented
* code to write to it, and that SPSR_EL2 and ELR_EL2 are restored by the fixup.
*/
.macro _kvm_extable, from, to
.pushsection __kvm_ex_table, "a"
.align 3
.long (\from - .), (\to - .)
.popsection
.endm
#define CPU_XREG_OFFSET(x) (CPU_USER_PT_REGS + 8*x)
#define CPU_LR_OFFSET CPU_XREG_OFFSET(30)
#define CPU_SP_EL0_OFFSET (CPU_LR_OFFSET + 8)
/*
* We treat x18 as callee-saved as the host may use it as a platform
* register (e.g. for shadow call stack).
*/
.macro save_callee_saved_regs ctxt
str x18, [\ctxt, #CPU_XREG_OFFSET(18)]
stp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)]
stp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)]
stp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)]
stp x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)]
stp x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)]
stp x29, lr, [\ctxt, #CPU_XREG_OFFSET(29)]
.endm
.macro restore_callee_saved_regs ctxt
// We require \ctxt is not x18-x28
ldr x18, [\ctxt, #CPU_XREG_OFFSET(18)]
ldp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)]
ldp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)]
ldp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)]
ldp x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)]
ldp x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)]
ldp x29, lr, [\ctxt, #CPU_XREG_OFFSET(29)]
.endm
.macro save_sp_el0 ctxt, tmp
mrs \tmp, sp_el0
str \tmp, [\ctxt, #CPU_SP_EL0_OFFSET]
.endm
.macro restore_sp_el0 ctxt, tmp
ldr \tmp, [\ctxt, #CPU_SP_EL0_OFFSET]
msr sp_el0, \tmp
.endm
#endif
#endif /* __ARM_KVM_ASM_H__ */
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