host.S

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright (C) 2020 - Google Inc
 * Author: Andrew Scull <[email protected]>
 */

#include <linux/linkage.h>

#include <asm/assembler.h>
#include <asm/kvm_arm.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_mmu.h>
#include <asm/kvm_ptrauth.h>

	.text

SYM_FUNC_START(__host_exit)
	get_host_ctxt	x0, x1

	/* Store the host regs x2 and x3 */
	stp	x2, x3,   [x0, #CPU_XREG_OFFSET(2)]

	/* Retrieve the host regs x0-x1 from the stack */
	ldp	x2, x3, [sp], #16	// x0, x1

	/* Store the host regs x0-x1 and x4-x17 */
	stp	x2, x3,   [x0, #CPU_XREG_OFFSET(0)]
	stp	x4, x5,   [x0, #CPU_XREG_OFFSET(4)]
	stp	x6, x7,   [x0, #CPU_XREG_OFFSET(6)]
	stp	x8, x9,   [x0, #CPU_XREG_OFFSET(8)]
	stp	x10, x11, [x0, #CPU_XREG_OFFSET(10)]
	stp	x12, x13, [x0, #CPU_XREG_OFFSET(12)]
	stp	x14, x15, [x0, #CPU_XREG_OFFSET(14)]
	stp	x16, x17, [x0, #CPU_XREG_OFFSET(16)]

	/* Store the host regs x18-x29, lr */
	save_callee_saved_regs x0

	/* Save the host context pointer in x29 across the function call */
	mov	x29, x0

#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
alternative_if_not ARM64_HAS_ADDRESS_AUTH
b __skip_pauth_save
alternative_else_nop_endif

alternative_if ARM64_KVM_PROTECTED_MODE
	/* Save kernel ptrauth keys. */
	add x18, x29, #CPU_APIAKEYLO_EL1
	ptrauth_save_state x18, x19, x20

	/* Use hyp keys. */
	adr_this_cpu x18, kvm_hyp_ctxt, x19
	add x18, x18, #CPU_APIAKEYLO_EL1
	ptrauth_restore_state x18, x19, x20
	isb
alternative_else_nop_endif
__skip_pauth_save:
#endif /* CONFIG_ARM64_PTR_AUTH_KERNEL */

	bl	handle_trap

__host_enter_restore_full:
	/* Restore kernel keys. */
#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
alternative_if_not ARM64_HAS_ADDRESS_AUTH
b __skip_pauth_restore
alternative_else_nop_endif

alternative_if ARM64_KVM_PROTECTED_MODE
	add x18, x29, #CPU_APIAKEYLO_EL1
	ptrauth_restore_state x18, x19, x20
alternative_else_nop_endif
__skip_pauth_restore:
#endif /* CONFIG_ARM64_PTR_AUTH_KERNEL */

	/* Restore host regs x0-x17 */
	ldp	x0, x1,   [x29, #CPU_XREG_OFFSET(0)]
	ldp	x2, x3,   [x29, #CPU_XREG_OFFSET(2)]
	ldp	x4, x5,   [x29, #CPU_XREG_OFFSET(4)]
	ldp	x6, x7,   [x29, #CPU_XREG_OFFSET(6)]

	/* x0-7 are use for panic arguments */
__host_enter_for_panic:
	ldp	x8, x9,   [x29, #CPU_XREG_OFFSET(8)]
	ldp	x10, x11, [x29, #CPU_XREG_OFFSET(10)]
	ldp	x12, x13, [x29, #CPU_XREG_OFFSET(12)]
	ldp	x14, x15, [x29, #CPU_XREG_OFFSET(14)]
	ldp	x16, x17, [x29, #CPU_XREG_OFFSET(16)]

	/* Restore host regs x18-x29, lr */
	restore_callee_saved_regs x29

	/* Do not touch any register after this! */
__host_enter_without_restoring:
	eret
	sb
SYM_FUNC_END(__host_exit)

/*
 * void __noreturn __host_enter(struct kvm_cpu_context *host_ctxt);
 */
SYM_FUNC_START(__host_enter)
	mov	x29, x0
	b	__host_enter_restore_full
SYM_FUNC_END(__host_enter)

/*
 * void __noreturn __hyp_do_panic(struct kvm_cpu_context *host_ctxt, u64 spsr,
 * 				  u64 elr, u64 par);
 */
SYM_FUNC_START(__hyp_do_panic)
	/* Prepare and exit to the host's panic function. */
	mov	lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
		      PSR_MODE_EL1h)
	msr	spsr_el2, lr
	adr_l	lr, nvhe_hyp_panic_handler
	hyp_kimg_va lr, x6
	msr	elr_el2, lr

	mov	x29, x0

#ifdef CONFIG_NVHE_EL2_DEBUG
	/* Ensure host stage-2 is disabled */
	mrs	x0, hcr_el2
	bic	x0, x0, #HCR_VM
	msr_hcr_el2 x0
	isb
	tlbi	vmalls12e1
	dsb	nsh
#endif

	/* Load the panic arguments into x0-7 */
	mrs	x0, esr_el2
	mov	x4, x3
	mov	x3, x2
	hyp_pa	x3, x6
	get_vcpu_ptr x5, x6
	mrs	x6, far_el2
	mrs	x7, hpfar_el2

	/* Enter the host, conditionally restoring the host context. */
	cbz	x29, __host_enter_without_restoring
	b	__host_enter_for_panic
SYM_FUNC_END(__hyp_do_panic)

SYM_FUNC_START(__host_hvc)
	ldp	x0, x1, [sp]		// Don't fixup the stack yet

	/* No stub for you, sonny Jim */
alternative_if ARM64_KVM_PROTECTED_MODE
	b	__host_exit
alternative_else_nop_endif

	/* Check for a stub HVC call */
	cmp	x0, #HVC_STUB_HCALL_NR
	b.hs	__host_exit

	add	sp, sp, #16
	/*
	 * Compute the idmap address of __kvm_handle_stub_hvc and
	 * jump there.
	 *
	 * Preserve x0-x4, which may contain stub parameters.
	 */
	adr_l	x5, __kvm_handle_stub_hvc
	hyp_pa	x5, x6
	br	x5
SYM_FUNC_END(__host_hvc)

.macro host_el1_sync_vect
	.align 7
.L__vect_start\@:
	stp	x0, x1, [sp, #-16]!
	mrs	x0, esr_el2
	ubfx	x0, x0, #ESR_ELx_EC_SHIFT, #ESR_ELx_EC_WIDTH
	cmp	x0, #ESR_ELx_EC_HVC64
	b.eq	__host_hvc
	b	__host_exit
.L__vect_end\@:
.if ((.L__vect_end\@ - .L__vect_start\@) > 0x80)
	.error "host_el1_sync_vect larger than vector entry"
.endif
.endm

.macro invalid_host_el2_vect
	.align 7

	/*
	 * Test whether the SP has overflowed, without corrupting a GPR.
	 * nVHE hypervisor stacks are aligned so that the NVHE_STACK_SHIFT bit
	 * of SP should always be 1.
	 */
	add	sp, sp, x0			// sp' = sp + x0
	sub	x0, sp, x0			// x0' = sp' - x0 = (sp + x0) - x0 = sp
	tbz	x0, #NVHE_STACK_SHIFT, .L__hyp_sp_overflow\@
	sub	x0, sp, x0			// x0'' = sp' - x0' = (sp + x0) - sp = x0
	sub	sp, sp, x0			// sp'' = sp' - x0 = (sp + x0) - x0 = sp

	/*
	 * The panic may not be clean if the exception is taken before the host
	 * context has been saved by __host_exit or after the hyp context has
	 * been partially clobbered by __host_enter.
	 */
	b	hyp_panic

.L__hyp_sp_overflow\@:
	/* Switch to the overflow stack */
	adr_this_cpu sp, overflow_stack + OVERFLOW_STACK_SIZE, x0

	b	hyp_panic_bad_stack
	ASM_BUG()
.endm

.macro invalid_host_el1_vect
	.align 7
	mov	x0, xzr		/* restore_host = false */
	mrs	x1, spsr_el2
	mrs	x2, elr_el2
	mrs	x3, par_el1
	b	__hyp_do_panic
.endm

/*
 * The host vector does not use an ESB instruction in order to avoid consuming
 * SErrors that should only be consumed by the host. Guest entry is deferred by
 * __guest_enter if there are any pending asynchronous exceptions so hyp will
 * always return to the host without having consumerd host SErrors.
 *
 * CONFIG_KVM_INDIRECT_VECTORS is not applied to the host vectors because the
 * host knows about the EL2 vectors already, and there is no point in hiding
 * them.
 */
	.align 11
SYM_CODE_START(__kvm_hyp_host_vector)
	invalid_host_el2_vect			// Synchronous EL2t
	invalid_host_el2_vect			// IRQ EL2t
	invalid_host_el2_vect			// FIQ EL2t
	invalid_host_el2_vect			// Error EL2t

	invalid_host_el2_vect			// Synchronous EL2h
	invalid_host_el2_vect			// IRQ EL2h
	invalid_host_el2_vect			// FIQ EL2h
	invalid_host_el2_vect			// Error EL2h

	host_el1_sync_vect			// Synchronous 64-bit EL1/EL0
	invalid_host_el1_vect			// IRQ 64-bit EL1/EL0
	invalid_host_el1_vect			// FIQ 64-bit EL1/EL0
	invalid_host_el1_vect			// Error 64-bit EL1/EL0

	host_el1_sync_vect			// Synchronous 32-bit EL1/EL0
	invalid_host_el1_vect			// IRQ 32-bit EL1/EL0
	invalid_host_el1_vect			// FIQ 32-bit EL1/EL0
	invalid_host_el1_vect			// Error 32-bit EL1/EL0
SYM_CODE_END(__kvm_hyp_host_vector)

/*
 * Forward SMC with arguments in struct kvm_cpu_context, and
 * store the result into the same struct. Assumes SMCCC 1.2 or older.
 *
 * x0: struct kvm_cpu_context*
 */
SYM_CODE_START(__kvm_hyp_host_forward_smc)
	/*
	 * Use x18 to keep the pointer to the host context because
	 * x18 is callee-saved in SMCCC but not in AAPCS64.
	 */
	mov	x18, x0

	ldp	x0, x1,   [x18, #CPU_XREG_OFFSET(0)]
	ldp	x2, x3,   [x18, #CPU_XREG_OFFSET(2)]
	ldp	x4, x5,   [x18, #CPU_XREG_OFFSET(4)]
	ldp	x6, x7,   [x18, #CPU_XREG_OFFSET(6)]
	ldp	x8, x9,   [x18, #CPU_XREG_OFFSET(8)]
	ldp	x10, x11, [x18, #CPU_XREG_OFFSET(10)]
	ldp	x12, x13, [x18, #CPU_XREG_OFFSET(12)]
	ldp	x14, x15, [x18, #CPU_XREG_OFFSET(14)]
	ldp	x16, x17, [x18, #CPU_XREG_OFFSET(16)]

	smc	#0

	stp	x0, x1,   [x18, #CPU_XREG_OFFSET(0)]
	stp	x2, x3,   [x18, #CPU_XREG_OFFSET(2)]
	stp	x4, x5,   [x18, #CPU_XREG_OFFSET(4)]
	stp	x6, x7,   [x18, #CPU_XREG_OFFSET(6)]
	stp	x8, x9,   [x18, #CPU_XREG_OFFSET(8)]
	stp	x10, x11, [x18, #CPU_XREG_OFFSET(10)]
	stp	x12, x13, [x18, #CPU_XREG_OFFSET(12)]
	stp	x14, x15, [x18, #CPU_XREG_OFFSET(14)]
	stp	x16, x17, [x18, #CPU_XREG_OFFSET(16)]

	ret
SYM_CODE_END(__kvm_hyp_host_forward_smc)

/*
 * kvm_host_psci_cpu_entry is called through br instruction, which requires
 * bti j instruction as compilers (gcc and llvm) doesn't insert bti j for external
 * functions, but bti c instead.
 */
SYM_CODE_START(kvm_host_psci_cpu_entry)
       bti j
       b __kvm_host_psci_cpu_entry
SYM_CODE_END(kvm_host_psci_cpu_entry)