arch/x86/xen/xen-asm.S - linux - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Asm versions of Xen pv-ops, suitable for direct use.
  *
  * We only bother with direct forms (ie, vcpu in percpu data) of the
  * operations here; the indirect forms are better handled in C.
  */

 #include <asm/errno.h>
 #include <asm/asm-offsets.h>
 #include <asm/percpu.h>
 #include <asm/processor-flags.h>
 #include <asm/segment.h>
 #include <asm/thread_info.h>
 #include <asm/asm.h>
 #include <asm/frame.h>

 #include <xen/interface/xen.h>

 #include <linux/init.h>
 #include <linux/linkage.h>

 /*
  * Enable events.  This clears the event mask and tests the pending
  * event status with one and operation.  If there are pending events,
  * then enter the hypervisor to get them handled.
  */
 SYM_FUNC_START(xen_irq_enable_direct)
 	FRAME_BEGIN
 	/* Unmask events */
 	movb $0, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask

 	/*
 	 * Preempt here doesn't matter because that will deal with any
 	 * pending interrupts.  The pending check may end up being run
 	 * on the wrong CPU, but that doesn't hurt.
 	 */

 	/* Test for pending */
 	testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
 	jz 1f

 	call check_events
 1:
 	FRAME_END
 	ret
 SYM_FUNC_END(xen_irq_enable_direct)


 /*
  * Disabling events is simply a matter of making the event mask
  * non-zero.
  */
 SYM_FUNC_START(xen_irq_disable_direct)
 	movb $1, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
 	ret
 SYM_FUNC_END(xen_irq_disable_direct)

 /*
  * (xen_)save_fl is used to get the current interrupt enable status.
  * Callers expect the status to be in X86_EFLAGS_IF, and other bits
  * may be set in the return value.  We take advantage of this by
  * making sure that X86_EFLAGS_IF has the right value (and other bits
  * in that byte are 0), but other bits in the return value are
  * undefined.  We need to toggle the state of the bit, because Xen and
  * x86 use opposite senses (mask vs enable).
  */
 SYM_FUNC_START(xen_save_fl_direct)
 	testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
 	setz %ah
 	addb %ah, %ah
 	ret
 SYM_FUNC_END(xen_save_fl_direct)


 /*
  * In principle the caller should be passing us a value return from
  * xen_save_fl_direct, but for robustness sake we test only the
  * X86_EFLAGS_IF flag rather than the whole byte. After setting the
  * interrupt mask state, it checks for unmasked pending events and
  * enters the hypervisor to get them delivered if so.
  */
 SYM_FUNC_START(xen_restore_fl_direct)
 	FRAME_BEGIN
 	testw $X86_EFLAGS_IF, %di
 	setz PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
 	/*
 	 * Preempt here doesn't matter because that will deal with any
 	 * pending interrupts.  The pending check may end up being run
 	 * on the wrong CPU, but that doesn't hurt.
 	 */

 	/* check for unmasked and pending */
 	cmpw $0x0001, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
 	jnz 1f
 	call check_events
 1:
 	FRAME_END
 	ret
 SYM_FUNC_END(xen_restore_fl_direct)


 /*
  * Force an event check by making a hypercall, but preserve regs
  * before making the call.
  */
 SYM_FUNC_START(check_events)
 	FRAME_BEGIN
 	push %rax
 	push %rcx
 	push %rdx
 	push %rsi
 	push %rdi
 	push %r8
 	push %r9
 	push %r10
 	push %r11
 	call xen_force_evtchn_callback
 	pop %r11
 	pop %r10
 	pop %r9
 	pop %r8
 	pop %rdi
 	pop %rsi
 	pop %rdx
 	pop %rcx
 	pop %rax
 	FRAME_END
 	ret
 SYM_FUNC_END(check_events)

 SYM_FUNC_START(xen_read_cr2)
 	FRAME_BEGIN
 	_ASM_MOV PER_CPU_VAR(xen_vcpu), %_ASM_AX
 	_ASM_MOV XEN_vcpu_info_arch_cr2(%_ASM_AX), %_ASM_AX
 	FRAME_END
 	ret
 SYM_FUNC_END(xen_read_cr2);

 SYM_FUNC_START(xen_read_cr2_direct)
 	FRAME_BEGIN
 	_ASM_MOV PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_arch_cr2, %_ASM_AX
 	FRAME_END
 	ret
 SYM_FUNC_END(xen_read_cr2_direct);

 .macro xen_pv_trap name
 SYM_CODE_START(xen_\name)
 	pop %rcx
 	pop %r11
 	jmp  \name
 SYM_CODE_END(xen_\name)
 _ASM_NOKPROBE(xen_\name)
 .endm

 xen_pv_trap asm_exc_divide_error
 xen_pv_trap asm_xenpv_exc_debug
 xen_pv_trap asm_exc_int3
 xen_pv_trap asm_xenpv_exc_nmi
 xen_pv_trap asm_exc_overflow
 xen_pv_trap asm_exc_bounds
 xen_pv_trap asm_exc_invalid_op
 xen_pv_trap asm_exc_device_not_available
 xen_pv_trap asm_exc_double_fault
 xen_pv_trap asm_exc_coproc_segment_overrun
 xen_pv_trap asm_exc_invalid_tss
 xen_pv_trap asm_exc_segment_not_present
 xen_pv_trap asm_exc_stack_segment
 xen_pv_trap asm_exc_general_protection
 xen_pv_trap asm_exc_page_fault
 xen_pv_trap asm_exc_spurious_interrupt_bug
 xen_pv_trap asm_exc_coprocessor_error
 xen_pv_trap asm_exc_alignment_check
 #ifdef CONFIG_X86_MCE
 xen_pv_trap asm_exc_machine_check
 #endif /* CONFIG_X86_MCE */
 xen_pv_trap asm_exc_simd_coprocessor_error
 #ifdef CONFIG_IA32_EMULATION
 xen_pv_trap entry_INT80_compat
 #endif
 xen_pv_trap asm_exc_xen_unknown_trap
 xen_pv_trap asm_exc_xen_hypervisor_callback

 	__INIT
 SYM_CODE_START(xen_early_idt_handler_array)
 	i = 0
 	.rept NUM_EXCEPTION_VECTORS
 	pop %rcx
 	pop %r11
 	jmp early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE
 	i = i + 1
 	.fill xen_early_idt_handler_array + i*XEN_EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
 	.endr
 SYM_CODE_END(xen_early_idt_handler_array)
 	__FINIT

 hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
 /*
  * Xen64 iret frame:
  *
  *	ss
  *	rsp
  *	rflags
  *	cs
  *	rip		<-- standard iret frame
  *
  *	flags
  *
  *	rcx		}
  *	r11		}<-- pushed by hypercall page
  * rsp->rax		}
  */
 SYM_CODE_START(xen_iret)
 	pushq $0
 	jmp hypercall_iret
 SYM_CODE_END(xen_iret)

 SYM_CODE_START(xen_sysret64)
 	/*
 	 * We're already on the usermode stack at this point, but
 	 * still with the kernel gs, so we can easily switch back.
 	 *
 	 * tss.sp2 is scratch space.
 	 */
 	movq %rsp, PER_CPU_VAR(cpu_tss_rw + TSS_sp2)
 	movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp

 	pushq $__USER_DS
 	pushq PER_CPU_VAR(cpu_tss_rw + TSS_sp2)
 	pushq %r11
 	pushq $__USER_CS
 	pushq %rcx

 	pushq $VGCF_in_syscall
 	jmp hypercall_iret
 SYM_CODE_END(xen_sysret64)

 /*
  * Xen handles syscall callbacks much like ordinary exceptions, which
  * means we have:
  * - kernel gs
  * - kernel rsp
  * - an iret-like stack frame on the stack (including rcx and r11):
  *	ss
  *	rsp
  *	rflags
  *	cs
  *	rip
  *	r11
  * rsp->rcx
  */

 /* Normal 64-bit system call target */
 SYM_FUNC_START(xen_syscall_target)
 	popq %rcx
 	popq %r11

 	/*
 	 * Neither Xen nor the kernel really knows what the old SS and
 	 * CS were.  The kernel expects __USER_DS and __USER_CS, so
 	 * report those values even though Xen will guess its own values.
 	 */
 	movq $__USER_DS, 4*8(%rsp)
 	movq $__USER_CS, 1*8(%rsp)

 	jmp entry_SYSCALL_64_after_hwframe
 SYM_FUNC_END(xen_syscall_target)

 #ifdef CONFIG_IA32_EMULATION

 /* 32-bit compat syscall target */
 SYM_FUNC_START(xen_syscall32_target)
 	popq %rcx
 	popq %r11

 	/*
 	 * Neither Xen nor the kernel really knows what the old SS and
 	 * CS were.  The kernel expects __USER32_DS and __USER32_CS, so
 	 * report those values even though Xen will guess its own values.
 	 */
 	movq $__USER32_DS, 4*8(%rsp)
 	movq $__USER32_CS, 1*8(%rsp)

 	jmp entry_SYSCALL_compat_after_hwframe
 SYM_FUNC_END(xen_syscall32_target)

 /* 32-bit compat sysenter target */
 SYM_FUNC_START(xen_sysenter_target)
 	/*
 	 * NB: Xen is polite and clears TF from EFLAGS for us.  This means
 	 * that we don't need to guard against single step exceptions here.
 	 */
 	popq %rcx
 	popq %r11

 	/*
 	 * Neither Xen nor the kernel really knows what the old SS and
 	 * CS were.  The kernel expects __USER32_DS and __USER32_CS, so
 	 * report those values even though Xen will guess its own values.
 	 */
 	movq $__USER32_DS, 4*8(%rsp)
 	movq $__USER32_CS, 1*8(%rsp)

 	jmp entry_SYSENTER_compat_after_hwframe
 SYM_FUNC_END(xen_sysenter_target)

 #else /* !CONFIG_IA32_EMULATION */

 SYM_FUNC_START_ALIAS(xen_syscall32_target)
 SYM_FUNC_START(xen_sysenter_target)
 	lea 16(%rsp), %rsp	/* strip %rcx, %r11 */
 	mov $-ENOSYS, %rax
 	pushq $0
 	jmp hypercall_iret
 SYM_FUNC_END(xen_sysenter_target)
 SYM_FUNC_END_ALIAS(xen_syscall32_target)

 #endif	/* CONFIG_IA32_EMULATION */
	/* SPDX-License-Identifier: GPL-2.0 */
	/*
	* Asm versions of Xen pv-ops, suitable for direct use.
	*
	* We only bother with direct forms (ie, vcpu in percpu data) of the
	* operations here; the indirect forms are better handled in C.
	*/

	#include <asm/errno.h>
	#include <asm/asm-offsets.h>
	#include <asm/percpu.h>
	#include <asm/processor-flags.h>
	#include <asm/segment.h>
	#include <asm/thread_info.h>
	#include <asm/asm.h>
	#include <asm/frame.h>

	#include <xen/interface/xen.h>

	#include <linux/init.h>
	#include <linux/linkage.h>

	/*
	* Enable events. This clears the event mask and tests the pending
	* event status with one and operation. If there are pending events,
	* then enter the hypervisor to get them handled.
	*/
	SYM_FUNC_START(xen_irq_enable_direct)
	FRAME_BEGIN
	/* Unmask events */
	movb $0, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask

	/*
	* Preempt here doesn't matter because that will deal with any
	* pending interrupts. The pending check may end up being run
	* on the wrong CPU, but that doesn't hurt.
	*/

	/* Test for pending */
	testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
	jz 1f

	call check_events
	1:
	FRAME_END
	ret
	SYM_FUNC_END(xen_irq_enable_direct)


	/*
	* Disabling events is simply a matter of making the event mask
	* non-zero.
	*/
	SYM_FUNC_START(xen_irq_disable_direct)
	movb $1, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
	ret
	SYM_FUNC_END(xen_irq_disable_direct)

	/*
	* (xen_)save_fl is used to get the current interrupt enable status.
	* Callers expect the status to be in X86_EFLAGS_IF, and other bits
	* may be set in the return value. We take advantage of this by
	* making sure that X86_EFLAGS_IF has the right value (and other bits
	* in that byte are 0), but other bits in the return value are
	* undefined. We need to toggle the state of the bit, because Xen and
	* x86 use opposite senses (mask vs enable).
	*/
	SYM_FUNC_START(xen_save_fl_direct)
	testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
	setz %ah
	addb %ah, %ah
	ret
	SYM_FUNC_END(xen_save_fl_direct)


	/*
	* In principle the caller should be passing us a value return from
	* xen_save_fl_direct, but for robustness sake we test only the
	* X86_EFLAGS_IF flag rather than the whole byte. After setting the
	* interrupt mask state, it checks for unmasked pending events and
	* enters the hypervisor to get them delivered if so.
	*/
	SYM_FUNC_START(xen_restore_fl_direct)
	FRAME_BEGIN
	testw $X86_EFLAGS_IF, %di
	setz PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
	/*
	* Preempt here doesn't matter because that will deal with any
	* pending interrupts. The pending check may end up being run
	* on the wrong CPU, but that doesn't hurt.
	*/

	/* check for unmasked and pending */
	cmpw $0x0001, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
	jnz 1f
	call check_events
	1:
	FRAME_END
	ret
	SYM_FUNC_END(xen_restore_fl_direct)


	/*
	* Force an event check by making a hypercall, but preserve regs
	* before making the call.
	*/
	SYM_FUNC_START(check_events)
	FRAME_BEGIN
	push %rax
	push %rcx
	push %rdx
	push %rsi
	push %rdi
	push %r8
	push %r9
	push %r10
	push %r11
	call xen_force_evtchn_callback
	pop %r11
	pop %r10
	pop %r9
	pop %r8
	pop %rdi
	pop %rsi
	pop %rdx
	pop %rcx
	pop %rax
	FRAME_END
	ret
	SYM_FUNC_END(check_events)

	SYM_FUNC_START(xen_read_cr2)
	FRAME_BEGIN
	_ASM_MOV PER_CPU_VAR(xen_vcpu), %_ASM_AX
	_ASM_MOV XEN_vcpu_info_arch_cr2(%_ASM_AX), %_ASM_AX
	FRAME_END
	ret
	SYM_FUNC_END(xen_read_cr2);

	SYM_FUNC_START(xen_read_cr2_direct)
	FRAME_BEGIN
	_ASM_MOV PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_arch_cr2, %_ASM_AX
	FRAME_END
	ret
	SYM_FUNC_END(xen_read_cr2_direct);

	.macro xen_pv_trap name
	SYM_CODE_START(xen_\name)
	pop %rcx
	pop %r11
	jmp \name
	SYM_CODE_END(xen_\name)
	_ASM_NOKPROBE(xen_\name)
	.endm

	xen_pv_trap asm_exc_divide_error
	xen_pv_trap asm_xenpv_exc_debug
	xen_pv_trap asm_exc_int3
	xen_pv_trap asm_xenpv_exc_nmi
	xen_pv_trap asm_exc_overflow
	xen_pv_trap asm_exc_bounds
	xen_pv_trap asm_exc_invalid_op
	xen_pv_trap asm_exc_device_not_available
	xen_pv_trap asm_exc_double_fault
	xen_pv_trap asm_exc_coproc_segment_overrun
	xen_pv_trap asm_exc_invalid_tss
	xen_pv_trap asm_exc_segment_not_present
	xen_pv_trap asm_exc_stack_segment
	xen_pv_trap asm_exc_general_protection
	xen_pv_trap asm_exc_page_fault
	xen_pv_trap asm_exc_spurious_interrupt_bug
	xen_pv_trap asm_exc_coprocessor_error
	xen_pv_trap asm_exc_alignment_check
	#ifdef CONFIG_X86_MCE
	xen_pv_trap asm_exc_machine_check
	#endif /* CONFIG_X86_MCE */
	xen_pv_trap asm_exc_simd_coprocessor_error
	#ifdef CONFIG_IA32_EMULATION
	xen_pv_trap entry_INT80_compat
	#endif
	xen_pv_trap asm_exc_xen_unknown_trap
	xen_pv_trap asm_exc_xen_hypervisor_callback

	__INIT
	SYM_CODE_START(xen_early_idt_handler_array)
	i = 0
	.rept NUM_EXCEPTION_VECTORS
	pop %rcx
	pop %r11
	jmp early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE
	i = i + 1
	.fill xen_early_idt_handler_array + i*XEN_EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
	.endr
	SYM_CODE_END(xen_early_idt_handler_array)
	__FINIT

	hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
	/*
	* Xen64 iret frame:
	*
	* ss
	* rsp
	* rflags
	* cs
	* rip <-- standard iret frame
	*
	* flags
	*
	* rcx }
	* r11 }<-- pushed by hypercall page
	* rsp->rax }
	*/
	SYM_CODE_START(xen_iret)
	pushq $0
	jmp hypercall_iret
	SYM_CODE_END(xen_iret)

	SYM_CODE_START(xen_sysret64)
	/*
	* We're already on the usermode stack at this point, but
	* still with the kernel gs, so we can easily switch back.
	*
	* tss.sp2 is scratch space.
	*/
	movq %rsp, PER_CPU_VAR(cpu_tss_rw + TSS_sp2)
	movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp

	pushq $__USER_DS
	pushq PER_CPU_VAR(cpu_tss_rw + TSS_sp2)
	pushq %r11
	pushq $__USER_CS
	pushq %rcx

	pushq $VGCF_in_syscall
	jmp hypercall_iret
	SYM_CODE_END(xen_sysret64)

	/*
	* Xen handles syscall callbacks much like ordinary exceptions, which
	* means we have:
	* - kernel gs
	* - kernel rsp
	* - an iret-like stack frame on the stack (including rcx and r11):
	* ss
	* rsp
	* rflags
	* cs
	* rip
	* r11
	* rsp->rcx
	*/

	/* Normal 64-bit system call target */
	SYM_FUNC_START(xen_syscall_target)
	popq %rcx
	popq %r11

	/*
	* Neither Xen nor the kernel really knows what the old SS and
	* CS were. The kernel expects __USER_DS and __USER_CS, so
	* report those values even though Xen will guess its own values.
	*/
	movq $__USER_DS, 4*8(%rsp)
	movq $__USER_CS, 1*8(%rsp)

	jmp entry_SYSCALL_64_after_hwframe
	SYM_FUNC_END(xen_syscall_target)

	#ifdef CONFIG_IA32_EMULATION

	/* 32-bit compat syscall target */
	SYM_FUNC_START(xen_syscall32_target)
	popq %rcx
	popq %r11

	/*
	* Neither Xen nor the kernel really knows what the old SS and
	* CS were. The kernel expects __USER32_DS and __USER32_CS, so
	* report those values even though Xen will guess its own values.
	*/
	movq $__USER32_DS, 4*8(%rsp)
	movq $__USER32_CS, 1*8(%rsp)

	jmp entry_SYSCALL_compat_after_hwframe
	SYM_FUNC_END(xen_syscall32_target)

	/* 32-bit compat sysenter target */
	SYM_FUNC_START(xen_sysenter_target)
	/*
	* NB: Xen is polite and clears TF from EFLAGS for us. This means
	* that we don't need to guard against single step exceptions here.
	*/
	popq %rcx
	popq %r11

	/*
	* Neither Xen nor the kernel really knows what the old SS and
	* CS were. The kernel expects __USER32_DS and __USER32_CS, so
	* report those values even though Xen will guess its own values.
	*/
	movq $__USER32_DS, 4*8(%rsp)
	movq $__USER32_CS, 1*8(%rsp)

	jmp entry_SYSENTER_compat_after_hwframe
	SYM_FUNC_END(xen_sysenter_target)

	#else /* !CONFIG_IA32_EMULATION */

	SYM_FUNC_START_ALIAS(xen_syscall32_target)
	SYM_FUNC_START(xen_sysenter_target)
	lea 16(%rsp), %rsp /* strip %rcx, %r11 */
	mov $-ENOSYS, %rax
	pushq $0
	jmp hypercall_iret
	SYM_FUNC_END(xen_sysenter_target)
	SYM_FUNC_END_ALIAS(xen_syscall32_target)

	#endif /* CONFIG_IA32_EMULATION */