CoCalc -- xen-asm

GitHub Repository: awilliam/linux-vfio
Path: blob/master/arch/x86/xen/xen-asm_64.S
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/*
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 * Asm versions of Xen pv-ops, suitable for either direct use or
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 * inlining.  The inline versions are the same as the direct-use
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 * versions, with the pre- and post-amble chopped off.
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 *
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 * This code is encoded for size rather than absolute efficiency, with
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 * a view to being able to inline as much as possible.
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 *
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 * We only bother with direct forms (ie, vcpu in pda) of the
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 * operations here; the indirect forms are better handled in C, since
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 * they're generally too large to inline anyway.
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 */
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#include <asm/errno.h>
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#include <asm/percpu.h>
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#include <asm/processor-flags.h>
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#include <asm/segment.h>
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#include <xen/interface/xen.h>
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#include "xen-asm.h"
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ENTRY(xen_adjust_exception_frame)
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	mov 8+0(%rsp), %rcx
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	mov 8+8(%rsp), %r11
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	ret $16
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hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
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/*
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 * Xen64 iret frame:
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 *
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 *	ss
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 *	rsp
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 *	rflags
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 *	cs
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 *	rip		<-- standard iret frame
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 *
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 *	flags
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 *
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 *	rcx		}
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 *	r11		}<-- pushed by hypercall page
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 * rsp->rax		}
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 */
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ENTRY(xen_iret)
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	pushq $0
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1:	jmp hypercall_iret
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ENDPATCH(xen_iret)
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RELOC(xen_iret, 1b+1)
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/*
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 * sysexit is not used for 64-bit processes, so it's only ever used to
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 * return to 32-bit compat userspace.
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 */
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ENTRY(xen_sysexit)
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	pushq $__USER32_DS
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	pushq %rcx
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	pushq $X86_EFLAGS_IF
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	pushq $__USER32_CS
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	pushq %rdx
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	pushq $0
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1:	jmp hypercall_iret
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ENDPATCH(xen_sysexit)
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RELOC(xen_sysexit, 1b+1)
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ENTRY(xen_sysret64)
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	/*
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	 * We're already on the usermode stack at this point, but
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	 * still with the kernel gs, so we can easily switch back
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	 */
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	movq %rsp, PER_CPU_VAR(old_rsp)
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	movq PER_CPU_VAR(kernel_stack), %rsp
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	pushq $__USER_DS
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	pushq PER_CPU_VAR(old_rsp)
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	pushq %r11
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	pushq $__USER_CS
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	pushq %rcx
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	pushq $VGCF_in_syscall
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1:	jmp hypercall_iret
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ENDPATCH(xen_sysret64)
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RELOC(xen_sysret64, 1b+1)
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ENTRY(xen_sysret32)
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	/*
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	 * We're already on the usermode stack at this point, but
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	 * still with the kernel gs, so we can easily switch back
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	 */
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	movq %rsp, PER_CPU_VAR(old_rsp)
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	movq PER_CPU_VAR(kernel_stack), %rsp
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	pushq $__USER32_DS
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	pushq PER_CPU_VAR(old_rsp)
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	pushq %r11
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	pushq $__USER32_CS
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	pushq %rcx
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	pushq $0
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1:	jmp hypercall_iret
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ENDPATCH(xen_sysret32)
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RELOC(xen_sysret32, 1b+1)
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/*
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 * Xen handles syscall callbacks much like ordinary exceptions, which
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 * means we have:
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 * - kernel gs
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 * - kernel rsp
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 * - an iret-like stack frame on the stack (including rcx and r11):
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 *	ss
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 *	rsp
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 *	rflags
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 *	cs
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 *	rip
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 *	r11
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 * rsp->rcx
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 *
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 * In all the entrypoints, we undo all that to make it look like a
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 * CPU-generated syscall/sysenter and jump to the normal entrypoint.
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 */
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.macro undo_xen_syscall
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	mov 0*8(%rsp), %rcx
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	mov 1*8(%rsp), %r11
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	mov 5*8(%rsp), %rsp
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.endm
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/* Normal 64-bit system call target */
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ENTRY(xen_syscall_target)
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	undo_xen_syscall
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	jmp system_call_after_swapgs
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ENDPROC(xen_syscall_target)
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#ifdef CONFIG_IA32_EMULATION
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/* 32-bit compat syscall target */
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ENTRY(xen_syscall32_target)
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	undo_xen_syscall
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	jmp ia32_cstar_target
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ENDPROC(xen_syscall32_target)
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/* 32-bit compat sysenter target */
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ENTRY(xen_sysenter_target)
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	undo_xen_syscall
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	jmp ia32_sysenter_target
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ENDPROC(xen_sysenter_target)
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#else /* !CONFIG_IA32_EMULATION */
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ENTRY(xen_syscall32_target)
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ENTRY(xen_sysenter_target)
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	lea 16(%rsp), %rsp	/* strip %rcx, %r11 */
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	mov $-ENOSYS, %rax
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	pushq $0
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	jmp hypercall_iret
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ENDPROC(xen_syscall32_target)
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ENDPROC(xen_sysenter_target)
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#endif	/* CONFIG_IA32_EMULATION */
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