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