LXR linux/arch/x86/xen/xen-asm

   1/*
   2 * Asm versions of Xen pv-ops, suitable for either direct use or
   3 * inlining.  The inline versions are the same as the direct-use
   4 * versions, with the pre- and post-amble chopped off.
   5 *
   6 * This code is encoded for size rather than absolute efficiency, with
   7 * a view to being able to inline as much as possible.
   8 *
   9 * We only bother with direct forms (ie, vcpu in pda) of the
  10 * operations here; the indirect forms are better handled in C, since
  11 * they're generally too large to inline anyway.
  12 */
  13
  14#include <asm/errno.h>
  15#include <asm/percpu.h>
  16#include <asm/processor-flags.h>
  17#include <asm/segment.h>
  18
  19#include <xen/interface/xen.h>
  20
  21#include "xen-asm.h"
  22
  23ENTRY(xen_adjust_exception_frame)
  24        mov 8+0(%rsp), %rcx
  25        mov 8+8(%rsp), %r11
  26        ret $16
  27
  28hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
  29/*
  30 * Xen64 iret frame:
  31 *
  32 *      ss
  33 *      rsp
  34 *      rflags
  35 *      cs
  36 *      rip             <-- standard iret frame
  37 *
  38 *      flags
  39 *
  40 *      rcx             }
  41 *      r11             }<-- pushed by hypercall page
  42 * rsp->rax             }
  43 */
  44ENTRY(xen_iret)
  45        pushq $0
  461:      jmp hypercall_iret
  47ENDPATCH(xen_iret)
  48RELOC(xen_iret, 1b+1)
  49
  50/*
  51 * sysexit is not used for 64-bit processes, so it's only ever used to
  52 * return to 32-bit compat userspace.
  53 */
  54ENTRY(xen_sysexit)
  55        pushq $__USER32_DS
  56        pushq %rcx
  57        pushq $X86_EFLAGS_IF
  58        pushq $__USER32_CS
  59        pushq %rdx
  60
  61        pushq $0
  621:      jmp hypercall_iret
  63ENDPATCH(xen_sysexit)
  64RELOC(xen_sysexit, 1b+1)
  65
  66ENTRY(xen_sysret64)
  67        /*
  68         * We're already on the usermode stack at this point, but
  69         * still with the kernel gs, so we can easily switch back
  70         */
  71        movq %rsp, PER_CPU_VAR(old_rsp)
  72        movq PER_CPU_VAR(kernel_stack), %rsp
  73
  74        pushq $__USER_DS
  75        pushq PER_CPU_VAR(old_rsp)
  76        pushq %r11
  77        pushq $__USER_CS
  78        pushq %rcx
  79
  80        pushq $VGCF_in_syscall
  811:      jmp hypercall_iret
  82ENDPATCH(xen_sysret64)
  83RELOC(xen_sysret64, 1b+1)
  84
  85ENTRY(xen_sysret32)
  86        /*
  87         * We're already on the usermode stack at this point, but
  88         * still with the kernel gs, so we can easily switch back
  89         */
  90        movq %rsp, PER_CPU_VAR(old_rsp)
  91        movq PER_CPU_VAR(kernel_stack), %rsp
  92
  93        pushq $__USER32_DS
  94        pushq PER_CPU_VAR(old_rsp)
  95        pushq %r11
  96        pushq $__USER32_CS
  97        pushq %rcx
  98
  99        pushq $0
 1001:      jmp hypercall_iret
 101ENDPATCH(xen_sysret32)
 102RELOC(xen_sysret32, 1b+1)
 103
 104/*
 105 * Xen handles syscall callbacks much like ordinary exceptions, which
 106 * means we have:
 107 * - kernel gs
 108 * - kernel rsp
 109 * - an iret-like stack frame on the stack (including rcx and r11):
 110 *      ss
 111 *      rsp
 112 *      rflags
 113 *      cs
 114 *      rip
 115 *      r11
 116 * rsp->rcx
 117 *
 118 * In all the entrypoints, we undo all that to make it look like a
 119 * CPU-generated syscall/sysenter and jump to the normal entrypoint.
 120 */
 121
 122.macro undo_xen_syscall
 123        mov 0*8(%rsp), %rcx
 124        mov 1*8(%rsp), %r11
 125        mov 5*8(%rsp), %rsp
 126.endm
 127
 128/* Normal 64-bit system call target */
 129ENTRY(xen_syscall_target)
 130        undo_xen_syscall
 131        jmp system_call_after_swapgs
 132ENDPROC(xen_syscall_target)
 133
 134#ifdef CONFIG_IA32_EMULATION
 135
 136/* 32-bit compat syscall target */
 137ENTRY(xen_syscall32_target)
 138        undo_xen_syscall
 139        jmp ia32_cstar_target
 140ENDPROC(xen_syscall32_target)
 141
 142/* 32-bit compat sysenter target */
 143ENTRY(xen_sysenter_target)
 144        undo_xen_syscall
 145        jmp ia32_sysenter_target
 146ENDPROC(xen_sysenter_target)
 147
 148#else /* !CONFIG_IA32_EMULATION */
 149
 150ENTRY(xen_syscall32_target)
 151ENTRY(xen_sysenter_target)
 152        lea 16(%rsp), %rsp      /* strip %rcx, %r11 */
 153        mov $-ENOSYS, %rax
 154        pushq $0
 155        jmp hypercall_iret
 156ENDPROC(xen_syscall32_target)
 157ENDPROC(xen_sysenter_target)
 158
 159#endif  /* CONFIG_IA32_EMULATION */
 160