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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 <linux/linkage.h>
#include <asm/asm-offsets.h>
#include <asm/processor-flags.h>
#include <asm/errno.h>
#include <asm/segment.h>
#include <xen/interface/xen.h>
#define RELOC(x, v) .globl x##_reloc; x##_reloc=v
#define ENDPATCH(x) .globl x##_end; x##_end=.
/* Pseudo-flag used for virtual NMI, which we don't implement yet */
#define XEN_EFLAGS_NMI 0x80000000
#if 1
/*
x86-64 does not yet support direct access to percpu variables
via a segment override, so we just need to make sure this code
never gets used
*/
#define BUG ud2a
#define PER_CPU_VAR(var, off) 0xdeadbeef
#endif
/*
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.
*/
ENTRY(xen_irq_enable_direct)
BUG
/* 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
2: call check_events
1:
ENDPATCH(xen_irq_enable_direct)
ret
ENDPROC(xen_irq_enable_direct)
RELOC(xen_irq_enable_direct, 2b+1)
/*
Disabling events is simply a matter of making the event mask
non-zero.
*/
ENTRY(xen_irq_disable_direct)
BUG
movb $1, PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_mask)
ENDPATCH(xen_irq_disable_direct)
ret
ENDPROC(xen_irq_disable_direct)
RELOC(xen_irq_disable_direct, 0)
/*
(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).
*/
ENTRY(xen_save_fl_direct)
BUG
testb $0xff, PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_mask)
setz %ah
addb %ah,%ah
ENDPATCH(xen_save_fl_direct)
ret
ENDPROC(xen_save_fl_direct)
RELOC(xen_save_fl_direct, 0)
/*
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.
*/
ENTRY(xen_restore_fl_direct)
BUG
testb $X86_EFLAGS_IF>>8, %ah
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)
jz 1f
2: call check_events
1:
ENDPATCH(xen_restore_fl_direct)
ret
ENDPROC(xen_restore_fl_direct)
RELOC(xen_restore_fl_direct, 2b+1)
/*
Force an event check by making a hypercall,
but preserve regs before making the call.
*/
check_events:
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
ret
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, %gs:pda_oldrsp
movq %gs:pda_kernelstack,%rsp
pushq $__USER_DS
pushq %gs:pda_oldrsp
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, %gs:pda_oldrsp
movq %gs:pda_kernelstack, %rsp
pushq $__USER32_DS
pushq %gs:pda_oldrsp
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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