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If Xen wants to return to a 32b usermode with sysret it must use the right form. When using VCGF_in_syscall to trigger this, it looks at the code segment and does a 32b sysret if it is FLAT_USER_CS32. However, this is different from __USER32_CS, so it fails to return properly if we use the normal Linux segment. So avoid the whole mess by dropping VCGF_in_syscall and simply use plain iret to return to usermode. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Acked-by: Jan Beulich <jbeulich@novell.com> Cc: Stable Kernel <stable@kernel.org>
160 lines
3.3 KiB
ArmAsm
160 lines
3.3 KiB
ArmAsm
/*
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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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