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xen: use iret for return from 64b kernel to 32b usermode

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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>
This commit is contained in:
Jeremy Fitzhardinge 2009-11-25 13:15:38 -08:00
parent 922cc38ab7
commit 6aaf5d633b
1 changed files with 2 additions and 2 deletions
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4
arch/x86/xen/xen-asm_64.S
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@ -96,7 +96,7 @@ ENTRY(xen_sysret32)
pushq $__USER32_CS
pushq %rcx
pushq $VGCF_in_syscall
pushq $0
1: jmp hypercall_iret
ENDPATCH(xen_sysret32)
RELOC(xen_sysret32, 1b+1)
@ -151,7 +151,7 @@ ENTRY(xen_syscall32_target)
ENTRY(xen_sysenter_target)
lea 16(%rsp), %rsp /* strip %rcx, %r11 */
mov $-ENOSYS, %rax
pushq $VGCF_in_syscall
pushq $0
jmp hypercall_iret
ENDPROC(xen_syscall32_target)
ENDPROC(xen_sysenter_target)