Commit 6aaf5d63 authored Nov 25, 2009 by Jeremy Fitzhardinge

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



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>

parent 922cc38a

arch/x86/xen/xen-asm_64.S

+2 −2

Original line number	Diff line number	Diff line
		@@ -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)