From: Jeremy Fitzhardinge Date: Wed, 25 Nov 2009 21:15:38 +0000 (-0800) Subject: xen: use iret for return from 64b kernel to 32b usermode X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=6aaf5d633bb6cead81b396d861d7bae4b9a0ba7e;p=openwrt%2Fstaging%2Fblogic.git 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 Acked-by: Jan Beulich Cc: Stable Kernel --- diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S index 02f496a8dbaa..53adefda4275 100644 --- a/arch/x86/xen/xen-asm_64.S +++ b/arch/x86/xen/xen-asm_64.S @@ -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)