x86/paravirt: add sysret/sysexit pvops for returning to 32-bit compatibility userspace

In a 64-bit system, we need separate sysret/sysexit operations to
return to a 32-bit userspace.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citirx.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 15 insertions, 6 deletions

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 3aefbce2de48..2a4c42427d9a 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -61,6 +61,19 @@
         CFI_UNDEFINED   r15
         .endm
 
+#ifdef CONFIG_PARAVIRT
+ENTRY(native_usergs_sysret32)
+        swapgs
+        sysretl
+ENDPROC(native_usergs_sysret32)
+
+ENTRY(native_irq_enable_sysexit)
+        swapgs
+        sti
+        sysexit
+ENDPROC(native_irq_enable_sysexit)
+#endif
+
 /*
  * 32bit SYSENTER instruction entry.
  *
@@ -151,10 +164,7 @@ sysenter_do_call:
         CFI_ADJUST_CFA_OFFSET -8
         CFI_REGISTER rsp,rcx
         TRACE_IRQS_ON
-        swapgs
-        sti             /* sti only takes effect after the next instruction */
-        /* sysexit */
-        .byte   0xf, 0x35
+        ENABLE_INTERRUPTS_SYSEXIT32
 
 sysenter_tracesys:
         CFI_RESTORE_STATE
@@ -254,8 +264,7 @@ cstar_do_call:
         TRACE_IRQS_ON
         movl RSP-ARGOFFSET(%rsp),%esp
         CFI_RESTORE rsp
-        swapgs
-        sysretl
+        USERGS_SYSRET32
         
 cstar_tracesys: 
         CFI_RESTORE_STATE