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Diffstat (limited to 'arch/x86/xen/xen-asm.S')
-rw-r--r--arch/x86/xen/xen-asm.S42
1 files changed, 28 insertions, 14 deletions
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S
index fe161ed4b01..2497a30f41d 100644
--- a/arch/x86/xen/xen-asm.S
+++ b/arch/x86/xen/xen-asm.S
@@ -108,6 +108,20 @@ ENDPATCH(xen_restore_fl_direct)
RELOC(xen_restore_fl_direct, 2b+1)
/*
+ We can't use sysexit directly, because we're not running in ring0.
+ But we can easily fake it up using iret. Assuming xen_sysexit
+ is jumped to with a standard stack frame, we can just strip it
+ back to a standard iret frame and use iret.
+ */
+ENTRY(xen_sysexit)
+ movl PT_EAX(%esp), %eax /* Shouldn't be necessary? */
+ orl $X86_EFLAGS_IF, PT_EFLAGS(%esp)
+ lea PT_EIP(%esp), %esp
+
+ jmp xen_iret
+ENDPROC(xen_sysexit)
+
+/*
This is run where a normal iret would be run, with the same stack setup:
8: eflags
4: cs
@@ -184,8 +198,12 @@ iret_restore_end:
region is OK. */
je xen_hypervisor_callback
- iret
+1: iret
xen_iret_end_crit:
+.section __ex_table,"a"
+ .align 4
+ .long 1b,iret_exc
+.previous
hyper_iret:
/* put this out of line since its very rarely used */
@@ -219,9 +237,7 @@ hyper_iret:
ds } SAVE_ALL state
eax }
: :
- ebx }
- ----------------
- return addr <- esp
+ ebx }<- esp
----------------
In order to deliver the nested exception properly, we need to shift
@@ -236,10 +252,8 @@ hyper_iret:
it's usermode state which we eventually need to restore.
*/
ENTRY(xen_iret_crit_fixup)
- /* offsets +4 for return address */
-
/*
- Paranoia: Make sure we're really coming from userspace.
+ Paranoia: Make sure we're really coming from kernel space.
One could imagine a case where userspace jumps into the
critical range address, but just before the CPU delivers a GP,
it decides to deliver an interrupt instead. Unlikely?
@@ -248,32 +262,32 @@ ENTRY(xen_iret_crit_fixup)
jump instruction itself, not the destination, but some virtual
environments get this wrong.
*/
- movl PT_CS+4(%esp), %ecx
+ movl PT_CS(%esp), %ecx
andl $SEGMENT_RPL_MASK, %ecx
cmpl $USER_RPL, %ecx
je 2f
- lea PT_ORIG_EAX+4(%esp), %esi
- lea PT_EFLAGS+4(%esp), %edi
+ lea PT_ORIG_EAX(%esp), %esi
+ lea PT_EFLAGS(%esp), %edi
/* If eip is before iret_restore_end then stack
hasn't been restored yet. */
cmp $iret_restore_end, %eax
jae 1f
- movl 0+4(%edi),%eax /* copy EAX */
- movl %eax, PT_EAX+4(%esp)
+ movl 0+4(%edi),%eax /* copy EAX (just above top of frame) */
+ movl %eax, PT_EAX(%esp)
lea ESP_OFFSET(%edi),%edi /* move dest up over saved regs */
/* set up the copy */
1: std
- mov $(PT_EIP+4) / 4, %ecx /* copy ret+saved regs up to orig_eax */
+ mov $PT_EIP / 4, %ecx /* saved regs up to orig_eax */
rep movsl
cld
lea 4(%edi),%esp /* point esp to new frame */
-2: ret
+2: jmp xen_do_upcall
/*