lkml.org 
[lkml]   [2015]   [Nov]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit
From
Date


On 11/13/2015 06:26 PM, Andy Lutomirski wrote:
> On Fri, Nov 13, 2015 at 3:18 PM, Boris Ostrovsky
> <boris.ostrovsky@oracle.com> wrote:
>> After 32-bit syscall rewrite, and specifically after commit 5f310f739b4c
>> ("x86/entry/32: Re-implement SYSENTER using the new C path"), the stack
>> frame that is passed to xen_sysexit is no longer a "standard" one (i.e.
>> it's not pt_regs).
>>
>> We need to adjust it so that subsequent xen_iret can use it.
> I'm wondering if this should be more straightforward:
>
> movq %rsp, %rdi
> call do_fast_syscall_32
> testl %eax, %eax
> jz .Lsyscall_32_done
>
> /* Opportunistic SYSRET */
> sysret32_from_system_call:
> XEN_DO_SYSRET32
>
> where XEN_DO_SYSRET32 is a simple pv op that, on Xen, jumps to a
> variant of Xen's iret path that knows that the fast path is okay.


This patch is for 32-bit kernel. I actually haven't looked at compat
code (probably because our tests don't try that), I need to do that too.

As for XEN_DO_SYSRET32 --- we'd presumably need to have a nop for
baremetal otherwise current paravirt op will use native_usergs_sysret32
(for compat code). Which means a new pv_op, I think.

-boris


\
 
 \ /
  Last update: 2015-11-14 02:41    [W:0.052 / U:0.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site