On Tue, Dec 1, 2015 at 5:40 AM, Andrew Cooper <andrew.coop...@citrix.com>
wrote:
> On 01/12/15 01:21, Tamas K Lengyel wrote:
>
>
>
> On Mon, Nov 30, 2015 at 7:01 PM, Razvan Cojocaru <
> rcojoc...@bitdefender.com> wrote:
>
>> On 12/01/2015 01:32 AM, Tamas K Lengyel wrote:
>> > Hi all,
>> > I'm trying to extend the current vm_event system to be able to emulate
>> > over an in-guest breakpoint using the VM_EVENT_FLAG_SET_EMUL_READ_DATA
>> > feature. The idea is to have the vm_event listener send back the
>> > contents of the memory that was overwritten by the breakpoint
>> > instruction, have Xen emulate one instruction, and resume execution
>> > normally afterwards. This would eliminate the need of removing the
>> > breakpoint, singlestepping, and placing the breakpoint back again.
>> >
>> > Unfortunately I encounter this crash when I call
>> > hvm_mem_access_emulate_one in the event response handler:
>> >
>> > (XEN) vm_event.c:72:d0v0 Checking flags on int3 response 37
>> > (XEN) Xen BUG at /share/src/xen/xen/include/asm/hvm/vmx/vmx.h:372
>>
>
> This BUG() is the cause of the crash.
>
> It is a bad parameter to VMREAD, by the looks of it.
>
> ~Andrew
>
So this is quite confusing. The error seems to stem from
(XEN) [<ffff82d0801d557e>] hvm_emulate_prepare+0x23/0x6c
in the line
hvmemul_ctxt->intr_shadow = hvm_funcs.get_interrupt_shadow(current);
which is effectively a simple
__vmread(GUEST_INTERRUPTIBILITY_INFO, &intr_shadow);
My printk after this doesn't show up in the console so this must be where
the bug triggers.
(XEN) emulate.c:1828:d1v0 get interrupt shadow
(XEN) emulate.c:1830:d1v0 get interrupt shadow done
(XEN) emulate.c:1836:d1v0 get seg cs
(XEN) emulate.c:1838:d1v0 get seg ss
(XEN) vm_event.c:72:d0v0 Checking flags on int3 response 37
(XEN) emulate.c:1828:d0v0 get interrupt shadow
(XEN) Xen BUG at /share/src/xen/xen/include/asm/hvm/vmx/vmx.h:372
(XEN) ----[ Xen-4.7-unstable x86_64 debug=y Tainted: C ]----
(XEN) CPU: 0
(XEN) RIP: e008:[<ffff82d080202e00>] vmx_vmenter_helper+0x3d/0x1cd
(XEN) RFLAGS: 0000000000010203 CONTEXT: hypervisor (d0v0)
(XEN) rax: 0000000000004824 rbx: ffff8300ae30fb68 rcx: 0000000000000000
(XEN) rdx: ffff8300ae308000 rsi: 000000000000000a rdi: ffff8300ae550000
(XEN) rbp: ffff8300ae30fb28 rsp: ffff8300ae30fb28 r8: ffff830430de0000
(XEN) r9: 0000000000000004 r10: 0000000000000004 r11: 0000000000000001
(XEN) r12: ffff8300ae308000 r13: ffff8300ae30ff18 r14: ffff8300ae0f8000
(XEN) r15: ffff82d08028a480 cr0: 0000000080050033 cr4: 00000000000426e0
(XEN) cr3: 000000043df79000 cr2: 00007f761d656000
(XEN) ds: 0000 es: 0000 fs: 0000 gs: 0000 ss: e010 cs: e008
(XEN) Xen stack trace from rsp=ffff8300ae30fb28:
(XEN) ffff8300ae30fb58 ffff82d0801d55ab 00007cff51cf0497 0000000000000006
(XEN) 00000000ffffffff 0000000000000002 ffff8300ae30fc98 ffff82d0801d5776
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000048 ffff8300ae30fcd0
(XEN) ffff8300ae30fcd0 ffff830412da0c50 ffff8300ae30fcb8 ffff82d0801c02c1
(XEN) ffff8300ae30fcd0 ffff83040fbaf000 ffff8300ae30fe38 ffff82d08013a483
(XEN) 00007cff51cf0307 0000002500000001 0000000000000006 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) c214c48300000008 0000000064900010 0000000000000000 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000
(XEN) Xen call trace:
(XEN) [<ffff82d080202e00>] vmx_vmenter_helper+0x3d/0x1cd
(XEN) [<ffff82d0801d55ab>] hvm_emulate_prepare+0x50/0x10e
(XEN) [<ffff82d0801d5776>] hvm_mem_access_emulate_one+0x49/0xd3
(XEN) [<ffff82d0801c02c1>] vm_event_interrupt_emulate_check+0x5c/0x63
(XEN) [<ffff82d08013a483>] vm_event_resume+0xa1/0x131
(XEN) [<ffff82d08013a914>] vm_event.c#monitor_notification+0x25/0x28
(XEN) [<ffff82d080108554>] evtchn_send+0x126/0x17e
(XEN) [<ffff82d080109a74>] do_event_channel_op+0xe66/0x14be
(XEN) [<ffff82d08024d992>] lstar_enter+0xe2/0x13c
(XEN)
(XEN)
(XEN) ****************************************
(XEN) Panic on CPU 0:
(XEN) Xen BUG at /share/src/xen/xen/include/asm/hvm/vmx/vmx.h:372
Why would that vmread fail there and why would the call trace tell me it's
in vmx_vmenter_helper?
Tamas
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
