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Re: [Xen-devel] Re: [Xen-users] boot a existing windows in hvm domain



You could give that a try, but really it shouldn't be going at
0xc0000-0x100000 at all. There are usually ROM images residing there.

This is more likely to be a mis-emulation. Can you get a dump of the bytes
around 0xd680-0xd780? Then we could try and work out what the guest is
trying to execute, and see whether emulation is going wrong. A register dump
from the guest (dump_regs()) at the start of every call to opcode() might
also be useful.

 -- Keir

On 8/8/07 09:25, "Brady Chen" <chenchp@xxxxxxxxx> wrote:

> Hi Keir,
> I think the 7th issue I mentioned is the root cause,
> so I have a question.
> For real mode simulation, the simulator is running in the same space
> with the codes to-be-simulated? then how to protect simulator from
> being modified by to-be-simulated code?
> 
> can I change the address of vmxassist to a higher address? just try to
> give more space to the to-be-simulated windows.
> 
> On 8/8/07, Brady Chen <chenchp@xxxxxxxxx> wrote:
>> it's possible.
>> any ideas to trace the function stack of xen guest? like "bt" command in gdb.
>> 
>> I did some analysis:
>> 1. the call flow is opcode()->fetch8()->address()
>> 2. only the printf in address() will change the behaver of crash.
>> 3. and the crash EIP (0xD0800) is in the address() from the objdump.
>> 4. the address() will be invoked more then 40, 000 times in one
>> simulation, before the crash.
>> 5. seems there are no recursive invoking in opcode(), fetch8(), address()
>> 6. from the output of "xen dmesg", before the crash, a instructions
>> sequence is simulated several times (you could check the  previous
>> mails i send for "xen dmesg" output)
>> 7. before the trap, the simulated instruction is "movw %ax, *0xD07FE",
>> and the "*0xD07FE" is just the address of address(), (you could get
>> the objdump output from previous mails too), so i think it's the
>> simulation which crash the memory of address().
>> 
>> On 8/8/07, Keir Fraser <keir@xxxxxxxxxxxxx> wrote:
>>> Stack corruption/overflow, possibly?
>>> 
>>>  K.
>>> 
>>> On 7/8/07 17:06, "Brady Chen" <chenchp@xxxxxxxxx> wrote:
>>> 
>>>> Yes, the printfs are the only changes. once I remove these prints, the
>>>> trap comes back, with the same EIP (D0800)
>>>> 
>>>> I tried to keep the first two printfs, the trap comes with different
>>>> EIP(D19FD)
>>>> static unsigned
>>>> address(struct regs *regs, unsigned seg, unsigned off)
>>>> {
>>>>         uint64_t gdt_phys_base;
>>>>         unsigned long long entry;
>>>>         unsigned seg_base, seg_limit;
>>>>         unsigned entry_low, entry_high;
>>>> 
>>>>         printf("f 1\n");
>>>>         if (seg == 0) {
>>>>                 if (mode == VM86_REAL || mode == VM86_REAL_TO_PROTECTED)
>>>>                         return off;
>>>>                 else
>>>>                         panic("segment is zero, but not in real mode!\n");
>>>>         }
>>>> 
>>>>         printf("f 2\n");
>>>> 
>>>> xen dmesg output:
>>>> (XEN) HVM3: 0x0000D71F: 0xD00:0x071F (0) opc 0x83
>>>> (XEN) HVM3: f 1
>>>> (XEN) HVM3: f 2
>>>> (XEN) HVM3: 0x0000D71F: 0xD00:0x071F (0) external interrupt 8
>>>> (XEN) HVM3: f 1
>>>> (XEN) HVM3: f 1
>>>> (XEN) HVM3: f 1
>>>> (XEN) HVM3: Trap (0x6) while in real mode
>>>> (XEN) HVM3: eax        CFAE ecx           0 edx           0 ebx       D75B4
>>>> (XEN) HVM3: esp       D7564 ebp       D75A0 esi         71F edi           8
>>>> (XEN) HVM3: trapno        6 errno         0
>>>> (XEN) HVM3: eip       D19FD cs           10 eflags    13046
>>>> (XEN) HVM3: uesp       CFAE uss           0
>>>> (XEN) HVM3: ves       D4C44 vds           8 vfs          83 vgs         71F
>>>> (XEN) HVM3: cr0       50032 cr2           0 cr3           0 cr4         651
>>>> (XEN) HVM3:
>>>> (XEN) HVM3: Halt called from %eip 0xD037C
>>>> 
>>>> 
>>>> and the objdump shows that:
>>>> 000d1970 <interrupt>:
>>>>    d1970:       55                      push   %ebp
>>>>    d1971:       89 e5                   mov    %esp,%ebp
>>>>    d1973:       57                      push   %edi
>>>>    d1974:       89 d7                   mov    %edx,%edi
>>>>    d1976:       56                      push   %esi
>>>>   ....
>>>>    d19f8:       66 89 30                mov    %si,(%eax)
>>>>    d19fb:       31 d2                   xor    %edx,%edx
>>>>    d19fd:       8d 34 bd 00 00 00 00    lea    0x0(,%edi,4),%esi
>>>>    d1a04:       81 63 30 ff fd ff ff    andl   $0xfffffdff,0x30(%ebx)
>>>>    d1a0b:       89 d8                   mov    %ebx,%eax
>>>>    d1a0d:       89 34 24                mov    %esi,(%esp)
>>>> 
>>>> 
>>>> On 8/7/07, Keir Fraser <keir@xxxxxxxxxxxxx> wrote:
>>>>> Very weird. The emulations now aren't at the same address as before either
>>>>> (0xd4c3 rather than 0xd71b). Is the *only* difference that you added these
>>>>> printf()s -- is it at all possible that the guest is executing down a
>>>>> different path here for other reasons? If it's really down to the
>>>>> printf()s
>>>>> then I guess you'll have to shuffle/remove printf()s to get the old
>>>>> behaviour back.
>>>>> 
>>>>>  -- Keir
>>>>> 
>>>>> On 7/8/07 12:35, "Brady Chen" <chenchp@xxxxxxxxx> wrote:
>>>>> 
>>>>>> it's strange:
>>>>>> if i add these prints, i get " Unknown opcode", not "trap".
>>>>>> ===added printf
>>>>>> [root@localhost firmware]# hg diff -p  vmxassist/vm86.c
>>>>>> diff -r 6f18f5bdeea3 tools/firmware/vmxassist/vm86.c
>>>>>> --- a/tools/firmware/vmxassist/vm86.c   Mon Aug 06 15:33:42 2007 +0100
>>>>>> +++ b/tools/firmware/vmxassist/vm86.c   Tue Aug 07 19:33:55 2007 +0800
>>>>>> @@ -40,7 +40,7 @@ static struct regs saved_rm_regs;
>>>>>>  static struct regs saved_rm_regs;
>>>>>> 
>>>>>>  #ifdef DEBUG
>>>>>> -int traceset = 0;
>>>>>> +int traceset = ~0;
>>>>>> 
>>>>>>  char *states[] = {
>>>>>>         "<VM86_REAL>",
>>>>>> @@ -128,6 +128,7 @@ address(struct regs *regs, unsigned seg,
>>>>>>         unsigned seg_base, seg_limit;
>>>>>>         unsigned entry_low, entry_high;
>>>>>> 
>>>>>> +       printf("f 1\n");
>>>>>>         if (seg == 0) {
>>>>>>                 if (mode == VM86_REAL || mode == VM86_REAL_TO_PROTECTED)
>>>>>>                         return off;
>>>>>> @@ -135,12 +136,16 @@ address(struct regs *regs, unsigned seg,
>>>>>>                         panic("segment is zero, but not in real
>>>>>> mode!\n");
>>>>>>         }
>>>>>> 
>>>>>> +       printf("f 2\n");
>>>>>>         if (mode == VM86_REAL || seg > oldctx.gdtr_limit ||
>>>>>>                 (mode == VM86_REAL_TO_PROTECTED && regs->cs == seg))
>>>>>>                 return ((seg & 0xFFFF) << 4) + off;
>>>>>> 
>>>>>> +       printf("f 3\n");
>>>>>>         gdt_phys_base = guest_linear_to_phys(oldctx.gdtr_base);
>>>>>> +       printf("f 4\n");
>>>>>>         if (gdt_phys_base != (uint32_t)gdt_phys_base) {
>>>>>> +               printf("f 5\n");
>>>>>>                 printf("gdt base address above 4G\n");
>>>>>>                 cpuid_addr_value(gdt_phys_base + 8 * (seg >> 3), &entry);
>>>>>>         } else
>>>>>> @@ -152,14 +157,17 @@ address(struct regs *regs, unsigned seg,
>>>>>>         seg_base  = (entry_high & 0xFF000000) | ((entry >> 16) &
>>>>>> 0xFFFFFF);
>>>>>>         seg_limit = (entry_high & 0xF0000) | (entry_low & 0xFFFF);
>>>>>> 
>>>>>> +       printf("f 6\n");
>>>>>>         if (entry_high & 0x8000 &&
>>>>>>                 ((entry_high & 0x800000 && off >> 12 <= seg_limit) ||
>>>>>>                 (!(entry_high & 0x800000) && off <= seg_limit)))
>>>>>>                 return seg_base + off;
>>>>>> +       printf("f 7\n");
>>>>>> 
>>>>>>         panic("should never reach here in function address():\n\t"
>>>>>>                   "entry=0x%08x%08x, mode=%d, seg=0x%08x,
>>>>>> offset=0x%08x\n",
>>>>>>                   entry_high, entry_low, mode, seg, off);
>>>>>> +       printf("f 8\n");
>>>>>> 
>>>>>>         return 0;
>>>>>>  }
>>>>>> @@ -286,6 +294,7 @@ fetch8(struct regs *regs)
>>>>>>         unsigned addr = address(regs, regs->cs, MASK16(regs->eip));
>>>>>> 
>>>>>>         regs->eip++;
>>>>>> +       printf("f 9\n");
>>>>>>         return read8(addr);
>>>>>>  }
>>>>>> 
>>>>>> ===output when add many printf
>>>>>> (XEN) HVM12: 0x0000D4C3: 0xD00:0x04C3 (0) addr32addr32f 1
>>>>>> (XEN) HVM12: f 2
>>>>>> (XEN) HVM12: f 9
>>>>>> (XEN) HVM12: f 1
>>>>>> (XEN) HVM12: f 2
>>>>>> (XEN) HVM12: 0x0000D4C3: 0xD00:0x04C3 (0) data32data32f 1
>>>>>> (XEN) HVM12: f 2
>>>>>> (XEN) HVM12: f 9
>>>>>> (XEN) HVM12: f 1
>>>>>> (XEN) HVM12: f 2
>>>>>> (XEN) HVM12: 0x0000D4C3: 0xD00:0x04C3 (0) opc 0x83opc 0xD7704f 1
>>>>>> (XEN) HVM12: f 2
>>>>>> (XEN) HVM12: Unknown opcode at 0D00:04C3=0xD4C3
>>>>>> (XEN) HVM12: Halt called from %eip 0xD3B4A
>>>>>> 
>>>>>> On 8/7/07, Brady Chen <chenchp@xxxxxxxxx> wrote:
>>>>>>> Hi, yes, it's crashed in fetch8. it's very slow after I add this print
>>>>>>> info.
>>>>>>> the main function of fetch8 seems to be address(). seems crashed in
>>>>>>> address().
>>>>>>> 
>>>>>>> (XEN) HVM7: after write16 of movw
>>>>>>> (XEN) HVM7: top of opcode
>>>>>>> (XEN) HVM7: Before fetch8
>>>>>>> (XEN) HVM7: eax        7E80 ecx        2D1B edx           0 ebx
>>>>>>> 404E
>>>>>>> (XEN) HVM7: esp       D76F4 ebp        1FF0 esi         7BE edi
>>>>>>> C37FE
>>>>>>> (XEN) HVM7: trapno        D errno         0
>>>>>>> (XEN) HVM7: eip         71F cs          D00 eflags    33206
>>>>>>> (XEN) HVM7: uesp       CFB4 uss           0
>>>>>>> (XEN) HVM7: ves         D00 vds         D00 vfs           0 vgs
>>>>>>> 0
>>>>>>> (XEN) HVM7: cr0       50032 cr2           0 cr3           0 cr4
>>>>>>> 651
>>>>>>> (XEN) HVM7:
>>>>>>> (XEN) HVM7: Trap (0x6) while in real mode
>>>>>>> (XEN) HVM7: eax         D00 ecx           0 edx         71F ebx
>>>>>>> 89
>>>>>>> (XEN) HVM7: esp       D75E4 ebp       D7630 esi       D7620 edi
>>>>>>> D00
>>>>>>> (XEN) HVM7: trapno        6 errno         0
>>>>>>> (XEN) HVM7: eip       D0800 cs           10 eflags    13046
>>>>>>> (XEN) HVM7: uesp        71F uss       D76D4
>>>>>>> (XEN) HVM7: ves       D7610 vds       D3AB9 vfs       D762C vgs
>>>>>>> D7644
>>>>>>> (XEN) HVM7: cr0       50032 cr2           0 cr3           0 cr4
>>>>>>> 651
>>>>>>> (XEN) HVM7:
>>>>>>> (XEN) HVM7: 0xd0800 is 0xFFFF
>>>>>>> (XEN) HVM7: 0xd0804 is 0x7D8B
>>>>>>> (XEN) HVM7: Halt called from %eip 0xD037C
>>>>>>> 
>>>>>>> 
>>>>>>> On 8/7/07, Keir Fraser <keir@xxxxxxxxxxxxx> wrote:
>>>>>>>> How about trying:
>>>>>>>>  printf("Before fetch8\n");
>>>>>>>>  dump_regs(regs);
>>>>>>>>  opc = fetch8(regs);
>>>>>>>>  printf("After fetch8\n");
>>>>>>>>  switch (opc) { ...
>>>>>>>> 
>>>>>>>> This will let you see what eip is being fetched from, and also confirm
>>>>>>>> that
>>>>>>>> the crash happens within fetch8().
>>>>>>>> 
>>>>>>>> You could also try adding more printf()s inside fetch8() and address()
>>>>>>>> to
>>>>>>>> find out which specific bit of fetch8() is crashing (if that indeed the
>>>>>>>> function that is crashing).
>>>>>>>> 
>>>>>>>>  -- Keir
>>>>>>>> 
>>>>>>>> On 7/8/07 11:30, "Brady Chen" <chenchp@xxxxxxxxx> wrote:
>>>>>>>> 
>>>>>>>>> Hi, Keir,
>>>>>>>>> I made the change as you said:
>>>>>>>>> change diff is:
>>>>>>>>> [root@localhost firmware]# hg diff vmxassist/vm86.c
>>>>>>>>> diff -r 6f18f5bdeea3 tools/firmware/vmxassist/vm86.c
>>>>>>>>> --- a/tools/firmware/vmxassist/vm86.c   Mon Aug 06 15:33:42 2007 +0100
>>>>>>>>> +++ b/tools/firmware/vmxassist/vm86.c   Tue Aug 07 18:26:12 2007 +0800
>>>>>>>>> @@ -40,7 +40,7 @@ static struct regs saved_rm_regs;
>>>>>>>>>  static struct regs saved_rm_regs;
>>>>>>>>> 
>>>>>>>>>  #ifdef DEBUG
>>>>>>>>> -int traceset = 0;
>>>>>>>>> +int traceset = ~0;
>>>>>>>>> 
>>>>>>>>>  char *states[] = {
>>>>>>>>>         "<VM86_REAL>",
>>>>>>>>> @@ -620,6 +620,7 @@ movr(struct regs *regs, unsigned prefix,
>>>>>>>>>                         TRACE((regs, regs->eip - eip,
>>>>>>>>>                                 "movw %%%s, *0x%x", rnames[r], addr));
>>>>>>>>>                         write16(addr, MASK16(val));
>>>>>>>>> +                       printf("after write16 of movw\n");
>>>>>>>>>                 }
>>>>>>>>>                 return 1;
>>>>>>>>> 
>>>>>>>>> @@ -1305,6 +1306,7 @@ opcode(struct regs *regs)
>>>>>>>>>         unsigned eip = regs->eip;
>>>>>>>>>         unsigned opc, modrm, disp;
>>>>>>>>>         unsigned prefix = 0;
>>>>>>>>> +       printf("top of opcode\n");
>>>>>>>>> 
>>>>>>>>>         if (mode == VM86_PROTECTED_TO_REAL &&
>>>>>>>>>                 oldctx.cs_arbytes.fields.default_ops_size) {
>>>>>>>>> @@ -1712,6 +1714,8 @@ trap(int trapno, int errno, struct regs
>>>>>>>>>                 if (trapno == 14)
>>>>>>>>>                         printf("Page fault address 0x%x\n",
>>>>>>>>> get_cr2());
>>>>>>>>>                 dump_regs(regs);
>>>>>>>>> +               printf("0xd0800 is 0x%0x\n", *((unsigned
>>>>>>>>> short*)0xd0800));
>>>>>>>>> +               printf("0xd0804 is 0x%0x\n", *((unsigned
>>>>>>>>> short*)0xd0804));
>>>>>>>>>                 halt();
>>>>>>>>>         }
>>>>>>>>>  }
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> here is the output:
>>>>>>>>> (XEN) HVM6: top of opcode
>>>>>>>>> (XEN) HVM6: 0x0000D71F: 0xD00:0x071F (0) data32
>>>>>>>>> (XEN) HVM6: 0x0000D71F: 0xD00:0x071F (0) opc 0x83
>>>>>>>>> (XEN) HVM6: top of opcode
>>>>>>>>> (XEN) HVM6: 0x0000D71B: 0xD00:0x071B (0) %es:
>>>>>>>>> (XEN) HVM6: 0x0000D71B: 0xD00:0x071B (0) addr32
>>>>>>>>> (XEN) HVM6: 0x0000D71D: 0xD00:0x071D (0) movw %ax, *0xD07FE
>>>>>>>>> (XEN) HVM6: after write16 of movw
>>>>>>>>> (XEN) HVM6: top of opcode
>>>>>>>>> (XEN) HVM6: Trap (0x6) while in real mode
>>>>>>>>> (XEN) HVM6: eax         D00 ecx           0 edx         71F ebx
>>>>>>>>> 71E
>>>>>>>>> (XEN) HVM6: esp       D7554 ebp       D75A0 esi       D7590 edi
>>>>>>>>> D00
>>>>>>>>> (XEN) HVM6: trapno        6 errno         0
>>>>>>>>> (XEN) HVM6: eip       D0800 cs           10 eflags    13046
>>>>>>>>> (XEN) HVM6: uesp      D4C29 uss           2
>>>>>>>>> (XEN) HVM6: ves       D4C18 vds       D4D9C vfs       D07FE vgs
>>>>>>>>> D75B4
>>>>>>>>> (XEN) HVM6: cr0       50032 cr2           0 cr3           0 cr4
>>>>>>>>> 651
>>>>>>>>> (XEN) HVM6:
>>>>>>>>> (XEN) HVM6: 0xd0800 is 0xFFFF
>>>>>>>>> (XEN) HVM6: 0xd0804 is 0x7D8B
>>>>>>>>> (XEN) HVM6: Halt called from %eip 0xD037C
>>>>>>>>> 
>>>>>>>>> objdump:
>>>>>>>>>    d07ef:       e9 2f ff ff ff          jmp    d0723 <address+0x23>
>>>>>>>>>    d07f4:       8b 55 08                mov    0x8(%ebp),%edx
>>>>>>>>>    d07f7:       89 f8                   mov    %edi,%eax
>>>>>>>>>    d07f9:       8b 5d f4                mov    0xfffffff4(%ebp),%ebx
>>>>>>>>>    d07fc:       8b 75 f8                mov    0xfffffff8(%ebp),%esi
>>>>>>>>>    d07ff:       25 ff ff 00 00          and    $0xffff,%eax
>>>>>>>>>    d0804:       8b 7d fc                mov    0xfffffffc(%ebp),%edi
>>>>>>>>>    d0807:       89 ec                   mov    %ebp,%esp
>>>>>>>>>    d0809:       c1 e0 04                shl    $0x4,%eax
>>>>>>>>>    d080c:       01 d0                   add    %edx,%eax
>>>>>>>>>    d080e:       5d                      pop    %ebp
>>>>>>>>> 
>>>>>>>>> seems the memory is correct, it's crashed in opcode()
>>>>>>>>> and i think it's fetch8(regs) which crash the system. I tried
>>>>>>>>> fetch8(regs) in trap(), but it cause more traps, and let the hvm guest
>>>>>>>>> be reset.
>>>>>>>>> 
>>>>>>>>> On 8/7/07, Keir Fraser <keir@xxxxxxxxxxxxx> wrote:
>>>>>>>>>> On 7/8/07 10:29, "Keir Fraser" <keir@xxxxxxxxxxxxx> wrote:
>>>>>>>>>> 
>>>>>>>>>>> What would be useful is to try to add tracing to see how far
>>>>>>>>>>> vmxassist
>>>>>>>>>>> gets
>>>>>>>>>>> after its last line of tracing before the trap occurs. That last
>>>>>>>>>>> line
>>>>>>>>>>> is
>>>>>>>>>>> currently from vm86.c, line 620. You might try adding extra printf()
>>>>>>>>>>> statements imemdiately after the write16() on line 622, and also at
>>>>>>>>>>> the
>>>>>>>>>>> top
>>>>>>>>>>> of the opcode() function. We need to find out at what point
>>>>>>>>>>> vmxassist
>>>>>>>>>>> is
>>>>>>>>>>> jumping to this bogus address d0800.
>>>>>>>>>> 
>>>>>>>>>> Oh, another possibility is that vmxassist has been corrupted in
>>>>>>>>>> memory.
>>>>>>>>>> This
>>>>>>>>>> is particularly likely because, according to the objdump, the
>>>>>>>>>> 'instruction'
>>>>>>>>>> that starts at d0800 is actually valid (it'd be an ADD of some sort).
>>>>>>>>>> 
>>>>>>>>>> So, within trap() you might want to read say 16 bytes starting at
>>>>>>>>>> 0xd0800
>>>>>>>>>> and printf() them. So we can see if they match what objdump says
>>>>>>>>>> should
>>>>>>>>>> be
>>>>>>>>>> there.
>>>>>>>>>> 
>>>>>>>>>>  -- Keir
>>>>>>>>>> 
>>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> _______________________________________________
>>>>>>>>> Xen-devel mailing list
>>>>>>>>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>>>>>>>>> http://lists.xensource.com/xen-devel
>>>>>>>> 
>>>>>>>> 
>>>>>>> 
>>>>>> 
>>>>>> _______________________________________________
>>>>>> Xen-devel mailing list
>>>>>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>>>>>> http://lists.xensource.com/xen-devel
>>>>> 
>>>>> 
>>>> 
>>>> _______________________________________________
>>>> Xen-devel mailing list
>>>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>>>> http://lists.xensource.com/xen-devel
>>> 
>>> 
>> 
> 
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