The segmentfault when using xl create domU

The segmentfault when using xl create domU

[duqi]

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 Hi there,
We tried to create domU with command "xl -vvv create -d domU_01" and met the below fault:

root@linaro-alip:~/domU# xl -vvv create -d domU_01
Parsing config from domU_test
unable to format domain config as JSON (YAJL:1)
libxl: debug: libxl_create.c:1342:do_domain_create: ao 0x1df8610: create: how=(nil) callback=(nil) poller=0x1df8658
Segmentation fault

Here is the context of domU_01:

   kernel = "/root/domU/zImage"
   memory = "64" 
   name = "domU" 
   vcpus = 1 
   serial="pty"
   disk = [ 'phy:/dev/loop0,xvda,w' ]
   vif=[ 'mac=00:16:3e:56:af:69,bridge=virbr0,type=netfront', ]

Here is our version and conigurations about xen:
Xen ： git://xenbits.xen.org/xen.git and 'RELEASE-4.4.0' branch
we used "make dist-xen XEN_TARGET_ARCH=arm32 CROSS_COMPILE=arm-linux-gnueabihf- CONFIG_EARLY_PRINTK=sun7i" to compile the xen.

Could you give us some  advices?
Thank you very much.

duqi.


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Re: The segmentfault when using xl create domU

[Ian Campbell]

On Tue, 2014-04-15 at 10:33 +0800, duqi wrote:
>  Hi there,
> We tried to create domU with command "xl -vvv create -d domU_01" and
> met the below fault:
> 
> root@linaro-alip:~/domU# xl -vvv create -d domU_01

Does this happen if you drop the "-d"?

please could you run under gdb and grab a backtrace. Someth8ing like:
	# gdb --args xl -vvv create -d domU_01
	(gdb) run
	....
	crash!
	(gdb) bt

> Parsing config from domU_test
> unable to format domain config as JSON (YAJL:1)
> libxl: debug: libxl_create.c:1342:do_domain_create: ao 0x1df8610:
> create: how=(nil) callback=(nil) poller=0x1df8658
> Segmentation fault
> 
> Here is the context of domU_01:
>    kernel = "/root/domU/zImage"
>    memory = "64" 
>    name = "domU" 
>    vcpus = 1 
>    serial="pty"
>    disk = [ 'phy:/dev/loop0,xvda,w' ]
>    vif=[ 'mac=00:16:3e:56:af:69,bridge=virbr0,type=netfront', ]
> Here is our version and conigurations about xen:
> Xen ： git://xenbits.xen.org/xen.git and 'RELEASE-4.4.0' branch
> we used "make dist-xen XEN_TARGET_ARCH=arm32
> CROSS_COMPILE=arm-linux-gnueabihf- CONFIG_EARLY_PRINTK=sun7i" to
> compile the xen.
> 
> Could you give us some  advices?
> Thank you very much.
> 
> duqi.
> 
> 
> 
> 



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Re: The segmentfault when using xl create domU

[duqi]

At 2014-04-15 04:53:41, "Ian Campbell" <Ian.Campbell@citrix.com> wrote:
>On Tue, 2014-04-15 at 10:33 +0800, duqi wrote:
>>  Hi there,
>> We tried to create domU with command "xl -vvv create -d domU_01" and
>> met the below fault:
>> 
>> root@linaro-alip:~/domU# xl -vvv create -d domU_01
>
>Does this happen if you drop the "-d"?
>
>please could you run under gdb and grab a backtrace. Someth8ing like:
>	# gdb --args xl -vvv create -d domU_01
>	(gdb) run
>	....
>	crash!
>	(gdb) bt
>

Hi, here is the gdb output:
Program received signal SIGSEGV, Segmentation fault.
0xb6f6bc30 in memcpy (__len=16, __src=0xbefe6e0c, __dest=0x39488)
    at /usr/lib/gcc-cross/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/include/bits/string3.h:51
51      /usr/lib/gcc-cross/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/include/bits/string3.h: No such file or direc.
(gdb) bt
#0  0xb6f6bc30 in memcpy (__len=16, __src=0xbefe6e0c, __dest=0x39488)
    at /usr/lib/gcc-cross/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/include/bits/string3.h:51
#1  libxl_list_vm (ctx=ctx@entry=0x33030, 
    nb_vm_out=nb_vm_out@entry=0xbeffee30) at libxl.c:689
#2  0xb6f7b934 in libxl__domain_make (gc=gc@entry=0x393d0, 
    info=info@entry=0xbefff040, domid=domid@entry=0xbeffeec0)
    at libxl_create.c:613
#3  0xb6f7cadc in initiate_domain_create (dcs=0x398a8, egc=0xbeffeec4)
    at libxl_create.c:791
#4  do_domain_create (ctx=ctx@entry=0x33030, 
    d_config=d_config@entry=0xbefff040, domid=domid@entry=0xbeffef80, 
    restore_fd=restore_fd@entry=-1, 
    checkpointed_stream=checkpointed_stream@entry=0, ao_how=ao_how@entry=0x0, 
    aop_console_how=aop_console_how@entry=0x0) at libxl_create.c:1424
#5  0xb6f7d428 in libxl_domain_create_new (ctx=0x33030, 
    d_config=d_config@entry=0xbefff040, domid=domid@entry=0xbeffef80, 
    ao_how=ao_how@entry=0x0, aop_console_how=aop_console_how@entry=0x0)
    at libxl_create.c:1449
#6  0x00017040 in create_domain (dom_info=0xbeffefdc) at xl_cmdimpl.c:2283
#7  main_create (argc=<optimized out>, argv=<optimized out>)
    at xl_cmdimpl.c:4469
#8  0x0000db84 in main (argc=3, argv=0xbefff82c) at xl.c:362
(gdb) 

Many thanks.

duqi.

>> Parsing config from domU_test
>> unable to format domain config as JSON (YAJL:1)
>> libxl: debug: libxl_create.c:1342:do_domain_create: ao 0x1df8610:
>> create: how=(nil) callback=(nil) poller=0x1df8658
>> Segmentation fault
>> 
>> Here is the context of domU_01:
>>    kernel = "/root/domU/zImage"
>>    memory = "64" 
>>    name = "domU" 
>>    vcpus = 1 
>>    serial="pty"
>>    disk = [ 'phy:/dev/loop0,xvda,w' ]
>>    vif=[ 'mac=00:16:3e:56:af:69,bridge=virbr0,type=netfront', ]
>> Here is our version and conigurations about xen:
>> Xen ： git://xenbits.xen.org/xen.git and 'RELEASE-4.4.0' branch
>> we used "make dist-xen XEN_TARGET_ARCH=arm32
>> CROSS_COMPILE=arm-linux-gnueabihf- CONFIG_EARLY_PRINTK=sun7i" to
>> compile the xen.
>> 
>> Could you give us some  advices?
>> Thank you very much.
>> 
>> duqi.
>> 
>> 
>> 
>> 
>
>
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Re: The segmentfault when using xl create domU

[Julien Grall]

Hello,

On 04/15/2014 10:45 AM, duqi wrote:
> At 2014-04-15 04:53:41, "Ian Campbell" <Ian.Campbell@citrix.com> wrote:
>> On Tue, 2014-04-15 at 10:33 +0800, duqi wrote:
>>>  Hi there,
>>> We tried to create domU with command "xl -vvv create -d domU_01" and
>>> met the below fault:
>>>
>>> root@linaro-alip:~/domU# xl -vvv create -d domU_01
>>
>> Does this happen if you drop the "-d"?
>>
>> please could you run under gdb and grab a backtrace. Someth8ing like:
>> 	# gdb --args xl -vvv create -d domU_01
>> 	(gdb) run
>> 	....
>> 	crash!
>> 	(gdb) bt
>>
> 
> Hi, here is the gdb output:
> Program received signal SIGSEGV, Segmentation fault.
> 0xb6f6bc30 in memcpy (__len=16, __src=0xbefe6e0c, __dest=0x39488)
>     at /usr/lib/gcc-cross/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/include/bits/string3.h:51
> 51      /usr/lib/gcc-cross/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/include/bits/string3.h: No such file or direc.
> (gdb) bt
> #0  0xb6f6bc30 in memcpy (__len=16, __src=0xbefe6e0c, __dest=0x39488)
>     at /usr/lib/gcc-cross/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/include/bits/string3.h:51
> #1  libxl_list_vm (ctx=ctx@entry=0x33030, 
>     nb_vm_out=nb_vm_out@entry=0xbeffee30) at libxl.c:689
> #2  0xb6f7b934 in libxl__domain_make (gc=gc@entry=0x393d0, 
>     info=info@entry=0xbefff040, domid=domid@entry=0xbeffeec0)
>     at libxl_create.c:613
> #3  0xb6f7cadc in initiate_domain_create (dcs=0x398a8, egc=0xbeffeec4)
>     at libxl_create.c:791
> #4  do_domain_create (ctx=ctx@entry=0x33030, 
>     d_config=d_config@entry=0xbefff040, domid=domid@entry=0xbeffef80, 
>     restore_fd=restore_fd@entry=-1, 
>     checkpointed_stream=checkpointed_stream@entry=0, ao_how=ao_how@entry=0x0, 
>     aop_console_how=aop_console_how@entry=0x0) at libxl_create.c:1424
> #5  0xb6f7d428 in libxl_domain_create_new (ctx=0x33030, 
>     d_config=d_config@entry=0xbefff040, domid=domid@entry=0xbeffef80, 
>     ao_how=ao_how@entry=0x0, aop_console_how=aop_console_how@entry=0x0)
>     at libxl_create.c:1449
> #6  0x00017040 in create_domain (dom_info=0xbeffefdc) at xl_cmdimpl.c:2283
> #7  main_create (argc=<optimized out>, argv=<optimized out>)
>     at xl_cmdimpl.c:4469
> #8  0x0000db84 in main (argc=3, argv=0xbefff82c) at xl.c:362
> (gdb) 

It's a compiler bug. For some reasons gcc doesn't generate the right assembly
when -O1 is specified on the command line. Which version of gcc do you use(4.7.*?)?
Which distribution are you using? 
Can you also call disas the crash and copy the output?

Gcc 4.8 doesn't seem to be affected.

FYI, I got this output from 4.7 with Linaro Ubuntu raring (gcc 4.7.3).

   0x76f71bd0 <+224>:   mov     r5, #0
   0x76f71bd4 <+228>:   mov     r4, r5
   0x76f71bd8 <+232>:   mov     r7, r5                                                <= r7 = r5 = 0
   0x76f71bdc <+236>:   sub     r6, r11, #98304 ; 0x18000
   0x76f71be0 <+240>:   sub     r6, r6, #36     ; 0x24
   0x76f71be4 <+244>:   mov     r9, r5
   0x76f71be8 <+248>:   str     r8, [r12, #-68] ; 0x44
   0x76f71bec <+252>:   sub     r3, r11, #98304 ; 0x18000
   0x76f71bf0 <+256>:   ldr     r0, [r3, #-68]  ; 0x44
   0x76f71bf4 <+260>:   ldrh    r1, [r6, r5]
   0x76f71bf8 <+264>:   mov     r2, r9
   0x76f71bfc <+268>:   bl      0x76f6d6ac
   0x76f71c00 <+272>:   cmp     r0, #0
   0x76f71c04 <+276>:   bne     0x76f71c50 <libxl_list_vm+352>
   0x76f71c08 <+280>:   add     r8, r7, r7, lsl #2                                     <= Last time we set r8 = r7 << 2 = 0
   0x76f71c0c <+284>:   sub     r12, r11, #98304        ; 0x18000
   0x76f71c10 <+288>:   str     r8, [r12, #-56] ; 0x38
   0x76f71c14 <+292>:   ldr     r3, [r12, #-60] ; 0x3c
   0x76f71c18 <+296>:   add     lr, r3, r8, lsl #2
   0x76f71c1c <+300>:   add     r12, r4, r4, lsl #1
   0x76f71c20 <+304>:   add     r12, r6, r12, lsl #5
   0x76f71c24 <+308>:   add     r12, r12, #76   ; 0x4c
   0x76f71c28 <+312>:   ldm     r12!, {r0, r1, r2, r3}
   0x76f71c2c <+316>:   mov     r12, r8
=> 0x76f71c30 <+320>:   ldr     r8, [r8, #-60]  ; 0x3c                                 <= r8 (=0) is dereferenced


Regards,


-- 
Julien Grall

Re: The segmentfault when using xl create domU

[Wei Huang]

On 04/15/2014 09:12 AM, Julien Grall wrote:
> Hello,
>
> On 04/15/2014 10:45 AM, duqi wrote:
>> At 2014-04-15 04:53:41, "Ian Campbell" <Ian.Campbell@citrix.com> wrote:
>>> On Tue, 2014-04-15 at 10:33 +0800, duqi wrote:
>>>>   Hi there,
>>>> We tried to create domU with command "xl -vvv create -d domU_01" and
>>>> met the below fault:
>>>>
>>>> root@linaro-alip:~/domU# xl -vvv create -d domU_01
>>>
>>> Does this happen if you drop the "-d"?
>>>
>>> please could you run under gdb and grab a backtrace. Someth8ing like:
>>> 	# gdb --args xl -vvv create -d domU_01
>>> 	(gdb) run
>>> 	....
>>> 	crash!
>>> 	(gdb) bt
>>>
>>
>> Hi, here is the gdb output:
>> Program received signal SIGSEGV, Segmentation fault.
>> 0xb6f6bc30 in memcpy (__len=16, __src=0xbefe6e0c, __dest=0x39488)
>>      at /usr/lib/gcc-cross/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/include/bits/string3.h:51
>> 51      /usr/lib/gcc-cross/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/include/bits/string3.h: No such file or direc.
>> (gdb) bt
>> #0  0xb6f6bc30 in memcpy (__len=16, __src=0xbefe6e0c, __dest=0x39488)
>>      at /usr/lib/gcc-cross/arm-linux-gnueabihf/4.7/../../../../arm-linux-gnueabihf/include/bits/string3.h:51
>> #1  libxl_list_vm (ctx=ctx@entry=0x33030,
>>      nb_vm_out=nb_vm_out@entry=0xbeffee30) at libxl.c:689
>> #2  0xb6f7b934 in libxl__domain_make (gc=gc@entry=0x393d0,
>>      info=info@entry=0xbefff040, domid=domid@entry=0xbeffeec0)
>>      at libxl_create.c:613
>> #3  0xb6f7cadc in initiate_domain_create (dcs=0x398a8, egc=0xbeffeec4)
>>      at libxl_create.c:791
>> #4  do_domain_create (ctx=ctx@entry=0x33030,
>>      d_config=d_config@entry=0xbefff040, domid=domid@entry=0xbeffef80,
>>      restore_fd=restore_fd@entry=-1,
>>      checkpointed_stream=checkpointed_stream@entry=0, ao_how=ao_how@entry=0x0,
>>      aop_console_how=aop_console_how@entry=0x0) at libxl_create.c:1424
>> #5  0xb6f7d428 in libxl_domain_create_new (ctx=0x33030,
>>      d_config=d_config@entry=0xbefff040, domid=domid@entry=0xbeffef80,
>>      ao_how=ao_how@entry=0x0, aop_console_how=aop_console_how@entry=0x0)
>>      at libxl_create.c:1449
>> #6  0x00017040 in create_domain (dom_info=0xbeffefdc) at xl_cmdimpl.c:2283
>> #7  main_create (argc=<optimized out>, argv=<optimized out>)
>>      at xl_cmdimpl.c:4469
>> #8  0x0000db84 in main (argc=3, argv=0xbefff82c) at xl.c:362
>> (gdb)
>
> It's a compiler bug. For some reasons gcc doesn't generate the right assembly
> when -O1 is specified on the command line. Which version of gcc do you use(4.7.*?)?
> Which distribution are you using?
> Can you also call disas the crash and copy the output?
>
> Gcc 4.8 doesn't seem to be affected.
>
> FYI, I got this output from 4.7 with Linaro Ubuntu raring (gcc 4.7.3).
>
>     0x76f71bd0 <+224>:   mov     r5, #0
>     0x76f71bd4 <+228>:   mov     r4, r5
>     0x76f71bd8 <+232>:   mov     r7, r5                                                <= r7 = r5 = 0
>     0x76f71bdc <+236>:   sub     r6, r11, #98304 ; 0x18000
>     0x76f71be0 <+240>:   sub     r6, r6, #36     ; 0x24
>     0x76f71be4 <+244>:   mov     r9, r5
>     0x76f71be8 <+248>:   str     r8, [r12, #-68] ; 0x44
>     0x76f71bec <+252>:   sub     r3, r11, #98304 ; 0x18000
>     0x76f71bf0 <+256>:   ldr     r0, [r3, #-68]  ; 0x44
>     0x76f71bf4 <+260>:   ldrh    r1, [r6, r5]
>     0x76f71bf8 <+264>:   mov     r2, r9
>     0x76f71bfc <+268>:   bl      0x76f6d6ac
>     0x76f71c00 <+272>:   cmp     r0, #0
>     0x76f71c04 <+276>:   bne     0x76f71c50 <libxl_list_vm+352>
>     0x76f71c08 <+280>:   add     r8, r7, r7, lsl #2                                     <= Last time we set r8 = r7 << 2 = 0
>     0x76f71c0c <+284>:   sub     r12, r11, #98304        ; 0x18000
>     0x76f71c10 <+288>:   str     r8, [r12, #-56] ; 0x38
>     0x76f71c14 <+292>:   ldr     r3, [r12, #-60] ; 0x3c
>     0x76f71c18 <+296>:   add     lr, r3, r8, lsl #2
>     0x76f71c1c <+300>:   add     r12, r4, r4, lsl #1
>     0x76f71c20 <+304>:   add     r12, r6, r12, lsl #5
>     0x76f71c24 <+308>:   add     r12, r12, #76   ; 0x4c
>     0x76f71c28 <+312>:   ldm     r12!, {r0, r1, r2, r3}
>     0x76f71c2c <+316>:   mov     r12, r8
> => 0x76f71c30 <+320>:   ldr     r8, [r8, #-60]  ; 0x3c                                 <= r8 (=0) is dereferenced
>
I saw the same thing on my system and ack'ed that this is compiler 
related. My compiler is 4.7.3. I was able to fix it with the following hack:

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 730f6e1..14eac6b 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -667,7 +667,8 @@ libxl_vminfo * libxl_list_vm(libxl_ctx *ctx, int 
*nb_vm_out)
  {
      GC_INIT(ctx);
      libxl_vminfo *ptr = NULL;
-    int idx, i, ret;
+    volatile int idx, i;
+    int ret;
      xc_domaininfo_t info[1024];

      ret = xc_domain_getinfolist(ctx->xch, 1, ARRAY_SIZE(info), info);

>
> Regards,
>
>

Re: The segmentfault when using xl create domU

[duqi]

It's a compiler bug. For some reasons gcc doesn't generate the right assembly
when -O1 is specified on the command line. Which version of gcc do you use(4.7.*?)?
Which distribution are you using? 
Can you also call disas the crash and copy the output?

Gcc 4.8 doesn't seem to be affected.

Hello, 

Thank you very much for your answer!
I replace the gcc 4.7.2 with the gcc 4.8.1 and everything works. 

On the other hand, when I used gcc 4.7.2, I have made the below changes like here:

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 730f6e1..7c8a5cc 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -668,7 +668,8 @@ libxl_vminfo * libxl_list_vm(libxl_ctx *ctx, int *nb_vm_out)
     GC_INIT(ctx);
     libxl_vminfo *ptr = NULL;
     int idx, i, ret;
-    xc_domaininfo_t info[1024];
+    //xc_domaininfo_t info[1024];
+    xc_domaininfo_t info[16];
 
     ret = xc_domain_getinfolist(ctx->xch, 1, ARRAY_SIZE(info), info);
     if (ret < 0) {

As a result , it also works. I'm not sure if this is useful to you . 

Many thanks again.

duqi.

Re: The segmentfault when using xl create domU

[Ian Campbell]

On Tue, 2014-04-15 at 17:07 -0500, Wei Huang wrote:
> > It's a compiler bug. For some reasons gcc doesn't generate the right assembly
> > when -O1 is specified on the command line. Which version of gcc do you use(4.7.*?)?
> > Which distribution are you using?
> > Can you also call disas the crash and copy the output?
> >
> > Gcc 4.8 doesn't seem to be affected.
> >
> > FYI, I got this output from 4.7 with Linaro Ubuntu raring (gcc 4.7.3).
> >[...]
> I saw the same thing on my system and ack'ed that this is compiler 
> related. My compiler is 4.7.3. I was able to fix it with the following hack:

Are you also using the Linaro compiler by any chance?

I've added warnings to
http://wiki.xen.org/wiki/Xen_ARM_with_Virtualization_Extensions/CrossCompiling
and
http://wiki.xen.org/wiki/Xen_ARM_with_Virtualization_Extensions#Building_Xen_on_ARM

Re: The segmentfault when using xl create domU

[Wei Huang]

On 04/16/2014 04:21 AM, Ian Campbell wrote:
> On Tue, 2014-04-15 at 17:07 -0500, Wei Huang wrote:
>>> It's a compiler bug. For some reasons gcc doesn't generate the right assembly
>>> when -O1 is specified on the command line. Which version of gcc do you use(4.7.*?)?
>>> Which distribution are you using?
>>> Can you also call disas the crash and copy the output?
>>>
>>> Gcc 4.8 doesn't seem to be affected.
>>>
>>> FYI, I got this output from 4.7 with Linaro Ubuntu raring (gcc 4.7.3).
>>> [...]
>> I saw the same thing on my system and ack'ed that this is compiler
>> related. My compiler is 4.7.3. I was able to fix it with the following hack:
>
> Are you also using the Linaro compiler by any chance?
I think so. Here is the GCC --version info:
arm-linux-gnueabihf-gcc (Ubuntu/Linaro 4.7.3-1ubuntu1) 4.7.3

>
> I've added warnings to
> http://wiki.xen.org/wiki/Xen_ARM_with_Virtualization_Extensions/CrossCompiling
> and
> http://wiki.xen.org/wiki/Xen_ARM_with_Virtualization_Extensions#Building_Xen_on_ARM
>
>

Re: The segmentfault when using xl create domU

[Julien Grall]

On 04/16/2014 04:50 PM, Wei Huang wrote:
> On 04/16/2014 04:21 AM, Ian Campbell wrote:
>> On Tue, 2014-04-15 at 17:07 -0500, Wei Huang wrote:
>>>> It's a compiler bug. For some reasons gcc doesn't generate the right
>>>> assembly
>>>> when -O1 is specified on the command line. Which version of gcc do
>>>> you use(4.7.*?)?
>>>> Which distribution are you using?
>>>> Can you also call disas the crash and copy the output?
>>>>
>>>> Gcc 4.8 doesn't seem to be affected.
>>>>
>>>> FYI, I got this output from 4.7 with Linaro Ubuntu raring (gcc 4.7.3).
>>>> [...]
>>> I saw the same thing on my system and ack'ed that this is compiler
>>> related. My compiler is 4.7.3. I was able to fix it with the
>>> following hack:
>>
>> Are you also using the Linaro compiler by any chance?
> I think so. Here is the GCC --version info:
> arm-linux-gnueabihf-gcc (Ubuntu/Linaro 4.7.3-1ubuntu1) 4.7.3

Linaro as shipped a new version of GCC 4.7 (based on 4.7.4) a couple of
days ago.

They don't plan to release another version of 4.7. So I don't think it's
useful to report the bug. Unless it's also happen with upstream GCC.

Regards,

-- 
Julien Grall