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Re: [Xen-devel] The segmentfault when using xl create domU
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@xxxxxxxxxx> 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,
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