need help when libxenlight.so is used

need help when libxenlight.so is used

[Kun Cheng]

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Hello Xen devs,

I'm learning code in xen-4.10.0/tools/xl to find out how to program with
libxl.

I've trying to use libxenlight.so (compiled and installed from xen 4.10.0
source code) to control my vms from my own code until I met this issue.
Now my test code follows xl_vmmcontrol.c and tries to create a VM from its
config file (file can be used to successfully create a vm with 'xl create').

My Xen make is successful and I can use 'xl' to manage all vms.

When I test my own code, I got such an error in dmesg"

test[16678]: segfault at 18 ip 00007f69fa6526ad sp 00007ffe1eadedf0 error 4
in libxenlight.so.4.10.0[7f69fa61a000+bc000] in dmesg

and also segmentation fault in my terminal.

I dumped my debugging info, hoping could give everyone some clue.

FYI, my program was compiled with:

gcc -m64 -pthread -std=gnu99  -g xl_executor.c xl_parse.c  xl_utils.c
xl_nic.c -lxenlight -lxlutil -lxentoollog  -lyajl  -o test

where xl_executor.c is my code of creating a vm, all other c file are
copied from tools/xl/

GDB bebugging info:

Breakpoint 3, parse_config_data (config_source=0x7fffffffe360
"/data/chengkun/vms/vm4/vm4.cfg",
    config_data=0x6155f0 "# ", '=' <repeats 69 times>, "\n# Example HVM
guest configuration\n# ", '=' <repeats 69 times>, "\n#\n# This is a fairly
m"..., config_len=1543,
    d_config=0x7fffffffdde0) at xl_parse.c:993

993         if (libxl_cpu_bitmap_alloc(ctx, &b_info->avail_vcpus, l)) {

(gdb) p *c_info
$3 = {type = LIBXL_DOMAIN_TYPE_HVM, hap = {val = 0}, oos = {val = 0},
ssidref = 0, ssid_label = 0x0, name = 0x6154f0 "test_vm", uuid = {
    uuid = "O\374\032\231+\330A\265\213rVސ\375\020\270"}, xsdata = 0x0,
platformdata = 0x0, poolid = 0, pool_name = 0x0, run_hotplug_scripts = {val
= 1}, driver_domain = {
    val = 0}}

(gdb) p *b_info
$4 = {max_vcpus = 0, avail_vcpus = {size = 0, map = 0x0}, cpumap = {size =
0, map = 0x0}, nodemap = {size = 0, map = 0x0}, num_vcpu_hard_affinity = 0,
  vcpu_hard_affinity = 0x0, num_vcpu_soft_affinity = 0, vcpu_soft_affinity
= 0x0, numa_placement = {val = 0}, tsc_mode = LIBXL_TSC_MODE_DEFAULT,
max_memkb = 4194304,
  target_memkb = 2097152, video_memkb = 18446744073709551615, shadow_memkb
= 18446744073709551615, rtc_timeoffset = 0, exec_ssidref = 0,
exec_ssid_label = 0x0,
  localtime = {val = 0}, disable_migrate = {val = 0}, cpuid = 0x0,
blkdev_start = 0x0, num_vnuma_nodes = 0, vnuma_nodes = 0x0,
max_grant_frames = 32,
  max_maptrack_frames = 1024, device_model_version =
LIBXL_DEVICE_MODEL_VERSION_UNKNOWN, device_model_stubdomain = {val = 0},
device_model = 0x0, device_model_ssidref = 0,
  device_model_ssid_label = 0x0, device_model_user = 0x0, extra = 0x0,
extra_pv = 0x0, extra_hvm = 0x0, sched_params = {sched =
LIBXL_SCHEDULER_UNKNOWN, weight = -1,
    cap = -1, period = -1, budget = -1, extratime = -1, slice = -1, latency
= -1}, num_ioports = 0, ioports = 0x0, num_irqs = 0, irqs = 0x0, num_iomem
= 0, iomem = 0x0,
  claim_mode = {val = 0}, event_channels = 0, kernel = 0x0, cmdline = 0x0,
ramdisk = 0x0, device_tree = 0x0, acpi = {val = 0}, bootloader = 0x0,
bootloader_args = 0x0,
  timer_mode = LIBXL_TIMER_MODE_UNKNOWN, nested_hvm = {val = 0}, apic =
{val = 0}, dm_restrict = {val = 0}, type = LIBXL_DOMAIN_TYPE_HVM, u = {hvm
= {firmware = 0x0,
      bios = LIBXL_BIOS_TYPE_UNKNOWN, pae = {val = 0}, apic = {val = 0},
acpi = {val = 0}, acpi_s3 = {val = 0}, acpi_s4 = {val = 0},
acpi_laptop_slate = {val = 0}, nx = {
        val = 0}, viridian = {val = 0}, viridian_enable = {size = 0, map =
0x0}, viridian_disable = {size = 0, map = 0x0}, timeoffset = 0x0, hpet =
{val = 0}, vpt_align = {
        val = 0}, mmio_hole_memkb = 18446744073709551615, timer_mode =
LIBXL_TIMER_MODE_UNKNOWN, nested_hvm = {val = 0}, altp2m = {val = 0},
system_firmware = 0x0,
      smbios_firmware = 0x0, acpi_firmware = 0x0, hdtype =
LIBXL_HDTYPE_IDE, nographic = {val = 0}, vga = {kind =
LIBXL_VGA_INTERFACE_TYPE_UNKNOWN}, vnc = {enable = {
          val = 0}, listen = 0x0, passwd = 0x0, display = 0, findunused =
{val = 0}}, keymap = 0x0, sdl = {enable = {val = 0}, opengl = {val = 0},
display = 0x0,
        xauthority = 0x0}, spice = {enable = {val = 0}, port = 0, tls_port
= 0, host = 0x0, disable_ticketing = {val = 0}, passwd = 0x0, agent_mouse =
{val = 0},
        vdagent = {val = 0}, clipboard_sharing = {val = 0}, usbredirection
= 0, image_compression = 0x0, streaming_video = 0x0}, gfx_passthru = {val =
0},
      gfx_passthru_kind = LIBXL_GFX_PASSTHRU_KIND_DEFAULT, serial = 0x0,
boot = 0x0, usb = {val = 0}, usbversion = 0, usbdevice = 0x0, soundhw =
0x0, xen_platform_pci = {
        val = 0}, usbdevice_list = 0x0, vendor_device =
LIBXL_VENDOR_DEVICE_NONE, ms_vm_genid = {bytes = '\000' <repeats 15
times>}, serial_list = 0x0, rdm = {
        strategy = LIBXL_RDM_RESERVE_STRATEGY_IGNORE, policy =
LIBXL_RDM_RESERVE_POLICY_INVALID}, rdm_mem_boundary_memkb =
18446744073709551615, mca_caps = 0}, pv = {
      kernel = 0x0, slack_memkb = 0, bootloader = 0x0, bootloader_args =
0x0, cmdline = 0x0, ramdisk = 0x0, features = 0x0, e820_host = {val = 0}}},
arch_arm = {
    gic_version = LIBXL_GIC_VERSION_DEFAULT, vuart =
LIBXL_VUART_TYPE_UNKNOWN}, altp2m = LIBXL_ALTP2M_MODE_DISABLED}

(gdb) p ctx
$5 = (libxl_ctx *) 0x0

(gdb) p *ctx
$6 = <incomplete type>

(gdb) s

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7b476ad in libxl.ptr_add () from
/usr/local/lib/libxenlight.so.4.10


Is that related to my compiling cmd?
Any help is appreciated.

Thanks,
K

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Re: need help when libxenlight.so is used

[Wei Liu]

On Sat, May 12, 2018 at 08:55:46PM +0800, Kun Cheng wrote:
> Hello Xen devs,
> 
> I'm learning code in xen-4.10.0/tools/xl to find out how to program with
> libxl.
> 
> I've trying to use libxenlight.so (compiled and installed from xen 4.10.0
> source code) to control my vms from my own code until I met this issue.
> Now my test code follows xl_vmmcontrol.c and tries to create a VM from its
> config file (file can be used to successfully create a vm with 'xl create').
> 
> My Xen make is successful and I can use 'xl' to manage all vms.
> 
> When I test my own code, I got such an error in dmesg"
> 
> test[16678]: segfault at 18 ip 00007f69fa6526ad sp 00007ffe1eadedf0 error 4
> in libxenlight.so.4.10.0[7f69fa61a000+bc000] in dmesg
> 
> and also segmentation fault in my terminal.
> 
> I dumped my debugging info, hoping could give everyone some clue.
> 
> FYI, my program was compiled with:
> 
> gcc -m64 -pthread -std=gnu99  -g xl_executor.c xl_parse.c  xl_utils.c
> xl_nic.c -lxenlight -lxlutil -lxentoollog  -lyajl  -o test
> 
> where xl_executor.c is my code of creating a vm, all other c file are
> copied from tools/xl/
> 
> GDB bebugging info:
> 
> Breakpoint 3, parse_config_data (config_source=0x7fffffffe360
> "/data/chengkun/vms/vm4/vm4.cfg",
>     config_data=0x6155f0 "# ", '=' <repeats 69 times>, "\n# Example HVM
> guest configuration\n# ", '=' <repeats 69 times>, "\n#\n# This is a fairly
> m"..., config_len=1543,
>     d_config=0x7fffffffdde0) at xl_parse.c:993
> 
> 993         if (libxl_cpu_bitmap_alloc(ctx, &b_info->avail_vcpus, l)) {
> 

One possibility: you didn't follow the convention of using libxl types,
which means you get memory corruption all over the place.

See  libxl.h:L490 for more information.

But for a more likely explanation, see below.

>     gic_version = LIBXL_GIC_VERSION_DEFAULT, vuart =
> LIBXL_VUART_TYPE_UNKNOWN}, altp2m = LIBXL_ALTP2M_MODE_DISABLED}
> 
> (gdb) p ctx
> $5 = (libxl_ctx *) 0x0

A NULL pointer? See xl.c:xl_ctx_alloc.

Wei.

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Re: need help when libxenlight.so is used

[Kun Cheng]

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Thank you, Wei.
I have solved it.  The error accured as 'ctx' was not correctly initailized.

On Tue, May 15, 2018 at 1:11 AM Wei Liu <wei.liu2@citrix.com> wrote:

> On Sat, May 12, 2018 at 08:55:46PM +0800, Kun Cheng wrote:
> > Hello Xen devs,
> >
> > I'm learning code in xen-4.10.0/tools/xl to find out how to program with
> > libxl.
> >
> > I've trying to use libxenlight.so (compiled and installed from xen 4.10.0
> > source code) to control my vms from my own code until I met this issue.
> > Now my test code follows xl_vmmcontrol.c and tries to create a VM from
> its
> > config file (file can be used to successfully create a vm with 'xl
> create').
> >
> > My Xen make is successful and I can use 'xl' to manage all vms.
> >
> > When I test my own code, I got such an error in dmesg"
> >
> > test[16678]: segfault at 18 ip 00007f69fa6526ad sp 00007ffe1eadedf0
> error 4
> > in libxenlight.so.4.10.0[7f69fa61a000+bc000] in dmesg
> >
> > and also segmentation fault in my terminal.
> >
> > I dumped my debugging info, hoping could give everyone some clue.
> >
> > FYI, my program was compiled with:
> >
> > gcc -m64 -pthread -std=gnu99  -g xl_executor.c xl_parse.c  xl_utils.c
> > xl_nic.c -lxenlight -lxlutil -lxentoollog  -lyajl  -o test
> >
> > where xl_executor.c is my code of creating a vm, all other c file are
> > copied from tools/xl/
> >
> > GDB bebugging info:
> >
> > Breakpoint 3, parse_config_data (config_source=0x7fffffffe360
> > "/data/chengkun/vms/vm4/vm4.cfg",
> >     config_data=0x6155f0 "# ", '=' <repeats 69 times>, "\n# Example HVM
> > guest configuration\n# ", '=' <repeats 69 times>, "\n#\n# This is a
> fairly
> > m"..., config_len=1543,
> >     d_config=0x7fffffffdde0) at xl_parse.c:993
> >
> > 993         if (libxl_cpu_bitmap_alloc(ctx, &b_info->avail_vcpus, l)) {
> >
>
> One possibility: you didn't follow the convention of using libxl types,
> which means you get memory corruption all over the place.
>
> See  libxl.h:L490 for more information.
>
> But for a more likely explanation, see below.
>
> >     gic_version = LIBXL_GIC_VERSION_DEFAULT, vuart =
> > LIBXL_VUART_TYPE_UNKNOWN}, altp2m = LIBXL_ALTP2M_MODE_DISABLED}
> >
> > (gdb) p ctx
> > $5 = (libxl_ctx *) 0x0
>
> A NULL pointer? See xl.c:xl_ctx_alloc.
>
> Wei.
>

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