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Greetings:

I've encountered a problem running gdb + gdbsx on Xen 4.11.1, running Linux kernel 4.18.0-15 on Ubuntu 18.04. Pertinent info is below.

Thanks in advance for any help!

--Matt

Here's my guest config file:

$ cat xen-vms/ub1804-dev.hvm
type = "hvm"
name = "ub18-dev-work"
viridian = 1

# Initial and max memory allocation (MB)
memory = 2048
maxmem = 2048

vcpus = 1
acpi = 1
apic = 1
# values: disabled, mixed, external, limited
altp2m = "mixed"
vif = [ 'bridge=xenbr0' ]
disk = [ 'phy:/dev/ubuntu-vg/xen_ubuntu_dev,xvda,w'
        ,'file:/home/matt/iso/ubuntu-18.04.1-desktop-amd64.iso,hdc:cdrom,r' ]
boot = 'c' # hard disk (c) / cdrom (d)
console = 1
_on_poweroff_ = "destroy"
on_reboot   = "restart"
on_crash    = "preserve"

Here are the two usages of gdbsx (both from Dom0). Note that domain 2 is 64 bit.

# xl list
Name                                        ID   Mem VCPUs      State   Time(s)
Domain-0                                     0 30098     8     r-----    8724.5
ub18-dev-work                                2 2040     1     -b----      24.9

# gdbsx -c 2 64 0
===> Context for DOMID:2

--> VCPU:0
rip:ffffffff9b1f52e6 rsp:ffffffff9bc03e10 flags:0000000000000246
rax:ffffffff9b1f4ff0 rbx:0000000000000000 rcx:ffffffff9bc6ff60
rdx:0000000000066e16 rsi:ffffffff9bc2ebc8 rdi:0000000000000000
r08:00000000505563be r09:0000000000000000 r10:0000000000000008
r11:0000000000000008 r12:0000000000000000 r13:0000000000000000
r14:0000000000000000 r15:0000000000000000 rbp:ffffffff9bc03e10
cs:0000000000000010 ds:0000000000000000 fs:0000000000000000 gs:0000000000000000

Call Trace:
   [ffffffff9b1f52e6]
   [ffffffff9bc03e38]
   [ffffffff9b1f5010]
   [ffffffff9be85ee0]
   [ffffffff9bc03e48]
   [ffffffff9a8394c5]
   [ffffffff9bc03e58]
   [ffffffff9b1f544c]
   [ffffffff9bc03ea0]
   [ffffffff9a8c3c84]
   [ffffffff9bf8c920]
# gdbsx -a 2 64 3333
Listening on port 3333
Remote debugging from host 127.0.0.1
readchar: Got EOF
Detaching from guest
Exiting.. Remote side has terminated connection

And here's the corresponding usage of gdb that led to the failure in gdbsx (again, from Dom0):

$ gdb -q
Currently logging to "/home/matt/gdb.log".
Logs will overwrite the log file.
Output will be logged and displayed.
gdb> set architecture i386:x86-64
The target architecture is assumed to be i386:x86-64
gdb> target remote localhost:3333
Remote debugging using localhost:3333
warning: No executable has been specified and target does not support
determining executable automatically. Try using the "file" command.
Truncated register 26 in remote 'g' packet
gdb> show version
GNU gdb (Ubuntu 8.2-0ubuntu1~18.04) 8.2
Copyright (C) 2018 Free Software Foundation, Inc.

[Xen-users] gdbsx +gdb: failure on Xen 4.11.1