The crash extension 'gcore' fails to retrieve a complete core dump.

Issue

• Running gcore command on a vmcore reports "invalid structure member offset: thread_struct_fs"

crash> set 1451
    PID: 1451
COMMAND: "rsyslogd"
   TASK: ffff8d15f748b100  [THREAD_INFO: ffff8d15f748b100]
    CPU: 0
  STATE: TASK_INTERRUPTIBLE 

crash> gcore 1451

gcore: invalid structure member offset: thread_struct_fs
       FILE: libgcore/gcore_x86.c  LINE: 1039  FUNCTION: restore_segment_registers()

[/usr/bin/crash] error trace: 7fd5337bf945 => 7fd5337c615f => 7fd5337c4ca0 => 547820

  547820: OFFSET_verify+144

gcore: invalid structure member offset: thread_struct_fs
       FILE: libgcore/gcore_x86.c  LINE: 1039  FUNCTION: restore_segment_registers()

Failed.

• The crash extension gcore fails to retrieve a complete core dump.

# file core.1451.rsyslogd 
core.1451.rsyslogd: ELF 64-bit LSB core file x86-64, version 1 (SYSV)

# gdb -c core.1451.rsyslogd -q
"/root/core.1451.rsyslogd" is not a core dump: file truncated
(gdb)