There is no simple way to add #if KERNEL_VERSION > 2.6.10
in the header file and leave the hardcoded values there ?

THIS_KERNEL_VERSION is based upon crash internal data variables in the
kernel_table data structure that get initialized in kernel_init(PRE_GDB)
based upon the contents of the kernel's "system_utsname" data structure
read from memory or the dumpfile.

I was mistaken in using the value of "_stext" as the qualifier, though,
since the __START_KERNEL_map value of 0xffffffff80000000 is still the same.
But there must be *some* difference in the symbol list that can be used
to determine which set of address values to use.  It could even be just
the *existence* of some new kernel variable introduced as part of the
change to the new scheme.  Doing an "nm -Bn" on the old and new
vmlinux files should yield something obvious.
 

bt -t seems to better.

crash> bt 3144
PID: 3144   TASK: ffff81011dd1e100  CPU: 0   COMMAND: "mingetty"
 #0 [ffff81011d6b9c68] schedule at ffffffff803b12b3
    RIP: 000000377c7b85b2  RSP: 00007fffff87a110  RFLAGS: 00010246
    RAX: 0000000000000000  RBX: ffffffff8010dc26  RCX: 00007fffff87a7b0
    RDX: 0000000000000001  RSI: 00007fffff87a8c7  RDI: 0000000000000000
    RBP: 00007fffff87aca0   R8: 00002aaaaaac9b00   R9: 0000000000000000
    R10: 0000000000000001  R11: 0000000000000246  R12: 00007fffff87a900
    R13: 0000000000502d20  R14: 0000000000000000  R15: 000000007c92d8c0
    ORIG_RAX: 0000000000000000  CS: 0033  SS: 002b
crash> bt -t 3144
PID: 3144   TASK: ffff81011dd1e100  CPU: 0   COMMAND: "mingetty"
              START: thread_return (schedule) at ffffffff803b12b3
  [ffff81011d6b9d10] do_con_write at ffffffff802689da
  [ffff81011d6b9d80] schedule_timeout at ffffffff803b1e4e
  [ffff81011d6b9db0] _spin_lock_irqsave at ffffffff803b28ce
  [ffff81011d6b9dc0] add_wait_queue at ffffffff8014cf5c
  [ffff81011d6b9de0] read_chan at ffffffff8025d1f7
  [ffff81011d6b9e48] default_wake_function at ffffffff80130c90
  [ffff81011d6b9e78] default_wake_function at ffffffff80130c90
  [ffff81011d6b9e90] tty_ldisc_deref at ffffffff802571c4
  [ffff81011d6b9ed0] tty_read at ffffffff802575ee
  [ffff81011d6b9f10] vfs_read at ffffffff80183a46
  [ffff81011d6b9f40] sys_read at ffffffff80183e03
  [ffff81011d6b9f80] system_call at ffffffff8010dc26
    RIP: 000000377c7b85b2  RSP: 00007fffff87a110  RFLAGS: 00010246
    RAX: 0000000000000000  RBX: ffffffff8010dc26  RCX: 00007fffff87a7b0
    RDX: 0000000000000001  RSI: 00007fffff87a8c7  RDI: 0000000000000000
    RBP: 00007fffff87aca0   R8: 00002aaaaaac9b00   R9: 0000000000000000
    R10: 0000000000000001  R11: 0000000000000246  R12: 00007fffff87a900
    R13: 0000000000502d20  R14: 0000000000000000  R15: 000000007c92d8c0
    ORIG_RAX: 0000000000000000  CS: 0033  SS: 002b
crash>

I still don't understand what happens in x86_64_low_budget_back_trace_cmd()
that causes the "bt" command to skip from the starting point in schedule()
to the end, where it dumps the user-mode entry exception frame, unless
the rsp has been bumped too high by the time it gets to this point:

        /*
         *  Walk the process stack.
         */
        for (i = (rsp - bt->stackbase)/sizeof(ulong);
             !done && (rsp < bt->stacktop); i++, rsp += sizeof(ulong)) {

...and that conceivably may have something to do with the exception stack
problem.  It's hard to say without being there...

Thanks,
  Dave