[Crash-utility] Problem in bt for ARM64

[Karlsson, Jan]

Hi Dave

I have experienced some problems in the bt command for ARM64. It seems that the test in arm64_print_exception_frame in arm64.c if the task is running in 32 or 64-bit mode in userland does not work. It "always" becomes 32-bit mode. Example:

crash> bt 1
PID: 1      TASK: ffffffe1f90f8000  CPU: 2   COMMAND: "init"
 #0 [ffffffe1f9103c80] __switch_to at ffffff85b6a862f8
 #1 [ffffffe1f9103ca0] __schedule at ffffff85b7b0d9b0
 #2 [ffffffe1f9103d00] schedule at ffffff85b7b0df28
 #3 [ffffffe1f9103d20] schedule_hrtimeout_range_clock at ffffff85b7b11308
 #4 [ffffffe1f9103da0] schedule_hrtimeout_range at ffffff85b7b11320
 #5 [ffffffe1f9103db0] sys_epoll_wait at ffffff85b6c394c8
 #6 [ffffffe1f9103e70] sys_epoll_pwait at ffffff85b6c396fc
 #7 [ffffffe1f9103ed0] el0_svc_naked at ffffff85b6a8312c
     PC: 00000004  LR: 00000000  SP: 00000000  PSTATE: 00000016
    X12: 00546694 X11: 3431206c616e6769 X10: 00546338  X9: 00000000
     X8: 00000112  X7: dfdab819254dd1e8  X6: 00000016  X5: 0000000a
     X4: 00000031  X3: 00000008  X2: 00000000  X1: ffffffff
     X0: 00000001

The register values are:
r0:                 4   r1:        7ff0b27f90
r2:                 1   r3:          ffffffff
r4:                 0   r5:                 8
r6:                31   r7:                 a
r8:                16   r9:  dfdab819254dd1e8
r10:              112   r11:                0
r12:           546338   r13: 3431206c616e6769
r14:           546694   r15:                0
r16:                0   r17:         f04245b7
r18:         51f2a993   r19:           5783c0
r20:           415254   r21:           527a5c
r22:           527e04   r23:         ffffffff
r24:         ffffffff   r25:           576000
r26:           578000   r27:           578000
r28:              3e8   fp:        7ff0b27ec0
lr:            4f4f24   sp:        7ff0b27eb0
pc:            4fb8d4   psr:         40000000

I have unfortunately not had the time to look for a solution, so I just want to report what I have seen. The kernel running in the example above is 4.4.74 and I have seen the same problem for a 4.9.40 kernel.

Jan