[Bug gdb/25215] systemtap probes appear to break armhf gdb with arm64 kernel

michael.hudson at canonical dot com sourceware-bugzilla@sourceware.org
Fri Nov 22 23:32:00 GMT 2019


--- Comment #8 from Michael Hudson-Doyle <michael.hudson at canonical dot com> ---
Also, the process is segfaulting for what looks like a valid reason:

root@disco:~# gdb --args /bin/true
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Reading symbols from /bin/true...
(No debugging symbols found in /bin/true)
(gdb) r
Starting program: /usr/bin/true 

Program received signal SIGSEGV, Segmentation fault.
0xf7fc8ee0 in ?? () from /lib/ld-linux-armhf.so.3
(gdb) x/i $pc
=> 0xf7fc8ee0:  ldr.w   r3, [r8]
(gdb) p $r8
$1 = 0

But trying to work out why $r8 is 0 didn't go so well:

(gdb) disassemble 
No function contains program counter for selected frame.
(gdb) disassemble $pc-12,$pc+12
Dump of assembler code from 0xf7fc8ed4 to 0xf7fc8eec:
   0xf7fc8ed4:  ldr.w   r8, [r2, #428]  ; 0x1ac
   0xf7fc8ed8:  add.w   r5, r5, #608    ; 0x260
   0xf7fc8edc:  mov     r4, r3
   0xf7fc8ede:  mov     r6, r2
=> 0xf7fc8ee0:  ldr.w   r3, [r8]
   0xf7fc8ee4:  cbz     r3, 0xf7fc8eec
   0xf7fc8ee6:  movs    r1, #0
   0xf7fc8ee8:  mov     r0, r5
   0xf7fc8eea:  blx     r3
End of assembler dump.
(gdb) br *0xf7fc8ed4
Breakpoint 1 at 0xf7fc8ed4
(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /usr/bin/true 
�&��K{Dh���1������uFF��: Assertion `&��K{Dh���1������uFF��' failed!
[Inferior 1 (process 2440) exited with code 0177]

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