• Naveen N. Rao's avatar
    powerpc/jprobes: Disable preemption when triggered through ftrace · 6baea433
    Naveen N. Rao authored
    KPROBES_SANITY_TEST throws the below splat when CONFIG_PREEMPT is
    enabled:
    
      Kprobe smoke test: started
      DEBUG_LOCKS_WARN_ON(val > preempt_count())
      ------------[ cut here ]------------
      WARNING: CPU: 19 PID: 1 at kernel/sched/core.c:3094 preempt_count_sub+0xcc/0x140
      Modules linked in:
      CPU: 19 PID: 1 Comm: swapper/0 Not tainted 4.13.0-rc7-nnr+ #97
      task: c0000000fea80000 task.stack: c0000000feb00000
      NIP:  c00000000011d3dc LR: c00000000011d3d8 CTR: c000000000a090d0
      REGS: c0000000feb03400 TRAP: 0700   Not tainted  (4.13.0-rc7-nnr+)
      MSR:  8000000000021033 <SF,ME,IR,DR,RI,LE>  CR: 28000282  XER: 00000000
      CFAR: c00000000015aa18 SOFTE: 0
      <snip>
      NIP preempt_count_sub+0xcc/0x140
      LR  preempt_count_sub+0xc8/0x140
      Call Trace:
        preempt_count_sub+0xc8/0x140 (unreliable)
        kprobe_handler+0x228/0x4b0
        program_check_exception+0x58/0x3b0
        program_check_common+0x16c/0x170
        --- interrupt: 0 at kprobe_target+0x8/0x20
                         LR = init_test_probes+0x248/0x7d0
        kp+0x0/0x80 (unreliable)
        livepatch_handler+0x38/0x74
        init_kprobes+0x1d8/0x208
        do_one_initcall+0x68/0x1d0
        kernel_init_freeable+0x298/0x374
        kernel_init+0x24/0x160
        ret_from_kernel_thread+0x5c/0x70
      Instruction dump:
      419effdc 3d22001b 39299240 81290000 2f890000 409effc8 3c82ffcb 3c62ffcb
      3884bc68 3863bc18 4803d5fd 60000000 <0fe00000> 4bffffa8 60000000 60000000
      ---[ end trace 432dd46b4ce3d29f ]---
      Kprobe smoke test: passed successfully
    
    The issue is that we aren't disabling preemption in
    kprobe_ftrace_handler(). Disable it.
    
    Fixes: ead514d5 ("powerpc/kprobes: Add support for KPROBES_ON_FTRACE")
    Acked-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
    Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
    [mpe: Trim oops a little for formatting]
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    6baea433
kprobes-ftrace.c 3.42 KB