[Bug kprobes/2091] New: system crash when running "./systemtap.stress/current.stp" on power

["jkenisto at us dot ibm dot com" <sourceware-bugzilla at sourceware dot org>]

"Gui,Jian" <guij@cn.ibm.com> reported:
-----
My environment is systemtap-snapshot1217, elfutils-0.118-0.1 and
redhat kernel 2.6.9-24.EL on an power4.

When I ran "tests/testsuite/systemtap.stress/current.stp", the system
always crashed. Here is the smallest code segment which will
cause the crash:

  probe kernel.function("*@kernel/sched.c"),
    kernel.function("*@kernel/sched.c").return {}

And here is more information at the breaking point:

0:mon> e
cpu 0x0: Vector: 700 (Program Check) at [c0000001b1313bb0]
    pc: d000000000570624: dwarf_kprobe_1+0x2a0c/0xfffffffffffaf828 
[stap_5462]
    lr: c000000000047dac: .kretprobe_trampoline_holder+0x0/0x8
    sp: c0000001b1313e30
   msr: 8000000000089432
  current = 0xc00000000fc2e040
  paca    = 0xc0000000003f2400
    pid   = 5523, comm = stpd
0:mon> t
[link register   ] c000000000047dac 
.kretprobe_trampoline_holder+0x0/0x8
[c0000001b1313e30] c000000000011280 syscall_exit+0x0/0x18 (unreliable)
--- Exception: c01 (System Call) at 000000000fd4c8d4
SP (ffffe2e0) is in userspace
0:mon> r
R00 = 0000000000000008   R16 = 0000000008028c78
R01 = c0000001b1313e30   R17 = 0000000008028cb0
R02 = c0000000004ec980   R18 = 0000000000000000
R03 = 0000000000004000   R19 = 0000000008008fa8
R04 = 0000000000000028   R20 = 0000000008028c80
R05 = 0000000044000428   R21 = 0000000000000001
R06 = 0000000000000000   R22 = 0000000000000001
R07 = 0000000000000080   R23 = 0000000010010000
R08 = 000000000000d032   R24 = 000000000ffa69d0
R09 = c0000001b1310000   R25 = 0000000010000000
R10 = 8000000000009032   R26 = 0000000010010000
R11 = c0000000002f9c44   R27 = 0000000010010000
R12 = c0000001b1310000   R28 = 0000000010010000
R13 = c0000000003f2400   R29 = 0000000000000004
R14 = 0000000000000001   R30 = 0000000010010000
R15 = 0000000000000000   R31 = 0000000010010000
pc  = d000000000570624 dwarf_kprobe_1+0x2a0c/0xfffffffffffaf828 
[stap_5462]
lr  = c000000000047dac .kretprobe_trampoline_holder+0x0/0x8
msr = 8000000000089432   cr  = 48000442
ctr = c0000000002f9c44   xer = 0000000000000000   trap = 700

Any suggestion about this ?
Thanks in advance.
-----
My suggestions for diagnosing this bug include:
1. Try the same thing without the entry probes.
2. Try the same thing without the return probes.
3. Run "stap -p3 xxx.stp > xxx.c" and extract the list of kretprobe probe
addresses (dwarf_kprobe_1[]?).  Build a C module that establishes entry kprobes
and/or return probes for all these functions.  See if that crashes.  If so, keep
removing functions from the list until you get a module that doesn't cause a
crash.  Keep playing with the list until you figure out a minimal list to
demonstrate the bug.

-- 
           Summary: system crash when running
                    "./systemtap.stress/current.stp" on power
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: kprobes
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: jkenisto at us dot ibm dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=2091

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