[Bug kprobes/2294] New: current.stp causes NX protection fault on i686 SMP

[Bug kprobes/2294] New: current.stp causes NX protection fault on i686 SMP

[joshua dot i dot stone at intel dot com]

It has been reported in two cases that current.stp causes an NX protection fault.

http://sources.redhat.com/ml/systemtap/2006-q1/msg00157.html
http://sources.redhat.com/ml/systemtap/2006-q1/msg00397.html

The two kernels reported to crash are 2.6.14-1.1656_FC4smp.i686 and
2.6.9-30.ELsmp.i686.  Both reports had a similar stack trace as well, starting with:

  kretprobe_trampoline
  do_timer
  timer_interrupt
  kretprobe_trampoline

Several other kernels and a different architecture (x86_64) were tested and did
not experience this crash.

-- 
           Summary: current.stp causes NX protection fault on i686 SMP
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: kprobes
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: joshua dot i dot stone at intel dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=2294

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[Bug kprobes/2294] current.stp causes NX protection fault on i686 SMP

[bibo dot mao at intel dot com]

------- Additional Comments From bibo dot mao at intel dot com  2006-02-09 03:22 -------
In RHEL4-U3 beta 2.6.9-30 version, kernel configuration CONFIG_X86_PAE set as 
N, and then current.stp will pass. Can you verify this in 2.6.14-
1.1656_FC4smp.i686  kernel version? 

_PAGE_NX is different by CONFIG_X86_PAE option, if PAE is enable, kprobe probed 
instruction should be placed in module_alloc() area, but no kprobe stucture. 
That is to say, arch_specific_insn structure should be defined as
struct arch_specific_insn {
	/* copy of the original instruction */
	kprobe_opcode_t *insn;
};
And instruction slot allocation/free will be same with x86_64 architecture.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=2294

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