[Bug kprobes/2453] New: kernel panic when probe elv_dequeue_request

["guanglei at cn dot ibm dot com" <sourceware-bugzilla at sourceware dot org>]

I am running ppc64/2.6.15.4, and the kernel will panic if I put probe on entry
of elv_dequeue_request

output of xmon:
4:mon> e
cpu 0x4: Vector: 700 (Program Check) at [c00000000ffdf660]
    pc: c0000000001f15bc: .elv_dequeue_request+0x10/0x58
    lr: c0000000002fe764: .scsi_request_fn+0x164/0x3b8
    sp: c00000000ffdf8e0
   msr: 8000000000021032
  current = 0xc00000005c33c040
  paca    = 0xc00000000056ac00
    pid   = 15159, comm = 05-wait_for_sys
kernel BUG in elv_dequeue_request at block/elevator.c:514!


the stap file:
probe kernel.function("elv_dequeue_request")
{
        log("here")
}

the generated c file shows that systemtap put the probe point at:

static struct kprobe dwarf_kprobe_0[1]= {
  {.addr= (void *) 0xc0000000001f15bc}
};


objdump of the assembly codes:

c0000000001f15ac <.elv_dequeue_request>:
c0000000001f15ac:       e8 04 00 00     ld      r0,0(r4)
c0000000001f15b0:       7c 00 22 78     xor     r0,r0,r4
c0000000001f15b4:       21 20 00 00     subfic  r9,r0,0
c0000000001f15b8:       7c 09 01 14     adde    r0,r9,r0
c0000000001f15bc:       0b 00 00 00     tdnei   r0,0
c0000000001f15c0:       e9 24 00 00     ld      r9,0(r4)
c0000000001f15c4:       e9 64 00 08     ld      r11,8(r4)
c0000000001f15c8:       f9 2b 00 00     std     r9,0(r11)
c0000000001f15cc:       f9 69 00 08     std     r11,8(r9)
c0000000001f15d0:       60 00 00 00     nop
c0000000001f15d4:       e8 04 00 10     ld      r0,16(r4)
c0000000001f15d8:       f8 84 00 00     std     r4,0(r4)
c0000000001f15dc:       f8 84 00 08     std     r4,8(r4)

-- 
           Summary: kernel panic when probe elv_dequeue_request
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: kprobes
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: guanglei at cn dot ibm dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=2453

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