[Bug uprobes/6879] New: does not currently support probing instruction first byte 0x65

[Bug uprobes/6879] New: does not currently support probing instruction first byte 0x65

[fche at redhat dot com]

A para-callgraph.stp trace of libc produces several dozen such printk warnings
per run.  This is on i686 rhel5.2ish, /lib/libc-2.5.so, __res_init, note
address 0x72e32a:

0072e310 <__res_init>:
  72e310:       55                      push   %ebp
  72e311:       89 e5                   mov    %esp,%ebp
  72e313:       83 ec 14                sub    $0x14,%esp
  72e316:       89 5d f4                mov    %ebx,0xfffffff4(%ebp)
  72e319:       e8 12 49 f3 ff          call   662c30 <__i686.get_pc_thunk.bx>
  72e31e:       81 c3 d6 dc 05 00       add    $0x5dcd6,%ebx
  72e324:       89 75 f8                mov    %esi,0xfffffff8(%ebp)
  72e327:       89 7d fc                mov    %edi,0xfffffffc(%ebp)
  72e32a:       65 a1 00 00 00 00       mov    %gs:0x0,%eax
  72e330:       03 83 bc fe ff ff       add    0xfffffebc(%ebx),%eax
  72e336:       8b 00                   mov    (%eax),%eax
  72e338:       8b 30                   mov    (%eax),%esi

-- 
           Summary: does not currently support probing instruction first
                    byte 0x65
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: uprobes
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: fche at redhat dot com
  GCC host triplet: i686


http://sourceware.org/bugzilla/show_bug.cgi?id=6879

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[Bug uprobes/6879] does not currently support probing instruction first byte 0x65

[jkenisto at us dot ibm dot com]

------- Additional Comments From jkenisto at us dot ibm dot com  2008-09-11 23:23 -------
Created an attachment (id=2944)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=2944&action=view)
Enable probing of instructions with the 0x65 (gs:) prefix

Here's a patch that changes i386, x86_64, and x86 uprobes so that they don't
reject probes on instructions with the 0x65 prefix.  I haven't tested it. 
Frank, could you give it a try?

I scanned a disassembly of libc on my i686 system and verified that none of the
other segment prefixes are used, but I haven't done an exhaustive search for
all possible opcodes.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=6879

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[Bug uprobes/6879] does not currently support probing instruction first byte 0x65

[jkenisto at us dot ibm dot com]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING


http://sourceware.org/bugzilla/show_bug.cgi?id=6879

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[Bug uprobes/6879] does not currently support probing instruction first byte 0x65

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2008-09-12 03:52 -------
The new code makes 
    probe process("/lib/libc-2.5.so").function("*").call { }
probes work well enough to insert them all.  It turns out we
later get
   "Task died at uprobe probepoint: ... probepoint = 0xaddr"
messages which I'm tracking down.

As for x86-64, we need first-byte-0x64 treatment:
0000003c2ea990a0 <__getpid>:
  3c2ea990a0:   64 8b 14 25 94 00 00    mov    %fs:0x94,%edx
  3c2ea990a7:   00 
  3c2ea990a8:   83 fa 00                cmp    $0x0,%edx
  3c2ea990ab:   89 d0                   mov    %edx,%eax


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
   Last reconfirmed|0000-00-00 00:00:00         |2008-09-12 03:52:10
               date|                            |


http://sourceware.org/bugzilla/show_bug.cgi?id=6879

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[Bug uprobes/6879] does not currently support probing instruction first byte 0x65

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2008-09-17 16:12 -------
Jim's patch 85d2b7f committed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


http://sourceware.org/bugzilla/show_bug.cgi?id=6879

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[Bug uprobes/6879] does not currently support probing instruction first byte 0x65

[jkenisto at us dot ibm dot com]

------- Additional Comments From jkenisto at us dot ibm dot com  2008-11-18 23:34 -------
Applied same fixes to runtime/uprobes2 -- commit 8590d03.

-- 


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