* [Bug uprobes/10324] New: x86-64 uprobes gives up on 0xf0 prefix (lock)
@ 2009-06-24 10:53 fche at redhat dot com
2009-06-24 14:57 ` [Bug uprobes/10324] " srikar at linux dot vnet dot ibm dot com
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: fche at redhat dot com @ 2009-06-24 10:53 UTC (permalink / raw)
To: systemtap
When probing multithreading libraries like libpthread, uprobes
rejects instructions like this for probing.
f0 64 0f b1 0c 25 c8 lock cmpxchg %ecx,%fs:0xc8
Jun 23 21:19:25 grid-wn353 kernel: Can't place uprobe at pid 21629 vaddr
0x2b8f90f09691: instruction type cannot be probed
--
Summary: x86-64 uprobes gives up on 0xf0 prefix (lock)
Product: systemtap
Version: unspecified
Status: NEW
Severity: enhancement
Priority: P2
Component: uprobes
AssignedTo: systemtap at sources dot redhat dot com
ReportedBy: fche at redhat dot com
http://sourceware.org/bugzilla/show_bug.cgi?id=10324
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* [Bug uprobes/10324] x86-64 uprobes gives up on 0xf0 prefix (lock)
2009-06-24 10:53 [Bug uprobes/10324] New: x86-64 uprobes gives up on 0xf0 prefix (lock) fche at redhat dot com
@ 2009-06-24 14:57 ` srikar at linux dot vnet dot ibm dot com
2009-06-24 21:47 ` jkenisto at us dot ibm dot com
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: srikar at linux dot vnet dot ibm dot com @ 2009-06-24 14:57 UTC (permalink / raw)
To: systemtap
------- Additional Comments From srikar at linux dot vnet dot ibm dot com 2009-06-24 14:56 -------
From runtime/uprobes2/uprobes_x86.c 0xf0(lock prefix is documented as not
supported)
---------------------------------------------------------------------
* others -- Do we need to support these?
* 0f - (floating-point?) prefetch instructions
* 07, 17, 1f - pop es, pop ss, pop ds
* 26, 2e, 36, 3e - es:, cs:, ss:, ds: segment prefixes --
* but 64 and 65 (fs: and gs:) seem to be used, so we support them
* 67 - addr16 prefix
* ce - into
* f0 - lock prefix
------------------------------------------------------------------------
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* [Bug uprobes/10324] x86-64 uprobes gives up on 0xf0 prefix (lock)
2009-06-24 10:53 [Bug uprobes/10324] New: x86-64 uprobes gives up on 0xf0 prefix (lock) fche at redhat dot com
2009-06-24 14:57 ` [Bug uprobes/10324] " srikar at linux dot vnet dot ibm dot com
@ 2009-06-24 21:47 ` jkenisto at us dot ibm dot com
2009-06-24 22:10 ` fche at redhat dot com
2009-08-13 17:47 ` fche at redhat dot com
3 siblings, 0 replies; 5+ messages in thread
From: jkenisto at us dot ibm dot com @ 2009-06-24 21:47 UTC (permalink / raw)
To: systemtap
------- Additional Comments From jkenisto at us dot ibm dot com 2009-06-24 21:47 -------
(In reply to comment #1)
> From runtime/uprobes2/uprobes_x86.c 0xf0(lock prefix is documented as not
> supported)
> ---------------------------------------------------------------------
> * others -- Do we need to support these?
...
> * f0 - lock prefix
> ------------------------------------------------------------------------
It's unsupported because I was vaguely uncomfortable about it and have never
tested probing locked instructions. You could certainly try it out by changing
the f0 bit from 0 to 1 in good_insns_32[] and good_insns_64[].
See PR #5273, "x86 arch_validate_probed_insn(): lighten up?"
--
http://sourceware.org/bugzilla/show_bug.cgi?id=10324
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* [Bug uprobes/10324] x86-64 uprobes gives up on 0xf0 prefix (lock)
2009-06-24 10:53 [Bug uprobes/10324] New: x86-64 uprobes gives up on 0xf0 prefix (lock) fche at redhat dot com
2009-06-24 14:57 ` [Bug uprobes/10324] " srikar at linux dot vnet dot ibm dot com
2009-06-24 21:47 ` jkenisto at us dot ibm dot com
@ 2009-06-24 22:10 ` fche at redhat dot com
2009-08-13 17:47 ` fche at redhat dot com
3 siblings, 0 replies; 5+ messages in thread
From: fche at redhat dot com @ 2009-06-24 22:10 UTC (permalink / raw)
To: systemtap
------- Additional Comments From fche at redhat dot com 2009-06-24 22:09 -------
> It's unsupported because I was vaguely uncomfortable about it and have never
> tested probing locked instructions. You could certainly try it out by changing
> the f0 bit from 0 to 1 in good_insns_32[] and good_insns_64[].
I wouldn't trust such an experiment, since "lock" is rich with
concurrency semantics, testing the correctness of the SSOL
emulation would not be trivial.
> See PR #5273, "x86 arch_validate_probed_insn(): lighten up?"
Yeah, if you like, CLOSE/DUPLICATE them.
--
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* [Bug uprobes/10324] x86-64 uprobes gives up on 0xf0 prefix (lock)
2009-06-24 10:53 [Bug uprobes/10324] New: x86-64 uprobes gives up on 0xf0 prefix (lock) fche at redhat dot com
` (2 preceding siblings ...)
2009-06-24 22:10 ` fche at redhat dot com
@ 2009-08-13 17:47 ` fche at redhat dot com
3 siblings, 0 replies; 5+ messages in thread
From: fche at redhat dot com @ 2009-08-13 17:47 UTC (permalink / raw)
To: systemtap
------- Additional Comments From fche at redhat dot com 2009-08-13 17:47 -------
*** This bug has been marked as a duplicate of 5273 ***
--
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |DUPLICATE
http://sourceware.org/bugzilla/show_bug.cgi?id=10324
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2009-06-24 10:53 [Bug uprobes/10324] New: x86-64 uprobes gives up on 0xf0 prefix (lock) fche at redhat dot com
2009-06-24 14:57 ` [Bug uprobes/10324] " srikar at linux dot vnet dot ibm dot com
2009-06-24 21:47 ` jkenisto at us dot ibm dot com
2009-06-24 22:10 ` fche at redhat dot com
2009-08-13 17:47 ` fche at redhat dot com
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