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Bug 597329 - Backport the uprobes singlestep bypass
Summary: Backport the uprobes singlestep bypass
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: systemtap
Version: 6.0
Hardware: All
OS: Linux
low
medium
Target Milestone: rc
: ---
Assignee: Frank Ch. Eigler
QA Contact: Petr Muller
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2010-05-28 16:34 UTC by Josh Stone
Modified: 2016-09-20 02:06 UTC (History)
3 users (show)

Fixed In Version: systemtap-1.2-5.el6
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2010-11-10 21:44:43 UTC
Target Upstream Version:
Embargoed:


Attachments (Terms of Use)

Description Josh Stone 2010-05-28 16:34:33 UTC
A recent change in systemtap's uprobes kernel module lets it skip singlestepping after a breakpoint on easily emulated instructions, especially NOPs.

http://sourceware.org/git/gitweb.cgi?p=systemtap.git;a=commit;h=f2c6cb7149b317baa7e1cb66312febc4b1ae5f9f

This is significant for SDT, our userspace static probes, because those probes always insert a NOP for systemtap to put a breakpoint on.  Using our benchmark scripts/probe_perf/bench.sh, which measures the overhead of nearly 4 million probe hits, I get these elapsed times:

   not instrumented:  0.86s
   uprobes w/ sstep: 16.46s
  uprobes w/o sstep:  7.81s

I believe this is a very worthwhile and easy change to backport into RHEL's systemtap package.

Comment 1 Josh Stone 2010-06-09 19:02:47 UTC
This commit is needed to fix powerpc:

http://sourceware.org/git/gitweb.cgi?p=systemtap.git;a=commit;h=8ea20756d7e3236da8aaee3f7db8cd76e5bbc3e6

We are also waiting on IBM folks to see if we need additions in powerpc's arch_validate_probed_insn().

Comment 2 Josh Stone 2010-06-14 22:53:09 UTC
uprobes_ppc: Don't emulate privileged MSR opcodes
http://sourceware.org/git/gitweb.cgi?p=systemtap.git;a=commit;h=51b7256

(FLW) I believe it's good to go...

Comment 5 releng-rhel@redhat.com 2010-11-10 21:44:43 UTC
Red Hat Enterprise Linux 6.0 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.


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