linux-kernel - [RFC] [PATCH 0/7] UBP, XOL and Uprobes

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Date:	Mon, 11 Jan 2010 17:55:21 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	utrace-devel <utrace-devel@...hat.com>,
	Mark Wielaard <mjw@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Maneesh Soni <maneesh@...ibm.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [RFC] [PATCH 0/7] UBP, XOL and Uprobes

Hi, 

This patchset implements Uprobes which enables you to dynamically
break into any routine in a user space application and collect
information non-disruptively.  Uprobes is based on utrace and uses
x86 instruction decoder.

When a uprobe is registered, Uprobes makes a copy of the probed
instruction, stops the probed application, replaces the first
byte(s) of the probed instruction with a breakpoint instruction and
allows the probed application to continue.  (Uprobes uses the same
copy-on-write mechanism so that the breakpoint affects only that
process.)

When a CPU hits the breakpoint instruction, Uprobes intercepts the
SIGTRAP and finds the associated uprobe.  It then executes the
associated handler.  Uprobes single-steps its copy of the probed
instruction and resumes execution of the probed process at the
instruction following the probepoint. Instruction copies to be
single-stepped are stored in a per-process "single-step out of line
(XOL) area,"

Uprobes can be used to take advantage of static markers available
in user space applications.

Advantages of uprobes over conventional debugging include:
1. Non-disruptive.
2. Uses Execution out of line(XOL), 
3. Much better handling of multithreaded programs because of XOL.
4. No context switch between tracer, tracee.

Here is the list of TODO Items.

- Provide a perf interface to uprobes.
- Return probes.
- Support for Other Architectures.
- Jump optimization.

This patchset provides
Subject: [RFC] [PATCH 0/7] UBP, XOL and Uprobes
Subject: [RFC] [PATCH 1/7] User Space Breakpoint Assistance Layer (UBP)
Subject: [RFC] [PATCH 2/7] x86 support for  UBP 
Subject: [RFC] [PATCH 3/7] Execution out of line (XOL)
Subject: [RFC] [PATCH 4/7] Uprobes Implementation
Subject: [RFC] [PATCH 5/7] X86 Support for Uprobes
Subject: [RFC] [PATCH 6/7] Uprobes Documentation
Subject: [RFC] [PATCH 7/7] Ftrace plugin for Uprobes

This patchset is based on 
git://git.kernel.org/pub/scm/linux/kernel/git/frob/linux-2.6-utrace.git

If and when utrace gets accepted into tip tree or Mainline, I will rebase
this patchset.

Please do provide your valuable comments.

--
Thanks and Regards
Srikar
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