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Presentation given by Marc Khouzam, at EclipseCon 2010 In many cases, debugging a program by stopping its execution is not acceptable, delays introduced by a debugger might cause the program to change its behavior drastically, or perhaps fail, even when the code itself is correct. Troubleshooting a live system, chasing a race condition, debugging problems happening only under heavy load or on a multi-core system, or investigating user interface issues, are such examples. To address this, DSF-GDB, the new debugger integration of the CDT, is being extended to support the use of tracepoints which can dynamically be inserted and controlled in a live system.In this talk we will cover such concepts as dynamic and static tracepoints, fast tracepoints, remote tracing, disconnected tracing, visualization of data and many more.Beyond the topic of tracepoints, we will also discuss what advanced debugging features (e.g. multi-core awareness) are planned for the next release of the CDT and of GDB.
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Copyright © 2010 Ericsson, Made available under the Eclipse Public License v 1.0
Real time debugging: using non-intrusive tracepoints to debug live systems
Marc Khouzam, Ericsson [email protected]
Copyright © 2010 Ericsson, Made available under the Eclipse Public License v 1.0 2
Agenda
DSF-GDB today
Tracepoints
The need
The solution
Dynamic Tracepoints and Eclipse demo Static tracepoints Trace data visualization and Eclipse demo
Questions
Copyright © 2010 Ericsson, Made available under the Eclipse Public License v 1.0 3
DSF-GDB today
Optimized GDB integration
Standard Debugging features
Multi-thread/Multi-process
Non-stop debugging
Extendable Pretty-printing with GDB 7.0
Linux, Windows, Mac
Reverse Debugging
Any-binary debugging (no need for a project)
Copyright © 2010 Ericsson, Made available under the Eclipse Public License v 1.0 4
DSF-GDB demo
Any-binary debugging
Debugging GDB itself
Copyright © 2010 Ericsson, Made available under the Eclipse Public License v 1.0 5
TRACEPOINTS
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The need
Extremely low intrusiveness
For live sites
For race conditions
For Real-time
For UI bugs
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The solution
Highly efficient tracing tool using tracepoints
Dynamic Tracepoints
Added dynamically while code is executing
Static Tracepoints
Added in the source code, before compilation
Disconnected tracing
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The solution
GDB (GNU Debugger)
Enhanced dynamic tracepoints
New control of static tracepoints
LTTng and UST (new User Space Tracing)
Can be controlled at run-time by GDB
Eclipse CDT
Extending the existing DSF-GDB integration
Copyright © 2010 Ericsson, Made available under the Eclipse Public License v 1.0 9
GDB’s New Tracepoint Feature
Tracepoint support using gdbserver (on Linux)
Tracing on the host can still be done using gdbserver
Tracepoints implemented by
Breakpoints (slow dynamic tracepoints)
Jump-patching (fast dynamic tracepoints)
User-space LTTng (static tracepoints)
Observer-mode to enforce tracing instead of debugging
Copyright © 2010 Ericsson, Made available under the Eclipse Public License v 1.0 10
Dynamic Tracepoints (DSF-GDB Demo)
Creation of tracepoint as is done as for breakpoints
Enable/Disable tracepoints
Dynamic condition can be assigned to a tracepoint
Specification of data to be gathered using symbolic expressions and memory addresses (actions)
Pass count per tracepoint to stop tracing automatically
Trace-state variables that can be used in conditions and actions
Tracepoints are only in effect if tracing is enabled
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Dynamic Tracepoints
Possible to define global actions (affecting all tracepoints)
Option to use a finite trace buffer or circular trace buffer
Disconnected data gathering
On-disk trace data storage for ‘small’ amounts of data
Automatic timestamp collection on successful tracepoint hit
Copyright © 2010 Ericsson, Made available under the Eclipse Public License v 1.0 16
Trace Data Visualization (DSF-GDB Demo)
Navigation through data records using GDB
Each data record is a snapshot of debug information
Records can be examined using standard debugger views
As if debugger was attached at a specific point in time
Only collected information can be shown
Highlighting of the tracepoint of interest
All collected data of a record can also be dumped as plain text
Trace data can be saved to file
Saved trace data can be examined offline
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Next Tracepoint Features
Disabling tracepoints during Tracing
Tracepoints Enhanced Visualization:
Currently the user must have an idea of what has been collected
Goal is to directly and only show what has been collected
Fast Tracepoints on 3-byte instruction
Currently fast tracepoints are 5-byte jumps insert in the code
New 3-byte jump to a nearby location to the 5-byte jump
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Future DSF-GDB work
Multi-core awareness
Reporting to the user which threads run on which cores
Enhanced multi-process support
Currently limited to single address-space targets
Will be extended to Linux
Flexible-hierarchy breakpoint view usage
Helios brings a new Flexible-hierarchy breakpoint view
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Future DSF-GDB work
Bringing more GDB features to DSF-GDB
Code patching (hot-swap?)
Checkpoints
Enhanced debugging console
Scripting
…
GDB is full of debugging feature, we just have to tap into that
Copyright © 2010 Ericsson, Made available under the Eclipse Public License v 1.0 20
Relevant Links
CDT Tracepoint wiki
http://wiki.eclipse.org/CDT/designs/Tracepoints
Features and screen shots
http://www.eclipse.org/dsdp/dd/development/relnotes/dd_news-1.1.html
http://wiki.eclipse.org/CDT/cdt-debug-default-integration
DSF-GDB feature-parity effort
http://wiki.eclipse.org/CDT/cdt-debug-feature-parity-effort
Reverse Debugging Webinar
http://live.eclipse.org/node/723
Copyright © 2010 Ericsson, Made available under the Eclipse Public License v 1.0 21
Questions?
