Rr
rr is the Record and Replay Framework, developped by Mozilla, and is a replacement for and powerful enhancement of gdb.
References
- rr homepage.
- Using rr in an IDE
- Building and Installing and rr Usage, from Mozilla wiki.
Install and configuration
On Debian, rr is available as a package:
sudo apt install rr
rr also requires the linux performance analysis package for the current kernel.
# Install linux perf
sudo apt install linux-perf-4.19
# Enable perf for user land (temporary)
sudo sysctl kernel.perf_event_paranoid=0
# Enable perf permanently - note: =1 might be enough
echo 'kernel.perf_event_paranoid=0' | sudo tee '/etc/sysctl.d/51-rr-enable-perf-events.conf'
# To squeeze max perf on laptop (even plugged on AC!):
sudo apt-get install cpufrequtils
sudo cpufreq-set -g performance # Must be redone at each reboot !!!
See rr usage page for more performance tuning and setting perf flag permanently.
Integration with cgdb
rr works nicely with cgdb:
rr replay -d cgdb
Example of use
Start recording the application:
rr record my_app
Then replay it with:
rr replay
In case the application fires several processes, we can tell rr to fast-forward until child is forked.
First we use rr ps to get the list of recorded processes, then we start rr with -f:
rr ps
rr replay -f 12345
During replay, rr behaves likes gdb, with the usual reverse debugging command (rc, rn, rs...).
See referenced links for more information.
NOTE: rr seems to ignore breakpoints if we do run instead of cont...
Troubleshoot
Potential issues in VM
- See this bug in VMWare [1]. Fix is to add
monitor_control.disable_hvsim_clusters = true. - See this bug in Xen [2].
- Discuss on rr in Hacker News.