projects / lttng-tools.git / blame
| Commit | Line | Data |
|---|---|---|
| 57f0bd0c CB |
1 | LTTng core dump snapshot handler |
| 2 | Christian Babeux, June 2013 | |
| 3 | ||
| 4 | This is a custom core dump program that will be called when a core dump | |
| 5 | occurs. The program will save the core data in CORE_PATH and also, if a | |
| 6 | root session daemon is running, will record a snapshot of tracing data | |
| 7 | using the lttng command line utility. | |
| 8 | ||
| 9 | The core dump snapshot handler can be installed by using the provided | |
| 10 | install.sh script or by adding the appropriate program pipe line to | |
| 11 | /proc/sys/kernel/core_pattern. Refer to core(5) for more information | |
| 12 | about the Linux kernel core dump handling and custom handler mechanism. | |
| 13 | ||
| 14 | Installation: | |
| 15 | ||
| 16 | # ./install.sh | |
| 17 | Backup current core_pattern in core_pattern.bkp. | |
| 18 | Successfully installed core_pattern. | |
| 19 | ||
| 20 | How to use: | |
| 21 | ||
| 22 | You can use the provided test.sh script to test that the core dump snapshot | |
| 23 | handler is working properly: | |
| 24 | ||
| 25 | # ./test.sh | |
| 26 | Setup... | |
| 27 | Spawning a session daemon | |
| 28 | Session auto-20130626-224838 created. | |
| 29 | Kernel channel chan enabled for session auto-20130626-224838 | |
| 30 | kernel event sched_switch created in channel chan | |
| 31 | Tracing started for session auto-20130626-224838 | |
| 32 | Sleeping... | |
| 33 | Crashing... | |
| 34 | ./test.sh: line 35: 16980 Segmentation fault (core dumped) | |
| 35 | $(dirname $0)/crash | |
| 36 | Waiting for data availability | |
| 37 | Tracing stopped for session auto-20130626-224838 | |
| 38 | Session auto-20130626-224838 destroyed | |
| 39 | Core dump and snapshot will be available in /tmp/lttng/{core,snapshot}. | |
| 40 | ||
| 41 | # tree /tmp/lttng | |
| 42 | /tmp/lttng | |
| 43 | |-- core | |
| 44 | | `-- core.16980 | |
| 45 | `-- snapshot | |
| 46 | `-- snapshot | |
| 47 | |-- chan_0 | |
| 48 | |-- chan_1 | |
| 49 | |-- chan_2 | |
| 50 | |-- chan_3 | |
| 51 | |-- chan_4 | |
| 52 | |-- chan_5 | |
| 53 | |-- chan_6 | |
| 54 | |-- chan_7 | |
| 55 | `-- metadata | |
| 56 | ||
| 57 | Chaining with other core dump handler: | |
| 58 | ||
| 59 | Some Linux distributions already use their own core dump handler | |
| 60 | (such as systemd 'systemd-coredump' utility). It is possible to chain these | |
| 61 | core dump utility with the core dump snapshot handler. In order to achieve | |
| 62 | this, the core dump snapshot handler must be first in the chain (e.g. | |
| 63 | installed in /proc/sys/kernel/core_pattern) and the other core dump | |
| 64 | handler must be called from within the core dump snapshot handler script. | |
| 65 | ||
| 66 | Example (chaining with systemd systemd-coredump): | |
| 67 | ||
| 68 | # cat /proc/sys/kernel/core_pattern | |
| 69 | |/path/to/lttng/handler.sh %p %u %g %s %t %h %e %E %c | |
| 70 | ||
| 71 | In LTTng handler.sh script: | |
| 72 | ||
| 73 | [...] | |
| 74 | # Save core dump from stdin. | |
| 75 | $MKDIR_BIN -p "${CORE_PATH}" | |
| 76 | ||
| 77 | # Optional, chain core dump handler with original systemd script. | |
| 78 | $CAT_BIN - | /usr/lib/systemd/systemd-coredump $p $u $g $s $t $e | |
| 79 | [...] |