Allow running bpftrace with an optional command #253
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There's another use case that someone wants at FB that would be similar to this. We want to exit bpftrace when |
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#294 lays down some supporting changes for this feature |
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danobi
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Dec 28, 2018
This patch adds a command running option to bpftrace. The user can now
run something like:
./bpftrace -e '...' -c 'sleep 5'
which is a convenience wrapper around something like:
sleep 5 & ./bpfrace -e '...' -p `pidof sleep`
`-c` is better because it:
* ensures a tighter tracing range around CMD (ie we trace less of the
system while it is not running CMD)
* makes bpftrace exit (which is convenient) when CMD terminates
* previously, it was not possible to get a full trace of CMDs
execution and have bpftrace exit upon CMD termination
Test Plan:
Trivial successful example:
```
$ sudo ./build/src/bpftrace -e 'tracepoint:syscalls:sys_enter_nanosleep
{ printf("%s nanoslept\n", comm); }' -c '/bin/sleep 1'
[sudo] password for dlxu:
chdir(/lib/modules/4.19.8-200.fc28.x86_64/build): No such file or
directory
Attaching 1 probe...
sleep nanoslept
splunkd nanoslept
webrtc_audio_mo nanoslept
gnome-terminal- nanoslept
webrtc_audio_mo nanoslept
gnome-terminal- nanoslept
gnome-terminal- nanoslept
gnome-terminal- nanoslept
gnome-terminal- nanoslept
gnome-terminal- nanoslept
gnome-terminal- nanoslept
gnome-terminal- nanoslept
gnome-terminal- nanoslept
gnome-terminal- nanoslept
gnome-terminal- nanoslept
$
```
Ambigous executable:
```
$ sudo ./build/src/bpftrace -e 'tracepoint:syscalls:sys_enter_nanosleep
{ printf("%s nanoslept\n", comm); }' -c 'sleep 1'
chdir(/lib/modules/4.19.8-200.fc28.x86_64/build): No such file or
directory
Attaching 1 probe...
execve: No such file or directory
Failed to spawn child=sleep 1
splunkd nanoslept
$
```
This closes bpftrace#253
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Running bpftrace with an optional command is useful when tracing an application in development environments and you want to trace only a specific process since it started. We could either receive the pid of the process as an argument (also related to #18), or it could filter the probe as if
-p PIDwas given.For example:
sudo ./bpftrace -e 'kprobe:do_nanosleep { printf("[%d] tick\n", pid); }' -c "sleep 10s".The text was updated successfully, but these errors were encountered: