----- On Dec 16, 2020, at 4:19 AM, lttng-dev <lttng-dev@lists.lttng.org> wrote:
Hi,

I send this email to consult that whether it is possible to customize lttng tracepoints in kernel space. I have learnt that lttng leverages linux tracepoint to collect audit logs like system calls. Also, I have found that user can define their customized tracepoints in user space by using lttng-ust so that they can trace their user applications.

Is it possible for lttng users to customize the existing tracepoints in kernel space? For example, after the system call sys_clone, or read, called and then collected by lttng, I want to process some data ( e.g., the return value of the syscall ), and place the result in a new field in the audit log ( or using another approach, by emitting a new type of event in the audit log ), and later when parsed by babeltrace, we can see the newly-added field or event in the parsed result.

Looking forward to your reply.

Hi,

You will want to start by having a look at this section of the LTTng documentation: https://lttng.org/docs/v2.12/#doc-instrumenting-linux-kernel

You can indeed modify lttng-modules to change the fields gathered by the system call tracing facility (see include/instrumentation/syscalls/README section (3)).
Those changes will be reflected in the resulting trace data.

Thanks,

Mathieu



Best wishes,

Serica

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--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com