[lttng-dev] Correctly using callstack-user context

Christophe Bédard bedard.christophe at gmail.com
Wed May 13 09:42:42 EDT 2020

On Tue, 12 May 2020 at 08:27, Mathieu Desnoyers <
mathieu.desnoyers at efficios.com> wrote:

> How does your test program issue the system call ? Is it directly with
> syscall() (see syscall(2) man page), or
> does it call into libc ? Is your entire libc compiled with
> -fno-omit-frame-pointer ?

Indirectly, through libc/libstdc++. We use the default system libs (which I
assume use -O, which in turn implies -fomit-frame-pointer).

> As soon as one library in the chain to the system call is compiled without
> frame pointers, this is where the
> stack walk stops. This is usually libc.

I see. Thanks for the information. Not sure we want to ship a custom libc

Related question: how feasible would adding the callstack-user context to
userspace events be? If it is feasible, is such a feature planned?

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