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From: "Christophe Bédard via lttng-dev" <lttng-dev@lists.lttng.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: lttng-dev <lttng-dev@lists.lttng.org>
Subject: Re: Correctly using callstack-user context
Date: Wed, 13 May 2020 09:42:42 -0400	[thread overview]
Message-ID: <CAAS9dobxi52FyWn=9zVDkMMpmZztc1Q1msdiErMKhkDEYCtqCA@mail.gmail.com> (raw)
In-Reply-To: <1486835767.11198.1589286441675.JavaMail.zimbra@efficios.com>


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On Tue, 12 May 2020 at 08:27, Mathieu Desnoyers <
mathieu.desnoyers@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
unfortunately.

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



Christophe

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WARNING: multiple messages have this Message-ID
From: "Christophe Bédard via lttng-dev" <lttng-dev@lists.lttng.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: lttng-dev <lttng-dev@lists.lttng.org>
Subject: Re: [lttng-dev] Correctly using callstack-user context
Date: Wed, 13 May 2020 09:42:42 -0400	[thread overview]
Message-ID: <CAAS9dobxi52FyWn=9zVDkMMpmZztc1Q1msdiErMKhkDEYCtqCA@mail.gmail.com> (raw)
Message-ID: <20200513134242.B8ftyiYEWF_mIXu9zk6HIUpz_e3Kwsy7zEtnX3GdY_g@z> (raw)
In-Reply-To: <1486835767.11198.1589286441675.JavaMail.zimbra@efficios.com>


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On Tue, 12 May 2020 at 08:27, Mathieu Desnoyers <
mathieu.desnoyers@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
unfortunately.

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



Christophe

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[-- Attachment #2: Type: text/plain, Size: 156 bytes --]

_______________________________________________
lttng-dev mailing list
lttng-dev@lists.lttng.org
https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

  reply	other threads:[~2020-05-13 13:43 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-11 21:09 Christophe Bédard via lttng-dev
2020-05-11 21:09 ` [lttng-dev] " Christophe Bédard via lttng-dev
2020-05-12 12:27 ` Mathieu Desnoyers via lttng-dev
2020-05-12 12:27   ` [lttng-dev] " Mathieu Desnoyers via lttng-dev
2020-05-13 13:42   ` Christophe Bédard via lttng-dev [this message]
2020-05-13 13:42     ` Christophe Bédard via lttng-dev
2020-05-13 14:02     ` Genevieve Bastien via lttng-dev
2020-05-13 14:02       ` [lttng-dev] " Genevieve Bastien via lttng-dev
2020-05-13 15:34       ` Christophe Bédard via lttng-dev
2020-05-13 15:34         ` [lttng-dev] " Christophe Bédard via lttng-dev

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