[lttng-dev] Making 32-bit user-space events on a 64-bit Linux system

[Woegerer, Paul]

Hi Daniel, Hi Jeremie

I tried this on my x86_64 system some time ago (with 2.2.0-rc2) and it
worked just fine.

The only thing that was needed was to build 32-bit variants of urcu and
lttng-ust (and also having all dependend libs as 32-bit variants on the
system).

The 64-bit version of lttng-tools works just fine with both, 32-bit and
64-bit userspace applications. No need to compile it as 32-bit variant.

Instrumented 32-bit applications automatically use the 32-bit
lttng-consumerd (from the lttng-ust 32-bit build),
instrumented 64-bit applications automatically use the 64-bit
lttng-consumerd (from the lttng-ust 64-bit build).

BTW, when you compile for the "-m32" multilib, it's better to use the
following:

$ ./configure CC="gcc -m32"

This way also the linking steps (performed by libtool) of your build
will know that you are building for m32 (on your x86_64 system) and you
don't need e.g. "--libdir ....".
For more information see:
http://doc.opensuse.org/documentation/html/openSUSE/opensuse-reference/cha.64bit.html#sec.64bit.biarch
or
https://developer.mozilla.org/en/docs/Compiling_32-bit_Firefox_on_a_Linux_64-bit_OS

> More generally, how does one add tracepoints to a 32-bit application running on a 64-bit system?

You simply compile your instrumented application to 32-bit the same way
you did it for the lttng-ust package (CC="gcc -m32").


Best,
Paul

-- 
Paul Woegerer, SW Development Engineer
Sourcery Analyzer <http://go.mentor.com/sourceryanalyzer>
Mentor Graphics, Embedded Software Division