Re: Problems on glibc UTRACE

[David Smith <dsmith at redhat dot com>]

On 11/20/2014 08:25 PM, Shane Wayne wrote:
> I've recently tap into malloc function of glibc, but I've encounter
> some problems.
> Firstly, I have install systemtap and glibc-dbg on Ubuntu 14.04(with
> kernel 3.13 and UTRACE kernel flag default on).

What UTRACE kernel flag are you talking about? In the past (RHEL5 &
RHEL6), there was an in-kernel utrace. Now utrace functionality is built
on top of kernel tracepoints.

> The result show that, I can tap into
> process("/lib/x86_64-linux-gnu/libc.so.6").function("malloc"), BUT,
> the question is that, I can't get the right $bytes in this system, the
> value I've got always like an pointer value start with 0x7f****. I've
> tried the script on my own micro benchmark, with a single malloc
> function invoke, the result also show that I can't get the right
> parameters out, what's more, my micro benchmark triggered the tap
> TWICE.
> Secondly, I migrate to CentOS 6.6, with kernel
> 2.6.32-504.1.3.el6.x86_64 and UTRACE kernel flag default on, at this
> time, I can get the right parameter $bytes out, but in my own micro
> benchmark, the twice triggered problem also appear.

Do you have glibc debuginfo installed on your Ubuntu system? Can you
show us your systemtap script?

-- 
David Smith
dsmith@redhat.com
Red Hat
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