Could not use "record btrace" even if I have Intel PT hardware feature

Could not use "record btrace" even if I have Intel PT hardware feature

[慕冬亮]

Dear all,

I encounter one problem when I try to leverage Intel PT to do branch tracing.

My cpu has Intel PT feature via "grep intel_pt /proc/cpuinfo".

$ grep intel_pt /proc/cpuinfo

flags : ...intel_pt...


$ gdb simple
.......
(gdb) b main
Breakpoint 1 at 0x40050c
(gdb) r
Starting program: .../Work/Projects/simple

Breakpoint 1, 0x000000000040050c in main ()
(gdb) record btrace
Target does not support branch tracing.
(gdb) record btrace pt
GDB does not support Intel Processor Trace.


--
My best regards to you.

     No System Is Safe!
     Dongliang Mu

Re: Could not use "record btrace" even if I have Intel PT hardware feature

[慕冬亮]

--
My best regards to you.

     No System Is Safe!
     Dongliang Mu


2016-09-06 10:59 GMT-04:00 Metzger, Markus T <markus.t.metzger@intel.com>:
>> -----Original Message-----
>> From: gdb-owner@sourceware.org [mailto:gdb-owner@sourceware.org] On
>> Behalf Of ???
>> Sent: Tuesday, September 6, 2016 4:37 PM
>> To: gdb@sourceware.org
>> Subject: Could not use "record btrace" even if I have Intel PT hardware feature
>
> Hello Dongliang,
>
>> I encounter one problem when I try to leverage Intel PT to do branch tracing.
>>
>> My cpu has Intel PT feature via "grep intel_pt /proc/cpuinfo".
>>
>> $ grep intel_pt /proc/cpuinfo
>>
>> flags : ...intel_pt...
>>
>>
>> $ gdb simple
>> .......
>> (gdb) b main
>> Breakpoint 1 at 0x40050c
>> (gdb) r
>> Starting program: .../Work/Projects/simple
>>
>> Breakpoint 1, 0x000000000040050c in main ()
>> (gdb) record btrace
>> Target does not support branch tracing.
>> (gdb) record btrace pt
>> GDB does not support Intel Processor Trace.
>
> You need a kernel that supports it (4.1+) and you need a GDB that supports it.

I am using Debian Testing with linux kernel 4.6.0-1 and gdb 7.11.1-2

>
> Newer Linux distributions should already provide GDB with Intel PT support.  If
> your distribution doesn't or if you want to build GDB yourself, please configure
> it with "--with-intel-pt".
>

I have installed libipt-dev and libipt1 packages.

> If your Linux distribution does not provide libipt(-devel), you may need to
> build it yourself.  You can get the sources from here:
>   https://github.com/01org/processor-trace.
>
> You may also need to configure GDB with "--with-libipt-prefix=<path-to-libipt>"
> if you don't (want to) install libipt in a standard place.
>
> You may further need to install kernel headers - GDB needs
> /usr/include/linux/perf_event.h.
>

And I have checked the existence of /usr/include/linux/perf_event.h.

Should I reboot my Debian to make kernel module for Intel PT effective?

> Regards,
> Markus.
>
> Intel Deutschland GmbH
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