sysroot for use with GDB

sysroot for use with GDB

[Wolfgang Denk]

Hello,

according to the documentation [1] the right way to debug applications
on the target is to load the target library information in GDB using

	set solib-absolute-prefix /path/to/tmp/rootfs

i. e. referring it to the libraries in the target root file system
image.  Assuming the target root file system uses by defualt stripped
libraries, we need to set up a copy of the rootfs with debug
information included.

But do we really have to?  Why cannot we use the libraries present in
the SDK's sysroot directory (i. e. what OECORE_TARGET_SYSROOT points
to) ?

Trying to do so, we see that it fails.  Our current suspicion is that
maybe prelinking of the target images and libraries introduces some
incompatibility.  Is this a reasonable assumption, and if so, is this
a problem that should be fixed, or unavoidable for some reason?  Or is
there a problem with the libraries in OECORE_TARGET_SYSROOT ?

All help welcome - thanks in advance.

[1] http://www.yoctoproject.org/docs/current/dev-manual/dev-manual.html#platdev-gdb-remotedebug-launch-gdb


Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
"Beware of bugs in the above code; I have only proved it correct, not
tried it."                                             - Donald Knuth

Re: sysroot for use with GDB

[Wolfgang Denk]

Hello,

nobody here who could help out?

In message <20121203124234.6327B200FF8@gemini.denx.de> I wrote:
> 
> according to the documentation [1] the right way to debug applications
> on the target is to load the target library information in GDB using
> 
> 	set solib-absolute-prefix /path/to/tmp/rootfs
> 
> i. e. referring it to the libraries in the target root file system
> image.  Assuming the target root file system uses by defualt stripped
> libraries, we need to set up a copy of the rootfs with debug
> information included.
> 
> But do we really have to?  Why cannot we use the libraries present in
> the SDK's sysroot directory (i. e. what OECORE_TARGET_SYSROOT points
> to) ?

It appears that documentation and code are inconsistent; at least the
eclipse plugin generates a .gdbinit script which contains a

	set sysroot /opt/poky/1.3/sysroots/armv7a-vfp-neon-poky-linux-gnueabi

statement, i. e. it uses OECORE_TARGET_SYSROOT as I thought should
work - but it doesn't.

> Trying to do so, we see that it fails.  Our current suspicion is that
> maybe prelinking of the target images and libraries introduces some
> incompatibility.  Is this a reasonable assumption, and if so, is this
> a problem that should be fixed, or unavoidable for some reason?  Or is
> there a problem with the libraries in OECORE_TARGET_SYSROOT ?
> 
> All help welcome - thanks in advance.
> 
> [1] http://www.yoctoproject.org/docs/current/dev-manual/dev-manual.html#platdev-gdb-remotedebug-launch-gdb

OK, guess I should enter a bug in bugzilla, then?


Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
Humanity has the  stars  in  its  future,  and  that  future  is  too
important  to be lost under the burden of juvenile folly and ignorant
superstition.                                          - Isaac Asimov

Re: sysroot for use with GDB

[Wolfgang Denk]

Hello,

In message <20121205123818.C17EB200FF2@gemini.denx.de> I wrote:
> 
> OK, guess I should enter a bug in bugzilla, then?

Done that; please see Bug 3540 - remote target debugging broken

https://bugzilla.yoctoproject.org/show_bug.cgi?id=3540

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
I can type faster than I can move a  mouse,  so  I  find  menu-driven
drawing packages time consuming and frustrating.      - W. R. Stevens

Re: sysroot for use with GDB

[Mark Hatle]

On 12/5/12 6:38 AM, Wolfgang Denk wrote:
> Hello,
>
> nobody here who could help out?
>
> In message <20121203124234.6327B200FF8@gemini.denx.de> I wrote:
>>
>> according to the documentation [1] the right way to debug applications
>> on the target is to load the target library information in GDB using
>>
>> 	set solib-absolute-prefix /path/to/tmp/rootfs
>>
>> i. e. referring it to the libraries in the target root file system
>> image.  Assuming the target root file system uses by defualt stripped
>> libraries, we need to set up a copy of the rootfs with debug
>> information included.
>>
>> But do we really have to?  Why cannot we use the libraries present in
>> the SDK's sysroot directory (i. e. what OECORE_TARGET_SYSROOT points
>> to) ?
>
> It appears that documentation and code are inconsistent; at least the
> eclipse plugin generates a .gdbinit script which contains a
>
> 	set sysroot /opt/poky/1.3/sysroots/armv7a-vfp-neon-poky-linux-gnueabi
>
> statement, i. e. it uses OECORE_TARGET_SYSROOT as I thought should
> work - but it doesn't.
>
>> Trying to do so, we see that it fails.  Our current suspicion is that
>> maybe prelinking of the target images and libraries introduces some
>> incompatibility.  Is this a reasonable assumption, and if so, is this
>> a problem that should be fixed, or unavoidable for some reason?  Or is
>> there a problem with the libraries in OECORE_TARGET_SYSROOT ?

Prelinking should not cause a problem.  GDB knows how to translate the debuginfo 
addresses to the end runtime addresses.

The only thing I've seen in the past that has caused a problem is when the dbg 
stuff was not installed into the sysroot.  GDB will fall back into loading the 
binaries from the sysroot, which will not contain the debug info causing problems.

It's best if you can set the sysroot to the same filesystem as being executed, 
but if you can't this is reasonable.

>> All help welcome - thanks in advance.
>>
>> [1] http://www.yoctoproject.org/docs/current/dev-manual/dev-manual.html#platdev-gdb-remotedebug-launch-gdb
>
> OK, guess I should enter a bug in bugzilla, then?


>
> Best regards,
>
> Wolfgang Denk
>