linux-kernel - Re: [RFC PATCH 2/8] perf probe powerpc: Fix symbol fixup issues due to ELF type

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Message-ID: <20141210093510.GG5318@naverao1-tp.in.ibm.com>
Date:	Wed, 10 Dec 2014 15:05:10 +0530
From:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	mpe@...erman.id.au, ananth@...ibm.com
Subject: Re: [RFC PATCH 2/8] perf probe powerpc: Fix symbol fixup issues due
 to ELF type

On 2014/12/09 06:07PM, Arnaldo Carvalho de Melo wrote:
> Em Tue, Dec 09, 2014 at 11:04:00PM +0530, Naveen N. Rao escreveu:
> > If using the symbol table, symbol addresses are not being fixed up
> > properly, resulting in probes being placed at wrong addresses:
> > 
> >   # perf probe do_fork
> >   Added new event:
> >     probe:do_fork        (on do_fork)
> > 
> >   You can now use it in all perf tools, such as:
> > 
> > 	  perf record -e probe:do_fork -aR sleep 1
> > 
> >   # cat /sys/kernel/debug/tracing/kprobe_events
> >   p:probe/do_fork _text+635952
> >   # printf "%x" 635952
> >   9b430
> >   # grep do_fork /boot/System.map
> >   c0000000000ab430 T .do_fork
> > 
> > Fix by checking for ELF type ET_DYN used by ppc64 kernels.
> 
> Are you sure this doesn't need to be enclosed in ifdef PPC64?

I felt this change is architecture-independent, though I'm actually not 
sure if there are other architectures using ET_DYN for their kernel. I 
can restrict this to ppc64 if you think that would be better.

- Naveen

> 
> - Arnaldo
> 
> > Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
> > ---
> >  tools/perf/util/symbol-elf.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> > index 1e23a5b..67e4392 100644
> > --- a/tools/perf/util/symbol-elf.c
> > +++ b/tools/perf/util/symbol-elf.c
> > @@ -629,7 +629,8 @@ int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
> >  						     NULL) != NULL);
> >  	} else {
> >  		ss->adjust_symbols = ehdr.e_type == ET_EXEC ||
> > -				     ehdr.e_type == ET_REL;
> > +				     ehdr.e_type == ET_REL ||
> > +				     ehdr.e_type == ET_DYN;
> >  	}
> >  
> >  	ss->name   = strdup(name);
> > -- 
> > 2.1.3
> 

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