Re: [PATCH] recordmcount: Fix handling of elf64 big-endian objects.

[David Daney]

On 12/19/2011 07:09 PM, Steven Rostedt wrote:
> On Mon, 2011-12-19 at 17:42 -0800, David Daney wrote:
> > From: David Daney<david.daney@xxxxxxxxxx>
> >
> > In ELF64, the sh_flags field is 64-bits wide.  recordmcount was
> > erroneously treating it as a 32-bit wide field.  For little endian
> > objects this works because the flags of interest (SHF_EXECINSTR)
> > reside in the lower 32 bits of the word, and you get the same result
> > with either a 32-bit or 64-bit read.  Big endian objects on the
> > other hand do not work at all with this error.
> >
> > The fix:  Correctly treat sh_flags as 64-bits wide in elf64 objects.
> >
> > The symptom I observed was that my
> > __start_mcount_loc..__stop_mcount_loc was empty even though ftrace
> > function tracing was enabled.
>
> OUCH!
>
> This looks like something that needs to go to stable. Let me play with
> this on my PPC64 tomorrow.

Hi Steven,

Any more feedback on this patch?  Should I look for it to appear in 3.3?

Thanks,
David Daney

> Thanks!
>
> -- Steve
>
> > Signed-off-by: David Daney<david.daney@xxxxxxxxxx>
> > ---
> >   scripts/recordmcount.h |    2 +-
> >   1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h
> > index f40a6af6..54e35c1 100644
> > --- a/scripts/recordmcount.h
> > +++ b/scripts/recordmcount.h
> > @@ -462,7 +462,7 @@ __has_rel_mcount(Elf_Shdr const *const relhdr,  /* is SHT_REL or SHT_RELA */
> >   		succeed_file();
> >   	}
> >   	if (w(txthdr->sh_type) != SHT_PROGBITS ||
> > -	    !(w(txthdr->sh_flags)&  SHF_EXECINSTR))
> > +	    !(_w(txthdr->sh_flags)&  SHF_EXECINSTR))
> >   		return NULL;
> >   	return txtname;
> >   }

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