On 5/24/19 8:10 AM, Shane Peelar wrote:
I did some reading into the sources in other architectures. The closest
match, arch_i386.c, makes the write conditional as you say.
So do other arches, including |arch_arm.c, |arch_sh.c, |arch-mips.c,
|arch-s390.c, |arch-s390x.c, and |arch-ia64.c.||||||
||||||
||||||
Notably, |||||||arch-cris.c||||||| has the same assert as
|||||||arch-x86_64.c||||||| instead of the conditional.
The code roughly looks like follows:||||||||||||||
||||||||||||||
|||||||
|||||||
1. Check for dso->info[DT_PLTGOT]. If it does not exist, return 0
2. Call addr_to_sec on dso->info[DT_PLTGOT], return 1 if error
3. Look for the section named ".plt" in the ELF.
4. If the section cannot be found, return 0
5. Otherwise, write the address of .plt + constant (dependent on arch)
to got[1]||||||||||||||
||||||||||||||
|||||||
|||||||
In |||||||arch-x86_64.c and arch-cris.c|||||||, step (4) above is an
assert:|||||||
|||||||1. Check for dso->info[DT_PLTGOT]. If it does not exist, return 0
2. Call addr_to_sec on dso->info[DT_PLTGOT], return 1 if error
3. Look for the section named ".plt" in the ELF.
4. Assert that the section was found
5. Write the address of .plt + constant (dependent on arch) to got[1]
I tested out making the assert conditional and nothing seemed to break
at least.
|||||||
|||||||
It seems ok to me.
On Fri, May 24, 2019 at 12:08 AM Khem Raj <raj.k...@gmail.com
<mailto:raj.k...@gmail.com>> wrote:
On 5/23/19 7:53 PM, Shane Peelar wrote:
> Any of them on the system pretty much, and yes they are also
built with
> -fno-plt.
OK, I think its better to them conditionally check for .plt section,
can you describe more of whats going on when sections are checked.
>
> On Thu, May 23, 2019 at 9:59 PM Khem Raj <raj.k...@gmail.com
<mailto:raj.k...@gmail.com>
> <mailto:raj.k...@gmail.com <mailto:raj.k...@gmail.com>>> wrote:
>
>
>
> On 5/23/19 8:05 AM, Shane Peelar wrote:
> > Hi Everyone @ the Yocto project,
> >
> > I'm Shane Peelar, a PhD Candidate at the University of
Windsor.
> > I'm writing to you about prelink-cross, as part of the
Yocto project.
> > Specifically, I'm looking at using it with executables
built using
> > `-fno-plt` under GCC.
> > I wasn't quite sure where to send this email to, so I
figured I'd
> try
> > here. If there's a better place to send this, please let
me know.
> >
> > Right now, prelink-cross seems to fail an assertion in
> arch-x86_64.c,
> > line 421, when
> > using it with an executable built with `-fno-plt`:
> >
> > ...
> > assert (i < dso->ehdr.e_shnum)
> > ...
> >
> > This snippet seems to be looking for the ".plt" section and,
> since it
> > can't find it, the assertion fires. This makes sense
because in
> > `-fno-plt` executables, the `.plt` section is missing
entirely.
> > I'm not an expert on ELF stuff, although I am learning
quickly. It
> > looks like
> > this code wants to write into GOT[1] the address of ".plt"
+ 0x16 --
> > since ".plt" doesn't
> > exist, does it make sense to just change this assert to an if
> statement
> > like so:
> >
> > ...
> > if (i < dso->ehdr.e_shnum)
> > { ... }
> > ...
> >
> > and skip over that part? Or is this a real error
condition for
> > prelink-cross and it really should not continue? The
executable in
> > question is also non-PIE, if that makes a difference.
> >
>
> what shared libs is this linking to ? are they also built with
> -fno-plt ?
>
> > Thanks for your time,
> > Shane
> >
>
--
_______________________________________________
yocto mailing list
yocto@yoctoproject.org
https://lists.yoctoproject.org/listinfo/yocto
