[yocto] prelink-cross with -fno-plt

[Khem Raj]

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.khem at gmail.com 
> <mailto:raj.khem at 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
>      >
>