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Re: why the DSO was loaded at address 0

On 05/21/2013 04:24 PM, Paul Pluzhnikov wrote:
On Tue, May 21, 2013 at 5:06 AM, Abin Xu <> wrote:

But the file "error" shows that "/lib/" was loaded to address 0!

No, it does not.

      14690:    file=/lib/ [0];  needed by ./test [0]
      14690:    file=/lib/ [0];  generating link map
      14690:      dynamic: 0x0043cd7c  base: 0x00000000   size: 0x00191988
      14690:        entry: 0x002c5e40  phdr: 0x002af034  phnum:         10

Presumably you are mis-interpreting base:0x00000000 is the load
address. It is not.

What it is is the relocation (difference) between linked-at address
and loaded-at address.

Usually, shared libraries are linked at address 0, and when they are,
the relocation is indeed the same as loaded-at address.  But your has been prelinked to address 0x002af000, and was loaded at
that address, giving you 0 relocation.

By the way, do you know the correct way to obtain an address from dladdr() which can be passed to addr2line? So far, I haven't managed to do this when prelinking is involved.

Florian Weimer / Red Hat Product Security Team

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