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Conflict between MIPS PLTS and abicalls stubs

From: Colin Burgess
Subject: Conflict between MIPS PLTS and abicalls stubs
Date: Tue, 24 Mar 2009 13:08:41 -0400
User-agent: Thunderbird (X11/20090318)

We have an issue where a nonPIC binary that is

* calling a function in a shared object
* calling another function in a shared object, which references the address of 
the first function, saving it as a function pointer.
* later, calling yet another function (in a shared object) which invokes the 
function pointer.

Because the executable itself doesn't refer directly to the address of the 
function, an abicalls stub is generated.
However, since the canonical address of the function is, as I understand it, 
the address of the stub in the
executable's .MIPS.stubs section, when the function invocation is performed it 
will mess up because the $gp
is pointing at the shared objects got, whereas the stub assumes that it points 
at the executables got.

If a the address of the function is taken in the executable, then all is well 
since this generates a PLT
entry with STO_MIPS_PLT.

Attached is an example application, which I've tried to comment as clearly as 

This is with binutils 2.19, under QNX 6.4.1




Attachment: example.tgz
Description: application/compressed-tar

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