[PATCH][M68K] Fix shared libraries on uClinux

[Maxim Kuvyrkov]

Hello,

At the moment binaries built for M68K uClinux -mid-shared-library fail 
with 'Illegal instruction' error.  The problem is in assembler piece of 
libgcc that provides FP routines for FPU-less cores.

The attached patch fixes this problem.  OK for trunk?

Analysis:

1. Libstdc++ library is compiled with -mid-shared-library.

2. A program that has floating point operation (e.g., compare) is 
compiled for an fpu-less CPU.  This FP operation is implemented with 
couple of functions: implementation (__cmpsf_internal) and wrapper 
(__eqsf2).  To handle FP operation an object file is being included from 
libgcc.a (_eqsf2.o).  As we compile against shared libstdc++, which 
already has linked in __cmpsf_internal, we only link in the wrapper 
(__eqsf2) to executable.

3. The wrapper (_eqsf2) contains PC-relative relocation to call the 
implementation (__cmpsf_internal).  When the wrapper is being linked 
into the executable, this relocation resolves to symbol in the shared 
library (libstdc++) and PC-relative offset is written to the binary. The 
linker assumes that the binary will be loaded at address 0x0.  At 
runtime the binary is not being loaded at 0x0 and the wrong offset 
triggers jump to nowhere.

The attached patch fixes this problem by using GOT instead of 
PC-relative addressing and by hiding implementation functions so that 
only wrappers are visible to outside world.


--
MaximK
CodeSourcery
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