In ptrace, when request is PPC_PTRACE_GETREGS, SETREGS, GETFPREGS and 
SETFPREGS, order of the last two arguments is not correct.

General format of ptrace is ptrace (request, pid, addr, data).  For the 
above mentioned request ids in ppc64, if we use ptrace like

 long reg[32];
 ptrace (PPC_PTRACE_GETREGS, pid, 0, &reg[0]);

the return value is always -1.

If we exchange the last two arguments like,

 ptrace (PPC_PTRACE_GETREGS, pid, &reg[0], 0);

it works!

This is because PPC_PTRACE_GETREGS option for powerpc is implemented 
such that general purpose
registers of the child process get copied to the address variable 
instead of data variable. Same is
the case with other PPC request options PPC_PTRACE_SETREGS, GETFPREGS 
and SETFPREGS.

Prepared a patch for this problem and tested with 2.6.18-rc6 kernel. 
This patch can be applied directly to
2.6.19-rc3 kernel.