linux-user: Implement do_setcontext for PPC64

Eliminate the stub for the do_setcontext() function for TARGET_PPC64.  The
implementation re-uses the existing TARGET_PPC32 code with the only change
being the computation of the address of the register save area.

Signed-off-by: Tom Musta <tommusta@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

linux-user/signal.c

@@ -4877,10 +4877,6 @@ long do_sigreturn(CPUPPCState *env)
 /* See arch/powerpc/kernel/signal_32.c.  */
 static int do_setcontext(struct target_ucontext *ucp, CPUPPCState *env, int sig)
 {
-#if defined(TARGET_PPC64)
-    fprintf(stderr, "do_setcontext: not implemented\n");
-    return 0;
-#else
     struct target_mcontext *mcp;
     target_ulong mcp_addr;
     sigset_t blocked;
@@ -4890,7 +4886,12 @@ static int do_setcontext(struct target_ucontext *ucp, CPUPPCState *env, int sig)
                        sizeof (set)))
         return 1;
 
+#if defined(TARGET_PPC64)
+    mcp_addr = h2g(ucp) +
+        offsetof(struct target_ucontext, tuc_sigcontext.mcontext);
+#else
     __get_user(mcp_addr, &ucp->tuc_regs);
+#endif
 
     if (!lock_user_struct(VERIFY_READ, mcp, mcp_addr, 1))
         return 1;
@@ -4901,7 +4902,6 @@ static int do_setcontext(struct target_ucontext *ucp, CPUPPCState *env, int sig)
 
     unlock_user_struct(mcp, mcp_addr, 1);
     return 0;
-#endif
 }
 
 long do_rt_sigreturn(CPUPPCState *env)