fix dumb error

Author: peadar

process.cc

@@ -1164,11 +1164,11 @@ ThreadStack::unwind(Process &p, const CoreRegisters &regs)
 
                    if (segment && segment->p_flags & PF_X) {
                        CoreRegisters newRegs = prev.regs;
-                       stack.back().cfa = newBp; // BP is the CFA of the previous frame.
 
                        SP(newRegs) = oldBp + ELF_BYTES * 2;
                        IP(newRegs) = newIp;
                        BP(newRegs) = newBp;
+                       stack.back().cfa = SP(newRegs);
 
                        stack.emplace_back(UnwindMechanism::FRAMEPOINTER, newRegs);
                        continue;