> So we rewrite the copy of instruction (stored in XOL) such that it > accesses its memory operand indirectly thro a scratch register. > The contents of the scratch register are stored before singlestep and > restored later. I see. That should work fine in principle, assuming you use a register that is not otherwise involved, of course. I hope you arrange to restore the register if the copied instruction is never run because of a signal or suchlike. In that case, it's important that the signal context get the original register and original PC rather than the fiddled state for running the copy. Likewise, if anyone is inspecting the registers right after the step. Thanks, Roland -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>