Hi Kevin, After looking into function compute_return_epc(regs), we find that it can just skip an instruction. But the instruction that cause exceptions should not be skipped. Regards, Colin ----- Original Message ----- From: "Kevin D. Kissell" <kevink@xxxxxxxx> To: "Nigel Stephens" <nigel@xxxxxxxx>; "colin" <colin@xxxxxxxxxxxxxx> Cc: <linux-mips@xxxxxxxxxxxxxx> Sent: Wednesday, March 29, 2006 10:32 PM Subject: Re: Using hardware watchpoint for applications debugging > > colin wrote:. > > > 2. When an exception happens and we find that it's not touching the righ > > > address, we will discard it. However, exception will happen again because > > > the former instruction will be re-executed when the exception is finished. > > > > > > > You'll need to single-step over the instruction which generated the > > unwanted watchpoint exception, with the watchpoint disabled. Then after > > handling the single step reenable the watchpoint and resume normal > > execution. > > There's actually a simpler and more efficient approach in Linux. The code > already exists in the MIPS Linux kernel to "skip" the instruction responsible > for the current exception, because the situation also arises for emulated > instructions. In do_watch(), in the cases where you want to ignore the > watchpoint, you should be able to just invoke compute_return_epc(regs) > and return. There should be no need to handle single-step exceptions > or disable/reenable the watchpoint. > > Regards, > > Kevin K.
