Is there a SPARC equivalent to x86's single step mode? What I want is to stop execution after every instruction and move control flow to a trap handler or something similar.
I thought of using the ta instruction in the delayed execution slot but this would not work when the previous instruction is a branching instruction with the annul bit set.
Sparc lacks a single step bit in PSR, so it's harder to single step. But I've used a trick to help get closer. Set TPC to the address of the instruction you want to single step, and set TNPC to an address someplace else where you've placed a trap instruction. When you execute the retry instruction to get back to the process context, it will single step the one instruction you want, then it will next execute the trap instruction which will bring you right back to the kernel, where you can do whatever you want. (n.b this is for sparc64, not sure about sparc32). This is a nice trick because you don't have modify existing instructions in the user's address space. This was important to me since I was single stepping instructions in the kernel.
Another idea I had, but never tried, was to simply set TNPC to an illegal address. Then after the instruction at TPC was executed, you'd get an automatic trap back into the kernel. And since the trap handling code knows that the process is being single stepped, there would be no confusion over a "real" illegal address trap.
