Hi Pratyush, On 08/24, Pratyush Anand wrote: > > > I don't think we want user_{enable,disable{_single_step in the long term, > > please look at 9bd1190a11c9d2 "uprobes/x86: Do not (ab)use TIF_SINGLESTEP > > /user_*_single_step() for single-stepping". it seems that ARM64 sets/clears > > TIF_SINGLESTEP. You can also lool at saved_tf logic, probably ARM64 needs > > the same. > > IIUC, then you mean that TIF_SINGLESTEP is a per task flag,
Yes, and nobody but ptrace should use it, otherwise ptrace/uprobes can confuse each other. And uprobes simply doesn't need to set/clear it. > while > arch_uprobe_pre/post_xol() should enable/disable single stepping using a per > uprobe_task, I can't really answer since I know nothing about arm. x86 just needs to set X86_EFLAGS_TF, I guess arm needs to modify some register too? > and we should have a flag in "struct arch_uprobe_task" to handle > this, right? Probably yes, because we need to record/restore X86_EFLAGS_TF in case it was already set by ptrace or something else. > > However, I agree we can do this later and initial version can use these > > ptrace helpers. > > Yes, I would also like to do that change latter, because these set of patches > have already been tested heavily with systemtap, so it would be better to go > with an incremental changes latter on. Yes, yes, I agree. Let me repeat that this patch looks good to me as initial version, but obviously I can't really revit it and/or ack. Oleg.