Hi David, I have additional comments on this.
On Thu, 2 Jun 2016 23:26:19 -0400 David Long <[email protected]> wrote: > +/* > + * The D-flag (Debug mask) is set (masked) upon deug exception entry. deug -> debug > + * Kprobes needs to clear (unmask) D-flag -ONLY- in case of recursive > + * probe i.e. when probe hit from kprobe handler context upon > + * executing the pre/post handlers. In this case we return with > + * D-flag clear so that single-stepping can be carried-out. > + * > + * Leave D-flag set in all other cases. > + */ > +static void __kprobes > +spsr_set_debug_flag(struct pt_regs *regs, int mask) > +{ > + unsigned long spsr = regs->pstate; > + > + if (mask) > + spsr |= PSR_D_BIT; > + else > + spsr &= ~PSR_D_BIT; > + > + regs->pstate = spsr; > +} > + [..] > + > +int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) > +{ > + struct kprobe *cur = kprobe_running(); > + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); > + > + switch (kcb->kprobe_status) { > + case KPROBE_HIT_SS: > + case KPROBE_REENTER: > + /* > + * We are here because the instruction being single > + * stepped caused a page fault. We reset the current > + * kprobe and the ip points back to the probe address > + * and allow the page fault handler to continue as a > + * normal page fault. > + */ > + instruction_pointer(regs) = (unsigned long)cur->addr; > + if (!instruction_pointer(regs)) > + BUG(); As according to the recent x86 kprobe bug on fault handler discussion, here this also need kernel_disable_single_stap() and spsr_set_debug_flag() in case of KPROBE_REENTER as you did in kprobe_single_step_handler(). (Also, those code should be a function for reuse) > + if (kcb->kprobe_status == KPROBE_REENTER) > + restore_previous_kprobe(kcb); > + else > + reset_current_kprobe(); Thanks! -- Masami Hiramatsu <[email protected]>
