From 8afafa6fba7809c0785018b77c95b19e58b35b94 Mon Sep 17 00:00:00 2001 From: "Naveen N. Rao" Date: Fri, 15 Sep 2017 15:38:21 +0530 Subject: [PATCH] powerpc/kprobes: Update optprobes to use emulate_update_regs() Optprobes depended on an updated regs->nip from analyse_instr() to identify the location to branch back from the optprobes trampoline. However, since commit 3cdfcbfd32b9d ("powerpc: Change analyse_instr so it doesn't modify *regs"), analyse_instr() doesn't update the registers anymore. Due to this, we end up branching back from the optprobes trampoline to the same branch into the trampoline resulting in a loop. Fix this by calling out to emulate_update_regs() before using the nip. Additionally, explicitly compare the return value from analyse_instr() to 1, rather than just checking for !0 so as to guard against any future changes to analyse_instr() that may result in -1 being returned in more scenarios. Fixes: 3cdfcbfd32b9d ("powerpc: Change analyse_instr so it doesn't modify *regs") Signed-off-by: Naveen N. Rao Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/optprobes.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c index 6f8273f5e988..91e037ab20a1 100644 --- a/arch/powerpc/kernel/optprobes.c +++ b/arch/powerpc/kernel/optprobes.c @@ -104,8 +104,10 @@ static unsigned long can_optimize(struct kprobe *p) * and that can be emulated. */ if (!is_conditional_branch(*p->ainsn.insn) && - analyse_instr(&op, ®s, *p->ainsn.insn)) + analyse_instr(&op, ®s, *p->ainsn.insn) == 1) { + emulate_update_regs(®s, &op); nip = regs.nip; + } return nip; }