powerpc/kprobes: Do not suppress instruction emulation if a single run failed (a7b44038) · Commits · 戴 / test

Currently, we disable instruction emulation if emulate_step() fails for any reason. However, such failures could be transient and specific to a particular run. Instead, only disable instruction emulation if we have never been able to emulate this. If we had emulated this instruction successfully at least once, then we single step only this probe hit and continue to try emulating the instruction in subsequent probe hits. Signed-off-by:

Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Signed-off-by:

Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/kprobes.c

+14 −3

Original line number	Diff line number	Diff line
		@@ -261,9 +261,20 @@ static int try_to_emulate(struct kprobe p, struct pt_regs regs)
		*/
		printk("Can't step on instruction %x\n", insn);
		BUG();
		} else
		/* This instruction can't be boosted */
		} else {
		/*
		* If we haven't previously emulated this instruction, then it
		* can't be boosted. Note it down so we don't try to do so again.
		*
		* If, however, we had emulated this instruction in the past,
		* then this is just an error with the current run (for
		* instance, exceptions due to a load/store). We return 0 so
		* that this is now single-stepped, but continue to try
		* emulating it in subsequent probe hits.
		*/
		if (unlikely(p->ainsn.boostable != 1))
		p->ainsn.boostable = -1;
		}

		return ret;
		}

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