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SubjectRe: [RFC PATCH 01/11] ARM: kprobes: directly modify code if kprobe is not initialized.
(2015/01/07 16:35), Wang Nan wrote:
> If kprobe is optimized before kprobe is initialized, there should
> be only one core, the probed instruction is not armed with breakpoint,
> so simply patch text is okay.

This patch looks very hacky. If kprobes is not initialized, why anyone
can optimize kprobes? I think you must introduce early kprobes init
routine and set init flag at that point.

Thank you,

>
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> ---
> arch/arm/probes/kprobes/opt-arm.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/probes/kprobes/opt-arm.c b/arch/arm/probes/kprobes/opt-arm.c
> index 15b37c0..a021474 100644
> --- a/arch/arm/probes/kprobes/opt-arm.c
> +++ b/arch/arm/probes/kprobes/opt-arm.c
> @@ -325,8 +325,17 @@ void __kprobes arch_optimize_kprobes(struct list_head *oplist)
> * Similar to __arch_disarm_kprobe, operations which
> * removing breakpoints must be wrapped by stop_machine
> * to avoid racing.
> + *
> + * If this function is called before kprobes initialized,
> + * the kprobe should be an early kprobe, the instruction
> + * is not armed with breakpoint. There should be only
> + * one core now, so directly __patch_text is enough.
> */
> - kprobes_remove_breakpoint(op->kp.addr, insn);
> + if (unlikely(!kprobes_initialized)) {
> + BUG_ON(!(op->kp.flags & KPROBE_FLAG_EARLY));
> + __patch_text(op->kp.addr, insn);
> + } else
> + kprobes_remove_breakpoint(op->kp.addr, insn);
>
> list_del_init(&op->list);
> }
>


--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com




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