On Mon, 12 Mar 2018 19:00:49 +0900
Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
> Since the kprobe which was optimized by jump can not change
> the execution path, the kprobe for error-injection must not
> be optimized. To prohibit it, set a dummy post-handler as
> officially stated in Documentation/kprobes.txt.
Note that trace-probe based BPF is not affected, because it
ensures the trace-probe is based on ftrace, which is not
jump optimized.
Thanks,
>
> Fixes: 4b1a29a7f542 ("error-injection: Support fault injection framework")
> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> ---
> kernel/fail_function.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/kernel/fail_function.c b/kernel/fail_function.c
> index 21b0122cb39c..1d5632d8bbcc 100644
> --- a/kernel/fail_function.c
> +++ b/kernel/fail_function.c
> @@ -14,6 +14,15 @@
>
> static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs);
>
> +static void fei_post_handler(struct kprobe *kp, struct pt_regs *regs,
> + unsigned long flags)
> +{
> + /*
> + * A dummy post handler is required to prohibit optimizing, because
> + * jump optimization does not support execution path overriding.
> + */
> +}
> +
> struct fei_attr {
> struct list_head list;
> struct kprobe kp;
> @@ -56,6 +65,7 @@ static struct fei_attr *fei_attr_new(const char *sym, unsigned long addr)
> return NULL;
> }
> attr->kp.pre_handler = fei_kprobe_handler;
> + attr->kp.post_handler = fei_post_handler;
> attr->retval = adjust_error_retval(addr, 0);
> INIT_LIST_HEAD(&attr->list);
> }
>
--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>
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