Re: [PATCH ftrace/core v3 3/3] kprobes: Set IPMODIFY flag only if the probe can change regs->ip

[Namhyung Kim]

Hi Masami,

On Tue, 15 Jul 2014 06:00:35 +0000, Masami Hiramatsu wrote:
> +static int __ftrace_add_filter_ip(struct ftrace_ops *ops, unsigned long ip,
> +                               int *ref)
> +{
> +     int ret;
> +
> +     /* Try to set given ip to filter */
> +     ret = ftrace_set_filter_ip(ops, ip, 0, 0);
> +     if (ret < 0)
> +             return ret;
> +
> +     (*ref)++;
> +     if (*ref == 1) {
> +             ret = register_ftrace_function(ops);
> +             if (ret < 0) {
> +                     /* Rollback refcounter and filter */
> +                     (*ref)--;
> +                     ftrace_set_filter_ip(ops, ip, 1, 0);
> +             }
> +     }
> +
> +     return ret;
> +}

This function also can be changed in a similar way:

        if (*ref == 0) {
                ret = register_ftrace_function(ops);
                if (ret < 0) {
                        /* Rollback filter if failed */
                        ftrace_set_filter_ip(ops, ip, 1, 0);
                        return ret;
                }
        }

        (*ref)++;

        return 0;


Thanks,
Namhyung

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