On Wed, 10 Jan 2018 15:38:10 +0800
Alan Kao <noner...@gmail.com> wrote:
> +static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
> + bool enable)
> +{
> + unsigned int offset = (unsigned int)(target - hook_pos);
> + unsigned int auipc_call = to_auipc_insn(offset);
> + unsigned int jalr_call = to_jalr_insn(offset);
> + unsigned int calls[2] = {auipc_call, jalr_call};
> + unsigned int nops[2] = {NOP4, NOP4};
> + int ret = 0;
> +
> + /* when ftrace_make_nop is called */
> + if (!enable)
> + ret = ftrace_check_current_call(hook_pos, calls);
> +
> + if (ret)
> + goto out;
> +
> + /* replace the auipc-jalr pair at once */
> + ret = probe_kernel_write((void *)hook_pos, enable ? calls : nops,
> + MCOUNT_INSN_SIZE);
> + if (ret)
You don't want to return the return of probe_kernel_write() here. For
ftrace bug to work properly, if a fail to write occurs, you need to
return -EPERM.
-- Steve
> + goto out;
> +
> + smp_mb();
> + flush_icache_range((void *)hook_pos, (void *)hook_pos +
> MCOUNT_INSN_SIZE);
> +
> +out:
> + return ret;
> +}
> +
> +int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
> +{
> + int ret = ftrace_check_current_call(rec->ip, NULL);
> +
> + if (ret)
> + return ret;
> +
> + return __ftrace_modify_call(rec->ip, addr, true);
> +}
> +
> +int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
> + unsigned long addr)
> +{
> + return __ftrace_modify_call(rec->ip, addr, false);
> +}
> +
> +int ftrace_update_ftrace_func(ftrace_func_t func)
> +{
> + int ret = __ftrace_modify_call((unsigned long)&ftrace_call,
> + (unsigned long)func, true);
> + if (!ret) {
> + ret = __ftrace_modify_call((unsigned long)&ftrace_regs_call,
> + (unsigned long)func, true);
> + }
> +
> + return ret;
> +}
> +
> +int __init ftrace_dyn_arch_init(void)
> +{
> + return 0;
> +}
> +#endif
