Messages in this thread | | | Date | Thu, 11 Jan 2018 16:02:57 +0800 | From | Alan Kao <> | Subject | Re: [PATCH 2/6] riscv/ftrace: Add dynamic function tracer support |
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On Wed, Jan 10, 2018 at 11:36:43AM -0500, Steven Rostedt wrote: > On Wed, 10 Jan 2018 15:38:10 +0800 > Alan Kao <nonerkao@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 > Thanks for the correction and the style fix in the previous mail. These problems will be fixed in the next version patch.
Alan
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