On Thu, 15 Oct 2020 11:49:31 -0400 Steven Rostedt <[email protected]> wrote:
> On Thu, 15 Oct 2020 23:54:58 +0900 > Masami Hiramatsu <[email protected]> wrote: > > > Hi, > > > > Here is the 3rd version of the series for real address printing in trace > > log. > > > > Here is the previous version, I've fixed [1/3] to use krealloc(), fix memory > > allocation error check and add __printf() attribute, according to Steve's > > comment. > > > > https://lore.kernel.org/lkml/160275239876.115066.10891356497426857018.stgit@devnote2/ > > > > > > Since trace_seq_printf() use in-kernel vsprintf() at last, the %p is always > > converted to the hash value instead of real address. > > > > For the dmesg it maybe secure, but for the ftrace, I think it is > > meaningless because > > > > - tracefs is used by root user, so no need to hide it. > > - tracefs user can access percpu/cpu*/trace_pipe_raw which stores real > > address on the trace buffer. > > - external commands like perf doesn't convert to the hash value. > > > > And when debugging kernel, we would like to know real address which tells > > us the address is in which area in the kernel by comparing with kernel > > memory mapping. > > > > However, to compare the trace log with dmesg, we also need a bridging > > information. So 3/3 gives the options/hash-ptr knob which switches > > the output format. > > > > Thanks Masami, > > I'm going to hold off on adding this for this merge window, and look at > applying it for the next window. Thank you very much! I got it, anyway I can use kernelshark or perf script to decode raw event data, or I will use kprobe event to fetch the real address :) -- Masami Hiramatsu <[email protected]>
