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    SubjectRe: small dmesg regression in kernel 4.17.3
    On Fri, Jun 29, 2018 at 1:13 AM, Schmauss, Erik <erik.schmauss@intel.com> wrote:
    >> On Tue, Jun 26, 2018 at 8:57 PM, Toralf Förster <toralf.foerster@gmx.de>
    >> wrote:
    >> > The attached dmesg contains non printable chars 0x01 33 around "ACPI
    >> > BIOS Error (bug): Could not resolve" which is a new issue compared to
    >> > the dmesg of 4.17.2
    >> >
    >> > System is a stable hardened Gentoo Linux at a ThinkPad T440s.
    >>
    >> I bet the below commit makes this.
    >>
    >> commit 2e78935d1e27d31955ad2dad4abe6c453cf669fd
    >> Author: Erik Schmauss <erik.schmauss@intel.com>
    >> Date: Fri Jun 1 12:06:43 2018 -0700
    >>
    >> ACPICA: AML parser: attempt to continue loading table after error
    >>
    >>
    > Hi Andy,
    >
    >> So, it does add leading '\n' which flushes buffers followed by printing the
    >> message you see. But, I'm guessing now, kernel adds a default level since it's
    >> going to dmesg which you can see as unprintable symbols.
    >
    > What do you mean by a default level?

    I can't find fast the better example, though if you look at printk_get_level()
    https://elixir.bootlin.com/linux/latest/source/include/linux/printk.h#L16

    it will shed a light on a format. Thus, 0x01 0x33 means start of the
    kernel error message (error is a level).

    Kernel messaging protocol is defined in
    https://elixir.bootlin.com/linux/latest/source/include/linux/kern_levels.h

    This is my understanding on what's going on (I might be mistaken).

    --
    With Best Regards,
    Andy Shevchenko

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