On Fri, Jun 29, 2018 at 1:13 AM, Schmauss, Erik <[email protected]> wrote: >> On Tue, Jun 26, 2018 at 8:57 PM, Toralf Förster <[email protected]> >> 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 <[email protected]> >> 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
