linux-kernel - Re: [PATCH] efistub: Lower default log level

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CALHNRZ8YUVvQ--Y-EfXW04WYXiKNsj6KSs-OaLMcEnG3_xDMSg@mail.gmail.com>
Date: Mon, 25 Aug 2025 11:34:05 -0500
From: Aaron Kling <webgeek1234@...il.com>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Jan Kiszka <jan.kiszka@...mens.com>, linux-efi@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] efistub: Lower default log level

On Mon, Aug 25, 2025 at 5:44 AM Ard Biesheuvel <ardb@...nel.org> wrote:
>
> On Sun, 24 Aug 2025 at 16:47, Jan Kiszka <jan.kiszka@...mens.com> wrote:
> >
> > On 24.08.25 02:31, Ard Biesheuvel wrote:
> > > On Sat, 16 Aug 2025 at 16:52, Jan Kiszka <jan.kiszka@...mens.com> wrote:
> > >>
> > >> On 15.07.25 03:35, Ard Biesheuvel wrote:
> > >>> On Tue, 8 Jul 2025 at 17:31, Aaron Kling <webgeek1234@...il.com> wrote:
> > >>>>
> > >>>> On Tue, Jul 8, 2025 at 2:30 AM Aaron Kling via B4 Relay
> > >>>> <devnull+webgeek1234.gmail.com@...nel.org> wrote:
> > >>>>>
> > >>>>> From: Aaron Kling <webgeek1234@...il.com>
> > >>>>>
> > >>>>> Some uefi implementations will write the efistub logs to the display
> > >>>>> over a splash image. This is not desirable for debug and info logs, so
> > >>>>> lower the default efi log level to exclude them.
> > >>>>>
> > >>>>> Suggested-by: Ard Biesheuvel <ardb@...nel.org>
> > >>>>> Signed-off-by: Aaron Kling <webgeek1234@...il.com>
> > >>>>> ---
> > >>>>>  drivers/firmware/efi/libstub/printk.c | 4 ++--
> > >>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
> > >>>>>
> > >>>>> diff --git a/drivers/firmware/efi/libstub/printk.c b/drivers/firmware/efi/libstub/printk.c
> > >>>>> index 3a67a2cea7bdf1aa215d48dbf9ece4ceec6e4c28..bc599212c05dd746a9c54abbbe61a4bf70f1a8c4 100644
> > >>>>> --- a/drivers/firmware/efi/libstub/printk.c
> > >>>>> +++ b/drivers/firmware/efi/libstub/printk.c
> > >>>>> @@ -5,13 +5,13 @@
> > >>>>>  #include <linux/ctype.h>
> > >>>>>  #include <linux/efi.h>
> > >>>>>  #include <linux/kernel.h>
> > >>>>> -#include <linux/printk.h> /* For CONSOLE_LOGLEVEL_* */
> > >>>>> +#include <linux/kern_levels.h>
> > >>>>>  #include <asm/efi.h>
> > >>>>>  #include <asm/setup.h>
> > >>>>>
> > >>>>>  #include "efistub.h"
> > >>>>>
> > >>>>> -int efi_loglevel = CONSOLE_LOGLEVEL_DEFAULT;
> > >>>>> +int efi_loglevel = LOGLEVEL_NOTICE;
> > >>>>>
> > >>>>>  /**
> > >>>>>   * efi_char16_puts() - Write a UCS-2 encoded string to the console
> > >>>>>
> > >>>>> ---
> > >>>>> base-commit: d7b8f8e20813f0179d8ef519541a3527e7661d3a
> > >>>>> change-id: 20250708-efi-default-loglevel-4da5a36cac87
> > >>>>>
> > >>>>> Best regards,
> > >>>>> --
> > >>>>> Aaron Kling <webgeek1234@...il.com>
> > >>>>
> > >>>> This patch was originally suggested a few months ago [0], but as far
> > >>>> as I can tell was never queued for merge. Since I'm also hitting a
> > >>>> case where this is relevant, I'm sending this in to bring attention
> > >>>> back to it.
> > >>>>
> > >>>
> > >>> I've queued this up now - thanks.
> > >>>
> > >>
> > >> And how can I get back the loglevel info? It seems I can only choose
> > >> between notice, silent and debug now. And the latter two only by also
> > >> touching the kernel's loglevel.
> > >>
> > >> I'm particularly missing [1] in my UART logs now which is helpful in
> > >> understanding this essential system state.
> > >>
> > >
> > > Hi Jan,
> > >
> > > Is efi=debug too noisy for you?
> >
> > Yes, also because it affects the kernel even more. I'm looking for
> > "efi=info".
> >
> > I don't get the reason behind this change anymore as well. If you have a
> > splash screen shown, weren't you booting with "quiet" before already,
> > thus also without any stub messages?
> >
>
> Yeah, good point. IIRC that came up in the discussion but I can't
> remember the motivation so it can't have been very convincing.
>
> So should we just revert this change?

I'd prefer not to have to set quiet to get a clean splash screen. That
doesn't seem like an unreasonable expectation, getting default
non-debug logs and not having stuff written on top of the splash
image. But if this needs to be reverted, It would be nice to have an
option like the original patch which allowed setting the efi loglevel
separately. Or perhaps leave this as is and add the option to turn up
the efi loglevel independently.

Aaron