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[45.160.37.218]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-5013bd680a1sm10831771cf.16.2026.01.13.04.41.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Jan 2026 04:41:51 -0800 (PST) Message-ID: Subject: Re: [PATCH 00/19] printk cleanup - part 3 From: Marcos Paulo de Souza To: Daniel Thompson Cc: Richard Weinberger , Anton Ivanov , Johannes Berg , Greg Kroah-Hartman , Jason Wessel , Daniel Thompson , Douglas Anderson , Petr Mladek , Steven Rostedt , John Ogness , Sergey Senozhatsky , Jiri Slaby , Breno Leitao , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Geert Uytterhoeven , Kees Cook , Tony Luck , "Guilherme G. Piccoli" , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Andreas Larsson , Alexander Shishkin , Maxime Coquelin , Alexandre Torgue , Jacky Huang , Shan-Chun Hung , Laurentiu Tudor , linux-um@lists.infradead.org, linux-kernel@vger.kernel.org, kgdb-bugreport@lists.sourceforge.net, linux-serial@vger.kernel.org, netdev@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-hardening@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org Date: Tue, 13 Jan 2026 09:41:34 -0300 In-Reply-To: References: <20251227-printk-cleanup-part3-v1-0-21a291bcf197@suse.com> Autocrypt: addr=mpdesouza@suse.com; prefer-encrypt=mutual; keydata=mDMEZ/0YqhYJKwYBBAHaRw8BAQdA4JZz0FED+JD5eKlhkNyjDrp6lAGmgR3LPTduPYGPT Km0Kk1hcmNvcyBQYXVsbyBkZSBTb3V6YSA8bXBkZXNvdXphQHN1c2UuY29tPoiTBBMWCgA7FiEE2g gC66iLbhUsCBoBemssEuRpLLUFAmf9GKoCGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgk QemssEuRpLLWGxwD/S1I0bjp462FlKb81DikrOfWbeJ0FOJP44eRzmn20HmEBALBZIMrfIH2dJ5eM GO8seNG8sYiP6JfRjl7Hyqca6YsE Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.2 (by Flathub.org) Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2026-01-05 at 14:08 +0000, Daniel Thompson wrote: > On Mon, Jan 05, 2026 at 12:52:14PM +0000, Daniel Thompson wrote: > > Hi Marcos > >=20 > > On Sat, Dec 27, 2025 at 09:16:07AM -0300, Marcos Paulo de Souza > > wrote: > > > The parts 1 and 2 can be found here [1] and here[2]. > > >=20 > > > The changes proposed in this part 3 are mostly to clarify the > > > usage of > > > the interfaces for NBCON, and use the printk helpers more > > > broadly. > > > Besides it, it also introduces a new way to register consoles > > > and drop thes the CON_ENABLED flag. It seems too much, but in > > > reality > > > the changes are not complex, and as the title says, it's > > > basically a > > > cleanup without changing the functional changes. > >=20 > > I ran this patchset through the kgdb test suite and I'm afraid it > > is > > reporting functional changes. > >=20 > > Specifically the earlycon support for kdb has regressed (FWIW the > > problem bisects down to the final patch in the series where > > CON_ENABLED > > is removed). > >=20 > > Reproduction on x86-64 KVM outside of the test suite should be > > easy: > >=20 > > =C2=A0=C2=A0=C2=A0 make defconfig > > =C2=A0=C2=A0=C2=A0 scripts/config \ > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 --enable DEBUG_INFO \ > > --enable DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT \ > > --enable DEBUG_FS \ > > --enable KALLSYMS_ALL \ > > --enable MAGIC_SYSRQ \ > > --enable KGDB \ > > --enable KGDB_TESTS \ > > --enable KGDB_KDB \ > > --enable KDB_KEYBOARD \ > > --enable LKDTM \ > > --enable SECURITY_LOCKDOWN_LSM > > =C2=A0=C2=A0=C2=A0 make olddefconfig > > =C2=A0=C2=A0=C2=A0 make -j$(nproc) > > =C2=A0=C2=A0=C2=A0 qemu-system-x86_64 \ > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 -m 1G -smp 2 -nographic \ > > -kernel arch/x86/boot/bzImage \ > > -append "console=3DttyS0,115200 kgdboc=3DttyS0 > > earlycon=3Duart8250,io,0x3f8 kgdboc_earlycon kgdbwait" >=20 > Actually I realized there was a simpler reproduction (hinted at by > the > missing "printk: legacy bootconsole [uart8250] enabled" in the > regressed > case). It looks like the earlycon simply doesn't work and that means > the > reproduction doesn't require anything related to kgdb at all. Simply: >=20 > =C2=A0=C2=A0=C2=A0 make defconfig > =C2=A0=C2=A0=C2=A0 make -j$(nproc) > =C2=A0=C2=A0=C2=A0 qemu-system-x86_64 -m 1G -smp 2 -nographic -kernel > arch/x86/boot/bzImage \ > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 -append "earlycon=3Duart8250,i= o,0x3f8" >=20 > With the part 3 patchset applied I get no output from the earlycon > (without the patch set I get the early boot messages which, as > expected, > stop when tty0 comes up). Hi Daniel, sorry for the late reply! Lots of things to check lately :) Ok, I reproduced here, thanks a lot for testing kgdboc, it's a quick way to check that the new register_console_force is not working. Let me take a look to find what's wrong. Thanks a lot for finding this issue! >=20 >=20 > Daniel.