linux-kernel - [PATCH v3 0/4] Handle NBCON consoles on KDB

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-next>] [day] [month] [year] [list]

Message-Id: <20250902-nbcon-kgdboc-v3-0-cd30a8106f1c@suse.com>
Date: Tue, 02 Sep 2025 15:33:51 -0300
From: Marcos Paulo de Souza <mpdesouza@...e.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Petr Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, 
 John Ogness <john.ogness@...utronix.de>, 
 Sergey Senozhatsky <senozhatsky@...omium.org>, 
 Jason Wessel <jason.wessel@...driver.com>, 
 Daniel Thompson <danielt@...nel.org>, 
 Douglas Anderson <dianders@...omium.org>
Cc: linux-kernel@...r.kernel.org, kgdb-bugreport@...ts.sourceforge.net, 
 Marcos Paulo de Souza <mpdesouza@...e.com>
Subject: [PATCH v3 0/4] Handle NBCON consoles on KDB

These changes reached v3 (since the first version was tagged as v2 by me...),
thanks to all reviewers for the suggestions and questions about the code.

A new patch was introduced this time (3/4), adding an exception to nbcon
code when trying to acquire the context of a console when KDB is running,
suggested by John and Petr. Thanks a lot!

Testing
-------

I did the tests using qemu and reapplying commit f79b163c4231
('Revert "serial: 8250: Switch to nbcon console"') created originally by
John, just to exercise the common 8250 serial from qemu. The commit can
be checked on [1]. I had to solve some conflicts since the code has been
reworked after the commit was reverted.

Without the patches, I can't see any mirrored messages on the NBCON
console when KDB is triggered. With the patches I can see the messages.

[1]: https://github.com/marcosps/linux/commit/618bd49f8533db85d9c322f9ad1cb0da22aca9ee

Signed-off-by: Marcos Paulo de Souza <mpdesouza@...e.com>
---
Changes in v3:
- Only call nbcon_context_release if nbcon_context_exit_unsafe returns true (John Ogness)
- Dropped the prototype of console_is_usable from kernel/printk/internal. (Petr Mladek)
- Add comments to the new functions introduced (Petr Mladek)
- Flush KDB console on nbcon_kdb_release (Petr Mladek)
- Add an exception for KDB on nbcon_context_try_acquire_direct (John Ogness and Petr Mladek)
- Link to v2: https://lore.kernel.org/r/20250811-nbcon-kgdboc-v2-0-c7c72bcdeaf6@suse.com

Changes in v2:
- Set by mistake ..
- Link to v1: https://lore.kernel.org/r/20250713-nbcon-kgdboc-v1-0-51eccd9247a8@suse.com

---
Marcos Paulo de Souza (4):
      printk: nbcon: Export console_is_usable
      printk: nbcon: Introduce KDB helpers
      printk: nbcon: Allow KDB to acquire the NBCON context
      kdb: Adapt kdb_msg_write to work with NBCON consoles

 include/linux/console.h   | 50 +++++++++++++++++++++++++++++++++
 kernel/debug/kdb/kdb_io.c | 46 +++++++++++++++++++++----------
 kernel/printk/internal.h  | 44 -----------------------------
 kernel/printk/nbcon.c     | 70 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 151 insertions(+), 59 deletions(-)
---
base-commit: 618bd49f8533db85d9c322f9ad1cb0da22aca9ee
change-id: 20250713-nbcon-kgdboc-efcfc37fde46

Best regards,
-- 
Marcos Paulo de Souza <mpdesouza@...e.com>