user/sven/linux.git/kernel/printk, branch v6.1.110

printk: Update @console_may_schedule in console_trylock_spinning()

2024-04-03T13:19:44Z

[ Upstream commit 8076972468584d4a21dab9aa50e388b3ea9ad8c7 ] console_trylock_spinning() may takeover the console lock from a schedulable context. Update @console_may_schedule to make sure it reflects a trylock acquire. Reported-by: Mukesh Ojha Closes: https://lore.kernel.org/lkml/20240222090538.23017-1-quic_mojha@quicinc.com Fixes: dbdda842fe96 ("printk: Add console owner and waiter logic to load balance console writes") Signed-off-by: John Ogness Reviewed-by: Mukesh Ojha Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/875xybmo2z.fsf@jogness.linutronix.de Signed-off-by: Petr Mladek Signed-off-by: Sasha Levin

serial: Lock console when calling into driver before registration

2024-04-03T13:19:31Z

[ Upstream commit 801410b26a0e8b8a16f7915b2b55c9528b69ca87 ] During the handoff from earlycon to the real console driver, we have two separate drivers operating on the same device concurrently. In the case of the 8250 driver these concurrent accesses cause problems due to the driver's use of banked registers, controlled by LCR.DLAB. It is possible for the setup(), config_port(), pm() and set_mctrl() callbacks to set DLAB, which can cause the earlycon code that intends to access TX to instead access DLL, leading to missed output and corruption on the serial line due to unintended modifications to the baud rate. In particular, for setup() we have: univ8250_console_setup() -> serial8250_console_setup() -> uart_set_options() -> serial8250_set_termios() -> serial8250_do_set_termios() -> serial8250_do_set_divisor() For config_port() we have: serial8250_config_port() -> autoconfig() For pm() we have: serial8250_pm() -> serial8250_do_pm() -> serial8250_set_sleep() For set_mctrl() we have (for some devices): serial8250_set_mctrl() -> omap8250_set_mctrl() -> __omap8250_set_mctrl() To avoid such problems, let's make it so that the console is locked during pre-registration calls to these callbacks, which will prevent the earlycon driver from running concurrently. Remove the partial solution to this problem in the 8250 driver that locked the console only during autoconfig_irq(), as this would result in a deadlock with the new approach. The console continues to be locked during autoconfig_irq() because it can only be called through uart_configure_port(). Although this patch introduces more locking than strictly necessary (and in particular it also locks during the call to rs485_config() which is not affected by this issue as far as I can tell), it follows the principle that it is the responsibility of the generic console code to manage the earlycon handoff by ensuring that earlycon and real console driver code cannot run concurrently, and not the individual drivers. Signed-off-by: Peter Collingbourne Reviewed-by: John Ogness Link: https://linux-review.googlesource.com/id/I7cf8124dcebf8618e6b2ee543fa5b25532de55d8 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240304214350.501253-1-pcc@google.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

printk: Disable passing console lock owner completely during panic()

2024-03-26T22:20:34Z

[ Upstream commit d04d5882cd678b898a9d7c5aee6afbe9e6e77fcd ] The commit d51507098ff91 ("printk: disable optimistic spin during panic") added checks to avoid becoming a console waiter if a panic is in progress. However, the transition to panic can occur while there is already a waiter. The current owner should not pass the lock to the waiter because it might get stopped or blocked anytime. Also the panic context might pass the console lock owner to an already stopped waiter by mistake. It might happen when console_flush_on_panic() ignores the current lock owner, for example: CPU0 CPU1 ---- ---- console_lock_spinning_enable() console_trylock_spinning() [CPU1 now console waiter] NMI: panic() panic_other_cpus_shutdown() [stopped as console waiter] console_flush_on_panic() console_lock_spinning_enable() [print 1 record] console_lock_spinning_disable_and_check() [handover to stopped CPU1] This results in panic() not flushing the panic messages. Fix these problems by disabling all spinning operations completely during panic(). Another advantage is that it prevents possible deadlocks caused by "console_owner_lock". The panic() context does not need to take it any longer. The lockless checks are safe because the functions become NOPs when they see the panic in progress. All operations manipulating the state are still synchronized by the lock even when non-panic CPUs would notice the panic synchronously. The current owner might stay spinning. But non-panic() CPUs would get stopped anyway and the panic context will never start spinning. Fixes: dbdda842fe96 ("printk: Add console owner and waiter logic to load balance console writes") Signed-off-by: John Ogness Link: https://lore.kernel.org/r/20240207134103.1357162-12-john.ogness@linutronix.de Signed-off-by: Petr Mladek Signed-off-by: Sasha Levin

printk: Consolidate console deferred printing

2023-09-23T09:11:07Z

[ Upstream commit 696ffaf50e1f8dbc66223ff614473f945f5fb8d8 ] Printing to consoles can be deferred for several reasons: - explicitly with printk_deferred() - printk() in NMI context - recursive printk() calls The current implementation is not consistent. For printk_deferred(), irq work is scheduled twice. For NMI und recursive, panic CPU suppression and caller delays are not properly enforced. Correct these inconsistencies by consolidating the deferred printing code so that vprintk_deferred() is the top-level function for deferred printing and vprintk_emit() will perform whichever irq_work queueing is appropriate. Also add kerneldoc for wake_up_klogd() and defer_console_output() to clarify their differences and appropriate usage. Signed-off-by: John Ogness Reviewed-by: Sergey Senozhatsky Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20230717194607.145135-6-john.ogness@linutronix.de Signed-off-by: Sasha Levin

printk: Keep non-panic-CPUs out of console lock

2023-09-23T09:11:07Z

[ Upstream commit 51a1d258e50e03a0216bf42b6af9ff34ec402ac1 ] When in a panic situation, non-panic CPUs should avoid holding the console lock so as not to contend with the panic CPU. This is already implemented with abandon_console_lock_in_panic(), which is checked after each printed line. However, non-panic CPUs should also avoid trying to acquire the console lock during a panic. Modify console_trylock() to fail and console_lock() to block() when called from a non-panic CPU during a panic. Signed-off-by: John Ogness Reviewed-by: Sergey Senozhatsky Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20230717194607.145135-4-john.ogness@linutronix.de Signed-off-by: Sasha Levin

printk: ringbuffer: Fix truncating buffer size min_t cast

2023-09-13T07:43:00Z

commit 53e9e33ede37a247d926db5e4a9e56b55204e66c upstream. If an output buffer size exceeded U16_MAX, the min_t(u16, ...) cast in copy_data() was causing writes to truncate. This manifested as output bytes being skipped, seen as %NUL bytes in pstore dumps when the available record size was larger than 65536. Fix the cast to no longer truncate the calculation. Cc: Petr Mladek Cc: Sergey Senozhatsky Cc: Steven Rostedt Cc: John Ogness Reported-by: Vijay Balakrishna Link: https://lore.kernel.org/lkml/d8bb1ec7-a4c5-43a2-9de0-9643a70b899f@linux.microsoft.com/ Fixes: b6cf8b3f3312 ("printk: add lockless ringbuffer") Cc: stable@vger.kernel.org Signed-off-by: Kees Cook Tested-by: Vijay Balakrishna Tested-by: Guilherme G. Piccoli # Steam Deck Reviewed-by: Tyler Hicks (Microsoft) Tested-by: Tyler Hicks (Microsoft) Reviewed-by: John Ogness Reviewed-by: Sergey Senozhatsky Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20230811054528.never.165-kees@kernel.org Signed-off-by: Greg Kroah-Hartman

kernel/printk/index.c: fix memory leak with using debugfs_lookup()

2023-03-11T12:55:32Z

[ Upstream commit 55bf243c514553e907efcf2bda92ba090eca8c64 ] When calling debugfs_lookup() the result must have dput() called on it, otherwise the memory will leak over time. To make things simpler, just call debugfs_lookup_and_remove() instead which handles all of the logic at once. Cc: Chris Down Cc: Petr Mladek Cc: Sergey Senozhatsky Cc: Steven Rostedt Cc: John Ogness Cc: linux-kernel@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Reviewed-by: Sergey Senozhatsky Reviewed-by: John Ogness Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20230202151411.2308576-1-gregkh@linuxfoundation.org Signed-off-by: Sasha Levin

printk: Mark printk percpu data ready ro_after_init

2022-09-29T13:20:52Z

This variable cannot change post boot. Signed-off-by: Thomas Gleixner Signed-off-by: John Ogness Reviewed-by: Sergey Senozhatsky Reviewed-by: Petr Mladek Reviewed-by: Greg Kroah-Hartman Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20220924000454.3319186-6-john.ogness@linutronix.de

printk: Remove bogus comment vs. boot consoles

2022-09-29T13:20:44Z

The comment about unregistering boot consoles is just not matching the reality. Remove it. Signed-off-by: Thomas Gleixner Signed-off-by: John Ogness Reviewed-by: Sergey Senozhatsky Reviewed-by: Petr Mladek Reviewed-by: Greg Kroah-Hartman Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20220924000454.3319186-5-john.ogness@linutronix.de

printk: Remove write only variable nr_ext_console_drivers

2022-09-29T13:20:36Z

Commit a699449bb13b ("printk: refactor and rework printing logic") removed the need for @nr_ext_console_drivers. Remove the unneeded variable. Signed-off-by: Thomas Gleixner Signed-off-by: John Ogness Reviewed-by: Sergey Senozhatsky Reviewed-by: Petr Mladek Reviewed-by: Greg Kroah-Hartman Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20220924000454.3319186-4-john.ogness@linutronix.de