linux-stable.git/kernel/printk, branch v5.15.78

printk: wake waiters for safe and NMI contexts

2022-06-09T08:22:49+00:00

[ Upstream commit 5341b93dea8c39d7612f7a227015d4b1d5cf30db ]

When printk() is called from safe or NMI contexts, it will directly
store the record (vprintk_store()) and then defer the console output.
However, defer_console_output() only causes console printing and does
not wake any waiters of new records.

Wake waiters from defer_console_output() so that they also are aware
of the new records from safe and NMI contexts.

Fixes: 03fc7f9c99c1 ("printk/nmi: Prevent deadlock when accessing the main log buffer in NMI")
Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20220421212250.565456-6-john.ogness@linutronix.de
Signed-off-by: Sasha Levin

printk: add missing memory barrier to wake_up_klogd()

2022-06-09T08:22:48+00:00

[ Upstream commit 1f5d783094cf28b4905f51cad846eb5d1db6673e ]

It is important that any new records are visible to preparing
waiters before the waker checks if the wait queue is empty.
Otherwise it is possible that:

- there are new records available
- the waker sees an empty wait queue and does not wake
- the preparing waiter sees no new records and begins to wait

This is exactly the problem that the function description of
waitqueue_active() warns about.

Use wq_has_sleeper() instead of waitqueue_active() because it
includes the necessary full memory barrier.

Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20220421212250.565456-4-john.ogness@linutronix.de
Signed-off-by: Sasha Levin

printk: use atomic updates for klogd work

2022-06-09T08:22:48+00:00

[ Upstream commit 2ba3673d70178bf07fb75ff25c54bc478add4021 ]

The per-cpu @printk_pending variable can be updated from
sleepable contexts, such as:

  get_random_bytes()
    warn_unseeded_randomness()
      printk_deferred()
        defer_console_output()

and can be updated from interrupt contexts, such as:

  handle_irq_event_percpu()
    __irq_wake_thread()
      wake_up_process()
        try_to_wake_up()
          select_task_rq()
            select_fallback_rq()
              printk_deferred()
                defer_console_output()

and can be updated from NMI contexts, such as:

  vprintk()
    if (in_nmi()) defer_console_output()

Therefore the atomic variant of the updating functions must be used.

Replace __this_cpu_xchg() with this_cpu_xchg().
Replace __this_cpu_or() with this_cpu_or().

Reported-by: Sebastian Andrzej Siewior 
Signed-off-by: John Ogness 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/87iltld4ue.fsf@jogness.linutronix.de
Signed-off-by: Sasha Levin

printk: fix return value of printk.devkmsg __setup handler

2022-04-08T12:23:19+00:00

[ Upstream commit b665eae7a788c5e2bc10f9ac3c0137aa0ad1fc97 ]

If an invalid option value is used with "printk.devkmsg=",
it is silently ignored.
If a valid option value is used, it is honored but the wrong return
value (0) is used, indicating that the command line option had an
error and was not handled. This string is not added to init's
environment strings due to init/main.c::unknown_bootoption()
checking for a '.' in the boot option string and then considering
that string to be an "Unused module parameter".

Print a warning message if a bad option string is used.
Always return 1 from the __setup handler to indicate that the command
line option has been handled.

Fixes: 750afe7babd1 ("printk: add kernel parameter to control writes to /dev/kmsg")
Signed-off-by: Randy Dunlap 
Reported-by: Igor Zhbanov 
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru
Cc: Borislav Petkov 
Cc: Andrew Morton 
Cc: Petr Mladek 
Cc: Sergey Senozhatsky 
Cc: Steven Rostedt 
Cc: John Ogness 
Reviewed-by: John Ogness 
Reviewed-by: Sergey Senozhatsky 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20220228220556.23484-1-rdunlap@infradead.org
Signed-off-by: Sasha Levin

printk: restore flushing of NMI buffers on remote CPUs after NMI backtraces

2021-11-25T08:48:45+00:00

commit 5d5e4522a7f404d1a96fd6c703989d32a9c9568d upstream.

printk from NMI context relies on irq work being raised on the local CPU
to print to console. This can be a problem if the NMI was raised by a
lockup detector to print lockup stack and regs, because the CPU may not
enable irqs (because it is locked up).

Introduce printk_trigger_flush() that can be called another CPU to try
to get those messages to the console, call that where printk_safe_flush
was previously called.

Fixes: 93d102f094be ("printk: remove safe buffers")
Cc: stable@vger.kernel.org # 5.15
Signed-off-by: Nicholas Piggin 
Reviewed-by: Petr Mladek 
Reviewed-by: John Ogness 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20211107045116.1754411-1-npiggin@gmail.com
Signed-off-by: Greg Kroah-Hartman

memblock: introduce saner 'memblock_free_ptr()' interface

2021-09-14T20:23:22+00:00

The boot-time allocation interface for memblock is a mess, with
'memblock_alloc()' returning a virtual pointer, but then you are
supposed to free it with 'memblock_free()' that takes a _physical_
address.

Not only is that all kinds of strange and illogical, but it actually
causes bugs, when people then use it like a normal allocation function,
and it fails spectacularly on a NULL pointer:

   https://lore.kernel.org/all/20210912140820.GD25450@xsang-OptiPlex-9020/

or just random memory corruption if the debug checks don't catch it:

   https://lore.kernel.org/all/61ab2d0c-3313-aaab-514c-e15b7aa054a0@suse.cz/

I really don't want to apply patches that treat the symptoms, when the
fundamental cause is this horribly confusing interface.

I started out looking at just automating a sane replacement sequence,
but because of this mix or virtual and physical addresses, and because
people have used the "__pa()" macro that can take either a regular
kernel pointer, or just the raw "unsigned long" address, it's all quite
messy.

So this just introduces a new saner interface for freeing a virtual
address that was allocated using 'memblock_alloc()', and that was kept
as a regular kernel pointer.  And then it converts a couple of users
that are obvious and easy to test, including the 'xbc_nodes' case in
lib/bootconfig.c that caused problems.

Reported-by: kernel test robot 
Fixes: 40caa127f3c7 ("init: bootconfig: Remove all bootconfig data when the init memory is removed")
Cc: Steven Rostedt 
Cc: Mike Rapoport 
Cc: Andrew Morton 
Cc: Ingo Molnar 
Cc: Masami Hiramatsu 
Cc: Vlastimil Babka 
Signed-off-by: Linus Torvalds

Merge branch 'rework/printk_safe-removal' into for-linus

2021-08-30T14:36:10+00:00

Merge branch 'rework/fixup-for-5.15' into for-linus

2021-08-30T14:33:04+00:00

Merge branch 'for-5.15-verbose-console' into for-linus

2021-08-30T12:56:28+00:00

printk/index: Fix -Wunused-function warning

2021-08-27T14:42:44+00:00

If CONFIG_MODULES is n, we got this:

kernel/printk/index.c:146:13: warning: ‘pi_remove_file’ defined but not used [-Wunused-function]

Move it inside #ifdef block to fix this warning.

Reported-by: Hulk Robot 
Signed-off-by: YueHaibing 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20210804130105.18732-1-yuehaibing@huawei.com