We need interrupts disabled when calling console_trylock_for_printk()
only so that cpu id we pass to can_use_console() remains valid (for
other things console_sem provides all the exclusion we need and
deadlocks on console_sem due to interrupts are impossible because we use
down_trylock()). However if we are rescheduled, we are guaranteed to
run on an online cpu so we can easily just get the cpu id in
can_use_console().
We can lose a bit of performance when we enable interrupts in
vprintk_emit() and then disable them again in console_unlock() but OTOH
it can somewhat reduce interrupt latency caused by console_unlock().
We differ from (reverted) commit 939f04bec1 in that we avoid calling
console_unlock() from vprintk_emit() with lockdep enabled as that has
unveiled quite some bugs leading to system freezes during boot (e.g.
https://lkml.org/lkml/2014/5/30/242,
https://lkml.org/lkml/2014/6/28/521).
Signed-off-by: Jan Kara <jack@suse.cz>
Tested-by: Andreas Bombe <aeb@debian.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Some small cleanups to kernel/printk/printk.c. None of them should
cause any change in behavior.
- When CONFIG_PRINTK is defined, parenthesize the value of LOG_LINE_MAX.
- When CONFIG_PRINTK is *not* defined, there is an extra LOG_LINE_MAX
definition; delete it.
- Pull an assignment out of a conditional expression in console_setup().
- Use isdigit() in console_setup() rather than open coding it.
- In update_console_cmdline(), drop a NUL-termination assignment;
the strlcpy() call that precedes it guarantees it's not needed.
- Simplify some logic in printk_timed_ratelimit().
Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Jan Kara <jack@suse.cz>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use the IS_ENABLED() macro rather than #ifdef blocks to set certain
global values.
Signed-off-by: Alex Elder <elder@linaro.org>
Acked-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix a few comments that don't accurately describe their corresponding
code. It also fixes some minor typographical errors.
Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Jan Kara <jack@suse.cz>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit a8fe19ebfb ("kernel/printk: use symbolic defines for console
loglevels") makes consistent use of symbolic values for printk() log
levels.
The naming scheme used is different from the one used for
DEFAULT_MESSAGE_LOGLEVEL though. Change that symbol name to be
MESSAGE_LOGLEVEL_DEFAULT for consistency. And because the value of that
symbol comes from a similarly-named config option, rename
CONFIG_DEFAULT_MESSAGE_LOGLEVEL as well.
Signed-off-by: Alex Elder <elder@linaro.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Jan Kara <jack@suse.cz>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In do_syslog() there's a path used by kmsg_poll() and kmsg_read() that
only needs to know whether there's any data available to read (and not
its size). These callers only check for non-zero return. As a
shortcut, do_syslog() returns the difference between what has been
logged and what has been "seen."
The comments say that the "count of records" should be returned but it's
not. Instead it returns (log_next_idx - syslog_idx), which is a
difference between buffer offsets--and the result could be negative.
The behavior is the same (it'll be zero or not in the same cases), but
the count of records is more meaningful and it matches what the comments
say. So change the code to return that.
Signed-off-by: Alex Elder <elder@linaro.org>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Joe Perches <joe@perches.com>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The default size of the ring buffer is too small for machines with a
large amount of CPUs under heavy load. What ends up happening when
debugging is the ring buffer overlaps and chews up old messages making
debugging impossible unless the size is passed as a kernel parameter.
An idle system upon boot up will on average spew out only about one or
two extra lines but where this really matters is on heavy load and that
will vary widely depending on the system and environment.
There are mechanisms to help increase the kernel ring buffer for tracing
through debugfs, and those interfaces even allow growing the kernel ring
buffer per CPU. We also have a static value which can be passed upon
boot. Relying on debugfs however is not ideal for production, and
relying on the value passed upon bootup is can only used *after* an
issue has creeped up. Instead of being reactive this adds a proactive
measure which lets you scale the amount of contributions you'd expect to
the kernel ring buffer under load by each CPU in the worst case
scenario.
We use num_possible_cpus() to avoid complexities which could be
introduced by dynamically changing the ring buffer size at run time,
num_possible_cpus() lets us use the upper limit on possible number of
CPUs therefore avoiding having to deal with hotplugging CPUs on and off.
This introduces the kernel configuration option LOG_CPU_MAX_BUF_SHIFT
which is used to specify the maximum amount of contributions to the
kernel ring buffer in the worst case before the kernel ring buffer flips
over, the size is specified as a power of 2. The total amount of
contributions made by each CPU must be greater than half of the default
kernel ring buffer size (1 << LOG_BUF_SHIFT bytes) in order to trigger
an increase upon bootup. The kernel ring buffer is increased to the
next power of two that would fit the required minimum kernel ring buffer
size plus the additional CPU contribution. For example if LOG_BUF_SHIFT
is 18 (256 KB) you'd require at least 128 KB contributions by other CPUs
in order to trigger an increase of the kernel ring buffer. With a
LOG_CPU_BUF_SHIFT of 12 (4 KB) you'd require at least anything over > 64
possible CPUs to trigger an increase. If you had 128 possible CPUs the
amount of minimum required kernel ring buffer bumps to:
((1 << 18) + ((128 - 1) * (1 << 12))) / 1024 = 764 KB
Since we require the ring buffer to be a power of two the new required
size would be 1024 KB.
This CPU contributions are ignored when the "log_buf_len" kernel
parameter is used as it forces the exact size of the ring buffer to an
expected power of two value.
[pmladek@suse.cz: fix build]
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Tested-by: Davidlohr Bueso <davidlohr@hp.com>
Tested-by: Petr Mladek <pmladek@suse.cz>
Reviewed-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Joe Perches <joe@perches.com>
Cc: Arun KS <arunks.linux@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In practice the power of 2 practice of the size of the kernel ring
buffer remains purely historical but not a requirement, specially now
that we have LOG_ALIGN and use it for both static and dynamic
allocations. It could have helped with implicit alignment back in the
days given the even the dynamically sized ring buffer was guaranteed to
be aligned so long as CONFIG_LOG_BUF_SHIFT was set to produce a
__LOG_BUF_LEN which is architecture aligned, since log_buf_len=n would
be allowed only if it was > __LOG_BUF_LEN and we always ended up
rounding the log_buf_len=n to the next power of 2 with
roundup_pow_of_two(), any multiple of 2 then should be also architecture
aligned. These assumptions of course relied heavily on
CONFIG_LOG_BUF_SHIFT producing an aligned value but users can always
change this.
We now have precise alignment requirements set for the log buffer size
for both static and dynamic allocations, but lets upkeep the old
practice of using powers of 2 for its size to help with easy expected
scalable values and the allocators for dynamic allocations. We'll reuse
this later so move this into a helper.
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Joe Perches <joe@perches.com>
Cc: Arun KS <arunks.linux@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We have to consider alignment for the ring buffer both for the default
static size, and then also for when an dynamic allocation is made when
the log_buf_len=n kernel parameter is passed to set the size
specifically to a size larger than the default size set by the
architecture through CONFIG_LOG_BUF_SHIFT.
The default static kernel ring buffer can be aligned properly if
architectures set CONFIG_LOG_BUF_SHIFT properly, we provide ranges for
the size though so even if CONFIG_LOG_BUF_SHIFT has a sensible aligned
value it can be reduced to a non aligned value. Commit 6ebb017de9
("printk: Fix alignment of buf causing crash on ARM EABI") by Andrew
Lunn ensures the static buffer is always aligned and the decision of
alignment is done by the compiler by using __alignof__(struct log).
When log_buf_len=n is used we allocate the ring buffer dynamically.
Dynamic allocation varies, for the early allocation called before
setup_arch() memblock_virt_alloc() requests a page aligment and for the
default kernel allocation memblock_virt_alloc_nopanic() requests no
special alignment, which in turn ends up aligning the allocation to
SMP_CACHE_BYTES, which is L1 cache aligned.
Since we already have the required alignment for the kernel ring buffer
though we can do better and request explicit alignment for LOG_ALIGN.
This does that to be safe and make dynamic allocation alignment
explicit.
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Tested-by: Petr Mladek <pmladek@suse.cz>
Acked-by: Petr Mladek <pmladek@suse.cz>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Joe Perches <joe@perches.com>
Cc: Arun KS <arunks.linux@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Revert commit 939f04bec1 ("printk: enable interrupts before calling
console_trylock_for_printk()").
Andreas reported:
: None of the post 3.15 kernel boot for me. They all hang at the GRUB
: screen telling me it loaded and started the kernel, but the kernel
: itself stops before it prints anything (or even replaces the GRUB
: background graphics).
939f04bec1 is modest latency reduction. Revert it until we understand
the reason for these failures.
Reported-by: Andreas Bombe <aeb@debian.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
... instead of naked numbers.
Stuff in sysrq.c used to set it to 8 which is supposed to mean above
default level so set it to DEBUG instead as we're terminating/killing all
tasks and we want to be verbose there.
Also, correct the check in x86_64_start_kernel which should be >= as
we're clearly issuing the string there for all debug levels, not only
the magical 10.
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Joe Perches <joe@perches.com>
Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If the log ring buffer becomes full, we silently overwrite old messages
with new data. console_unlock will detect this case and fast-forward the
console_* pointers to skip over the corrupted data, but nothing will be
reported to the user.
This patch hijacks the first valid log message after detecting that we
dropped messages and prefixes it with a note detailing how many messages
were dropped. For long (~1000 char) messages, this will result in some
truncation of the real message, but given that we're dropping things
anyway, that doesn't seem to be the end of the world.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
After learning we'll need some sort of deferred printk functionality in
the timekeeping core, Peter suggested we rename the printk_sched function
so it can be reused by needed subsystems.
This only changes the function name. No logic changes.
Signed-off-by: John Stultz <john.stultz@linaro.org>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Bohac <jbohac@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
An earlier change in -mm (printk: remove separate printk_sched
buffers...), removed the printk_sched irqsave/restore lines since it was
safe for current users. Since we may be expanding usage of
printk_sched(), disable preepmtion for this function to make it more
generally safe to call.
Signed-off-by: John Stultz <john.stultz@linaro.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Bohac <jbohac@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
To prevent deadlocks with doing a printk inside the scheduler,
printk_sched() was created. The issue is that printk has a console_sem
that it can grab and release. The release does a wake up if there's a
task pending on the sem, and this wake up grabs the rq locks that is
held in the scheduler. This leads to a possible deadlock if the wake up
uses the same rq as the one with the rq lock held already.
What printk_sched() does is to save the printk write in a per cpu buffer
and sets the PRINTK_PENDING_SCHED flag. On a timer tick, if this flag is
set, the printk() is done against the buffer.
There's a couple of issues with this approach.
1) If two printk_sched()s are called before the tick, the second one
will overwrite the first one.
2) The temporary buffer is 512 bytes and is per cpu. This is a quite a
bit of space wasted for something that is seldom used.
In order to remove this, the printk_sched() can use the printk buffer
instead, and delay the console_trylock()/console_unlock() to the queued
work.
Because printk_sched() would then be taking the logbuf_lock, the
logbuf_lock must not be held while doing anything that may call into the
scheduler functions, which includes wake ups. Unfortunately, printk()
also has a console_sem that it uses, and on release, the up(&console_sem)
may do a wake up of any pending waiters. This must be avoided while
holding the logbuf_lock.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We need interrupts disabled when calling console_trylock_for_printk()
only so that cpu id we pass to can_use_console() remains valid (for
other things console_sem provides all the exclusion we need and
deadlocks on console_sem due to interrupts are impossible because we use
down_trylock()). However if we are rescheduled, we are guaranteed to
run on an online cpu so we can easily just get the cpu id in
can_use_console().
We can lose a bit of performance when we enable interrupts in
vprintk_emit() and then disable them again in console_unlock() but OTOH
it can somewhat reduce interrupt latency caused by console_unlock()
especially since later in the patch series we will want to spin on
console_sem in console_trylock_for_printk().
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Printk calls mutex_acquire() / mutex_release() by hand to instrument
lockdep about console_sem. However in some corner cases the
instrumentation is missing. Fix the problem by creating helper functions
for locking / unlocking console_sem which take care of lockdep
instrumentation as well.
Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Fabio Estevam <festevam@gmail.com>
Reported-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
Tested-By: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There's no reason to hold lockbuf_lock when entering
console_trylock_for_printk().
The first thing this function does is to call down_trylock(console_sem)
and if that fails it immediately unlocks lockbuf_lock. So lockbuf_lock
isn't needed for that branch. When down_trylock() succeeds, the rest of
console_trylock() is OK without lockbuf_lock (it is called without it
from other places), and the only remaining thing in
console_trylock_for_printk() is can_use_console() call. For that call
console_sem is enough (it iterates all consoles and checks CON_ANYTIME
flag).
So we drop logbuf_lock before entering console_trylock_for_printk() which
simplifies the code.
[akpm@linux-foundation.org: fix have_callable_console() comment]
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Comment about interesting interlocking between lockbuf_lock and
console_sem is outdated.
It was added in 2002 by commit a880f45a48be during conversion of
console_lock to console_sem + lockbuf_lock.
At that time release_console_sem() (today's equivalent is
console_unlock()) was indeed using lockbuf_lock to avoid races between
trylock on console_sem in printk() and unlock of console_sem. However
these days the interlocking is gone and the races are avoided by
rechecking logbuf state after releasing console_sem.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I wonder if anyone uses printk return value but it is there and should be
counted correctly.
This patch modifies log_store() to return the number of really stored
bytes from the 'text' part. Also it handles the return value in
vprintk_emit().
Note that log_store() is used also in cont_flush() but we could ignore the
return value there. The function works with characters that were already
counted earlier. In addition, the store could newer fail here because the
length of the printed text is limited by the "cont" buffer and "dict" is
NULL.
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We might want to print at least part of too long messages and add some
warning for debugging purpose.
The question is how long the shrunken message should be. If we use the
whole buffer, it might get rotated too soon. Let's try to use only 1/4 of
the buffer for now.
Also shrink the whole dictionary. We do not want to parse it or break it
in the middle of some pair of values. It would not cause any real harm
but still.
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We will want to recompute the message size when shrinking too long
messages. Let's put the code into separate function.
The side effect of setting "pad_len" is not nice but it is worth removing
the code duplication. Note that I will probably have one more usage for
this function when handling messages safe way in NMI context.
This patch does not change the existing behavior.
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There was no check for too long messages. The check for free space always
passed when first_seq and next_seq were equal. Enough free space was not
guaranteed, though.
log_store() might be called to store messages up to 64kB + 64kB + 16B.
This is sum of maximal text_len, dict_len values, and the size of the
structure printk_log.
On the other hand, the minimal size for the main log buffer currently is
4kB and it is enforced only by Kconfig.
The good news is that the usage looks safe right now. log_store() is
called only from vprintk_emit() and cont_flush(). Here the "text" part is
always passed via a static buffer and the length is limited to
LOG_LINE_MAX which is 1024. The "dict" part is NULL in most cases. The
only exceptions is when vprintk_emit() is called from printk_emit() and
dev_vprintk_emit(). But printk_emit() is currently used only in
devkmsg_writev() and here "dict" is NULL as well. In dev_vprintk_emit(),
"dict" is limited by the static buffer "hdr" of the size 128 bytes. It
meas that the current maximal printed text is 1024B + 128B + 16B and it
always fit the log buffer.
But it is only matter of time when someone calls printk_emit() with unsafe
parameters, especially the "dict" one.
This patch adds a check for the free space when the buffer is empty. It
reuses the already existing log_has_space() function but it has to add an
extra parameter. It defines whether the buffer is empty. Note that the
same values of "first_idx" and "next_idx" might also mean that the buffer
is full.
If the buffer is empty, we must respect the current position of the
indexes. We cannot reset them to the beginning of the buffer. Otherwise,
the functions reading the buffer would get crazy.
The question is what to do when the message is too long. This patch uses
the easiest solution and just ignores the problematic message. Let's do
something better in a followup patch.
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The check for free space in the log buffer always passes when "first_seq"
and "next_seq" are equal. In theory, it might cause writing outside of
the log buffer.
Fortunately, the current usage looks safe because the used "text" and
"dict" buffers are quite limited. See the second patch for more details.
Anyway, it is better to be on the safe side and add a check. An easy
solution is done in the 2nd patch and it is improved in the 4th patch.
5th patch fixes the computation of the printed message length.
1st and 3rd patches just do some code refactoring to make the other
patches easier.
This patch (of 5):
There will be needed some fixes in the check for free space. They will be
easier if the code is moved outside of the quite long log_store()
function.
This patch does not change the existing behavior.
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Here is the big tty / serial driver pull request for 3.16-rc1.
A variety of different serial driver fixes and updates and additions,
nothing huge, and no real major core tty changes at all.
All have been in linux-next for a while.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'tty-3.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty into next
Pull tty/serial driver updates from Greg KH:
"Here is the big tty / serial driver pull request for 3.16-rc1.
A variety of different serial driver fixes and updates and additions,
nothing huge, and no real major core tty changes at all.
All have been in linux-next for a while"
* tag 'tty-3.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (84 commits)
Revert "serial: imx: remove the DMA wait queue"
serial: kgdb_nmi: Improve console integration with KDB I/O
serial: kgdb_nmi: Switch from tasklets to real timers
serial: kgdb_nmi: Use container_of() to locate private data
serial: cpm_uart: No LF conversion in put_poll_char()
serial: sirf: Fix compilation failure
console: Remove superfluous readonly check
console: Use explicit pointer type for vc_uni_pagedir* fields
vgacon: Fix & cleanup refcounting
ARM: tty: Move HVC DCC assembly to arch/arm
tty/hvc/hvc_console: Fix wakeup of HVC thread on hvc_kick()
drivers/tty/n_hdlc.c: replace kmalloc/memset by kzalloc
vt: emulate 8- and 24-bit colour codes.
printk/of_serial: fix serial console cessation part way through boot.
serial: 8250_dma: check the result of TX buffer mapping
serial: uart: add hw flow control support configuration
tty/serial: at91: add interrupts for modem control lines
tty/serial: at91: use mctrl_gpio helpers
tty/serial: Add GPIOLIB helpers for controlling modem lines
ARM: at91: gpio: implement get_direction
...
Commit 5f5c9ae56c
"serial_core: Unregister console in uart_remove_one_port()"
fixed a crash where a serial port was removed but
not deregistered as a console.
There is a side effect of that commit for platforms having serial consoles
and of_serial configured (CONFIG_SERIAL_OF_PLATFORM). The serial console
is disabled midway through the boot process.
This cessation of the serial console affects PowerPC computers
such as the MVME5100 and SAM440EP.
The sequence is:
bootconsole [udbg0] enabled
....
serial8250/16550 driver initialises and registers its UARTS,
one of these is the serial console.
console [ttyS0] enabled
....
of_serial probes "platform" devices, registering them as it goes.
One of these is the serial console.
console [ttyS0] disabled.
The disabling of the serial console is due to:
a. unregister_console in printk not clearing the
CONS_ENABLED bit in the console flags,
even though it has announced that the console is disabled; and
b. of_platform_serial_probe in of_serial not setting the port type
before it registers with serial8250_register_8250_port.
This patch ensures that the serial console is re-enabled when of_serial
registers a serial port that corresponds to the designated console.
Signed-off-by: Stephen Chivers <schivers@csc.com>
Tested-by: Stephen Chivers <schivers@csc.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> [unregister_console]
Cc: stable <stable@vger.kernel.org> # 3.15
===
The above failure was identified in Linux-3.15-rc2.
Tested using MVME5100 and SAM440EP PowerPC computers with
kernels built from Linux-3.15-rc5 and tty-next.
The continued operation of the serial console is vital for computers
such as the MVME5100 as that Single Board Computer does not
have any grapical/display hardware.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
As requested by Linus add explicit __visible to the asmlinkage users.
This marks functions visible to assembler.
Tree sweep for rest of tree.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1398984278-29319-4-git-send-email-andi@firstfloor.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Fix a warning about possible circular locking dependency.
If do in following sequence:
enter suspend -> resume -> plug-out CPUx (echo 0 > cpux/online)
lockdep will show warning as following:
======================================================
[ INFO: possible circular locking dependency detected ]
3.10.0 #2 Tainted: G O
-------------------------------------------------------
sh/1271 is trying to acquire lock:
(console_lock){+.+.+.}, at: console_cpu_notify+0x20/0x2c
but task is already holding lock:
(cpu_hotplug.lock){+.+.+.}, at: cpu_hotplug_begin+0x2c/0x58
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (cpu_hotplug.lock){+.+.+.}:
lock_acquire+0x98/0x12c
mutex_lock_nested+0x50/0x3d8
cpu_hotplug_begin+0x2c/0x58
_cpu_up+0x24/0x154
cpu_up+0x64/0x84
smp_init+0x9c/0xd4
kernel_init_freeable+0x78/0x1c8
kernel_init+0x8/0xe4
ret_from_fork+0x14/0x2c
-> #1 (cpu_add_remove_lock){+.+.+.}:
lock_acquire+0x98/0x12c
mutex_lock_nested+0x50/0x3d8
disable_nonboot_cpus+0x8/0xe8
suspend_devices_and_enter+0x214/0x448
pm_suspend+0x1e4/0x284
try_to_suspend+0xa4/0xbc
process_one_work+0x1c4/0x4fc
worker_thread+0x138/0x37c
kthread+0xa4/0xb0
ret_from_fork+0x14/0x2c
-> #0 (console_lock){+.+.+.}:
__lock_acquire+0x1b38/0x1b80
lock_acquire+0x98/0x12c
console_lock+0x54/0x68
console_cpu_notify+0x20/0x2c
notifier_call_chain+0x44/0x84
__cpu_notify+0x2c/0x48
cpu_notify_nofail+0x8/0x14
_cpu_down+0xf4/0x258
cpu_down+0x24/0x40
store_online+0x30/0x74
dev_attr_store+0x18/0x24
sysfs_write_file+0x16c/0x19c
vfs_write+0xb4/0x190
SyS_write+0x3c/0x70
ret_fast_syscall+0x0/0x48
Chain exists of:
console_lock --> cpu_add_remove_lock --> cpu_hotplug.lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(cpu_hotplug.lock);
lock(cpu_add_remove_lock);
lock(cpu_hotplug.lock);
lock(console_lock);
*** DEADLOCK ***
There are three locks involved in two sequence:
a) pm suspend:
console_lock (@suspend_console())
cpu_add_remove_lock (@disable_nonboot_cpus())
cpu_hotplug.lock (@_cpu_down())
b) Plug-out CPUx:
cpu_add_remove_lock (@(cpu_down())
cpu_hotplug.lock (@_cpu_down())
console_lock (@console_cpu_notify()) => Lockdeps prints warning log.
There should be not real deadlock, as flag of console_suspended can
protect this.
Although console_suspend() releases console_sem, it doesn't tell lockdep
about it. That results in the lockdep warning about circular locking
when doing the following: enter suspend -> resume -> plug-out CPUx (echo
0 > cpux/online)
Fix the problem by telling lockdep we actually released the semaphore in
console_suspend() and acquired it again in console_resume().
Signed-off-by: Jane Li <jiel@marvell.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is just a tiny optimization. It removes duplicate computation of
the message size.
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It seems that we have newer used the last byte in the ring buffer. In
fact, we have newer used the last 4 bytes because of padding.
First problem is in the check for free space. The exact number of free
bytes is enough to store the length of data.
Second problem is in the check where the ring buffer is rotated. The
left side counts the first unused index. It is unused, so it might be
the same as the size of the buffer.
Note that the first problem has to be fixed together with the second
one. Otherwise, the buffer is rotated even when there is enough space
on the end of the buffer. Then the beginning of the buffer is rewritten
and valid entries get corrupted.
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is no check for potential "text_len" overflow. It is not needed
because only valid level is detected. It took me some time to
understand why. It would deserve a comment ;-)
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The kernel log level "c" was removed in commit 61e99ab8e3 ("printk:
remove the now unnecessary "C" annotation for KERN_CONT"). It is no
longer detected in printk_get_level(). Hence we do not need to check it
in vprintk_emit.
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is not a buffer overflow in the traditional sense: we don't
overflow any *kernel* buffers, but we do mis-count the amount of data we
copy back to user space for the SYSLOG_ACTION_READ_ALL case.
In particular, if the user buffer is too small to hold everything, and
*if* there is a continuation line at just the right place, we can end up
giving the user more data than he asked for.
The reason is that we first count up the number of bytes all the log
records contains, then we walk the records again until we've skipped the
records at the beginning that won't fit, and then we walk the rest of
the records and copy them to the user space buffer.
And in between that "skip the initial records that won't fit" and the
"copy the records that *will* fit to user space", we reset the 'prev'
variable that contained the record information for the last record not
copied. That meant that when we started copying to user space, we now
had a different character count than what we had originally calculated
in the first record walk-through.
The fix is to simply not clear the 'prev' flags value (in both cases
where we had the same logic: syslog_print_all and kmsg_dump_get_buffer:
the latter is used for pstore-like dumping)
Reported-and-tested-by: Debabrata Banerjee <dbanerje@akamai.com>
Acked-by: Kay Sievers <kay@vrfy.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
An earlier newline was missing and current print is from different task.
In this scenario flush the continuation line and store this line
seperatly.
This patch fix the below scenario of timestamp interleaving,
[ 28.154370 ] read_word_reg : reg[0x 3], reg[0x 4] data [0x 642]
[ 28.155428 ] uart disconnect
[ 31.947341 ] dvfs[cpufreq.c<275>]:plug-in cpu<1> done
[ 28.155445 ] UART detached : send switch state 201
[ 32.014112 ] read_reg : reg[0x 3] data[0x21]
[akpm@linux-foundation.org: simplify and condense the code]
Signed-off-by: Arun KS <getarunks@gmail.com>
Signed-off-by: Arun KS <arun.ks@broadcom.com>
Cc: Joe Perches <joe@perches.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Switch to memblock interfaces for early memory allocator instead of
bootmem allocator. No functional change in beahvior than what it is in
current code from bootmem users points of view.
Archs already converted to NO_BOOTMEM now directly use memblock
interfaces instead of bootmem wrappers build on top of memblock. And
the archs which still uses bootmem, these new apis just fallback to
exiting bootmem APIs.
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In one of those comments a typo was fixed, too.
Signed-off-by: Dirk Gouders <dirk@gouders.net>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
boot_delay does not work for earlyprintk because the kernel cmdline
parsing is late.
Change to use early_param so early kernel messages can also be delayed.
Signed-off-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This reports the names of consoles as they're being disabled to help
identify which is which during cut-over. Helps answer the question
"which boot console actually got activated?" once the regular console is
running, mostly when debugging boot console failures.
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch guards the console_drivers list to be corrupted. The
for_each_console() macro insist on a strictly forward list ended by NULL:
con0->next->con1->next->NULL
Without this patch it may happen easily to destroy this list for example by
adding 'earlyprintk' twice, especially on embedded devices where the early
console is often a single static instance. This will result in the following
list:
con0->next->con0
This in turn will result in an endless loop in console_unlock() later on by
printing the first __log_buf line endlessly.
Signed-off-by: Andreas Bießmann <andreas@biessmann.de>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Rename the struct to enable moving portions of
printk.c to separate files.
The rename changes output of /proc/vmcoreinfo.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Make the code a bit more compact by always using a pointer for the active
console_cmdline.
Move overly indented code to correct indent level.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Create files with prototypes and static inlines for braille support. Make
braille_console functions return 1 on success.
Corrected CONFIG_A11Y_BRAILLE_CONSOLE=n _braille_console_setup
return value to NULL.
Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add an include file for the console_cmdline struct so that the braille
console driver can be separated.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Make it easier to break up printk into bite-sized chunks.
Remove printk path/filename from comment.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
