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* kernel: printk: specify alignment for struct printk_logAndrey Ryabinin2016-01-201-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | On architectures that have support for efficient unaligned access struct printk_log has 4-byte alignment. Specify alignment attribute in type declaration. The whole point of this patch is to fix deadlock which happening when UBSAN detects unaligned access in printk() thus UBSAN recursively calls printk() with logbuf_lock held by top printk() call. Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Michal Marek <mmarek@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Yury Gribov <y.gribov@samsung.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Kostya Serebryany <kcc@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: change recursion_bug type to boolSergey Senozhatsky2016-01-161-3/+3
| | | | | | | | `recursion_bug' is used as recursion_bug toggle, so make it `bool'. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: do cond_resched() between lines while outputting to consolesTejun Heo2016-01-161-1/+34
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | @console_may_schedule tracks whether console_sem was acquired through lock or trylock. If the former, we're inside a sleepable context and console_conditional_schedule() performs cond_resched(). This allows console drivers which use console_lock for synchronization to yield while performing time-consuming operations such as scrolling. However, the actual console outputting is performed while holding irq-safe logbuf_lock, so console_unlock() clears @console_may_schedule before starting outputting lines. Also, only a few drivers call console_conditional_schedule() to begin with. This means that when a lot of lines need to be output by console_unlock(), for example on a console registration, the task doing console_unlock() may not yield for a long time on a non-preemptible kernel. If this happens with a slow console devices, for example a serial console, the outputting task may occupy the cpu for a very long time. Long enough to trigger softlockup and/or RCU stall warnings, which in turn pile more messages, sometimes enough to trigger the next cycle of warnings incapacitating the system. Fix it by making console_unlock() insert cond_resched() between lines if @console_may_schedule. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Calvin Owens <calvinowens@fb.com> Acked-by: Jan Kara <jack@suse.com> Cc: Dave Jones <davej@codemonkey.org.uk> Cc: Kyle McMartin <kyle@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: only unregister boot consoles when necessaryThierry Reding2016-01-161-1/+25
| | | | | | | | | | | | | | | | | | | | | | | | | | | Boot consoles are typically replaced by proper consoles during the boot process. This can be problematic if the boot console data is part of the init section that is reclaimed late during boot. If the proper console does not register before this point in time, the boot console will need to be removed (so that the freed memory is not accessed), leaving the system without output for some time. There are various reasons why the proper console may not register early enough, such as deferred probe or the driver being a loadable module. If that happens, there is some amount of time where no console messages are visible to the user, which in turn can mean that they won't see crashes or other potentially useful information. To avoid this situation, only remove the boot console when it resides in the init section. Code exists to replace the boot console by the proper console when it is registered, keeping a seamless transition between the boot and proper consoles. Signed-off-by: Thierry Reding <treding@nvidia.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: prevent userland from spoofing kernel messagesMathias Krause2015-11-061-5/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The following statement of ABI/testing/dev-kmsg is not quite right: It is not possible to inject messages from userspace with the facility number LOG_KERN (0), to make sure that the origin of the messages can always be reliably determined. Userland actually can inject messages with a facility of 0 by abusing the fact that the facility is stored in a u8 data type. By using a facility which is a multiple of 256 the assignment of msg->facility in log_store() implicitly truncates it to 0, i.e. LOG_KERN, allowing users of /dev/kmsg to spoof kernel messages as shown below: The following call... # printf '<%d>Kernel panic - not syncing: beer empty\n' 0 >/dev/kmsg ...leads to the following log entry (dmesg -x | tail -n 1): user :emerg : [ 66.137758] Kernel panic - not syncing: beer empty However, this call... # printf '<%d>Kernel panic - not syncing: beer empty\n' 0x800 >/dev/kmsg ...leads to the slightly different log entry (note the kernel facility): kern :emerg : [ 74.177343] Kernel panic - not syncing: beer empty Fix that by limiting the user provided facility to 8 bit right from the beginning and catch the truncation early. Fixes: 7ff9554bb578 ("printk: convert byte-buffer to variable-length...") Signed-off-by: Mathias Krause <minipli@googlemail.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Petr Mladek <pmladek@suse.cz> Cc: Alex Elder <elder@linaro.org> Cc: Joe Perches <joe@perches.com> Cc: Kay Sievers <kay@vrfy.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* pstore: add pstore unregisterGeliang Tang2015-10-221-0/+1
| | | | | | | | | | | | | | pstore doesn't support unregistering yet. It was marked as TODO. This patch adds some code to fix it: 1) Add functions to unregister kmsg/console/ftrace/pmsg. 2) Add a function to free compression buffer. 3) Unmap the memory and free it. 4) Add a function to unregister pstore filesystem. Signed-off-by: Geliang Tang <geliangtang@163.com> Acked-by: Kees Cook <keescook@chromium.org> [Removed __exit annotation from ramoops_remove(). Reported by Arnd Bergmann] Signed-off-by: Tony Luck <tony.luck@intel.com>
* kexec: split kexec_load syscall from kexec core codeDave Young2015-09-101-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There are two kexec load syscalls, kexec_load another and kexec_file_load. kexec_file_load has been splited as kernel/kexec_file.c. In this patch I split kexec_load syscall code to kernel/kexec.c. And add a new kconfig option KEXEC_CORE, so we can disable kexec_load and use kexec_file_load only, or vice verse. The original requirement is from Ted Ts'o, he want kexec kernel signature being checked with CONFIG_KEXEC_VERIFY_SIG enabled. But kexec-tools use kexec_load syscall can bypass the checking. Vivek Goyal proposed to create a common kconfig option so user can compile in only one syscall for loading kexec kernel. KEXEC/KEXEC_FILE selects KEXEC_CORE so that old config files still work. Because there's general code need CONFIG_KEXEC_CORE, so I updated all the architecture Kconfig with a new option KEXEC_CORE, and let KEXEC selects KEXEC_CORE in arch Kconfig. Also updated general kernel code with to kexec_load syscall. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Dave Young <dyoung@redhat.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Petr Tesarik <ptesarik@suse.cz> Cc: Theodore Ts'o <tytso@mit.edu> Cc: Josh Boyer <jwboyer@fedoraproject.org> Cc: David Howells <dhowells@redhat.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: improve the description of /dev/kmsg line formatAntonio Ospite2015-06-301-4/+4
| | | | | | | | | | | | | | | | The comment about /dev/kmsg does not mention the additional values which may actually be exported, fix that. Also move up the part of the comment instructing the users to ignore these additional values, this way the reading is more fluent and logically compact. Signed-off-by: Antonio Ospite <ao2@ao2.it> Cc: Joe Perches <joe@perches.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* check_syslog_permissions() cleanupVasily Averin2015-06-251-5/+5
| | | | | | | | | | | | | | | | | | | | | Patch fixes drawbacks in heck_syslog_permissions() noticed by AKPM: "from_file handling makes me cry. That's not a boolean - it's an enumerated value with two values currently defined. But the code in check_syslog_permissions() treats it as a boolean and also hardwires the knowledge that SYSLOG_FROM_PROC == 1 (or == `true`). And the name is wrong: it should be called from_proc to match SYSLOG_FROM_PROC." Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Cc: Kees Cook <keescook@chromium.org> Cc: Josh Boyer <jwboyer@redhat.com> Cc: Eric Paris <eparis@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* security_syslog() should be called once onlyVasily Averin2015-06-251-7/+4
| | | | | | | | | | | | | | | | | | | | | | | | | The final version of commit 637241a900cb ("kmsg: honor dmesg_restrict sysctl on /dev/kmsg") lost few hooks, as result security_syslog() are processed incorrectly: - open of /dev/kmsg checks syslog access permissions by using check_syslog_permissions() where security_syslog() is not called if dmesg_restrict is set. - syslog syscall and /proc/kmsg calls do_syslog() where security_syslog can be executed twice (inside check_syslog_permissions() and then directly in do_syslog()) With this patch security_syslog() is called once only in all syslog-related operations regardless of dmesg_restrict value. Fixes: 637241a900cb ("kmsg: honor dmesg_restrict sysctl on /dev/kmsg") Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Cc: Kees Cook <keescook@chromium.org> Cc: Josh Boyer <jwboyer@redhat.com> Cc: Eric Paris <eparis@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: implement support for extended console driversTejun Heo2015-06-251-8/+58
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | printk log_buf keeps various metadata for each message including its sequence number and timestamp. The metadata is currently available only through /dev/kmsg and stripped out before passed onto console drivers. We want this metadata to be available to console drivers too so that console consumers can get full information including the metadata and dictionary, which among other things can be used to detect whether messages got lost in transit. This patch implements support for extended console drivers. Consoles can indicate that they want extended messages by setting the new CON_EXTENDED flag and they'll be fed messages formatted the same way as /dev/kmsg. "<level>,<sequnum>,<timestamp>,<contflag>;<message text>\n" If extended consoles exist, in-kernel fragment assembly is disabled. This ensures that all messages emitted to consoles have full metadata including sequence number. The contflag carries enough information to reassemble the fragments from the reader side trivially. Note that this only affects /dev/kmsg. Regular console and /proc/kmsg outputs are not affected by this change. * Extended message formatting for console drivers is enabled iff there are registered extended consoles. * Comment describing /dev/kmsg message format updated to add missing contflag field and help distinguishing variable from verbatim terms. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: David Miller <davem@davemloft.net> Cc: Kay Sievers <kay@vrfy.org> Reviewed-by: Petr Mladek <pmladek@suse.cz> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: factor out message formatting from devkmsg_read()Tejun Heo2015-06-251-66/+80
| | | | | | | | | | | | | | | | The extended message formatting used for /dev/kmsg will be used implement extended consoles. Factor out msg_print_ext_header() and msg_print_ext_body() from devkmsg_read(). This is pure restructuring. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: David Miller <davem@davemloft.net> Cc: Kay Sievers <kay@vrfy.org> Reviewed-by: Petr Mladek <pmladek@suse.cz> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: guard the amount written per line by devkmsg_read()Tejun Heo2015-06-251-12/+22
| | | | | | | | | | | | | | | | | | | | | | | | | | This patchset updates netconsole so that it can emit messages with the same header as used in /dev/kmsg which gives neconsole receiver full log information which enables things like structured logging and detection of lost messages. This patch (of 7): devkmsg_read() uses 8k buffer and assumes that the formatted output message won't overrun which seems safe given LOG_LINE_MAX, the current use of dict and the escaping method being used; however, we're planning to use devkmsg formatting wider and accounting for the buffer size properly isn't that complicated. This patch defines CONSOLE_EXT_LOG_MAX as 8192 and updates devkmsg_read() so that it limits output accordingly. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: David Miller <davem@davemloft.net> Cc: Kay Sievers <kay@vrfy.org> Reviewed-by: Petr Mladek <pmladek@suse.cz> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge tag 'tty-4.1-rc1' of ↵Linus Torvalds2015-04-211-35/+18
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty Pull tty/serial updates from Greg KH: "Here's the big tty/serial driver update for 4.1-rc1. It was delayed for a bit due to some questions surrounding some of the console command line parsing changes that are in here. There's still one tiny regression for people who were previously putting multiple console command lines and expecting them all to be ignored for some odd reason, but Peter is working on fixing that. If not, I'll send a revert for the offending patch, but I have faith that Peter can address it. Other than the console work here, there's the usual serial driver updates and changes, and a buch of 8250 reworks to try to make that driver easier to maintain over time, and have it support more devices in the future. All of these have been in linux-next for a while" * tag 'tty-4.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (119 commits) n_gsm: Drop unneeded cast on netdev_priv sc16is7xx: expose RTS inversion in RS-485 mode serial: 8250_pci: port failed after wakeup from S3 earlycon: 8250: Document kernel command line options earlycon: 8250: Fix command line regression earlycon: Fix __earlycon_table stride tty: clean up the tty time logic a bit serial: 8250_dw: only get the clock rate in one place serial: 8250_dw: remove useless ACPI ID check dmaengine: hsu: move memory allocation to GFP_NOWAIT dmaengine: hsu: remove redundant pieces of code serial: 8250_pci: add Intel Tangier support dmaengine: hsu: add Intel Tangier PCI ID serial: 8250_pci: replace switch-case by formula for Intel MID serial: 8250_pci: replace switch-case by formula tty: cpm_uart: replace CONFIG_8xx by CONFIG_CPM1 serial: jsm: some off by one bugs serial: xuartps: Fix check in console_setup(). serial: xuartps: Get rid of register access macros. serial: xuartps: Fix iobase use. ...
| * console: Add extensible console matchingPeter Hurley2015-03-261-34/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add match() method to struct console which allows the console to perform console command line matching instead of (or in addition to) default console matching (ie., by fixed name and index). The match() method returns 0 to indicate a successful match; normal console matching occurs if no match() method is defined or the match() method returns non-zero. The match() method is expected to set the console index if required. Re-implement earlycon-to-console-handoff with direct matching of "console=uart|uart8250,..." to the 8250 ttyS console. Acked-by: Rob Herring <robh@kernel.org> Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| * Merge 4.0-rc3 into tty-testingGreg Kroah-Hartman2015-03-091-1/+0
| |\ | | | | | | | | | | | | | | | This resolves a merge issue in drivers/tty/serial/8250/8250_pci.c Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| | * console: Preserve index after console setup()Peter Hurley2015-03-071-1/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Before register_console() calls the setup() method of the matched console, the registering console index is already equal to the index from the console command line; ie. newcon->index == c->index. This change is also required to support extensible console matching; (the command line index may have no relation to the console index assigned by the console-defined match() function). Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* | | Merge branch 'iocb' into for-nextAl Viro2015-04-111-2/+2
|\ \ \ | |/ / |/| |
| * | fs: move struct kiocb to fs.hChristoph Hellwig2015-03-251-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | struct kiocb now is a generic I/O container, so move it to fs.h. Also do a #include diet for aio.h while we're at it. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
| * | fs: remove ki_nbytesChristoph Hellwig2015-03-121-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | There is no need to pass the total request length in the kiocb, as we already get passed in through the iov_iter argument. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* | | console: Fix console name size mismatchPeter Hurley2015-03-072-1/+2
| |/ |/| | | | | | | | | | | | | | | | | | | | | commit 6ae9200f2cab7 ("enlarge console.name") increased the storage for the console name to 16 bytes, but not the corresponding struct console_cmdline::name storage. Console names longer than 8 bytes cause read beyond end-of-string and failure to match console; I'm not sure if there are other unexpected consequences. Cc: <stable@vger.kernel.org> # 2.6.22+ Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* | Merge tag 'for_linux-3.20-rc1' of ↵Linus Torvalds2015-02-201-1/+1
|\ \ | |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb Pull kgdb/kdb updates from Jason Wessel: "KGDB/KDB New: - KDB: improved searching - No longer enter debug core on panic if panic timeout is set KGDB/KDB regressions / cleanups - fix pdf doc build errors - prevent junk characters on kdb console from printk levels" * tag 'for_linux-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb: kgdb, docs: Fix <para> pdfdocs build errors debug: prevent entering debug mode on panic/exception. kdb: Const qualifier for kdb_getstr's prompt argument kdb: Provide forward search at more prompt kdb: Fix a prompt management bug when using | grep kdb: Remove stack dump when entering kgdb due to NMI kdb: Avoid printing KERN_ levels to consoles kdb: Fix off by one error in kdb_cpu() kdb: fix incorrect counts in KDB summary command output
| * kdb: Avoid printing KERN_ levels to consolesDaniel Thompson2015-02-191-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently when kdb traps printk messages then the raw log level prefix (consisting of '\001' followed by a numeral) does not get stripped off before the message is issued to the various I/O handlers supported by kdb. This causes annoying visual noise as well as causing problems grepping for ^. It is also a change of behaviour compared to normal usage of printk() usage. For example <SysRq>-h ends up with different output to that of kdb's "sr h". This patch addresses the problem by stripping log levels from messages before they are issued to the I/O handlers. printk() which can also act as an i/o handler in some cases is special cased; if the caller provided a log level then the prefix will be preserved when sent to printk(). The addition of non-printable characters to the output of kdb commands is a regression, albeit and extremely elderly one, introduced by commit 04d2c8c83d0e ("printk: convert the format for KERN_<LEVEL> to a 2 byte pattern"). Note also that this patch does *not* restore the original behaviour from v3.5. Instead it makes printk() from within a kdb command display the message without any prefix (i.e. like printk() normally does). Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Cc: Joe Perches <joe@perches.com> Cc: stable@vger.kernel.org Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
* | printk: correct timeout comment, neaten MODULE_PARM_DESCJoe Perches2015-02-121-6/+6
|/ | | | | | | | | Neaten the MODULE_PARAM_DESC message. Use 30 seconds in the comment for the zap console locks timeout. Signed-off-by: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge tag 'trace-seq-buf-3.19-v2' of ↵Linus Torvalds2014-12-131-2/+8
|\ | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace Pull tracing fixlet from Steven Rostedt: "Remove unnecessary preempt_disable in printk()" * tag 'trace-seq-buf-3.19-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: printk: Do not disable preemption for accessing printk_func
| * printk: Do not disable preemption for accessing printk_funcSteven Rostedt (Red Hat)2014-12-111-2/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | As printk_func will either be the default function, or a per_cpu function for the current CPU, there's no reason to disable preemption to access it from printk. That's because if the printk_func is not the default then the caller had better disabled preemption as they were the one to change it. Link: http://lkml.kernel.org/r/CA+55aFz5-_LKW4JHEBoWinN9_ouNcGRWAF2FUA35u46FRN-Kxw@mail.gmail.com Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
* | Merge tag 'trace-seq-buf-3.19' of ↵Linus Torvalds2014-12-101-9/+32
|\ \ | |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace Pull nmi-safe seq_buf printk update from Steven Rostedt: "This code is a fork from the trace-3.19 pull as it needed the trace_seq clean ups from that branch. This code solves the issue of performing stack dumps from NMI context. The issue is that printk() is not safe from NMI context as if the NMI were to trigger when a printk() was being performed, the NMI could deadlock from the printk() internal locks. This has been seen in practice. With lots of review from Petr Mladek, this code went through several iterations, and we feel that it is now at a point of quality to be accepted into mainline. Here's what is contained in this patch set: - Creates a "seq_buf" generic buffer utility that allows a descriptor to be passed around where functions can write their own "printk()" formatted strings into it. The generic version was pulled out of the trace_seq() code that was made specifically for tracing. - The seq_buf code was change to model the seq_file code. I have a patch (not included for 3.19) that converts the seq_file.c code over to use seq_buf.c like the trace_seq.c code does. This was done to make sure that seq_buf.c is compatible with seq_file.c. I may try to get that patch in for 3.20. - The seq_buf.c file was moved to lib/ to remove it from being dependent on CONFIG_TRACING. - The printk() was updated to allow for a per_cpu "override" of the internal calls. That is, instead of writing to the console, a call to printk() may do something else. This made it easier to allow the NMI to change what printk() does in order to call dump_stack() without needing to update that code as well. - Finally, the dump_stack from all CPUs via NMI code was converted to use the seq_buf code. The caller to trigger the NMI code would wait till all the NMIs finished, and then it would print the seq_buf data to the console safely from a non NMI context One added bonus is that this code also makes the NMI dump stack work on PREEMPT_RT kernels. As printk() includes sleeping locks on PREEMPT_RT, printk() only writes to console if the console does not use any rt_mutex converted spin locks. Which a lot do" * tag 'trace-seq-buf-3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: x86/nmi: Fix use of unallocated cpumask_var_t printk/percpu: Define printk_func when printk is not defined x86/nmi: Perform a safe NMI stack trace on all CPUs printk: Add per_cpu printk func to allow printk to be diverted seq_buf: Move the seq_buf code to lib/ seq-buf: Make seq_buf_bprintf() conditional on CONFIG_BINARY_PRINTF tracing: Add seq_buf_get_buf() and seq_buf_commit() helper functions tracing: Have seq_buf use full buffer seq_buf: Add seq_buf_can_fit() helper function tracing: Add paranoid size check in trace_printk_seq() tracing: Use trace_seq_used() and seq_buf_used() instead of len tracing: Clean up tracing_fill_pipe_page() seq_buf: Create seq_buf_used() to find out how much was written tracing: Add a seq_buf_clear() helper and clear len and readpos in init tracing: Convert seq_buf fields to be like seq_file fields tracing: Convert seq_buf_path() to be like seq_path() tracing: Create seq_buf layer in trace_seq
| * printk/percpu: Define printk_func when printk is not definedSteven Rostedt (Red Hat)2014-11-211-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | To avoid include hell, the per_cpu variable printk_func was declared in percpu.h. But it is only defined if printk is defined. As users of printk may also use the printk_func variable, it needs to be defined even if CONFIG_PRINTK is not. Also add a printk.h include in percpu.h just to be safe. Link: http://lkml.kernel.org/r/20141121183215.01ba539c@canb.auug.org.au Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
| * printk: Add per_cpu printk func to allow printk to be divertedSteven Rostedt (Red Hat)2014-11-191-9/+29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Being able to divert printk to call another function besides the normal logging is useful for such things like NMI handling. If some functions are to be called from NMI that does printk() it is possible to lock up the box if the nmi handler triggers when another printk is happening. One example of this use is to perform a stack trace on all CPUs via NMI. But if the NMI is to do the printk() it can cause the system to lock up. By allowing the printk to be diverted to another function that can safely record the printk output and then print it when it in a safe context then NMIs will be safe to call these functions like show_regs(). Link: http://lkml.kernel.org/p/20140619213952.209176403@goodmis.org Tested-by: Jiri Kosina <jkosina@suse.cz> Acked-by: Jiri Kosina <jkosina@suse.cz> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Petr Mladek <pmladek@suse.cz> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
* | Merge branch 'akpm' (patchbomb from Andrew)Linus Torvalds2014-12-101-27/+22
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Merge first patchbomb from Andrew Morton: - a few minor cifs fixes - dma-debug upadtes - ocfs2 - slab - about half of MM - procfs - kernel/exit.c - panic.c tweaks - printk upates - lib/ updates - checkpatch updates - fs/binfmt updates - the drivers/rtc tree - nilfs - kmod fixes - more kernel/exit.c - various other misc tweaks and fixes * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (190 commits) exit: pidns: fix/update the comments in zap_pid_ns_processes() exit: pidns: alloc_pid() leaks pid_namespace if child_reaper is exiting exit: exit_notify: re-use "dead" list to autoreap current exit: reparent: call forget_original_parent() under tasklist_lock exit: reparent: avoid find_new_reaper() if no children exit: reparent: introduce find_alive_thread() exit: reparent: introduce find_child_reaper() exit: reparent: document the ->has_child_subreaper checks exit: reparent: s/while_each_thread/for_each_thread/ in find_new_reaper() exit: reparent: fix the cross-namespace PR_SET_CHILD_SUBREAPER reparenting exit: reparent: fix the dead-parent PR_SET_CHILD_SUBREAPER reparenting exit: proc: don't try to flush /proc/tgid/task/tgid exit: release_task: fix the comment about group leader accounting exit: wait: drop tasklist_lock before psig->c* accounting exit: wait: don't use zombie->real_parent exit: wait: cleanup the ptrace_reparented() checks usermodehelper: kill the kmod_thread_locker logic usermodehelper: don't use CLONE_VFORK for ____call_usermodehelper() fs/hfs/catalog.c: fix comparison bug in hfs_cat_keycmp nilfs2: fix the nilfs_iget() vs. nilfs_new_inode() races ...
| * | printk: drop logbuf_cpu volatile qualifierAlex Elder2014-12-101-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pranith Kumar posted a patch in which removed the "volatile" qualifier for the "logbuf_cpu" variable in vprintk_emit(). https://lkml.org/lkml/2014/11/13/894 In his patch, he used ACCESS_ONCE() for all references to that symbol to provide whatever protection was intended. There was some discussion that followed, and in the end Steven Rostedt concluded that not only was "volatile" not needed, neither was it required to use ACCESS_ONCE(). I offered an elaborate description that concluded Steven was right, and Pranith asked me to submit an alternative patch. And this is it. The basic reason "volatile" is not needed is that "logbuf_cpu" has static storage duration, and vprintk_emit() is an exported interface. This means that the value of logbuf_cpu must be read from memory the first time it is used in a particular call of vprintk_emit(). The variable's value is read only once in that function, when it's read it'll be the copy from memory (or cache). In addition, the value of "logbuf_cpu" is only ever written under protection of a spinlock. So the value that is read is the "real" value (and not an out-of-date cached one). If its value is not UINT_MAX, it is the current CPU's processor id, and it will have been last written by the running CPU. Signed-off-by: Alex Elder <elder@linaro.org> Reported-by: Pranith Kumar <bobby.prani@gmail.com> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Petr Mladek <pmladek@suse.cz> Cc: Luis R. Rodriguez <mcgrof@suse.com> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * | printk: add and use LOGLEVEL_<level> defines for KERN_<LEVEL> equivalentsJoe Perches2014-12-101-15/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Use #defines instead of magic values. Signed-off-by: Joe Perches <joe@perches.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jason Baron <jbaron@akamai.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * | printk: remove used-once early_vprintkJoe Perches2014-12-101-11/+8
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Eliminate the unlikely possibility of message interleaving for early_printk/early_vprintk use. early_vprintk can be done via the %pV extension so remove this unnecessary function and change early_printk to have the equivalent vprintk code. All uses of early_printk already end with a newline so also remove the unnecessary newline from the early_printk function. Signed-off-by: Joe Perches <joe@perches.com> Acked-by: Chris Metcalf <cmetcalf@tilera.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | pstore: Honor dmesg_restrict sysctl on dmesg dumpsSebastian Schmidt2014-11-051-1/+1
|/ | | | | | | | | | | | | | | | When the kernel.dmesg_restrict restriction is in place, only users with CAP_SYSLOG should be able to access crash dumps (like: attacker is trying to exploit a bug, watchdog reboots, attacker can happily read crash dumps and logs). This puts the restriction on console-* types as well as sensitive information could have been leaked there. Other log types are unaffected. Signed-off-by: Sebastian Schmidt <yath@yath.de> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Tony Luck <tony.luck@intel.com>
* Merge branch 'for-3.18-consistent-ops' of ↵Linus Torvalds2014-10-151-2/+2
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu Pull percpu consistent-ops changes from Tejun Heo: "Way back, before the current percpu allocator was implemented, static and dynamic percpu memory areas were allocated and handled separately and had their own accessors. The distinction has been gone for many years now; however, the now duplicate two sets of accessors remained with the pointer based ones - this_cpu_*() - evolving various other operations over time. During the process, we also accumulated other inconsistent operations. This pull request contains Christoph's patches to clean up the duplicate accessor situation. __get_cpu_var() uses are replaced with with this_cpu_ptr() and __this_cpu_ptr() with raw_cpu_ptr(). Unfortunately, the former sometimes is tricky thanks to C being a bit messy with the distinction between lvalues and pointers, which led to a rather ugly solution for cpumask_var_t involving the introduction of this_cpu_cpumask_var_ptr(). This converts most of the uses but not all. Christoph will follow up with the remaining conversions in this merge window and hopefully remove the obsolete accessors" * 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (38 commits) irqchip: Properly fetch the per cpu offset percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t -fix ia64: sn_nodepda cannot be assigned to after this_cpu conversion. Use __this_cpu_write. percpu: Resolve ambiguities in __get_cpu_var/cpumask_var_t Revert "powerpc: Replace __get_cpu_var uses" percpu: Remove __this_cpu_ptr clocksource: Replace __this_cpu_ptr with raw_cpu_ptr sparc: Replace __get_cpu_var uses avr32: Replace __get_cpu_var with __this_cpu_write blackfin: Replace __get_cpu_var uses tile: Use this_cpu_ptr() for hardware counters tile: Replace __get_cpu_var uses powerpc: Replace __get_cpu_var uses alpha: Replace __get_cpu_var ia64: Replace __get_cpu_var uses s390: cio driver &__get_cpu_var replacements s390: Replace __get_cpu_var uses mips: Replace __get_cpu_var uses MIPS: Replace __get_cpu_var uses in FPU emulator. arm: Replace __this_cpu_ptr with raw_cpu_ptr ...
| * kernel misc: Replace __get_cpu_var usesChristoph Lameter2014-08-261-2/+2
| | | | | | | | | | | | | | | | Replace uses of __get_cpu_var for address calculation with this_cpu_ptr. Cc: akpm@linux-foundation.org Signed-off-by: Christoph Lameter <cl@linux.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* | printk: git rid of [sched_delayed] message for printk_deferredMarkus Trippelsdorf2014-10-141-6/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 458df9fd4815 ("printk: remove separate printk_sched buffers and use printk buf instead") hardcodes printk_deferred() to KERN_WARNING and inserts the string "[sched_delayed] " before the actual message. However it doesn't take into account the KERN_* prefix of the message, that now ends up in the middle of the output: [sched_delayed] ^a4CE: hpet increased min_delta_ns to 20115 nsec Fix this by just getting rid of the "[sched_delayed] " scnprintf(). The prefix is useless since 458df9fd4815 anyway since from that moment printk_deferred() inserts the message into the kernel printk buffer immediately. So if the message eventually gets printed to console, it is printed in the correct order with other messages and there's no need for any special prefix. And if the kernel crashes before the message makes it to console, then prefix in the printk buffer doesn't make the situation any better. Link: http://lkml.org/lkml/2014/9/14/4 Signed-off-by: Markus Trippelsdorf <markus@trippelsdorf.de> Acked-by: Jan Kara <jack@suse.cz> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | printk: don't bother using LOG_CPU_MAX_BUF_SHIFT on !SMPGeert Uytterhoeven2014-10-141-1/+6
| | | | | | | | | | | | | | | | | | | | | | When configuring a uniprocessor kernel, don't bother the user with an irrelevant LOG_CPU_MAX_BUF_SHIFT question, and don't build the unused code. Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> Acked-by: Luis R. Rodriguez <mcgrof@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | switch /dev/kmsg to ->write_iter()Al Viro2014-10-091-13/+7
| | | | | | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* | kernel/printk/printk.c: fix faulty logic in the case of recursive printkPatrick Palka2014-09-101-3/+3
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We shouldn't set text_len in the code path that detects printk recursion because text_len corresponds to the length of the string inside textbuf. A few lines down from the line text_len = strlen(recursion_msg); is the line text_len += vscnprintf(text + text_len, ...); So if printk detects recursion, it sets text_len to 29 (the length of recursion_msg) and logs an error. Then the message supplied by the caller of printk is stored inside textbuf but offset by 29 bytes. This means that the output of the recursive call to printk will contain 29 bytes of garbage in front of it. This defect is caused by commit 458df9fd4815 ("printk: remove separate printk_sched buffers and use printk buf instead") which turned the line text_len = vscnprintf(text, ...); into text_len += vscnprintf(text + text_len, ...); To fix this, this patch avoids setting text_len when logging the printk recursion error. This patch also marks unlikely() the branch leading up to this code. Fixes: 458df9fd4815b478 ("printk: remove separate printk_sched buffers and use printk buf instead") Signed-off-by: Patrick Palka <patrick@parcs.ath.cx> Reviewed-by: Petr Mladek <pmladek@suse.cz> Reviewed-by: Jan Kara <jack@suse.cz> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: Add function to return log buffer address and sizeVasant Hegde2014-08-131-0/+12
| | | | | | | | | | | | | | | | | Platforms like IBM Power Systems supports service processor assisted dump. It provides interface to add memory region to be captured when system is crashed. During initialization/running we can add kernel memory region to be collected. Presently we don't have a way to get the log buffer base address and size. This patch adds support to return log buffer address and size. Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Acked-by: Andrew Morton <akpm@linux-foundation.org>
* kernel/printk/printk.c: fix bool assignementsNeil Zhang2014-08-061-3/+3
| | | | | | | | Fix coccinelle warnings. Signed-off-by: Neil Zhang <zhangwm@marvell.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* printk: enable interrupts before calling console_trylock_for_printk()Jan Kara2014-08-061-10/+21
| | | | | | | | | | | | | | | | | | | | | | | | | 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 939f04bec1a4 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>
* printk: miscellaneous cleanupsAlex Elder2014-08-061-13/+13
| | | | | | | | | | | | | | | | | | | | | | | | 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>
* printk: use a clever macroAlex Elder2014-08-061-10/+2
| | | | | | | | | | | | | | | 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>
* printk: fix some commentsAlex Elder2014-08-061-11/+12
| | | | | | | | | | | | | | | 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>
* printk: rename DEFAULT_MESSAGE_LOGLEVELAlex Elder2014-08-061-1/+1
| | | | | | | | | | | | | | | | | | | | | | Commit a8fe19ebfbfd ("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>
* printk: tweak do_syslog() to match commentsAlex Elder2014-08-061-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | 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>
* printk: allow increasing the ring buffer depending on the number of CPUsLuis R. Rodriguez2014-08-061-0/+34
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* printk: make dynamic units clear for the kernel ring bufferLuis R. Rodriguez2014-08-061-1/+1
| | | | | | | | | | | | | | | | | | Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com> Suggested-by: Davidlohr Bueso <davidlohr@hp.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>
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