- Mar 16, 2023
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commit 9fc9e278 upstream. Like oops_limit, add warn_limit for limiting the number of warnings when panic_on_warn is not set. Cc: Jonathan Corbet <corbet@lwn.net> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Cc: Eric Biggers <ebiggers@google.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Petr Mladek <pmladek@suse.com> Cc: tangmeng <tangmeng@uniontech.com> Cc: "Guilherme G. Piccoli" <gpiccoli@igalia.com> Cc: Tiezhu Yang <yangtiezhu@loongson.cn> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: linux-doc@vger.kernel.org Reviewed-by:
Luis Chamberlain <mcgrof@kernel.org> Signed-off-by:
Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20221117234328.594699-5-keescook@chromium.org Signed-off-by:
Eric Biggers <ebiggers@google.com> Signed-off-by:
Sasha Levin <sashal@kernel.org>
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commit de92f657 upstream. In preparation for keeping oops_limit logic in sync with warn_limit, have oops_limit == 0 disable checking the Oops counter. Cc: Jann Horn <jannh@google.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Cc: Eric Biggers <ebiggers@google.com> Cc: Huang Ying <ying.huang@intel.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: linux-doc@vger.kernel.org Signed-off-by:
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commit d4ccd54d upstream. Many Linux systems are configured to not panic on oops; but allowing an attacker to oops the system **really** often can make even bugs that look completely unexploitable exploitable (like NULL dereferences and such) if each crash elevates a refcount by one or a lock is taken in read mode, and this causes a counter to eventually overflow. The most interesting counters for this are 32 bits wide (like open-coded refcounts that don't use refcount_t). (The ldsem reader count on 32-bit platforms is just 16 bits, but probably nobody cares about 32-bit platforms that much nowadays.) So let's panic the system if the kernel is constantly oopsing. The speed of oopsing 2^32 times probably depends on several factors, like how long the stack trace is and which unwinder you're using; an empirically important one is whether your console is showing a graphical environment or a text console that oopses will be printed to. In a quick single-threaded benchmark, it looks like oopsing in a vfork() child with a very short stack trace only takes ~510 microseconds per run when a graphical console is active; but switching to a text console that oopses are printed to slows it down around 87x, to ~45 milliseconds per run. (Adding more threads makes this faster, but the actual oops printing happens under &die_lock on x86, so you can maybe speed this up by a factor of around 2 and then any further improvement gets eaten up by lock contention.) It looks like it would take around 8-12 days to overflow a 32-bit counter with repeated oopsing on a multi-core X86 system running a graphical environment; both me (in an X86 VM) and Seth (with a distro kernel on normal hardware in a standard configuration) got numbers in that ballpark. 12 days aren't *that* short on a desktop system, and you'd likely need much longer on a typical server system (assuming that people don't run graphical desktop environments on their servers), and this is a *very* noisy and violent approach to exploiting the kernel; and it also seems to take orders of magnitude longer on some machines, probably because stuff like EFI pstore will slow it down a ton if that's active. Signed-off-by:
Jann Horn <jannh@google.com> Link: https://lore.kernel.org/r/20221107201317.324457-1-jannh@google.com Reviewed-by:
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commit 069c4ea6 upstream. A semicolon was missing, and the almost-alphabetical-but-not ordering was confusing, so regroup these by category instead. Signed-off-by:
Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 95e6060c upstream. With tools like kbench9000 giving more finegrained responses, and this basically never having been used ever since it was initially added, let's just get rid of this. There *is* still work to be done on the interrupt handler, but this really isn't the way it's being developed. Cc: Theodore Ts'o <tytso@mit.edu> Reviewed-by:
Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by:
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commit 489c7fc4 upstream. Now that POOL_BITS == POOL_MIN_BITS, we must unconditionally wake up entropy writers after every extraction. Therefore there's no point of write_wakeup_threshold, so we can move it to the dustbin of unused compatibility sysctls. While we're at it, we can fix a small comparison where we were waking up after <= min rather than < min. Cc: Theodore Ts'o <tytso@mit.edu> Suggested-by:
Eric Biggers <ebiggers@kernel.org> Reviewed-by:
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commit 08389d88 upstream. Add a kconfig knob which allows for unprivileged bpf to be disabled by default. If set, the knob sets /proc/sys/kernel/unprivileged_bpf_disabled to value of 2. This still allows a transition of 2 -> {0,1} through an admin. Similarly, this also still keeps 1 -> {1} behavior intact, so that once set to permanently disabled, it cannot be undone aside from a reboot. We've also added extra2 with max of 2 for the procfs handler, so that an admin still has a chance to toggle between 0 <-> 2. Either way, as an additional alternative, applications can make use of CAP_BPF that we added a while ago. Signed-off-by:
Daniel Borkmann <daniel@iogearbox.net> Signed-off-by:
Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/74ec548079189e4e4dffaeb42b8987bb3c852eee.1620765074.git.daniel@iogearbox.net [fllinden@amazon.com: backported to 5.4] Signed-off-by:
Frank van der Linden <fllinden@amazon.com> Signed-off-by:
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- Jul 15, 2019
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Mauro Carvalho Chehab authored
There are lots of documents that belong to the admin-guide but are on random places (most under Documentation root dir). Move them to the admin guide. Signed-off-by:
Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by:
Alexandre Belloni <alexandre.belloni@bootlin.com> Acked-by:
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
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Mauro Carvalho Chehab authored
The stuff under sysctl describes /sys interface from userspace point of view. So, add it to the admin-guide and remove the :orphan: from its index file. Signed-off-by: -
Mauro Carvalho Chehab authored
Rename the /proc/sys/ documentation files to ReST, using the README file as a template for an index.rst, adding the other files there via TOC markup. Despite being written on different times with different styles, try to make them somewhat coherent with a similar look and feel, ensuring that they'll look nice as both raw text file and as via the html output produced by the Sphinx build system. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by:
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- Jun 19, 2019
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Heiko Carstens authored
This feature has never been used, so remove it. Acked-by:
Vasily Gorbik <gor@linux.ibm.com> Acked-by:
Hendrik Brueckner <brueckner@linux.ibm.com> Signed-off-by:
Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by:
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- Jun 08, 2019
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Mauro Carvalho Chehab authored
Mostly due to x86 and acpi conversion, several documentation links are still pointing to the old file. Fix them. Signed-off-by:
Wolfram Sang <wsa@the-dreams.de> Reviewed-by:
Sven Van Asbroeck <TheSven73@gmail.com> Reviewed-by:
Bhupesh Sharma <bhsharma@redhat.com> Acked-by:
Mark Brown <broonie@kernel.org> Signed-off-by:
Jonathan Corbet <corbet@lwn.net>
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- Mar 25, 2019
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Jakub Wilk authored
The buffer size for core_pattern is 128, but one character is used for terminating null byte, so the actual limit is 127: # printf '%0999d' > /proc/sys/kernel/core_pattern # tr -d '\n' < /proc/sys/kernel/core_pattern | wc -c 127 Signed-off-by:Jakub Wilk <jwilk@jwilk.net> Signed-off-by:
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- Jan 27, 2019
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Quentin Perret authored
In its current state, Energy Aware Scheduling (EAS) starts automatically on asymmetric platforms having an Energy Model (EM). However, there are users who want to have an EM (for thermal management for example), but don't want EAS with it. In order to let users disable EAS explicitly, introduce a new sysctl called 'sched_energy_aware'. It is enabled by default so that EAS can start automatically on platforms where it makes sense. Flipping it to 0 rebuilds the scheduling domains and disables EAS. Signed-off-by:
Quentin Perret <quentin.perret@arm.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: adharmap@codeaurora.org Cc: chris.redpath@arm.com Cc: currojerez@riseup.net Cc: dietmar.eggemann@arm.com Cc: edubezval@gmail.com Cc: gregkh@linuxfoundation.org Cc: javi.merino@kernel.org Cc: joel@joelfernandes.org Cc: juri.lelli@redhat.com Cc: morten.rasmussen@arm.com Cc: patrick.bellasi@arm.com Cc: pkondeti@codeaurora.org Cc: rjw@rjwysocki.net Cc: skannan@codeaurora.org Cc: smuckle@google.com Cc: srinivas.pandruvada@linux.intel.com Cc: thara.gopinath@linaro.org Cc: tkjos@google.com Cc: valentin.schneider@arm.com Cc: vincent.guittot@linaro.org Cc: viresh.kumar@linaro.org Link: https://lkml.kernel.org/r/20181203095628.11858-11-quentin.perret@arm.com Signed-off-by:
Ingo Molnar <mingo@kernel.org>
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- Jan 08, 2019
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Thorsten Leemhuis authored
Add a section about decoding /proc/sys/kernel/tainted, create a more understandable intro and a hopefully explain better the tainted flags in bugs, oops or panics messages. Only thing missing then is a table that quickly describes the various bits and taint flags before going into more detail, so add that as well. That table is partly based on a section from Documentation/sysctl/kernel.txt, but a bit more compact. To avoid confusion I added the shortened version to kernel.txt; the same table is used in three different places now: ./tools/debugging/kernel-chktaint, Documentation/admin-guide/tainted-kernels.rst and Documentation/sysctl/kernel.txt During review of v1 (see above) a number of existing issues with the text were raised, like outdated usages as well as incomplete or missing descriptions. Address most of those as well. Signed-off-by:
Thorsten Leemhuis <linux@leemhuis.info> [jc: tightened up changelog] Signed-off-by:
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- Jan 04, 2019
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Feng Tang authored
So that we can also runtime chose to print out the needed system info for panic, other than setting the kernel cmdline. Link: http://lkml.kernel.org/r/1543398842-19295-3-git-send-email-feng.tang@intel.com Signed-off-by:
Feng Tang <feng.tang@intel.com> Suggested-by:
Steven Rostedt <rostedt@goodmis.org> Acked-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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- Sep 04, 2018
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Alexander Popov authored
Introduce CONFIG_STACKLEAK_RUNTIME_DISABLE option, which provides 'stack_erasing' sysctl. It can be used in runtime to control kernel stack erasing for kernels built with CONFIG_GCC_PLUGIN_STACKLEAK. Suggested-by:
Alexander Popov <alex.popov@linux.com> Tested-by:
Laura Abbott <labbott@redhat.com> Signed-off-by:
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- Aug 22, 2018
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Manfred Spraul authored
ipc_addid() initializes kern_ipc_perm.seq after having called idr_alloc() (within ipc_idr_alloc()). Thus a parallel semop() or msgrcv() that uses ipc_obtain_object_check() may see an uninitialized value. The patch moves the initialization of kern_ipc_perm.seq before the calls of idr_alloc(). Notes: 1) This patch has a user space visible side effect: If /proc/sys/kernel/*_next_id is used (i.e.: checkpoint/restore) and if semget()/msgget()/shmget() fails in the final step of adding the id to the rhash tree, then .._next_id is cleared. Before the patch, is remained unmodified. There is no change of the behavior after a successful ..get() call: It always clears .._next_id, there is no impact to non checkpoint/restore code as that code does not use .._next_id. 2) The patch correctly documents that after a call to ipc_idr_alloc(), the full tear-down sequence must be used. The callers of ipc_addid() do not fullfill that, i.e. more bugfixes are required. The patch is a squash of a patch from Dmitry and my own changes. Link: http://lkml.kernel.org/r/20180712185241.4017-3-manfred@colorfullife.com Reported-by:
<syzbot+2827ef6b3385deb07eaf@syzkaller.appspotmail.com> Signed-off-by:
Manfred Spraul <manfred@colorfullife.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Davidlohr Bueso <dbueso@suse.de> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by:
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Dmitry Vyukov authored
Currently task hung checking interval is equal to timeout, as the result hung is detected anywhere between timeout and 2*timeout. This is fine for most interactive environments, but this hurts automated testing setups (syzbot). In an automated setup we need to strictly order CPU lockup < RCU stall < workqueue lockup < task hung < silent loss, so that RCU stall is not detected as task hung and task hung is not detected as silent machine loss. The large variance in task hung detection timeout requires setting silent machine loss timeout to a very large value (e.g. if task hung is 3 mins, then silent loss need to be set to ~7 mins). The additional 3 minutes significantly reduce testing efficiency because usually we crash kernel within a minute, and this can add hours to bug localization process as it needs to do dozens of tests. Allow setting checking interval separately from timeout. This allows to set timeout to, say, 3 minutes, but checking interval to 10 secs. The interval is controlled via a new hung_task_check_interval_secs sysctl, similar to the existing hung_task_timeout_secs sysctl. The default value of 0 results in the current behavior: checking interval is equal to timeout. [akpm@linux-foundation.org: update hung_task_timeout_max's comment] Link: http://lkml.kernel.org/r/20180611111004.203513-1-dvyukov@google.com Signed-off-by:
Dmitry Vyukov <dvyukov@google.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by:
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- Jul 08, 2018
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Sunil Muthuswamy authored
In the VM mode on Hyper-V, currently, when the kernel panics, an error code and few register values are populated in an MSR and the Hypervisor notified. This information is collected on the host. The amount of information currently collected is found to be limited and not very actionable. To gather more actionable data, such as stack trace, the proposal is to write one page worth of kmsg data on an allocated page and the Hypervisor notified of the page address through the MSR. - Sysctl option to control the behavior, with ON by default. Cc: K. Y. Srinivasan <kys@microsoft.com> Cc: Stephen Hemminger <sthemmin@microsoft.com> Signed-off-by:
Sunil Muthuswamy <sunilmut@microsoft.com> Signed-off-by:
K. Y. Srinivasan <kys@microsoft.com> Signed-off-by:
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- Apr 11, 2018
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Kees Cook authored
Since the randstruct plugin can intentionally produce extremely unusual kernel structure layouts (even performance pathological ones), some maintainers want to be able to trivially determine if an Oops is coming from a randstruct-built kernel, so as to keep their sanity when debugging. This adds the new flag and initializes taint_mask immediately when built with randstruct. Link: http://lkml.kernel.org/r/1519084390-43867-4-git-send-email-keescook@chromium.org Signed-off-by:
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Kees Cook authored
This consolidates the taint bit documentation into a single place with both numeric and letter values. Additionally adds the missing TAINT_AUX documentation. Link: http://lkml.kernel.org/r/1519084390-43867-3-git-send-email-keescook@chromium.org Signed-off-by:
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- Dec 21, 2017
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Tobin C. Harding authored
Recently the behaviour of printk specifier %pK was changed. The documentation does not currently mirror this. Update documentation for sysctl kptr_restrict. Signed-off-by:
Tobin C. Harding <me@tobin.cc> Signed-off-by:
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- Dec 11, 2017
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Scott Wood authored
Commit ac1f5912 ("kernel/watchdog.c: add sysctl knob hardlockup_panic") added the hardlockup_panic sysctl, but did not add it to Documentation/sysctl/kernel.txt. Add this, and reference it from the corresponding entry in Documentation/admin-guide/kernel-parameters.txt. Signed-off-by:
Scott Wood <swood@redhat.com> Acked-by:
Christoph von Recklinghausen <crecklin@redhat.com> Acked-by:
Don Zickus <dzickus@redhat.com> Signed-off-by:
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- Aug 22, 2017
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Konstantin Khlebnikov authored
Fix misprint CAP_IOC_LOCK -> CAP_IPC_LOCK. This capability have nothing to do with raw tracepoints. This part is about bypassing mlock limits. Sysctl kernel.perf_event_paranoid = -1 allows raw and ftrace function tracepoints without CAP_SYS_ADMIN. Signed-off-by:
Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/150322916080.129746.11285255474738558340.stgit@buzz Signed-off-by:
Arnaldo Carvalho de Melo <acme@redhat.com>
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- Aug 14, 2017
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Tyler Hicks authored
This patch creates a read-only sysctl containing an ordered list of seccomp actions that the kernel supports. The ordering, from left to right, is the lowest action value (kill) to the highest action value (allow). Currently, a read of the sysctl file would return "kill trap errno trace allow". The contents of this sysctl file can be useful for userspace code as well as the system administrator. The path to the sysctl is: /proc/sys/kernel/seccomp/actions_avail libseccomp and other userspace code can easily determine which actions the current kernel supports. The set of actions supported by the current kernel may be different than the set of action macros found in kernel headers that were installed where the userspace code was built. In addition, this sysctl will allow system administrators to know which actions are supported by the kernel and make it easier to configure exactly what seccomp logs through the audit subsystem. Support for this level of logging configuration will come in a future patch. Signed-off-by:
Tyler Hicks <tyhicks@canonical.com> Signed-off-by:
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- Mar 03, 2017
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Krzysztof Kozlowski authored
Commit 9d85025b ("docs-rst: create an user's manual book") moved the sysrq.txt leaving old paths in the kernel docs. Signed-off-by:
Krzysztof Kozlowski <krzk@kernel.org> Reviewed-by:
Mauro Carvalho Chehab <mchehab@s-opensource.com> Signed-off-by:
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- Oct 25, 2016
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Josh Poimboeuf authored
For mostly historical reasons, the x86 oops dump shows the raw stack values: ... [registers] Stack: ffff880079af7350 ffff880079905400 0000000000000000 ffffc900008f3ae0 ffffffffa0196610 0000000000000001 00010000ffffffff 0000000087654321 0000000000000002 0000000000000000 0000000000000000 0000000000000000 Call Trace: ... This seems to be an artifact from long ago, and probably isn't needed anymore. It generally just adds noise to the dump, and it can be actively harmful because it leaks kernel addresses. Linus says: "The stack dump actually goes back to forever, and it used to be useful back in 1992 or so. But it used to be useful mainly because stacks were simpler and we didn't have very good call traces anyway. I definitely remember having used them - I just do not remember having used them in the last ten+ years. Of course, it's still true that if you can trigger an oops, you've likely already lost the security game, but since the stack dump is so useless, let's aim to just remove it and make games like the above harder." This also removes the related 'kstack=' cmdline option and the 'kstack_depth_to_print' sysctl. Suggested-by:
Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/e83bd50df52d8fe88e94d2566426ae40d813bf8f.1477405374.git.jpoimboe@redhat.com Signed-off-by:
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- Oct 24, 2016
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Mauro Carvalho Chehab authored
The previous patch renamed several files that are cross-referenced along the Kernel documentation. Adjust the links to point to the right places. Signed-off-by:
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- Aug 02, 2016
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Borislav Petkov authored
Add a "printk.devkmsg" kernel command line parameter which controls how userspace writes into /dev/kmsg. It has three options: * ratelimit - ratelimit logging from userspace. * on - unlimited logging from userspace * off - logging from userspace gets ignored The default setting is to ratelimit the messages written to it. This changes the kernel default setting of "on" to "ratelimit" and we do that because we want to keep userspace spamming /dev/kmsg to sane levels. This is especially moot when a small kernel log buffer wraps around and messages get lost. So the ratelimiting setting should be a sane setting where kernel messages should have a bit higher chance of survival from all the spamming. It additionally does not limit logging to /dev/kmsg while the system is booting if we haven't disabled it on the command line. Furthermore, we can control the logging from a lower priority sysctl interface - kernel.printk_devkmsg. That interface will succeed only if printk.devkmsg *hasn't* been supplied on the command line. If it has, then printk.devkmsg is a one-time setting which remains for the duration of the system lifetime. This "locking" of the setting is to prevent userspace from changing the logging on us through sysctl(2). This patch is based on previous patches from Linus and Steven. [bp@suse.de: fixes] Link: http://lkml.kernel.org/r/20160719072344.GC25563@nazgul.tnic Link: http://lkml.kernel.org/r/20160716061745.15795-3-bp@alien8.de Signed-off-by:
Borislav Petkov <bp@suse.de> Cc: Dave Young <dyoung@redhat.com> Cc: Franck Bui <fbui@suse.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by:
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- Jun 15, 2016
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Daniel Bristot de Oliveira authored
It is not always easy to determine the cause of an RCU stall just by analysing the RCU stall messages, mainly when the problem is caused by the indirect starvation of rcu threads. For example, when preempt_rcu is not awakened due to the starvation of a timer softirq. We have been hard coding panic() in the RCU stall functions for some time while testing the kernel-rt. But this is not possible in some scenarios, like when supporting customers. This patch implements the sysctl kernel.panic_on_rcu_stall. If set to 1, the system will panic() when an RCU stall takes place, enabling the capture of a vmcore. The vmcore provides a way to analyze all kernel/tasks states, helping out to point to the culprit and the solution for the stall. The kernel.panic_on_rcu_stall sysctl is disabled by default. Changes from v1: - Fixed a typo in the git log - The if(sysctl_panic_on_rcu_stall) panic() is in a static function - Fixed the CONFIG_TINY_RCU compilation issue - The var sysctl_panic_on_rcu_stall is now __read_mostly Cc: Jonathan Corbet <corbet@lwn.net> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Acked-by:
Christian Borntraeger <borntraeger@de.ibm.com> Reviewed-by:
Josh Triplett <josh@joshtriplett.org> Reviewed-by:
Arnaldo Carvalho de Melo <acme@kernel.org> Tested-by:
"Luis Claudio R. Goncalves" <lgoncalv@redhat.com> Signed-off-by:
Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by:
Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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- May 17, 2016
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Arnaldo Carvalho de Melo authored
The perf_sample->ip_callchain->nr value includes all the entries in the ip_callchain->ip[] array, real addresses and PERF_CONTEXT_{KERNEL,USER,etc}, while what the user expects is that what is in the kernel.perf_event_max_stack sysctl or in the upcoming per event perf_event_attr.sample_max_stack knob be honoured in terms of IP addresses in the stack trace. So allocate a bunch of extra entries for contexts, and do the accounting via perf_callchain_entry_ctx struct members. A new sysctl, kernel.perf_event_max_contexts_per_stack is also introduced for investigating possible bugs in the callchain implementation by some arch. Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Brendan Gregg <brendan.d.gregg@gmail.com> Cc: David Ahern <dsahern@gmail.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: He Kuang <hekuang@huawei.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Milian Wolff <milian.wolff@kdab.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: Wang Nan <wangnan0@huawei.com> Cc: Zefan Li <lizefan@huawei.com> Link: http://lkml.kernel.org/n/tip-3b4wnqk340c4sg4gwkfdi9yk@git.kernel.org Signed-off-by:
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- May 10, 2016
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Andy Lutomirski authored
Allowing unprivileged kernel profiling lets any user dump follow kernel control flow and dump kernel registers. This most likely allows trivial kASLR bypassing, and it may allow other mischief as well. (Off the top of my head, the PERF_SAMPLE_REGS_INTR output during /dev/urandom reads could be quite interesting.) Signed-off-by:
Andy Lutomirski <luto@kernel.org> Acked-by:
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- Apr 27, 2016
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Arnaldo Carvalho de Melo authored
The default remains 127, which is good for most cases, and not even hit most of the time, but then for some cases, as reported by Brendan, 1024+ deep frames are appearing on the radar for things like groovy, ruby. And in some workloads putting a _lower_ cap on this may make sense. One that is per event still needs to be put in place tho. The new file is: # cat /proc/sys/kernel/perf_event_max_stack 127 Chaging it: # echo 256 > /proc/sys/kernel/perf_event_max_stack # cat /proc/sys/kernel/perf_event_max_stack 256 But as soon as there is some event using callchains we get: # echo 512 > /proc/sys/kernel/perf_event_max_stack -bash: echo: write error: Device or resource busy # Because we only allocate the callchain percpu data structures when there is a user, which allows for changing the max easily, its just a matter of having no callchain users at that point. Reported-and-Tested-by:
Brendan Gregg <brendan.d.gregg@gmail.com> Reviewed-by:
Frederic Weisbecker <fweisbec@gmail.com> Acked-by:
David Ahern <dsahern@gmail.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: He Kuang <hekuang@huawei.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Milian Wolff <milian.wolff@kdab.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: Wang Nan <wangnan0@huawei.com> Cc: Zefan Li <lizefan@huawei.com> Link: http://lkml.kernel.org/r/20160426002928.GB16708@kernel.org Signed-off-by:
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- Mar 08, 2016
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Konstantin Khlebnikov authored
Logic has been changed in kernel 3.4 by commit e9aba515 ("tty: rework pty count limiting") but still not documented. Sysctl kernel.pty.max works as global limit, kernel.pty.reserve ptys are reserved for initial devpts instance (mounted without "newinstance"). Per-instance limit also could be set by mount option "max=%d". Signed-off-by:
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- Feb 09, 2016
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Mel Gorman authored
schedstats is very useful during debugging and performance tuning but it incurs overhead to calculate the stats. As such, even though it can be disabled at build time, it is often enabled as the information is useful. This patch adds a kernel command-line and sysctl tunable to enable or disable schedstats on demand (when it's built in). It is disabled by default as someone who knows they need it can also learn to enable it when necessary. The benefits are dependent on how scheduler-intensive the workload is. If it is then the patch reduces the number of cycles spent calculating the stats with a small benefit from reducing the cache footprint of the scheduler. These measurements were taken from a 48-core 2-socket machine with Xeon(R) E5-2670 v3 cpus although they were also tested on a single socket machine 8-core machine with Intel i7-3770 processors. netperf-tcp 4.5.0-rc1 4.5.0-rc1 vanilla nostats-v3r1 Hmean 64 560.45 ( 0.00%) 575.98 ( 2.77%) Hmean 128 766.66 ( 0.00%) 795.79 ( 3.80%) Hmean 256 950.51 ( 0.00%) 981.50 ( 3.26%) Hmean 1024 1433.25 ( 0.00%) 1466.51 ( 2.32%) Hmean 2048 2810.54 ( 0.00%) 2879.75 ( 2.46%) Hmean 3312 4618.18 ( 0.00%) 4682.09 ( 1.38%) Hmean 4096 5306.42 ( 0.00%) 5346.39 ( 0.75%) Hmean 8192 10581.44 ( 0.00%) 10698.15 ( 1.10%) Hmean 16384 18857.70 ( 0.00%) 18937.61 ( 0.42%) Small gains here, UDP_STREAM showed nothing intresting and neither did the TCP_RR tests. The gains on the 8-core machine were very similar. tbench4 4.5.0-rc1 4.5.0-rc1 vanilla nostats-v3r1 Hmean mb/sec-1 500.85 ( 0.00%) 522.43 ( 4.31%) Hmean mb/sec-2 984.66 ( 0.00%) 1018.19 ( 3.41%) Hmean mb/sec-4 1827.91 ( 0.00%) 1847.78 ( 1.09%) Hmean mb/sec-8 3561.36 ( 0.00%) 3611.28 ( 1.40%) Hmean mb/sec-16 5824.52 ( 0.00%) 5929.03 ( 1.79%) Hmean mb/sec-32 10943.10 ( 0.00%) 10802.83 ( -1.28%) Hmean mb/sec-64 15950.81 ( 0.00%) 16211.31 ( 1.63%) Hmean mb/sec-128 15302.17 ( 0.00%) 15445.11 ( 0.93%) Hmean mb/sec-256 14866.18 ( 0.00%) 15088.73 ( 1.50%) Hmean mb/sec-512 15223.31 ( 0.00%) 15373.69 ( 0.99%) Hmean mb/sec-1024 14574.25 ( 0.00%) 14598.02 ( 0.16%) Hmean mb/sec-2048 13569.02 ( 0.00%) 13733.86 ( 1.21%) Hmean mb/sec-3072 12865.98 ( 0.00%) 13209.23 ( 2.67%) Small gains of 2-4% at low thread counts and otherwise flat. The gains on the 8-core machine were slightly different tbench4 on 8-core i7-3770 single socket machine Hmean mb/sec-1 442.59 ( 0.00%) 448.73 ( 1.39%) Hmean mb/sec-2 796.68 ( 0.00%) 794.39 ( -0.29%) Hmean mb/sec-4 1322.52 ( 0.00%) 1343.66 ( 1.60%) Hmean mb/sec-8 2611.65 ( 0.00%) 2694.86 ( 3.19%) Hmean mb/sec-16 2537.07 ( 0.00%) 2609.34 ( 2.85%) Hmean mb/sec-32 2506.02 ( 0.00%) 2578.18 ( 2.88%) Hmean mb/sec-64 2511.06 ( 0.00%) 2569.16 ( 2.31%) Hmean mb/sec-128 2313.38 ( 0.00%) 2395.50 ( 3.55%) Hmean mb/sec-256 2110.04 ( 0.00%) 2177.45 ( 3.19%) Hmean mb/sec-512 2072.51 ( 0.00%) 2053.97 ( -0.89%) In constract, this shows a relatively steady 2-3% gain at higher thread counts. Due to the nature of the patch and the type of workload, it's not a surprise that the result will depend on the CPU used. hackbench-pipes 4.5.0-rc1 4.5.0-rc1 vanilla nostats-v3r1 Amean 1 0.0637 ( 0.00%) 0.0660 ( -3.59%) Amean 4 0.1229 ( 0.00%) 0.1181 ( 3.84%) Amean 7 0.1921 ( 0.00%) 0.1911 ( 0.52%) Amean 12 0.3117 ( 0.00%) 0.2923 ( 6.23%) Amean 21 0.4050 ( 0.00%) 0.3899 ( 3.74%) Amean 30 0.4586 ( 0.00%) 0.4433 ( 3.33%) Amean 48 0.5910 ( 0.00%) 0.5694 ( 3.65%) Amean 79 0.8663 ( 0.00%) 0.8626 ( 0.43%) Amean 110 1.1543 ( 0.00%) 1.1517 ( 0.22%) Amean 141 1.4457 ( 0.00%) 1.4290 ( 1.16%) Amean 172 1.7090 ( 0.00%) 1.6924 ( 0.97%) Amean 192 1.9126 ( 0.00%) 1.9089 ( 0.19%) Some small gains and losses and while the variance data is not included, it's close to the noise. The UMA machine did not show anything particularly different pipetest 4.5.0-rc1 4.5.0-rc1 vanilla nostats-v2r2 Min Time 4.13 ( 0.00%) 3.99 ( 3.39%) 1st-qrtle Time 4.38 ( 0.00%) 4.27 ( 2.51%) 2nd-qrtle Time 4.46 ( 0.00%) 4.39 ( 1.57%) 3rd-qrtle Time 4.56 ( 0.00%) 4.51 ( 1.10%) Max-90% Time 4.67 ( 0.00%) 4.60 ( 1.50%) Max-93% Time 4.71 ( 0.00%) 4.65 ( 1.27%) Max-95% Time 4.74 ( 0.00%) 4.71 ( 0.63%) Max-99% Time 4.88 ( 0.00%) 4.79 ( 1.84%) Max Time 4.93 ( 0.00%) 4.83 ( 2.03%) Mean Time 4.48 ( 0.00%) 4.39 ( 1.91%) Best99%Mean Time 4.47 ( 0.00%) 4.39 ( 1.91%) Best95%Mean Time 4.46 ( 0.00%) 4.38 ( 1.93%) Best90%Mean Time 4.45 ( 0.00%) 4.36 ( 1.98%) Best50%Mean Time 4.36 ( 0.00%) 4.25 ( 2.49%) Best10%Mean Time 4.23 ( 0.00%) 4.10 ( 3.13%) Best5%Mean Time 4.19 ( 0.00%) 4.06 ( 3.20%) Best1%Mean Time 4.13 ( 0.00%) 4.00 ( 3.39%) Small improvement and similar gains were seen on the UMA machine. The gain is small but it stands to reason that doing less work in the scheduler is a good thing. The downside is that the lack of schedstats and tracepoints may be surprising to experts doing performance analysis until they find the existence of the schedstats= parameter or schedstats sysctl. It will be automatically activated for latencytop and sleep profiling to alleviate the problem. For tracepoints, there is a simple warning as it's not safe to activate schedstats in the context when it's known the tracepoint may be wanted but is unavailable. Signed-off-by:Mel Gorman <mgorman@techsingularity.net> Reviewed-by:
Matt Fleming <matt@codeblueprint.co.uk> Reviewed-by:
Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <mgalbraith@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1454663316-22048-1-git-send-email-mgorman@techsingularity.net Signed-off-by:
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- Jan 26, 2016
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Ben Hutchings authored
perf_event_paranoid was only documented in source code and a perf error message. Copy the documentation from the error message to Documentation/sysctl/kernel.txt. perf_cpu_time_max_percent was already documented but missing from the list at the top, so add it there. Signed-off-by:
Ben Hutchings <ben@decadent.org.uk> Cc: Peter Zijlstra <peterz@infradead.org> Cc: linux-doc@vger.kernel.org Link: http://lkml.kernel.org/r/20160119213515.GG2637@decadent.org.uk [ Remove reference to external Documentation file, provide info inline, as before ] Signed-off-by:
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- Jan 21, 2016
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Kees Cook authored
SYSCTL_WRITES_WARN was added in commit f4aacea2 ("sysctl: allow for strict write position handling"), and released in v3.16 in August of 2014. Since then I can find only 1 instance of non-zero offset writing[1], and it was fixed immediately in CRIU[2]. As such, it appears safe to flip this to the strict state now. [1] https://www.google.com/search?q="when%20file%20position%20was%20not%200" [2] http://lists.openvz.org/pipermail/criu/2015-April/019819.html Signed-off-by:
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- Dec 19, 2015
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Hidehiro Kawai authored
kernel.panic_on_io_nmi sysctl was introduced by commit 5211a242 ("x86: Add sysctl to allow panic on IOCK NMI error") but its documentation is missing. So, add it. Signed-off-by:
Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> Requested-by:
Borislav Petkov <bp@alien8.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Baoquan He <bhe@redhat.com> Cc: Chris Metcalf <cmetcalf@ezchip.com> Cc: Don Zickus <dzickus@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Heinrich Schuchardt <xypron.glpk@gmx.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Jonathan Corbet <corbet@lwn.net> Cc: kexec@lists.infradead.org Cc: linux-doc@vger.kernel.org Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Nicolas Iooss <nicolas.iooss_linux@m4x.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Seth Jennings <sjenning@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: x86-ml <x86@kernel.org> Link: http://lkml.kernel.org/r/20151210014637.25437.71903.stgit@softrs Signed-off-by:
Thomas Gleixner <tglx@linutronix.de>
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- Nov 06, 2015
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Jiri Kosina authored
In many cases of hardlockup reports, it's actually not possible to know why it triggered, because the CPU that got stuck is usually waiting on a resource (with IRQs disabled) in posession of some other CPU is holding. IOW, we are often looking at the stacktrace of the victim and not the actual offender. Introduce sysctl / cmdline parameter that makes it possible to have hardlockup detector perform all-CPU backtrace. Signed-off-by:
Jiri Kosina <jkosina@suse.cz> Reviewed-by:
Aaron Tomlin <atomlin@redhat.com> Cc: Ulrich Obergfell <uobergfe@redhat.com> Acked-by:
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