Merge tag 'docs-5.1' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "A fairly routine cycle for docs - lots of typo fixes, some new
  documents, and more translations. There's also some LICENSES
  adjustments from Thomas"

* tag 'docs-5.1' of git://git.lwn.net/linux: (74 commits)
  docs: Bring some order to filesystem documentation
  Documentation/locking/lockdep: Drop last two chars of sample states
  doc: rcu: Suspicious RCU usage is a warning
  docs: driver-api: iio: fix errors in documentation
  Documentation/process/howto: Update for 4.x -> 5.x versioning
  docs: Explicitly state that the 'Fixes:' tag shouldn't split lines
  doc: security: Add kern-doc for lsm_hooks.h
  doc: sctp: Merge and clean up rst files
  Docs: Correct /proc/stat path
  scripts/spdxcheck.py: fix C++ comment style detection
  doc: fix typos in license-rules.rst
  Documentation: fix admin-guide/README.rst minimum gcc version requirement
  doc: process: complete removal of info about -git patches
  doc: translations: sync translations 'remove info about -git patches'
  perf-security: wrap paragraphs on 72 columns
  perf-security: elaborate on perf_events/Perf privileged users
  perf-security: document collected perf_events/Perf data categories
  perf-security: document perf_events/Perf resource control
  sysfs.txt: add note on available attribute macros
  docs: kernel-doc: typo "if ... if" -> "if ... is"
  ...

4 files changed, 336 insertions, 91 deletions

diff --git a/Documentation/admin-guide/README.rst b/Documentation/admin-guide/README.rst
index 47e577264198..a582c780c3bd 100644
--- a/Documentation/admin-guide/README.rst
+++ b/Documentation/admin-guide/README.rst
@@ -251,7 +251,7 @@ Configuring the kernel
 Compiling the kernel
 --------------------
 
- - Make sure you have at least gcc 3.2 available.
+ - Make sure you have at least gcc 4.6 available.
    For more information, refer to :ref:`Documentation/process/changes.rst <changes>`.
 
    Please note that you can still run a.out user programs with this kernel.
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 42379633801f..49f2acc5eece 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1197,9 +1197,10 @@
 			arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 
 	elevator=	[IOSCHED]
-			Format: {"cfq" | "deadline" | "noop"}
-			See Documentation/block/cfq-iosched.txt and
-			Documentation/block/deadline-iosched.txt for details.
+			Format: { "mq-deadline" | "kyber" | "bfq" }
+			See Documentation/block/deadline-iosched.txt,
+			Documentation/block/kyber-iosched.txt and
+			Documentation/block/bfq-iosched.txt for details.
 
 	elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
 			Specifies physical address of start of kernel core
@@ -1996,6 +1997,12 @@
 			Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
 			the default is off.
 
+	kpti=		[ARM64] Control page table isolation of user
+			and kernel address spaces.
+			Default: enabled on cores which need mitigation.
+			0: force disabled
+			1: force enabled
+
 	kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
 			Default is 0 (don't ignore, but inject #GP)
 
diff --git a/Documentation/admin-guide/perf-security.rst b/Documentation/admin-guide/perf-security.rst
index f73ebfe9bfe2..72effa7c23b9 100644
--- a/Documentation/admin-guide/perf-security.rst
+++ b/Documentation/admin-guide/perf-security.rst
@@ -6,83 +6,211 @@ Perf Events and tool security
 Overview
 --------
 
-Usage of Performance Counters for Linux (perf_events) [1]_ , [2]_ , [3]_ can
-impose a considerable risk of leaking sensitive data accessed by monitored
-processes. The data leakage is possible both in scenarios of direct usage of
-perf_events system call API [2]_ and over data files generated by Perf tool user
-mode utility (Perf) [3]_ , [4]_ . The risk depends on the nature of data that
-perf_events performance monitoring units (PMU) [2]_ collect and expose for
-performance analysis. Having that said perf_events/Perf performance monitoring
-is the subject for security access control management [5]_ .
+Usage of Performance Counters for Linux (perf_events) [1]_ , [2]_ , [3]_
+can impose a considerable risk of leaking sensitive data accessed by
+monitored processes. The data leakage is possible both in scenarios of
+direct usage of perf_events system call API [2]_ and over data files
+generated by Perf tool user mode utility (Perf) [3]_ , [4]_ . The risk
+depends on the nature of data that perf_events performance monitoring
+units (PMU) [2]_ and Perf collect and expose for performance analysis.
+Collected system and performance data may be split into several
+categories:
+
+1. System hardware and software configuration data, for example: a CPU
+   model and its cache configuration, an amount of available memory and
+   its topology, used kernel and Perf versions, performance monitoring
+   setup including experiment time, events configuration, Perf command
+   line parameters, etc.
+
+2. User and kernel module paths and their load addresses with sizes,
+   process and thread names with their PIDs and TIDs, timestamps for
+   captured hardware and software events.
+
+3. Content of kernel software counters (e.g., for context switches, page
+   faults, CPU migrations), architectural hardware performance counters
+   (PMC) [8]_ and machine specific registers (MSR) [9]_ that provide
+   execution metrics for various monitored parts of the system (e.g.,
+   memory controller (IMC), interconnect (QPI/UPI) or peripheral (PCIe)
+   uncore counters) without direct attribution to any execution context
+   state.
+
+4. Content of architectural execution context registers (e.g., RIP, RSP,
+   RBP on x86_64), process user and kernel space memory addresses and
+   data, content of various architectural MSRs that capture data from
+   this category.
+
+Data that belong to the fourth category can potentially contain
+sensitive process data. If PMUs in some monitoring modes capture values
+of execution context registers or data from process memory then access
+to such monitoring capabilities requires to be ordered and secured
+properly. So, perf_events/Perf performance monitoring is the subject for
+security access control management [5]_ .
 
 perf_events/Perf access control
 -------------------------------
 
-To perform security checks, the Linux implementation splits processes into two
-categories [6]_ : a) privileged processes (whose effective user ID is 0, referred
-to as superuser or root), and b) unprivileged processes (whose effective UID is
-nonzero). Privileged processes bypass all kernel security permission checks so
-perf_events performance monitoring is fully available to privileged processes
-without access, scope and resource restrictions.
-
-Unprivileged processes are subject to a full security permission check based on
-the process's credentials [5]_ (usually: effective UID, effective GID, and
-supplementary group list).
-
-Linux divides the privileges traditionally associated with superuser into
-distinct units, known as capabilities [6]_ , which can be independently enabled
-and disabled on per-thread basis for processes and files of unprivileged users.
-
-Unprivileged processes with enabled CAP_SYS_ADMIN capability are treated as
-privileged processes with respect to perf_events performance monitoring and
-bypass *scope* permissions checks in the kernel.
-
-Unprivileged processes using perf_events system call API is also subject for
-PTRACE_MODE_READ_REALCREDS ptrace access mode check [7]_ , whose outcome
-determines whether monitoring is permitted. So unprivileged processes provided
-with CAP_SYS_PTRACE capability are effectively permitted to pass the check.
-
-Other capabilities being granted to unprivileged processes can effectively
-enable capturing of additional data required for later performance analysis of
-monitored processes or a system. For example, CAP_SYSLOG capability permits
-reading kernel space memory addresses from /proc/kallsyms file.
+To perform security checks, the Linux implementation splits processes
+into two categories [6]_ : a) privileged processes (whose effective user
+ID is 0, referred to as superuser or root), and b) unprivileged
+processes (whose effective UID is nonzero). Privileged processes bypass
+all kernel security permission checks so perf_events performance
+monitoring is fully available to privileged processes without access,
+scope and resource restrictions.
+
+Unprivileged processes are subject to a full security permission check
+based on the process's credentials [5]_ (usually: effective UID,
+effective GID, and supplementary group list).
+
+Linux divides the privileges traditionally associated with superuser
+into distinct units, known as capabilities [6]_ , which can be
+independently enabled and disabled on per-thread basis for processes and
+files of unprivileged users.
+
+Unprivileged processes with enabled CAP_SYS_ADMIN capability are treated
+as privileged processes with respect to perf_events performance
+monitoring and bypass *scope* permissions checks in the kernel.
+
+Unprivileged processes using perf_events system call API is also subject
+for PTRACE_MODE_READ_REALCREDS ptrace access mode check [7]_ , whose
+outcome determines whether monitoring is permitted. So unprivileged
+processes provided with CAP_SYS_PTRACE capability are effectively
+permitted to pass the check.
+
+Other capabilities being granted to unprivileged processes can
+effectively enable capturing of additional data required for later
+performance analysis of monitored processes or a system. For example,
+CAP_SYSLOG capability permits reading kernel space memory addresses from
+/proc/kallsyms file.
+
+perf_events/Perf privileged users
+---------------------------------
+
+Mechanisms of capabilities, privileged capability-dumb files [6]_ and
+file system ACLs [10]_ can be used to create a dedicated group of
+perf_events/Perf privileged users who are permitted to execute
+performance monitoring without scope limits. The following steps can be
+taken to create such a group of privileged Perf users.
+
+1. Create perf_users group of privileged Perf users, assign perf_users
+   group to Perf tool executable and limit access to the executable for
+   other users in the system who are not in the perf_users group:
+
+::
+
+   # groupadd perf_users
+   # ls -alhF
+   -rwxr-xr-x  2 root root  11M Oct 19 15:12 perf
+   # chgrp perf_users perf
+   # ls -alhF
+   -rwxr-xr-x  2 root perf_users  11M Oct 19 15:12 perf
+   # chmod o-rwx perf
+   # ls -alhF
+   -rwxr-x---  2 root perf_users  11M Oct 19 15:12 perf
+
+2. Assign the required capabilities to the Perf tool executable file and
+   enable members of perf_users group with performance monitoring
+   privileges [6]_ :
+
+::
+
+   # setcap "cap_sys_admin,cap_sys_ptrace,cap_syslog=ep" perf
+   # setcap -v "cap_sys_admin,cap_sys_ptrace,cap_syslog=ep" perf
+   perf: OK
+   # getcap perf
+   perf = cap_sys_ptrace,cap_sys_admin,cap_syslog+ep
+
+As a result, members of perf_users group are capable of conducting
+performance monitoring by using functionality of the configured Perf
+tool executable that, when executes, passes perf_events subsystem scope
+checks.
+
+This specific access control management is only available to superuser
+or root running processes with CAP_SETPCAP, CAP_SETFCAP [6]_
+capabilities.
 
 perf_events/Perf unprivileged users
 -----------------------------------
 
-perf_events/Perf *scope* and *access* control for unprivileged processes is
-governed by perf_event_paranoid [2]_ setting:
+perf_events/Perf *scope* and *access* control for unprivileged processes
+is governed by perf_event_paranoid [2]_ setting:
 
 -1:
-     Impose no *scope* and *access* restrictions on using perf_events performance
-     monitoring. Per-user per-cpu perf_event_mlock_kb [2]_ locking limit is
-     ignored when allocating memory buffers for storing performance data.
-     This is the least secure mode since allowed monitored *scope* is
-     maximized and no perf_events specific limits are imposed on *resources*
-     allocated for performance monitoring.
+     Impose no *scope* and *access* restrictions on using perf_events
+     performance monitoring. Per-user per-cpu perf_event_mlock_kb [2]_
+     locking limit is ignored when allocating memory buffers for storing
+     performance data. This is the least secure mode since allowed
+     monitored *scope* is maximized and no perf_events specific limits
+     are imposed on *resources* allocated for performance monitoring.
 
 >=0:
      *scope* includes per-process and system wide performance monitoring
-     but excludes raw tracepoints and ftrace function tracepoints monitoring.
-     CPU and system events happened when executing either in user or
-     in kernel space can be monitored and captured for later analysis.
-     Per-user per-cpu perf_event_mlock_kb locking limit is imposed but
-     ignored for unprivileged processes with CAP_IPC_LOCK [6]_ capability.
+     but excludes raw tracepoints and ftrace function tracepoints
+     monitoring. CPU and system events happened when executing either in
+     user or in kernel space can be monitored and captured for later
+     analysis. Per-user per-cpu perf_event_mlock_kb locking limit is
+     imposed but ignored for unprivileged processes with CAP_IPC_LOCK
+     [6]_ capability.
 
 >=1:
-     *scope* includes per-process performance monitoring only and excludes
-     system wide performance monitoring. CPU and system events happened when
-     executing either in user or in kernel space can be monitored and
-     captured for later analysis. Per-user per-cpu perf_event_mlock_kb
-     locking limit is imposed but ignored for unprivileged processes with
-     CAP_IPC_LOCK capability.
+     *scope* includes per-process performance monitoring only and
+     excludes system wide performance monitoring. CPU and system events
+     happened when executing either in user or in kernel space can be
+     monitored and captured for later analysis. Per-user per-cpu
+     perf_event_mlock_kb locking limit is imposed but ignored for
+     unprivileged processes with CAP_IPC_LOCK capability.
 
 >=2:
-     *scope* includes per-process performance monitoring only. CPU and system
-     events happened when executing in user space only can be monitored and
-     captured for later analysis. Per-user per-cpu perf_event_mlock_kb
-     locking limit is imposed but ignored for unprivileged processes with
-     CAP_IPC_LOCK capability.
+     *scope* includes per-process performance monitoring only. CPU and
+     system events happened when executing in user space only can be
+     monitored and captured for later analysis. Per-user per-cpu
+     perf_event_mlock_kb locking limit is imposed but ignored for
+     unprivileged processes with CAP_IPC_LOCK capability.
+
+perf_events/Perf resource control
+---------------------------------
+
+Open file descriptors
++++++++++++++++++++++
+
+The perf_events system call API [2]_ allocates file descriptors for
+every configured PMU event. Open file descriptors are a per-process
+accountable resource governed by the RLIMIT_NOFILE [11]_ limit
+(ulimit -n), which is usually derived from the login shell process. When
+configuring Perf collection for a long list of events on a large server
+system, this limit can be easily hit preventing required monitoring
+configuration. RLIMIT_NOFILE limit can be increased on per-user basis
+modifying content of the limits.conf file [12]_ . Ordinarily, a Perf
+sampling session (perf record) requires an amount of open perf_event
+file descriptors that is not less than the number of monitored events
+multiplied by the number of monitored CPUs.
+
+Memory allocation
++++++++++++++++++
+
+The amount of memory available to user processes for capturing
+performance monitoring data is governed by the perf_event_mlock_kb [2]_
+setting. This perf_event specific resource setting defines overall
+per-cpu limits of memory allowed for mapping by the user processes to
+execute performance monitoring. The setting essentially extends the
+RLIMIT_MEMLOCK [11]_ limit, but only for memory regions mapped
+specifically for capturing monitored performance events and related data.
+
+For example, if a machine has eight cores and perf_event_mlock_kb limit
+is set to 516 KiB, then a user process is provided with 516 KiB * 8 =
+4128 KiB of memory above the RLIMIT_MEMLOCK limit (ulimit -l) for
+perf_event mmap buffers. In particular, this means that, if the user
+wants to start two or more performance monitoring processes, the user is
+required to manually distribute the available 4128 KiB between the
+monitoring processes, for example, using the --mmap-pages Perf record
+mode option. Otherwise, the first started performance monitoring process
+allocates all available 4128 KiB and the other processes will fail to
+proceed due to the lack of memory.
+
+RLIMIT_MEMLOCK and perf_event_mlock_kb resource constraints are ignored
+for processes with the CAP_IPC_LOCK capability. Thus, perf_events/Perf
+privileged users can be provided with memory above the constraints for
+perf_events/Perf performance monitoring purpose by providing the Perf
+executable with CAP_IPC_LOCK capability.
 
 Bibliography
 ------------
@@ -94,4 +222,9 @@ Bibliography
 .. [5] `<https://www.kernel.org/doc/html/latest/security/credentials.html>`_
 .. [6] `<http://man7.org/linux/man-pages/man7/capabilities.7.html>`_
 .. [7] `<http://man7.org/linux/man-pages/man2/ptrace.2.html>`_
+.. [8] `<https://en.wikipedia.org/wiki/Hardware_performance_counter>`_
+.. [9] `<https://en.wikipedia.org/wiki/Model-specific_register>`_
+.. [10] `<http://man7.org/linux/man-pages/man5/acl.5.html>`_
+.. [11] `<http://man7.org/linux/man-pages/man2/getrlimit.2.html>`_
+.. [12] `<http://man7.org/linux/man-pages/man5/limits.conf.5.html>`_
 
diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst
index 28a869c509a0..71e9184a9079 100644
--- a/Documentation/admin-guide/tainted-kernels.rst
+++ b/Documentation/admin-guide/tainted-kernels.rst
@@ -1,59 +1,164 @@
 Tainted kernels
 ---------------
 
-Some oops reports contain the string **'Tainted: '** after the program
-counter. This indicates that the kernel has been tainted by some
-mechanism.  The string is followed by a series of position-sensitive
-characters, each representing a particular tainted value.
-
- 1)  ``G`` if all modules loaded have a GPL or compatible license, ``P`` if
+The kernel will mark itself as 'tainted' when something occurs that might be
+relevant later when investigating problems. Don't worry too much about this,
+most of the time it's not a problem to run a tainted kernel; the information is
+mainly of interest once someone wants to investigate some problem, as its real
+cause might be the event that got the kernel tainted. That's why bug reports
+from tainted kernels will often be ignored by developers, hence try to reproduce
+problems with an untainted kernel.
+
+Note the kernel will remain tainted even after you undo what caused the taint
+(i.e. unload a proprietary kernel module), to indicate the kernel remains not
+trustworthy. That's also why the kernel will print the tainted state when it
+notices an internal problem (a 'kernel bug'), a recoverable error
+('kernel oops') or a non-recoverable error ('kernel panic') and writes debug
+information about this to the logs ``dmesg`` outputs. It's also possible to
+check the tainted state at runtime through a file in ``/proc/``.
+
+
+Tainted flag in bugs, oops or panics messages
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+You find the tainted state near the top in a line starting with 'CPU:'; if or
+why the kernel was tainted is shown after the Process ID ('PID:') and a shortened
+name of the command ('Comm:') that triggered the event::
+
+	BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
+	Oops: 0002 [#1] SMP PTI
+	CPU: 0 PID: 4424 Comm: insmod Tainted: P        W  O      4.20.0-0.rc6.fc30 #1
+	Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
+	RIP: 0010:my_oops_init+0x13/0x1000 [kpanic]
+	[...]
+
+You'll find a 'Not tainted: ' there if the kernel was not tainted at the
+time of the event; if it was, then it will print 'Tainted: ' and characters
+either letters or blanks. In above example it looks like this::
+
+	Tainted: P        W  O
+
+The meaning of those characters is explained in the table below. In tis case
+the kernel got tainted earlier because a proprietary Module (``P``) was loaded,
+a warning occurred (``W``), and an externally-built module was loaded (``O``).
+To decode other letters use the table below.
+
+
+Decoding tainted state at runtime
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+At runtime, you can query the tainted state by reading
+``cat /proc/sys/kernel/tainted``. If that returns ``0``, the kernel is not
+tainted; any other number indicates the reasons why it is. The easiest way to
+decode that number is the script ``tools/debugging/kernel-chktaint``, which your
+distribution might ship as part of a package called ``linux-tools`` or
+``kernel-tools``; if it doesn't you can download the script from
+`git.kernel.org <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/plain/tools/debugging/kernel-chktaint>`_
+and execute it with ``sh kernel-chktaint``, which would print something like
+this on the machine that had the statements in the logs that were quoted earlier::
+
+	Kernel is Tainted for following reasons:
+	 * Proprietary module was loaded (#0)
+	 * Kernel issued warning (#9)
+	 * Externally-built ('out-of-tree') module was loaded  (#12)
+	See Documentation/admin-guide/tainted-kernels.rst in the the Linux kernel or
+	 https://www.kernel.org/doc/html/latest/admin-guide/tainted-kernels.html for
+	 a more details explanation of the various taint flags.
+	Raw taint value as int/string: 4609/'P        W  O     '
+
+You can try to decode the number yourself. That's easy if there was only one
+reason that got your kernel tainted, as in this case you can find the number
+with the table below. If there were multiple reasons you need to decode the
+number, as it is a bitfield, where each bit indicates the absence or presence of
+a particular type of taint. It's best to leave that to the aforementioned
+script, but if you need something quick you can use this shell command to check
+which bits are set::
+
+	$ for i in $(seq 18); do echo $(($i-1)) $(($(cat /proc/sys/kernel/tainted)>>($i-1)&1));done
+
+Table for decoding tainted state
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+===  ===  ======  ========================================================
+Bit  Log  Number  Reason that got the kernel tainted
+===  ===  ======  ========================================================
+  0  G/P       1  proprietary module was loaded
+  1  _/F       2  module was force loaded
+  2  _/S       4  SMP kernel oops on an officially SMP incapable processor
+  3  _/R       8  module was force unloaded
+  4  _/M      16  processor reported a Machine Check Exception (MCE)
+  5  _/B      32  bad page referenced or some unexpected page flags
+  6  _/U      64  taint requested by userspace application
+  7  _/D     128  kernel died recently, i.e. there was an OOPS or BUG
+  8  _/A     256  ACPI table overridden by user
+  9  _/W     512  kernel issued warning
+ 10  _/C    1024  staging driver was loaded
+ 11  _/I    2048  workaround for bug in platform firmware applied
+ 12  _/O    4096  externally-built ("out-of-tree") module was loaded
+ 13  _/E    8192  unsigned module was loaded
+ 14  _/L   16384  soft lockup occurred
+ 15  _/K   32768  kernel has been live patched
+ 16  _/X   65536  auxiliary taint, defined for and used by distros
+ 17  _/T  131072  kernel was built with the struct randomization plugin
+===  ===  ======  ========================================================
+
+Note: The character ``_`` is representing a blank in this table to make reading
+easier.
+
+More detailed explanation for tainting
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+ 0)  ``G`` if all modules loaded have a GPL or compatible license, ``P`` if
      any proprietary module has been loaded.  Modules without a
      MODULE_LICENSE or with a MODULE_LICENSE that is not recognised by
      insmod as GPL compatible are assumed to be proprietary.
 
- 2)  ``F`` if any module was force loaded by ``insmod -f``, ``' '`` if all
+ 1)  ``F`` if any module was force loaded by ``insmod -f``, ``' '`` if all
      modules were loaded normally.
 
- 3)  ``S`` if the oops occurred on an SMP kernel running on hardware that
+ 2)  ``S`` if the oops occurred on an SMP kernel running on hardware that
      hasn't been certified as safe to run multiprocessor.
      Currently this occurs only on various Athlons that are not
      SMP capable.
 
- 4)  ``R`` if a module was force unloaded by ``rmmod -f``, ``' '`` if all
+ 3)  ``R`` if a module was force unloaded by ``rmmod -f``, ``' '`` if all
      modules were unloaded normally.
 
- 5)  ``M`` if any processor has reported a Machine Check Exception,
+ 4)  ``M`` if any processor has reported a Machine Check Exception,
      ``' '`` if no Machine Check Exceptions have occurred.
 
- 6)  ``B`` if a page-release function has found a bad page reference or
-     some unexpected page flags.
+ 5)  ``B`` If a page-release function has found a bad page reference or some
+     unexpected page flags. This indicates a hardware problem or a kernel bug;
+     there should be other information in the log indicating why this tainting
+     occured.
 
- 7)  ``U`` if a user or user application specifically requested that the
+ 6)  ``U`` if a user or user application specifically requested that the
      Tainted flag be set, ``' '`` otherwise.
 
- 8)  ``D`` if the kernel has died recently, i.e. there was an OOPS or BUG.
+ 7)  ``D`` if the kernel has died recently, i.e. there was an OOPS or BUG.
 
- 9)  ``A`` if the ACPI table has been overridden.
+ 8)  ``A`` if an ACPI table has been overridden.
 
- 10) ``W`` if a warning has previously been issued by the kernel.
+ 9)  ``W`` if a warning has previously been issued by the kernel.
      (Though some warnings may set more specific taint flags.)
 
- 11) ``C`` if a staging driver has been loaded.
+ 10) ``C`` if a staging driver has been loaded.
 
- 12) ``I`` if the kernel is working around a severe bug in the platform
+ 11) ``I`` if the kernel is working around a severe bug in the platform
      firmware (BIOS or similar).
 
- 13) ``O`` if an externally-built ("out-of-tree") module has been loaded.
+ 12) ``O`` if an externally-built ("out-of-tree") module has been loaded.
 
- 14) ``E`` if an unsigned module has been loaded in a kernel supporting
+ 13) ``E`` if an unsigned module has been loaded in a kernel supporting
      module signature.
 
- 15) ``L`` if a soft lockup has previously occurred on the system.
+ 14) ``L`` if a soft lockup has previously occurred on the system.
+
+ 15) ``K`` if the kernel has been live patched.
 
- 16) ``K`` if the kernel has been live patched.
+ 16) ``X`` Auxiliary taint, defined for and used by Linux distributors.
 
-The primary reason for the **'Tainted: '** string is to tell kernel
-debuggers if this is a clean kernel or if anything unusual has
-occurred.  Tainting is permanent: even if an offending module is
-unloaded, the tainted value remains to indicate that the kernel is not
-trustworthy.
+ 17) ``T`` Kernel was build with the randstruct plugin, which can intentionally
+     produce extremely unusual kernel structure layouts (even performance
+     pathological ones), which is important to know when debugging. Set at
+     build time.