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2c956a6077
linux_dsm_epyc7002/lib/Kconfig.debug
Jason A. Donenfeld 2c956a6077 siphash: add cryptographically secure PRF 
SipHash is a 64-bit keyed hash function that is actually a
cryptographically secure PRF, like HMAC. Except SipHash is super fast,
and is meant to be used as a hashtable keyed lookup function, or as a
general PRF for short input use cases, such as sequence numbers or RNG
chaining.

For the first usage:

There are a variety of attacks known as "hashtable poisoning" in which an
attacker forms some data such that the hash of that data will be the
same, and then preceeds to fill up all entries of a hashbucket. This is
a realistic and well-known denial-of-service vector. Currently
hashtables use jhash, which is fast but not secure, and some kind of
rotating key scheme (or none at all, which isn't good). SipHash is meant
as a replacement for jhash in these cases.

There are a modicum of places in the kernel that are vulnerable to
hashtable poisoning attacks, either via userspace vectors or network
vectors, and there's not a reliable mechanism inside the kernel at the
moment to fix it. The first step toward fixing these issues is actually
getting a secure primitive into the kernel for developers to use. Then
we can, bit by bit, port things over to it as deemed appropriate.

While SipHash is extremely fast for a cryptographically secure function,
it is likely a bit slower than the insecure jhash, and so replacements
will be evaluated on a case-by-case basis based on whether or not the
difference in speed is negligible and whether or not the current jhash usage
poses a real security risk.

For the second usage:

A few places in the kernel are using MD5 or SHA1 for creating secure
sequence numbers, syn cookies, port numbers, or fast random numbers.
SipHash is a faster and more fitting, and more secure replacement for MD5
in those situations. Replacing MD5 and SHA1 with SipHash for these uses is
obvious and straight-forward, and so is submitted along with this patch
series. There shouldn't be much of a debate over its efficacy.

Dozens of languages are already using this internally for their hash
tables and PRFs. Some of the BSDs already use this in their kernels.
SipHash is a widely known high-speed solution to a widely known set of
problems, and it's time we catch-up.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-01-09 13:58:57 -05:00

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menu "printk and dmesg options"
config PRINTK_TIME
bool "Show timing information on printks"
depends on PRINTK
help
Selecting this option causes time stamps of the printk()
messages to be added to the output of the syslog() system
call and at the console.
The timestamp is always recorded internally, and exported
to /dev/kmsg. This flag just specifies if the timestamp should
be included, not that the timestamp is recorded.
The behavior is also controlled by the kernel command line
parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst
config CONSOLE_LOGLEVEL_DEFAULT
int "Default console loglevel (1-15)"
range 1 15
default "7"
help
Default loglevel to determine what will be printed on the console.
Setting a default here is equivalent to passing in loglevel=<x> in
the kernel bootargs. loglevel=<x> continues to override whatever
value is specified here as well.
Note: This does not affect the log level of un-prefixed printk()
usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
option.
config MESSAGE_LOGLEVEL_DEFAULT
int "Default message log level (1-7)"
range 1 7
default "4"
help
Default log level for printk statements with no specified priority.
This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
that are auditing their logs closely may want to set it to a lower
priority.
Note: This does not affect what message level gets printed on the console
by default. To change that, use loglevel=<x> in the kernel bootargs,
or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
config BOOT_PRINTK_DELAY
bool "Delay each boot printk message by N milliseconds"
depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
help
This build option allows you to read kernel boot messages
by inserting a short delay after each one. The delay is
specified in milliseconds on the kernel command line,
using "boot_delay=N".
It is likely that you would also need to use "lpj=M" to preset
the "loops per jiffie" value.
See a previous boot log for the "lpj" value to use for your
system, and then set "lpj=M" before setting "boot_delay=N".
NOTE: Using this option may adversely affect SMP systems.
I.e., processors other than the first one may not boot up.
BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
what it believes to be lockup conditions.
config DYNAMIC_DEBUG
bool "Enable dynamic printk() support"
default n
depends on PRINTK
depends on DEBUG_FS
help
Compiles debug level messages into the kernel, which would not
otherwise be available at runtime. These messages can then be
enabled/disabled based on various levels of scope - per source file,
function, module, format string, and line number. This mechanism
implicitly compiles in all pr_debug() and dev_dbg() calls, which
enlarges the kernel text size by about 2%.
If a source file is compiled with DEBUG flag set, any
pr_debug() calls in it are enabled by default, but can be
disabled at runtime as below. Note that DEBUG flag is
turned on by many CONFIG_*DEBUG* options.
Usage:
Dynamic debugging is controlled via the 'dynamic_debug/control' file,
which is contained in the 'debugfs' filesystem. Thus, the debugfs
filesystem must first be mounted before making use of this feature.
We refer the control file as: <debugfs>/dynamic_debug/control. This
file contains a list of the debug statements that can be enabled. The
format for each line of the file is:
filename:lineno [module]function flags format
filename : source file of the debug statement
lineno : line number of the debug statement
module : module that contains the debug statement
function : function that contains the debug statement
flags : '=p' means the line is turned 'on' for printing
format : the format used for the debug statement
From a live system:
nullarbor:~ # cat <debugfs>/dynamic_debug/control
# filename:lineno [module]function flags format
fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
Example usage:
// enable the message at line 1603 of file svcsock.c
nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
<debugfs>/dynamic_debug/control
// enable all the messages in file svcsock.c
nullarbor:~ # echo -n 'file svcsock.c +p' >
<debugfs>/dynamic_debug/control
// enable all the messages in the NFS server module
nullarbor:~ # echo -n 'module nfsd +p' >
<debugfs>/dynamic_debug/control
// enable all 12 messages in the function svc_process()
nullarbor:~ # echo -n 'func svc_process +p' >
<debugfs>/dynamic_debug/control
// disable all 12 messages in the function svc_process()
nullarbor:~ # echo -n 'func svc_process -p' >
<debugfs>/dynamic_debug/control
See Documentation/dynamic-debug-howto.txt for additional information.
endmenu # "printk and dmesg options"
menu "Compile-time checks and compiler options"
config DEBUG_INFO
bool "Compile the kernel with debug info"
depends on DEBUG_KERNEL && !COMPILE_TEST
help
If you say Y here the resulting kernel image will include
debugging info resulting in a larger kernel image.
This adds debug symbols to the kernel and modules (gcc -g), and
is needed if you intend to use kernel crashdump or binary object
tools like crash, kgdb, LKCD, gdb, etc on the kernel.
Say Y here only if you plan to debug the kernel.
If unsure, say N.
config DEBUG_INFO_REDUCED
bool "Reduce debugging information"
depends on DEBUG_INFO
help
If you say Y here gcc is instructed to generate less debugging
information for structure types. This means that tools that
need full debugging information (like kgdb or systemtap) won't
be happy. But if you merely need debugging information to
resolve line numbers there is no loss. Advantage is that
build directory object sizes shrink dramatically over a full
DEBUG_INFO build and compile times are reduced too.
Only works with newer gcc versions.
config DEBUG_INFO_SPLIT
bool "Produce split debuginfo in .dwo files"
depends on DEBUG_INFO
help
Generate debug info into separate .dwo files. This significantly
reduces the build directory size for builds with DEBUG_INFO,
because it stores the information only once on disk in .dwo
files instead of multiple times in object files and executables.
In addition the debug information is also compressed.
Requires recent gcc (4.7+) and recent gdb/binutils.
Any tool that packages or reads debug information would need
to know about the .dwo files and include them.
Incompatible with older versions of ccache.
config DEBUG_INFO_DWARF4
bool "Generate dwarf4 debuginfo"
depends on DEBUG_INFO
help
Generate dwarf4 debug info. This requires recent versions
of gcc and gdb. It makes the debug information larger.
But it significantly improves the success of resolving
variables in gdb on optimized code.
config GDB_SCRIPTS
bool "Provide GDB scripts for kernel debugging"
depends on DEBUG_INFO
help
This creates the required links to GDB helper scripts in the
build directory. If you load vmlinux into gdb, the helper
scripts will be automatically imported by gdb as well, and
additional functions are available to analyze a Linux kernel
instance. See Documentation/dev-tools/gdb-kernel-debugging.rst
for further details.
config ENABLE_WARN_DEPRECATED
bool "Enable __deprecated logic"
default y
help
Enable the __deprecated logic in the kernel build.
Disable this to suppress the "warning: 'foo' is deprecated
(declared at kernel/power/somefile.c:1234)" messages.
config ENABLE_MUST_CHECK
bool "Enable __must_check logic"
default y
help
Enable the __must_check logic in the kernel build. Disable this to
suppress the "warning: ignoring return value of 'foo', declared with
attribute warn_unused_result" messages.
config FRAME_WARN
int "Warn for stack frames larger than (needs gcc 4.4)"
range 0 8192
default 0 if KASAN
default 2048 if GCC_PLUGIN_LATENT_ENTROPY
default 1024 if !64BIT
default 2048 if 64BIT
help
Tell gcc to warn at build time for stack frames larger than this.
Setting this too low will cause a lot of warnings.
Setting it to 0 disables the warning.
Requires gcc 4.4
config STRIP_ASM_SYMS
bool "Strip assembler-generated symbols during link"
default n
help
Strip internal assembler-generated symbols during a link (symbols
that look like '.Lxxx') so they don't pollute the output of
get_wchan() and suchlike.
config READABLE_ASM
bool "Generate readable assembler code"
depends on DEBUG_KERNEL
help
Disable some compiler optimizations that tend to generate human unreadable
assembler output. This may make the kernel slightly slower, but it helps
to keep kernel developers who have to stare a lot at assembler listings
sane.
config UNUSED_SYMBOLS
bool "Enable unused/obsolete exported symbols"
default y if X86
help
Unused but exported symbols make the kernel needlessly bigger. For
that reason most of these unused exports will soon be removed. This
option is provided temporarily to provide a transition period in case
some external kernel module needs one of these symbols anyway. If you
encounter such a case in your module, consider if you are actually
using the right API. (rationale: since nobody in the kernel is using
this in a module, there is a pretty good chance it's actually the
wrong interface to use). If you really need the symbol, please send a
mail to the linux kernel mailing list mentioning the symbol and why
you really need it, and what the merge plan to the mainline kernel for
your module is.
config PAGE_OWNER
bool "Track page owner"
depends on DEBUG_KERNEL && STACKTRACE_SUPPORT
select DEBUG_FS
select STACKTRACE
select STACKDEPOT
select PAGE_EXTENSION
help
This keeps track of what call chain is the owner of a page, may
help to find bare alloc_page(s) leaks. Even if you include this
feature on your build, it is disabled in default. You should pass
"page_owner=on" to boot parameter in order to enable it. Eats
a fair amount of memory if enabled. See tools/vm/page_owner_sort.c
for user-space helper.
If unsure, say N.
config DEBUG_FS
bool "Debug Filesystem"
select SRCU
help
debugfs is a virtual file system that kernel developers use to put
debugging files into. Enable this option to be able to read and
write to these files.
For detailed documentation on the debugfs API, see
Documentation/DocBook/filesystems.
If unsure, say N.
config HEADERS_CHECK
bool "Run 'make headers_check' when building vmlinux"
depends on !UML
help
This option will extract the user-visible kernel headers whenever
building the kernel, and will run basic sanity checks on them to
ensure that exported files do not attempt to include files which
were not exported, etc.
If you're making modifications to header files which are
relevant for userspace, say 'Y', and check the headers
exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
your build tree), to make sure they're suitable.
config DEBUG_SECTION_MISMATCH
bool "Enable full Section mismatch analysis"
help
The section mismatch analysis checks if there are illegal
references from one section to another section.
During linktime or runtime, some sections are dropped;
any use of code/data previously in these sections would
most likely result in an oops.
In the code, functions and variables are annotated with
__init,, etc. (see the full list in include/linux/init.h),
which results in the code/data being placed in specific sections.
The section mismatch analysis is always performed after a full
kernel build, and enabling this option causes the following
additional steps to occur:
- Add the option -fno-inline-functions-called-once to gcc commands.
When inlining a function annotated with __init in a non-init
function, we would lose the section information and thus
the analysis would not catch the illegal reference.
This option tells gcc to inline less (but it does result in
a larger kernel).
- Run the section mismatch analysis for each module/built-in.o file.
When we run the section mismatch analysis on vmlinux.o, we
lose valuable information about where the mismatch was
introduced.
Running the analysis for each module/built-in.o file
tells where the mismatch happens much closer to the
source. The drawback is that the same mismatch is
reported at least twice.
- Enable verbose reporting from modpost in order to help resolve
the section mismatches that are reported.
config SECTION_MISMATCH_WARN_ONLY
bool "Make section mismatch errors non-fatal"
default y
help
If you say N here, the build process will fail if there are any
section mismatch, instead of just throwing warnings.
If unsure, say Y.
#
# Select this config option from the architecture Kconfig, if it
# is preferred to always offer frame pointers as a config
# option on the architecture (regardless of KERNEL_DEBUG):
#
config ARCH_WANT_FRAME_POINTERS
bool
help
config FRAME_POINTER
bool "Compile the kernel with frame pointers"
depends on DEBUG_KERNEL && \
(CRIS || M68K || FRV || UML || \
AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
ARCH_WANT_FRAME_POINTERS
default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
help
If you say Y here the resulting kernel image will be slightly
larger and slower, but it gives very useful debugging information
in case of kernel bugs. (precise oopses/stacktraces/warnings)
config STACK_VALIDATION
bool "Compile-time stack metadata validation"
depends on HAVE_STACK_VALIDATION
default n
help
Add compile-time checks to validate stack metadata, including frame
pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure
that runtime stack traces are more reliable.
For more information, see
tools/objtool/Documentation/stack-validation.txt.
config DEBUG_FORCE_WEAK_PER_CPU
bool "Force weak per-cpu definitions"
depends on DEBUG_KERNEL
help
s390 and alpha require percpu variables in modules to be
defined weak to work around addressing range issue which
puts the following two restrictions on percpu variable
definitions.
1. percpu symbols must be unique whether static or not
2. percpu variables can't be defined inside a function
To ensure that generic code follows the above rules, this
option forces all percpu variables to be defined as weak.
endmenu # "Compiler options"
config MAGIC_SYSRQ
bool "Magic SysRq key"
depends on !UML
help
If you say Y here, you will have some control over the system even
if the system crashes for example during kernel debugging (e.g., you
will be able to flush the buffer cache to disk, reboot the system
immediately or dump some status information). This is accomplished
by pressing various keys while holding SysRq (Alt+PrintScreen). It
also works on a serial console (on PC hardware at least), if you
send a BREAK and then within 5 seconds a command keypress. The
keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
unless you really know what this hack does.
config MAGIC_SYSRQ_DEFAULT_ENABLE
hex "Enable magic SysRq key functions by default"
depends on MAGIC_SYSRQ
default 0x1
help
Specifies which SysRq key functions are enabled by default.
This may be set to 1 or 0 to enable or disable them all, or
to a bitmask as described in Documentation/sysrq.txt.
config DEBUG_KERNEL
bool "Kernel debugging"
help
Say Y here if you are developing drivers or trying to debug and
identify kernel problems.
menu "Memory Debugging"
source mm/Kconfig.debug
config DEBUG_OBJECTS
bool "Debug object operations"
depends on DEBUG_KERNEL
help
If you say Y here, additional code will be inserted into the
kernel to track the life time of various objects and validate
the operations on those objects.
config DEBUG_OBJECTS_SELFTEST
bool "Debug objects selftest"
depends on DEBUG_OBJECTS
help
This enables the selftest of the object debug code.
config DEBUG_OBJECTS_FREE
bool "Debug objects in freed memory"
depends on DEBUG_OBJECTS
help
This enables checks whether a k/v free operation frees an area
which contains an object which has not been deactivated
properly. This can make kmalloc/kfree-intensive workloads
much slower.
config DEBUG_OBJECTS_TIMERS
bool "Debug timer objects"
depends on DEBUG_OBJECTS
help
If you say Y here, additional code will be inserted into the
timer routines to track the life time of timer objects and
validate the timer operations.
config DEBUG_OBJECTS_WORK
bool "Debug work objects"
depends on DEBUG_OBJECTS
help
If you say Y here, additional code will be inserted into the
work queue routines to track the life time of work objects and
validate the work operations.
config DEBUG_OBJECTS_RCU_HEAD
bool "Debug RCU callbacks objects"
depends on DEBUG_OBJECTS
help
Enable this to turn on debugging of RCU list heads (call_rcu() usage).
config DEBUG_OBJECTS_PERCPU_COUNTER
bool "Debug percpu counter objects"
depends on DEBUG_OBJECTS
help
If you say Y here, additional code will be inserted into the
percpu counter routines to track the life time of percpu counter
objects and validate the percpu counter operations.
config DEBUG_OBJECTS_ENABLE_DEFAULT
int "debug_objects bootup default value (0-1)"
range 0 1
default "1"
depends on DEBUG_OBJECTS
help
Debug objects boot parameter default value
config DEBUG_SLAB
bool "Debug slab memory allocations"
depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
help
Say Y here to have the kernel do limited verification on memory
allocation as well as poisoning memory on free to catch use of freed
memory. This can make kmalloc/kfree-intensive workloads much slower.
config DEBUG_SLAB_LEAK
bool "Memory leak debugging"
depends on DEBUG_SLAB
config SLUB_DEBUG_ON
bool "SLUB debugging on by default"
depends on SLUB && SLUB_DEBUG && !KMEMCHECK
default n
help
Boot with debugging on by default. SLUB boots by default with
the runtime debug capabilities switched off. Enabling this is
equivalent to specifying the "slub_debug" parameter on boot.
There is no support for more fine grained debug control like
possible with slub_debug=xxx. SLUB debugging may be switched
off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
"slub_debug=-".
config SLUB_STATS
default n
bool "Enable SLUB performance statistics"
depends on SLUB && SYSFS
help
SLUB statistics are useful to debug SLUBs allocation behavior in
order find ways to optimize the allocator. This should never be
enabled for production use since keeping statistics slows down
the allocator by a few percentage points. The slabinfo command
supports the determination of the most active slabs to figure
out which slabs are relevant to a particular load.
Try running: slabinfo -DA
config HAVE_DEBUG_KMEMLEAK
bool
config DEBUG_KMEMLEAK
bool "Kernel memory leak detector"
depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
select DEBUG_FS
select STACKTRACE if STACKTRACE_SUPPORT
select KALLSYMS
select CRC32
help
Say Y here if you want to enable the memory leak
detector. The memory allocation/freeing is traced in a way
similar to the Boehm's conservative garbage collector, the
difference being that the orphan objects are not freed but
only shown in /sys/kernel/debug/kmemleak. Enabling this
feature will introduce an overhead to memory
allocations. See Documentation/dev-tools/kmemleak.rst for more
details.
Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
of finding leaks due to the slab objects poisoning.
In order to access the kmemleak file, debugfs needs to be
mounted (usually at /sys/kernel/debug).
config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
int "Maximum kmemleak early log entries"
depends on DEBUG_KMEMLEAK
range 200 40000
default 400
help
Kmemleak must track all the memory allocations to avoid
reporting false positives. Since memory may be allocated or
freed before kmemleak is initialised, an early log buffer is
used to store these actions. If kmemleak reports "early log
buffer exceeded", please increase this value.
config DEBUG_KMEMLEAK_TEST
tristate "Simple test for the kernel memory leak detector"
depends on DEBUG_KMEMLEAK && m
help
This option enables a module that explicitly leaks memory.
If unsure, say N.
config DEBUG_KMEMLEAK_DEFAULT_OFF
bool "Default kmemleak to off"
depends on DEBUG_KMEMLEAK
help
Say Y here to disable kmemleak by default. It can then be enabled
on the command line via kmemleak=on.
config DEBUG_STACK_USAGE
bool "Stack utilization instrumentation"
depends on DEBUG_KERNEL && !IA64
help
Enables the display of the minimum amount of free stack which each
task has ever had available in the sysrq-T and sysrq-P debug output.
This option will slow down process creation somewhat.
config DEBUG_VM
bool "Debug VM"
depends on DEBUG_KERNEL
help
Enable this to turn on extended checks in the virtual-memory system
that may impact performance.
If unsure, say N.
config DEBUG_VM_VMACACHE
bool "Debug VMA caching"
depends on DEBUG_VM
help
Enable this to turn on VMA caching debug information. Doing so
can cause significant overhead, so only enable it in non-production
environments.
If unsure, say N.
config DEBUG_VM_RB
bool "Debug VM red-black trees"
depends on DEBUG_VM
help
Enable VM red-black tree debugging information and extra validations.
If unsure, say N.
config DEBUG_VM_PGFLAGS
bool "Debug page-flags operations"
depends on DEBUG_VM
help
Enables extra validation on page flags operations.
If unsure, say N.
config DEBUG_VIRTUAL
bool "Debug VM translations"
depends on DEBUG_KERNEL && X86
help
Enable some costly sanity checks in virtual to page code. This can
catch mistakes with virt_to_page() and friends.
If unsure, say N.
config DEBUG_NOMMU_REGIONS
bool "Debug the global anon/private NOMMU mapping region tree"
depends on DEBUG_KERNEL && !MMU
help
This option causes the global tree of anonymous and private mapping
regions to be regularly checked for invalid topology.
config DEBUG_MEMORY_INIT
bool "Debug memory initialisation" if EXPERT
default !EXPERT
help
Enable this for additional checks during memory initialisation.
The sanity checks verify aspects of the VM such as the memory model
and other information provided by the architecture. Verbose
information will be printed at KERN_DEBUG loglevel depending
on the mminit_loglevel= command-line option.
If unsure, say Y
config MEMORY_NOTIFIER_ERROR_INJECT
tristate "Memory hotplug notifier error injection module"
depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
help
This option provides the ability to inject artificial errors to
memory hotplug notifier chain callbacks. It is controlled through
debugfs interface under /sys/kernel/debug/notifier-error-inject/memory
If the notifier call chain should be failed with some events
notified, write the error code to "actions/<notifier event>/error".
Example: Inject memory hotplug offline error (-12 == -ENOMEM)
# cd /sys/kernel/debug/notifier-error-inject/memory
# echo -12 > actions/MEM_GOING_OFFLINE/error
# echo offline > /sys/devices/system/memory/memoryXXX/state
bash: echo: write error: Cannot allocate memory
To compile this code as a module, choose M here: the module will
be called memory-notifier-error-inject.
If unsure, say N.
config DEBUG_PER_CPU_MAPS
bool "Debug access to per_cpu maps"
depends on DEBUG_KERNEL
depends on SMP
help
Say Y to verify that the per_cpu map being accessed has
been set up. This adds a fair amount of code to kernel memory
and decreases performance.
Say N if unsure.
config DEBUG_HIGHMEM
bool "Highmem debugging"
depends on DEBUG_KERNEL && HIGHMEM
help
This option enables additional error checking for high memory
systems. Disable for production systems.
config HAVE_DEBUG_STACKOVERFLOW
bool
config DEBUG_STACKOVERFLOW
bool "Check for stack overflows"
depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
---help---
Say Y here if you want to check for overflows of kernel, IRQ
and exception stacks (if your architecture uses them). This
option will show detailed messages if free stack space drops
below a certain limit.
These kinds of bugs usually occur when call-chains in the
kernel get too deep, especially when interrupts are
involved.
Use this in cases where you see apparently random memory
corruption, especially if it appears in 'struct thread_info'
If in doubt, say "N".
source "lib/Kconfig.kmemcheck"
source "lib/Kconfig.kasan"
endmenu # "Memory Debugging"
config ARCH_HAS_KCOV
bool
help
KCOV does not have any arch-specific code, but currently it is enabled
only for x86_64. KCOV requires testing on other archs, and most likely
disabling of instrumentation for some early boot code.
config KCOV
bool "Code coverage for fuzzing"
depends on ARCH_HAS_KCOV
select DEBUG_FS
select GCC_PLUGINS if !COMPILE_TEST
select GCC_PLUGIN_SANCOV if !COMPILE_TEST
help
KCOV exposes kernel code coverage information in a form suitable
for coverage-guided fuzzing (randomized testing).
If RANDOMIZE_BASE is enabled, PC values will not be stable across
different machines and across reboots. If you need stable PC values,
disable RANDOMIZE_BASE.
For more details, see Documentation/dev-tools/kcov.rst.
config KCOV_INSTRUMENT_ALL
bool "Instrument all code by default"
depends on KCOV
default y if KCOV
help
If you are doing generic system call fuzzing (like e.g. syzkaller),
then you will want to instrument the whole kernel and you should
say y here. If you are doing more targeted fuzzing (like e.g.
filesystem fuzzing with AFL) then you will want to enable coverage
for more specific subsets of files, and should say n here.
config DEBUG_SHIRQ
bool "Debug shared IRQ handlers"
depends on DEBUG_KERNEL
help
Enable this to generate a spurious interrupt as soon as a shared
interrupt handler is registered, and just before one is deregistered.
Drivers ought to be able to handle interrupts coming in at those
points; some don't and need to be caught.
menu "Debug Lockups and Hangs"
config LOCKUP_DETECTOR
bool "Detect Hard and Soft Lockups"
depends on DEBUG_KERNEL && !S390
help
Say Y here to enable the kernel to act as a watchdog to detect
hard and soft lockups.
Softlockups are bugs that cause the kernel to loop in kernel
mode for more than 20 seconds, without giving other tasks a
chance to run. The current stack trace is displayed upon
detection and the system will stay locked up.
Hardlockups are bugs that cause the CPU to loop in kernel mode
for more than 10 seconds, without letting other interrupts have a
chance to run. The current stack trace is displayed upon detection
and the system will stay locked up.
The overhead should be minimal. A periodic hrtimer runs to
generate interrupts and kick the watchdog task every 4 seconds.
An NMI is generated every 10 seconds or so to check for hardlockups.
The frequency of hrtimer and NMI events and the soft and hard lockup
thresholds can be controlled through the sysctl watchdog_thresh.
config HARDLOCKUP_DETECTOR
def_bool y
depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
config BOOTPARAM_HARDLOCKUP_PANIC
bool "Panic (Reboot) On Hard Lockups"
depends on HARDLOCKUP_DETECTOR
help
Say Y here to enable the kernel to panic on "hard lockups",
which are bugs that cause the kernel to loop in kernel
mode with interrupts disabled for more than 10 seconds (configurable
using the watchdog_thresh sysctl).
Say N if unsure.
config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
int
depends on HARDLOCKUP_DETECTOR
range 0 1
default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
default 1 if BOOTPARAM_HARDLOCKUP_PANIC
config BOOTPARAM_SOFTLOCKUP_PANIC
bool "Panic (Reboot) On Soft Lockups"
depends on LOCKUP_DETECTOR
help
Say Y here to enable the kernel to panic on "soft lockups",
which are bugs that cause the kernel to loop in kernel
mode for more than 20 seconds (configurable using the watchdog_thresh
sysctl), without giving other tasks a chance to run.
The panic can be used in combination with panic_timeout,
to cause the system to reboot automatically after a
lockup has been detected. This feature is useful for
high-availability systems that have uptime guarantees and
where a lockup must be resolved ASAP.
Say N if unsure.
config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
int
depends on LOCKUP_DETECTOR
range 0 1
default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
config DETECT_HUNG_TASK
bool "Detect Hung Tasks"
depends on DEBUG_KERNEL
default LOCKUP_DETECTOR
help
Say Y here to enable the kernel to detect "hung tasks",
which are bugs that cause the task to be stuck in
uninterruptible "D" state indefinitely.
When a hung task is detected, the kernel will print the
current stack trace (which you should report), but the
task will stay in uninterruptible state. If lockdep is
enabled then all held locks will also be reported. This
feature has negligible overhead.
config DEFAULT_HUNG_TASK_TIMEOUT
int "Default timeout for hung task detection (in seconds)"
depends on DETECT_HUNG_TASK
default 120
help
This option controls the default timeout (in seconds) used
to determine when a task has become non-responsive and should
be considered hung.
It can be adjusted at runtime via the kernel.hung_task_timeout_secs
sysctl or by writing a value to
/proc/sys/kernel/hung_task_timeout_secs.
A timeout of 0 disables the check. The default is two minutes.
Keeping the default should be fine in most cases.
config BOOTPARAM_HUNG_TASK_PANIC
bool "Panic (Reboot) On Hung Tasks"
depends on DETECT_HUNG_TASK
help
Say Y here to enable the kernel to panic on "hung tasks",
which are bugs that cause the kernel to leave a task stuck
in uninterruptible "D" state.
The panic can be used in combination with panic_timeout,
to cause the system to reboot automatically after a
hung task has been detected. This feature is useful for
high-availability systems that have uptime guarantees and
where a hung tasks must be resolved ASAP.
Say N if unsure.
config BOOTPARAM_HUNG_TASK_PANIC_VALUE
int
depends on DETECT_HUNG_TASK
range 0 1
default 0 if !BOOTPARAM_HUNG_TASK_PANIC
default 1 if BOOTPARAM_HUNG_TASK_PANIC
config WQ_WATCHDOG
bool "Detect Workqueue Stalls"
depends on DEBUG_KERNEL
help
Say Y here to enable stall detection on workqueues. If a
worker pool doesn't make forward progress on a pending work
item for over a given amount of time, 30s by default, a
warning message is printed along with dump of workqueue
state. This can be configured through kernel parameter
"workqueue.watchdog_thresh" and its sysfs counterpart.
endmenu # "Debug lockups and hangs"
config PANIC_ON_OOPS
bool "Panic on Oops"
help
Say Y here to enable the kernel to panic when it oopses. This
has the same effect as setting oops=panic on the kernel command
line.
This feature is useful to ensure that the kernel does not do
anything erroneous after an oops which could result in data
corruption or other issues.
Say N if unsure.
config PANIC_ON_OOPS_VALUE
int
range 0 1
default 0 if !PANIC_ON_OOPS
default 1 if PANIC_ON_OOPS
config PANIC_TIMEOUT
int "panic timeout"
default 0
help
Set the timeout value (in seconds) until a reboot occurs when the
the kernel panics. If n = 0, then we wait forever. A timeout
value n > 0 will wait n seconds before rebooting, while a timeout
value n < 0 will reboot immediately.
config SCHED_DEBUG
bool "Collect scheduler debugging info"
depends on DEBUG_KERNEL && PROC_FS
default y
help
If you say Y here, the /proc/sched_debug file will be provided
that can help debug the scheduler. The runtime overhead of this
option is minimal.
config SCHED_INFO
bool
default n
config SCHEDSTATS
bool "Collect scheduler statistics"
depends on DEBUG_KERNEL && PROC_FS
select SCHED_INFO
help
If you say Y here, additional code will be inserted into the
scheduler and related routines to collect statistics about
scheduler behavior and provide them in /proc/schedstat. These
stats may be useful for both tuning and debugging the scheduler
If you aren't debugging the scheduler or trying to tune a specific
application, you can say N to avoid the very slight overhead
this adds.
config SCHED_STACK_END_CHECK
bool "Detect stack corruption on calls to schedule()"
depends on DEBUG_KERNEL
default n
help
This option checks for a stack overrun on calls to schedule().
If the stack end location is found to be over written always panic as
the content of the corrupted region can no longer be trusted.
This is to ensure no erroneous behaviour occurs which could result in
data corruption or a sporadic crash at a later stage once the region
is examined. The runtime overhead introduced is minimal.
config DEBUG_TIMEKEEPING
bool "Enable extra timekeeping sanity checking"
help
This option will enable additional timekeeping sanity checks
which may be helpful when diagnosing issues where timekeeping
problems are suspected.
This may include checks in the timekeeping hotpaths, so this
option may have a (very small) performance impact to some
workloads.
If unsure, say N.
config TIMER_STATS
bool "Collect kernel timers statistics"
depends on DEBUG_KERNEL && PROC_FS
help
If you say Y here, additional code will be inserted into the
timer routines to collect statistics about kernel timers being
reprogrammed. The statistics can be read from /proc/timer_stats.
The statistics collection is started by writing 1 to /proc/timer_stats,
writing 0 stops it. This feature is useful to collect information
about timer usage patterns in kernel and userspace. This feature
is lightweight if enabled in the kernel config but not activated
(it defaults to deactivated on bootup and will only be activated
if some application like powertop activates it explicitly).
config DEBUG_PREEMPT
bool "Debug preemptible kernel"
depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
default y
help
If you say Y here then the kernel will use a debug variant of the
commonly used smp_processor_id() function and will print warnings
if kernel code uses it in a preemption-unsafe way. Also, the kernel
will detect preemption count underflows.
menu "Lock Debugging (spinlocks, mutexes, etc...)"
config DEBUG_RT_MUTEXES
bool "RT Mutex debugging, deadlock detection"
depends on DEBUG_KERNEL && RT_MUTEXES
help
This allows rt mutex semantics violations and rt mutex related
deadlocks (lockups) to be detected and reported automatically.
config DEBUG_SPINLOCK
bool "Spinlock and rw-lock debugging: basic checks"
depends on DEBUG_KERNEL
select UNINLINE_SPIN_UNLOCK
help
Say Y here and build SMP to catch missing spinlock initialization
and certain other kinds of spinlock errors commonly made. This is
best used in conjunction with the NMI watchdog so that spinlock
deadlocks are also debuggable.
config DEBUG_MUTEXES
bool "Mutex debugging: basic checks"
depends on DEBUG_KERNEL
help
This feature allows mutex semantics violations to be detected and
reported.
config DEBUG_WW_MUTEX_SLOWPATH
bool "Wait/wound mutex debugging: Slowpath testing"
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
select DEBUG_LOCK_ALLOC
select DEBUG_SPINLOCK
select DEBUG_MUTEXES
help
This feature enables slowpath testing for w/w mutex users by
injecting additional -EDEADLK wound/backoff cases. Together with
the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this
will test all possible w/w mutex interface abuse with the
exception of simply not acquiring all the required locks.
Note that this feature can introduce significant overhead, so
it really should not be enabled in a production or distro kernel,
even a debug kernel. If you are a driver writer, enable it. If
you are a distro, do not.
config DEBUG_LOCK_ALLOC
bool "Lock debugging: detect incorrect freeing of live locks"
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
select DEBUG_SPINLOCK
select DEBUG_MUTEXES
select LOCKDEP
help
This feature will check whether any held lock (spinlock, rwlock,
mutex or rwsem) is incorrectly freed by the kernel, via any of the
memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
vfree(), etc.), whether a live lock is incorrectly reinitialized via
spin_lock_init()/mutex_init()/etc., or whether there is any lock
held during task exit.
config PROVE_LOCKING
bool "Lock debugging: prove locking correctness"
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
select LOCKDEP
select DEBUG_SPINLOCK
select DEBUG_MUTEXES
select DEBUG_LOCK_ALLOC
select TRACE_IRQFLAGS
default n
help
This feature enables the kernel to prove that all locking
that occurs in the kernel runtime is mathematically
correct: that under no circumstance could an arbitrary (and
not yet triggered) combination of observed locking
sequences (on an arbitrary number of CPUs, running an
arbitrary number of tasks and interrupt contexts) cause a
deadlock.
In short, this feature enables the kernel to report locking
related deadlocks before they actually occur.
The proof does not depend on how hard and complex a
deadlock scenario would be to trigger: how many
participant CPUs, tasks and irq-contexts would be needed
for it to trigger. The proof also does not depend on
timing: if a race and a resulting deadlock is possible
theoretically (no matter how unlikely the race scenario
is), it will be proven so and will immediately be
reported by the kernel (once the event is observed that
makes the deadlock theoretically possible).
If a deadlock is impossible (i.e. the locking rules, as
observed by the kernel, are mathematically correct), the
kernel reports nothing.
NOTE: this feature can also be enabled for rwlocks, mutexes
and rwsems - in which case all dependencies between these
different locking variants are observed and mapped too, and
the proof of observed correctness is also maintained for an
arbitrary combination of these separate locking variants.
For more details, see Documentation/locking/lockdep-design.txt.
config PROVE_LOCKING_SMALL
bool
config LOCKDEP
bool
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
select STACKTRACE
select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
select KALLSYMS
select KALLSYMS_ALL
config LOCK_STAT
bool "Lock usage statistics"
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
select LOCKDEP
select DEBUG_SPINLOCK
select DEBUG_MUTEXES
select DEBUG_LOCK_ALLOC
default n
help
This feature enables tracking lock contention points
For more details, see Documentation/locking/lockstat.txt
This also enables lock events required by "perf lock",
subcommand of perf.
If you want to use "perf lock", you also need to turn on
CONFIG_EVENT_TRACING.
CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
(CONFIG_LOCKDEP defines "acquire" and "release" events.)
config DEBUG_LOCKDEP
bool "Lock dependency engine debugging"
depends on DEBUG_KERNEL && LOCKDEP
help
If you say Y here, the lock dependency engine will do
additional runtime checks to debug itself, at the price
of more runtime overhead.
config DEBUG_ATOMIC_SLEEP
bool "Sleep inside atomic section checking"
select PREEMPT_COUNT
depends on DEBUG_KERNEL
help
If you say Y here, various routines which may sleep will become very
noisy if they are called inside atomic sections: when a spinlock is
held, inside an rcu read side critical section, inside preempt disabled
sections, inside an interrupt, etc...
config DEBUG_LOCKING_API_SELFTESTS
bool "Locking API boot-time self-tests"
depends on DEBUG_KERNEL
help
Say Y here if you want the kernel to run a short self-test during
bootup. The self-test checks whether common types of locking bugs
are detected by debugging mechanisms or not. (if you disable
lock debugging then those bugs wont be detected of course.)
The following locking APIs are covered: spinlocks, rwlocks,
mutexes and rwsems.
config LOCK_TORTURE_TEST
tristate "torture tests for locking"
depends on DEBUG_KERNEL
select TORTURE_TEST
default n
help
This option provides a kernel module that runs torture tests
on kernel locking primitives. The kernel module may be built
after the fact on the running kernel to be tested, if desired.
Say Y here if you want kernel locking-primitive torture tests
to be built into the kernel.
Say M if you want these torture tests to build as a module.
Say N if you are unsure.
endmenu # lock debugging
config TRACE_IRQFLAGS
bool
help
Enables hooks to interrupt enabling and disabling for
either tracing or lock debugging.
config STACKTRACE
bool "Stack backtrace support"
depends on STACKTRACE_SUPPORT
help
This option causes the kernel to create a /proc/pid/stack for
every process, showing its current stack trace.
It is also used by various kernel debugging features that require
stack trace generation.
config DEBUG_KOBJECT
bool "kobject debugging"
depends on DEBUG_KERNEL
help
If you say Y here, some extra kobject debugging messages will be sent
to the syslog.
config DEBUG_KOBJECT_RELEASE
bool "kobject release debugging"
depends on DEBUG_OBJECTS_TIMERS
help
kobjects are reference counted objects. This means that their
last reference count put is not predictable, and the kobject can
live on past the point at which a driver decides to drop it's
initial reference to the kobject gained on allocation. An
example of this would be a struct device which has just been
unregistered.
However, some buggy drivers assume that after such an operation,
the memory backing the kobject can be immediately freed. This
goes completely against the principles of a refcounted object.
If you say Y here, the kernel will delay the release of kobjects
on the last reference count to improve the visibility of this
kind of kobject release bug.
config HAVE_DEBUG_BUGVERBOSE
bool
config DEBUG_BUGVERBOSE
bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
default y
help
Say Y here to make BUG() panics output the file name and line number
of the BUG call as well as the EIP and oops trace. This aids
debugging but costs about 70-100K of memory.
config DEBUG_LIST
bool "Debug linked list manipulation"
depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
help
Enable this to turn on extended checks in the linked-list
walking routines.
If unsure, say N.
config DEBUG_PI_LIST
bool "Debug priority linked list manipulation"
depends on DEBUG_KERNEL
help
Enable this to turn on extended checks in the priority-ordered
linked-list (plist) walking routines. This checks the entire
list multiple times during each manipulation.
If unsure, say N.
config DEBUG_SG
bool "Debug SG table operations"
depends on DEBUG_KERNEL
help
Enable this to turn on checks on scatter-gather tables. This can
help find problems with drivers that do not properly initialize
their sg tables.
If unsure, say N.
config DEBUG_NOTIFIERS
bool "Debug notifier call chains"
depends on DEBUG_KERNEL
help
Enable this to turn on sanity checking for notifier call chains.
This is most useful for kernel developers to make sure that
modules properly unregister themselves from notifier chains.
This is a relatively cheap check but if you care about maximum
performance, say N.
config DEBUG_CREDENTIALS
bool "Debug credential management"
depends on DEBUG_KERNEL
help
Enable this to turn on some debug checking for credential
management. The additional code keeps track of the number of
pointers from task_structs to any given cred struct, and checks to
see that this number never exceeds the usage count of the cred
struct.
Furthermore, if SELinux is enabled, this also checks that the
security pointer in the cred struct is never seen to be invalid.
If unsure, say N.
menu "RCU Debugging"
config PROVE_RCU
def_bool PROVE_LOCKING
config PROVE_RCU_REPEATEDLY
bool "RCU debugging: don't disable PROVE_RCU on first splat"
depends on PROVE_RCU
default n
help
By itself, PROVE_RCU will disable checking upon issuing the
first warning (or "splat"). This feature prevents such
disabling, allowing multiple RCU-lockdep warnings to be printed
on a single reboot.
Say Y to allow multiple RCU-lockdep warnings per boot.
Say N if you are unsure.
config SPARSE_RCU_POINTER
bool "RCU debugging: sparse-based checks for pointer usage"
default n
help
This feature enables the __rcu sparse annotation for
RCU-protected pointers. This annotation will cause sparse
to flag any non-RCU used of annotated pointers. This can be
helpful when debugging RCU usage. Please note that this feature
is not intended to enforce code cleanliness; it is instead merely
a debugging aid.
Say Y to make sparse flag questionable use of RCU-protected pointers
Say N if you are unsure.
config TORTURE_TEST
tristate
default n
config RCU_PERF_TEST
tristate "performance tests for RCU"
depends on DEBUG_KERNEL
select TORTURE_TEST
select SRCU
select TASKS_RCU
default n
help
This option provides a kernel module that runs performance
tests on the RCU infrastructure. The kernel module may be built
after the fact on the running kernel to be tested, if desired.
Say Y here if you want RCU performance tests to be built into
the kernel.
Say M if you want the RCU performance tests to build as a module.
Say N if you are unsure.
config RCU_TORTURE_TEST
tristate "torture tests for RCU"
depends on DEBUG_KERNEL
select TORTURE_TEST
select SRCU
select TASKS_RCU
default n
help
This option provides a kernel module that runs torture tests
on the RCU infrastructure. The kernel module may be built
after the fact on the running kernel to be tested, if desired.
Say Y here if you want RCU torture tests to be built into
the kernel.
Say M if you want the RCU torture tests to build as a module.
Say N if you are unsure.
config RCU_TORTURE_TEST_SLOW_PREINIT
bool "Slow down RCU grace-period pre-initialization to expose races"
depends on RCU_TORTURE_TEST
help
This option delays grace-period pre-initialization (the
propagation of CPU-hotplug changes up the rcu_node combining
tree) for a few jiffies between initializing each pair of
consecutive rcu_node structures. This helps to expose races
involving grace-period pre-initialization, in other words, it
makes your kernel less stable. It can also greatly increase
grace-period latency, especially on systems with large numbers
of CPUs. This is useful when torture-testing RCU, but in
almost no other circumstance.
Say Y here if you want your system to crash and hang more often.
Say N if you want a sane system.
config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY
int "How much to slow down RCU grace-period pre-initialization"
range 0 5
default 3
depends on RCU_TORTURE_TEST_SLOW_PREINIT
help
This option specifies the number of jiffies to wait between
each rcu_node structure pre-initialization step.
config RCU_TORTURE_TEST_SLOW_INIT
bool "Slow down RCU grace-period initialization to expose races"
depends on RCU_TORTURE_TEST
help
This option delays grace-period initialization for a few
jiffies between initializing each pair of consecutive
rcu_node structures. This helps to expose races involving
grace-period initialization, in other words, it makes your
kernel less stable. It can also greatly increase grace-period
latency, especially on systems with large numbers of CPUs.
This is useful when torture-testing RCU, but in almost no
other circumstance.
Say Y here if you want your system to crash and hang more often.
Say N if you want a sane system.
config RCU_TORTURE_TEST_SLOW_INIT_DELAY
int "How much to slow down RCU grace-period initialization"
range 0 5
default 3
depends on RCU_TORTURE_TEST_SLOW_INIT
help
This option specifies the number of jiffies to wait between
each rcu_node structure initialization.
config RCU_TORTURE_TEST_SLOW_CLEANUP
bool "Slow down RCU grace-period cleanup to expose races"
depends on RCU_TORTURE_TEST
help
This option delays grace-period cleanup for a few jiffies
between cleaning up each pair of consecutive rcu_node
structures. This helps to expose races involving grace-period
cleanup, in other words, it makes your kernel less stable.
It can also greatly increase grace-period latency, especially
on systems with large numbers of CPUs. This is useful when
torture-testing RCU, but in almost no other circumstance.
Say Y here if you want your system to crash and hang more often.
Say N if you want a sane system.
config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY
int "How much to slow down RCU grace-period cleanup"
range 0 5
default 3
depends on RCU_TORTURE_TEST_SLOW_CLEANUP
help
This option specifies the number of jiffies to wait between
each rcu_node structure cleanup operation.
config RCU_CPU_STALL_TIMEOUT
int "RCU CPU stall timeout in seconds"
depends on RCU_STALL_COMMON
range 3 300
default 21
help
If a given RCU grace period extends more than the specified
number of seconds, a CPU stall warning is printed. If the
RCU grace period persists, additional CPU stall warnings are
printed at more widely spaced intervals.
config RCU_TRACE
bool "Enable tracing for RCU"
depends on DEBUG_KERNEL
select TRACE_CLOCK
help
This option provides tracing in RCU which presents stats
in debugfs for debugging RCU implementation. It also enables
additional tracepoints for ftrace-style event tracing.
Say Y here if you want to enable RCU tracing
Say N if you are unsure.
config RCU_EQS_DEBUG
bool "Provide debugging asserts for adding NO_HZ support to an arch"
depends on DEBUG_KERNEL
help
This option provides consistency checks in RCU's handling of
NO_HZ. These checks have proven quite helpful in detecting
bugs in arch-specific NO_HZ code.
Say N here if you need ultimate kernel/user switch latencies
Say Y if you are unsure
endmenu # "RCU Debugging"
config DEBUG_WQ_FORCE_RR_CPU
bool "Force round-robin CPU selection for unbound work items"
depends on DEBUG_KERNEL
default n
help
Workqueue used to implicitly guarantee that work items queued
without explicit CPU specified are put on the local CPU. This
guarantee is no longer true and while local CPU is still
preferred work items may be put on foreign CPUs. Kernel
parameter "workqueue.debug_force_rr_cpu" is added to force
round-robin CPU selection to flush out usages which depend on the
now broken guarantee. This config option enables the debug
feature by default. When enabled, memory and cache locality will
be impacted.
config DEBUG_BLOCK_EXT_DEVT
bool "Force extended block device numbers and spread them"
depends on DEBUG_KERNEL
depends on BLOCK
default n
help
BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
YOU ARE DOING. Distros, please enable this and fix whatever
is broken.
Conventionally, block device numbers are allocated from
predetermined contiguous area. However, extended block area
may introduce non-contiguous block device numbers. This
option forces most block device numbers to be allocated from
the extended space and spreads them to discover kernel or
userland code paths which assume predetermined contiguous
device number allocation.
Note that turning on this debug option shuffles all the
device numbers for all IDE and SCSI devices including libata
ones, so root partition specified using device number
directly (via rdev or root=MAJ:MIN) won't work anymore.
Textual device names (root=/dev/sdXn) will continue to work.
Say N if you are unsure.
config CPU_HOTPLUG_STATE_CONTROL
bool "Enable CPU hotplug state control"
depends on DEBUG_KERNEL
depends on HOTPLUG_CPU
default n
help
Allows to write steps between "offline" and "online" to the CPUs
sysfs target file so states can be stepped granular. This is a debug
option for now as the hotplug machinery cannot be stopped and
restarted at arbitrary points yet.
Say N if your are unsure.
config NOTIFIER_ERROR_INJECTION
tristate "Notifier error injection"
depends on DEBUG_KERNEL
select DEBUG_FS
help
This option provides the ability to inject artificial errors to
specified notifier chain callbacks. It is useful to test the error
handling of notifier call chain failures.
Say N if unsure.
config PM_NOTIFIER_ERROR_INJECT
tristate "PM notifier error injection module"
depends on PM && NOTIFIER_ERROR_INJECTION
default m if PM_DEBUG
help
This option provides the ability to inject artificial errors to
PM notifier chain callbacks. It is controlled through debugfs
interface /sys/kernel/debug/notifier-error-inject/pm
If the notifier call chain should be failed with some events
notified, write the error code to "actions/<notifier event>/error".
Example: Inject PM suspend error (-12 = -ENOMEM)
# cd /sys/kernel/debug/notifier-error-inject/pm/
# echo -12 > actions/PM_SUSPEND_PREPARE/error
# echo mem > /sys/power/state
bash: echo: write error: Cannot allocate memory
To compile this code as a module, choose M here: the module will
be called pm-notifier-error-inject.
If unsure, say N.
config OF_RECONFIG_NOTIFIER_ERROR_INJECT
tristate "OF reconfig notifier error injection module"
depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
help
This option provides the ability to inject artificial errors to
OF reconfig notifier chain callbacks. It is controlled
through debugfs interface under
/sys/kernel/debug/notifier-error-inject/OF-reconfig/
If the notifier call chain should be failed with some events
notified, write the error code to "actions/<notifier event>/error".
To compile this code as a module, choose M here: the module will
be called of-reconfig-notifier-error-inject.
If unsure, say N.
config NETDEV_NOTIFIER_ERROR_INJECT
tristate "Netdev notifier error injection module"
depends on NET && NOTIFIER_ERROR_INJECTION
help
This option provides the ability to inject artificial errors to
netdevice notifier chain callbacks. It is controlled through debugfs
interface /sys/kernel/debug/notifier-error-inject/netdev
If the notifier call chain should be failed with some events
notified, write the error code to "actions/<notifier event>/error".
Example: Inject netdevice mtu change error (-22 = -EINVAL)
# cd /sys/kernel/debug/notifier-error-inject/netdev
# echo -22 > actions/NETDEV_CHANGEMTU/error
# ip link set eth0 mtu 1024
RTNETLINK answers: Invalid argument
To compile this code as a module, choose M here: the module will
be called netdev-notifier-error-inject.
If unsure, say N.
config FAULT_INJECTION
bool "Fault-injection framework"
depends on DEBUG_KERNEL
help
Provide fault-injection framework.
For more details, see Documentation/fault-injection/.
config FAILSLAB
bool "Fault-injection capability for kmalloc"
depends on FAULT_INJECTION
depends on SLAB || SLUB
help
Provide fault-injection capability for kmalloc.
config FAIL_PAGE_ALLOC
bool "Fault-injection capabilitiy for alloc_pages()"
depends on FAULT_INJECTION
help
Provide fault-injection capability for alloc_pages().
config FAIL_MAKE_REQUEST
bool "Fault-injection capability for disk IO"
depends on FAULT_INJECTION && BLOCK
help
Provide fault-injection capability for disk IO.
config FAIL_IO_TIMEOUT
bool "Fault-injection capability for faking disk interrupts"
depends on FAULT_INJECTION && BLOCK
help
Provide fault-injection capability on end IO handling. This
will make the block layer "forget" an interrupt as configured,
thus exercising the error handling.
Only works with drivers that use the generic timeout handling,
for others it wont do anything.
config FAIL_MMC_REQUEST
bool "Fault-injection capability for MMC IO"
depends on FAULT_INJECTION_DEBUG_FS && MMC
help
Provide fault-injection capability for MMC IO.
This will make the mmc core return data errors. This is
useful to test the error handling in the mmc block device
and to test how the mmc host driver handles retries from
the block device.
config FAIL_FUTEX
bool "Fault-injection capability for futexes"
select DEBUG_FS
depends on FAULT_INJECTION && FUTEX
help
Provide fault-injection capability for futexes.
config FAULT_INJECTION_DEBUG_FS
bool "Debugfs entries for fault-injection capabilities"
depends on FAULT_INJECTION && SYSFS && DEBUG_FS
help
Enable configuration of fault-injection capabilities via debugfs.
config FAULT_INJECTION_STACKTRACE_FILTER
bool "stacktrace filter for fault-injection capabilities"
depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
depends on !X86_64
select STACKTRACE
select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
help
Provide stacktrace filter for fault-injection capabilities
config LATENCYTOP
bool "Latency measuring infrastructure"
depends on DEBUG_KERNEL
depends on STACKTRACE_SUPPORT
depends on PROC_FS
select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
select KALLSYMS
select KALLSYMS_ALL
select STACKTRACE
select SCHEDSTATS
select SCHED_DEBUG
help
Enable this option if you want to use the LatencyTOP tool
to find out which userspace is blocking on what kernel operations.
source kernel/trace/Kconfig
menu "Runtime Testing"
config LKDTM
tristate "Linux Kernel Dump Test Tool Module"
depends on DEBUG_FS
depends on BLOCK
default n
help
This module enables testing of the different dumping mechanisms by
inducing system failures at predefined crash points.
If you don't need it: say N
Choose M here to compile this code as a module. The module will be
called lkdtm.
Documentation on how to use the module can be found in
Documentation/fault-injection/provoke-crashes.txt
config TEST_LIST_SORT
bool "Linked list sorting test"
depends on DEBUG_KERNEL
help
Enable this to turn on 'list_sort()' function test. This test is
executed only once during system boot, so affects only boot time.
If unsure, say N.
config KPROBES_SANITY_TEST
bool "Kprobes sanity tests"
depends on DEBUG_KERNEL
depends on KPROBES
default n
help
This option provides for testing basic kprobes functionality on
boot. A sample kprobe, jprobe and kretprobe are inserted and
verified for functionality.
Say N if you are unsure.
config BACKTRACE_SELF_TEST
tristate "Self test for the backtrace code"
depends on DEBUG_KERNEL
default n
help
This option provides a kernel module that can be used to test
the kernel stack backtrace code. This option is not useful
for distributions or general kernels, but only for kernel
developers working on architecture code.
Note that if you want to also test saved backtraces, you will
have to enable STACKTRACE as well.
Say N if you are unsure.
config RBTREE_TEST
tristate "Red-Black tree test"
depends on DEBUG_KERNEL
help
A benchmark measuring the performance of the rbtree library.
Also includes rbtree invariant checks.
config INTERVAL_TREE_TEST
tristate "Interval tree test"
depends on m && DEBUG_KERNEL
select INTERVAL_TREE
help
A benchmark measuring the performance of the interval tree library
config PERCPU_TEST
tristate "Per cpu operations test"
depends on m && DEBUG_KERNEL
help
Enable this option to build test module which validates per-cpu
operations.
If unsure, say N.
config ATOMIC64_SELFTEST
bool "Perform an atomic64_t self-test at boot"
help
Enable this option to test the atomic64_t functions at boot.
If unsure, say N.
config ASYNC_RAID6_TEST
tristate "Self test for hardware accelerated raid6 recovery"
depends on ASYNC_RAID6_RECOV
select ASYNC_MEMCPY
---help---
This is a one-shot self test that permutes through the
recovery of all the possible two disk failure scenarios for a
N-disk array. Recovery is performed with the asynchronous
raid6 recovery routines, and will optionally use an offload
engine if one is available.
If unsure, say N.
config TEST_HEXDUMP
tristate "Test functions located in the hexdump module at runtime"
config TEST_STRING_HELPERS
tristate "Test functions located in the string_helpers module at runtime"
config TEST_KSTRTOX
tristate "Test kstrto*() family of functions at runtime"
config TEST_PRINTF
tristate "Test printf() family of functions at runtime"
config TEST_BITMAP
tristate "Test bitmap_*() family of functions at runtime"
default n
help
Enable this option to test the bitmap functions at boot.
If unsure, say N.
config TEST_UUID
tristate "Test functions located in the uuid module at runtime"
config TEST_RHASHTABLE
tristate "Perform selftest on resizable hash table"
default n
help
Enable this option to test the rhashtable functions at boot.
If unsure, say N.
config TEST_HASH
tristate "Perform selftest on hash functions"
default n
help
Enable this option to test the kernel's integer (<linux/hash.h>),
string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
hash functions on boot (or module load).
This is intended to help people writing architecture-specific
optimized versions. If unsure, say N.
endmenu # runtime tests
config PROVIDE_OHCI1394_DMA_INIT
bool "Remote debugging over FireWire early on boot"
depends on PCI && X86
help
If you want to debug problems which hang or crash the kernel early
on boot and the crashing machine has a FireWire port, you can use
this feature to remotely access the memory of the crashed machine
over FireWire. This employs remote DMA as part of the OHCI1394
specification which is now the standard for FireWire controllers.
With remote DMA, you can monitor the printk buffer remotely using
firescope and access all memory below 4GB using fireproxy from gdb.
Even controlling a kernel debugger is possible using remote DMA.
Usage:
If ohci1394_dma=early is used as boot parameter, it will initialize
all OHCI1394 controllers which are found in the PCI config space.
As all changes to the FireWire bus such as enabling and disabling
devices cause a bus reset and thereby disable remote DMA for all
devices, be sure to have the cable plugged and FireWire enabled on
the debugging host before booting the debug target for debugging.
This code (~1k) is freed after boot. By then, the firewire stack
in charge of the OHCI-1394 controllers should be used instead.
See Documentation/debugging-via-ohci1394.txt for more information.
config DMA_API_DEBUG
bool "Enable debugging of DMA-API usage"
depends on HAVE_DMA_API_DEBUG
help
Enable this option to debug the use of the DMA API by device drivers.
With this option you will be able to detect common bugs in device
drivers like double-freeing of DMA mappings or freeing mappings that
were never allocated.
This also attempts to catch cases where a page owned by DMA is
accessed by the cpu in a way that could cause data corruption. For
example, this enables cow_user_page() to check that the source page is
not undergoing DMA.
This option causes a performance degradation. Use only if you want to
debug device drivers and dma interactions.
If unsure, say N.
config TEST_LKM
tristate "Test module loading with 'hello world' module"
default n
depends on m
help
This builds the "test_module" module that emits "Hello, world"
on printk when loaded. It is designed to be used for basic
evaluation of the module loading subsystem (for example when
validating module verification). It lacks any extra dependencies,
and will not normally be loaded by the system unless explicitly
requested by name.
If unsure, say N.
config TEST_USER_COPY
tristate "Test user/kernel boundary protections"
default n
depends on m
help
This builds the "test_user_copy" module that runs sanity checks
on the copy_to/from_user infrastructure, making sure basic
user/kernel boundary testing is working. If it fails to load,
a regression has been detected in the user/kernel memory boundary
protections.
If unsure, say N.
config TEST_BPF
tristate "Test BPF filter functionality"
default n
depends on m && NET
help
This builds the "test_bpf" module that runs various test vectors
against the BPF interpreter or BPF JIT compiler depending on the
current setting. This is in particular useful for BPF JIT compiler
development, but also to run regression tests against changes in
the interpreter code. It also enables test stubs for eBPF maps and
verifier used by user space verifier testsuite.
If unsure, say N.
config TEST_FIRMWARE
tristate "Test firmware loading via userspace interface"
default n
depends on FW_LOADER
help
This builds the "test_firmware" module that creates a userspace
interface for testing firmware loading. This can be used to
control the triggering of firmware loading without needing an
actual firmware-using device. The contents can be rechecked by
userspace.
If unsure, say N.
config TEST_UDELAY
tristate "udelay test driver"
default n
help
This builds the "udelay_test" module that helps to make sure
that udelay() is working properly.
If unsure, say N.
config MEMTEST
bool "Memtest"
depends on HAVE_MEMBLOCK
---help---
This option adds a kernel parameter 'memtest', which allows memtest
to be set.
memtest=0, mean disabled; -- default
memtest=1, mean do 1 test pattern;
...
memtest=17, mean do 17 test patterns.
If you are unsure how to answer this question, answer N.
config TEST_STATIC_KEYS
tristate "Test static keys"
default n
depends on m
help
Test the static key interfaces.
If unsure, say N.
config BUG_ON_DATA_CORRUPTION
bool "Trigger a BUG when data corruption is detected"
select DEBUG_LIST
help
Select this option if the kernel should BUG when it encounters
data corruption in kernel memory structures when they get checked
for validity.
If unsure, say N.
source "samples/Kconfig"
source "lib/Kconfig.kgdb"
source "lib/Kconfig.ubsan"
config ARCH_HAS_DEVMEM_IS_ALLOWED
bool
config STRICT_DEVMEM
bool "Filter access to /dev/mem"
depends on MMU && DEVMEM
depends on ARCH_HAS_DEVMEM_IS_ALLOWED
default y if TILE || PPC
---help---
If this option is disabled, you allow userspace (root) access to all
of memory, including kernel and userspace memory. Accidental
access to this is obviously disastrous, but specific access can
be used by people debugging the kernel. Note that with PAT support
enabled, even in this case there are restrictions on /dev/mem
use due to the cache aliasing requirements.
If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem
file only allows userspace access to PCI space and the BIOS code and
data regions. This is sufficient for dosemu and X and all common
users of /dev/mem.
If in doubt, say Y.
config IO_STRICT_DEVMEM
bool "Filter I/O access to /dev/mem"
depends on STRICT_DEVMEM
---help---
If this option is disabled, you allow userspace (root) access to all
io-memory regardless of whether a driver is actively using that
range. Accidental access to this is obviously disastrous, but
specific access can be used by people debugging kernel drivers.
If this option is switched on, the /dev/mem file only allows
userspace access to *idle* io-memory ranges (see /proc/iomem) This
may break traditional users of /dev/mem (dosemu, legacy X, etc...)
if the driver using a given range cannot be disabled.
If in doubt, say Y.
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