config PRINTK_TIME
bool "Show timing information on printks"
depends on PRINTK
help
Selecting this option causes timing information to be
included in printk output. This allows you to measure
the interval between kernel operations, including bootup
operations. This is useful for identifying long delays
in kernel startup.
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 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 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 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 DEBUG_FS
bool "Debug Filesystem"
depends on SYSFS
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.
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"
depends on UNDEFINED
# This option is on purpose disabled for now.
# It will be enabled when we are down to a resonable number
# of section mismatch warnings (< 10 for an allyesconfig build)
help
The section mismatch analysis checks if there are illegal
references from one section to another section.
Linux will during link or during runtime drop some sections
and any use of code/data previously in these sections will
most likely result in an oops.
In the code functions and variables are annotated with
__init, __devinit etc. (see full list in include/linux/init.h)
which results in the code/data being placed in specific sections.
The section mismatch analysis is always done after a full
kernel build but enabling this option will in addition
do the following:
- Add the option -fno-inline-functions-called-once to gcc
When inlining a function annotated __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 will also
result in a larger kernel.
- Run the section mismatch analysis for each module/built-in.o
When we run the section mismatch analysis on vmlinux.o we
lose valueble information about where the mismatch was
introduced.
Running the analysis for each module/built-in.o file
will tell where the mismatch happens much closer to the
source. The drawback is that we will report the same
mismatch at least twice.
- Enable verbose reporting from modpost to help solving
the section mismatches reported.
config DEBUG_KERNEL
bool "Kernel debugging"
help
Say Y here if you are developing drivers or trying to debug and
identify kernel problems.
config DEBUG_SHIRQ
bool "Debug shared IRQ handlers"
depends on DEBUG_KERNEL && GENERIC_HARDIRQS
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.
config DETECT_SOFTLOCKUP
bool "Detect Soft Lockups"
depends on DEBUG_KERNEL && !S390
default y
help
Say Y here to enable the kernel to detect "soft lockups",
which are bugs that cause the kernel to loop in kernel
mode for more than 10 seconds, without giving other tasks a
chance to run.
When a soft-lockup is detected, the kernel will print the
current stack trace (which you should report), but the
system will stay locked up. This feature has negligible
overhead.
(Note that "hard lockups" are separate type of bugs that
can be detected via the NMI-watchdog, on platforms that
support it.)
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 SCHEDSTATS
bool "Collect scheduler statistics"
depends on DEBUG_KERNEL && PROC_FS
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 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_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_SLAB
bool "Debug slab memory allocations"
depends on DEBUG_KERNEL && SLAB
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
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 && SLUB_DEBUG && 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 DEBUG_PREEMPT
bool "Debug preemptible kernel"
depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64)
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.
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_PI_LIST
bool
default y
depends on DEBUG_RT_MUTEXES
config RT_MUTEX_TESTER
bool "Built-in scriptable tester for rt-mutexes"
depends on DEBUG_KERNEL && RT_MUTEXES
help
This option enables a rt-mutex tester.
config DEBUG_SPINLOCK
bool "Spinlock and rw-lock debugging: basic checks"
depends on DEBUG_KERNEL
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_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
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/lockdep-design.txt.
config LOCKDEP
bool
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
select STACKTRACE
select FRAME_POINTER if !X86 && !MIPS
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/lockstat.txt
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 TRACE_IRQFLAGS
depends on DEBUG_KERNEL
bool
default y
depends on TRACE_IRQFLAGS_SUPPORT
depends on PROVE_LOCKING
config DEBUG_SPINLOCK_SLEEP
bool "Spinlock debugging: sleep-inside-spinlock checking"
depends on DEBUG_KERNEL
help
If you say Y here, various routines which may sleep will become very
noisy if they are called with a spinlock held.
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 STACKTRACE
bool
depends on DEBUG_KERNEL
depends on STACKTRACE_SUPPORT
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_HIGHMEM
bool "Highmem debugging"
depends on DEBUG_KERNEL && HIGHMEM
help
This options enables addition error checking for high memory systems.
Disable for production systems.
config DEBUG_BUGVERBOSE
bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED
depends on BUG
depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300
default !EMBEDDED
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_INFO
bool "Compile the kernel with debug info"
depends on DEBUG_KERNEL
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_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_WRITECOUNT
bool "Debug filesystem writers count"
depends on DEBUG_KERNEL
help
Enable this to catch wrong use of the writers count in struct
vfsmount. This will increase the size of each file struct by
32 bits.
If unsure, say N.
config DEBUG_LIST
bool "Debug linked list manipulation"
depends on DEBUG_KERNEL
help
Enable this to turn on extended checks in the linked-list
walking routines.
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 FRAME_POINTER
bool "Compile the kernel with frame pointers"
depends on DEBUG_KERNEL && \
(X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || \
AVR32 || SUPERH || BLACKFIN || MN10300)
default y if DEBUG_INFO && UML
help
If you say Y here the resulting kernel image will be slightly larger
and slower, but it might give very useful debugging information on
some architectures or if you use external debuggers.
If you don't debug the kernel, you can say N.
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 DETECT_SOFTLOCKUP to detect
what it believes to be lockup conditions.
config RCU_TORTURE_TEST
tristate "torture tests for RCU"
depends on DEBUG_KERNEL
depends on m
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 M if you want the RCU torture tests to build as a module.
Say N if you are unsure.
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.
Say N if you are unsure.
config LKDTM
tristate "Linux Kernel Dump Test Tool Module"
depends on DEBUG_KERNEL
depends on KPROBES
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
drivers/misc/lkdtm.c
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
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
help
Provide fault-injection capability for disk IO.
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
help
Provide stacktrace filter for fault-injection capabilities
config LATENCYTOP
bool "Latency measuring infrastructure"
select FRAME_POINTER if !MIPS
select KALLSYMS
select KALLSYMS_ALL
select STACKTRACE
select SCHEDSTATS
select SCHED_DEBUG
depends on HAVE_LATENCYTOP_SUPPORT
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
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 FIREWIRE_OHCI_REMOTE_DMA
bool "Remote debugging over FireWire with firewire-ohci"
depends on FIREWIRE_OHCI
help
This option lets you use the FireWire bus for remote debugging
with help of the firewire-ohci driver. It enables unfiltered
remote DMA in firewire-ohci.
See Documentation/debugging-via-ohci1394.txt for more information.
If unsure, say N.
source "samples/Kconfig"
source "lib/Kconfig.kgdb"
