![GeunSik Lim](/assets/img/avatar_default.png)
Many developers use "/debug/" or "/debugfs/" or "/sys/kernel/debug/" directory name to mount debugfs filesystem for ftrace according to ./Documentation/tracers/ftrace.txt file. And, three directory names(ex:/debug/, /debugfs/, /sys/kernel/debug/) is existed in kernel source like ftrace, DRM, Wireless, Documentation, Network[sky2]files to mount debugfs filesystem. debugfs means debug filesystem for debugging easy to use by greg kroah hartman. "/sys/kernel/debug/" name is suitable as directory name of debugfs filesystem. - debugfs related reference: http://lwn.net/Articles/334546/ Fix inconsistency of directory name to mount debugfs filesystem. * From Steven Rostedt - find_debugfs() and tracing_files() in this patch. Signed-off-by: GeunSik Lim <geunsik.lim@samsung.com> Acked-by : Inaky Perez-Gonzalez <inaky@linux.intel.com> Reviewed-by : Steven Rostedt <rostedt@goodmis.org> Reviewed-by : James Smart <james.smart@emulex.com> CC: Jiri Kosina <trivial@kernel.org> CC: David Airlie <airlied@linux.ie> CC: Peter Osterlund <petero2@telia.com> CC: Ananth N Mavinakayanahalli <ananth@in.ibm.com> CC: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> CC: Masami Hiramatsu <mhiramat@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
238 lines
6.4 KiB
Text
238 lines
6.4 KiB
Text
Fault injection capabilities infrastructure
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===========================================
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See also drivers/md/faulty.c and "every_nth" module option for scsi_debug.
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Available fault injection capabilities
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--------------------------------------
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o failslab
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injects slab allocation failures. (kmalloc(), kmem_cache_alloc(), ...)
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o fail_page_alloc
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injects page allocation failures. (alloc_pages(), get_free_pages(), ...)
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o fail_make_request
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injects disk IO errors on devices permitted by setting
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/sys/block/<device>/make-it-fail or
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/sys/block/<device>/<partition>/make-it-fail. (generic_make_request())
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Configure fault-injection capabilities behavior
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-----------------------------------------------
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o debugfs entries
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fault-inject-debugfs kernel module provides some debugfs entries for runtime
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configuration of fault-injection capabilities.
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- /sys/kernel/debug/fail*/probability:
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likelihood of failure injection, in percent.
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Format: <percent>
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Note that one-failure-per-hundred is a very high error rate
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for some testcases. Consider setting probability=100 and configure
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/sys/kernel/debug/fail*/interval for such testcases.
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- /sys/kernel/debug/fail*/interval:
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specifies the interval between failures, for calls to
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should_fail() that pass all the other tests.
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Note that if you enable this, by setting interval>1, you will
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probably want to set probability=100.
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- /sys/kernel/debug/fail*/times:
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specifies how many times failures may happen at most.
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A value of -1 means "no limit".
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- /sys/kernel/debug/fail*/space:
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specifies an initial resource "budget", decremented by "size"
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on each call to should_fail(,size). Failure injection is
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suppressed until "space" reaches zero.
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- /sys/kernel/debug/fail*/verbose
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Format: { 0 | 1 | 2 }
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specifies the verbosity of the messages when failure is
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injected. '0' means no messages; '1' will print only a single
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log line per failure; '2' will print a call trace too -- useful
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to debug the problems revealed by fault injection.
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- /sys/kernel/debug/fail*/task-filter:
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Format: { 'Y' | 'N' }
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A value of 'N' disables filtering by process (default).
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Any positive value limits failures to only processes indicated by
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/proc/<pid>/make-it-fail==1.
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- /sys/kernel/debug/fail*/require-start:
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- /sys/kernel/debug/fail*/require-end:
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- /sys/kernel/debug/fail*/reject-start:
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- /sys/kernel/debug/fail*/reject-end:
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specifies the range of virtual addresses tested during
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stacktrace walking. Failure is injected only if some caller
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in the walked stacktrace lies within the required range, and
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none lies within the rejected range.
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Default required range is [0,ULONG_MAX) (whole of virtual address space).
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Default rejected range is [0,0).
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- /sys/kernel/debug/fail*/stacktrace-depth:
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specifies the maximum stacktrace depth walked during search
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for a caller within [require-start,require-end) OR
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[reject-start,reject-end).
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- /sys/kernel/debug/fail_page_alloc/ignore-gfp-highmem:
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Format: { 'Y' | 'N' }
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default is 'N', setting it to 'Y' won't inject failures into
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highmem/user allocations.
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- /sys/kernel/debug/failslab/ignore-gfp-wait:
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- /sys/kernel/debug/fail_page_alloc/ignore-gfp-wait:
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Format: { 'Y' | 'N' }
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default is 'N', setting it to 'Y' will inject failures
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only into non-sleep allocations (GFP_ATOMIC allocations).
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- /sys/kernel/debug/fail_page_alloc/min-order:
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specifies the minimum page allocation order to be injected
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failures.
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o Boot option
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In order to inject faults while debugfs is not available (early boot time),
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use the boot option:
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failslab=
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fail_page_alloc=
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fail_make_request=<interval>,<probability>,<space>,<times>
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How to add new fault injection capability
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-----------------------------------------
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o #include <linux/fault-inject.h>
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o define the fault attributes
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DECLARE_FAULT_INJECTION(name);
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Please see the definition of struct fault_attr in fault-inject.h
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for details.
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o provide a way to configure fault attributes
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- boot option
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If you need to enable the fault injection capability from boot time, you can
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provide boot option to configure it. There is a helper function for it:
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setup_fault_attr(attr, str);
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- debugfs entries
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failslab, fail_page_alloc, and fail_make_request use this way.
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Helper functions:
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init_fault_attr_entries(entries, attr, name);
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void cleanup_fault_attr_entries(entries);
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- module parameters
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If the scope of the fault injection capability is limited to a
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single kernel module, it is better to provide module parameters to
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configure the fault attributes.
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o add a hook to insert failures
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Upon should_fail() returning true, client code should inject a failure.
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should_fail(attr, size);
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Application Examples
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--------------------
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o Inject slab allocation failures into module init/exit code
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#!/bin/bash
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FAILTYPE=failslab
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echo Y > /sys/kernel/debug/$FAILTYPE/task-filter
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echo 10 > /sys/kernel/debug/$FAILTYPE/probability
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echo 100 > /sys/kernel/debug/$FAILTYPE/interval
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echo -1 > /sys/kernel/debug/$FAILTYPE/times
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echo 0 > /sys/kernel/debug/$FAILTYPE/space
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echo 2 > /sys/kernel/debug/$FAILTYPE/verbose
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echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait
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faulty_system()
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{
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bash -c "echo 1 > /proc/self/make-it-fail && exec $*"
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}
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if [ $# -eq 0 ]
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then
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echo "Usage: $0 modulename [ modulename ... ]"
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exit 1
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fi
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for m in $*
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do
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echo inserting $m...
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faulty_system modprobe $m
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echo removing $m...
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faulty_system modprobe -r $m
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done
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------------------------------------------------------------------------------
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o Inject page allocation failures only for a specific module
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#!/bin/bash
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FAILTYPE=fail_page_alloc
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module=$1
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if [ -z $module ]
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then
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echo "Usage: $0 <modulename>"
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exit 1
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fi
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modprobe $module
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if [ ! -d /sys/module/$module/sections ]
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then
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echo Module $module is not loaded
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exit 1
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fi
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cat /sys/module/$module/sections/.text > /sys/kernel/debug/$FAILTYPE/require-start
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cat /sys/module/$module/sections/.data > /sys/kernel/debug/$FAILTYPE/require-end
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echo N > /sys/kernel/debug/$FAILTYPE/task-filter
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echo 10 > /sys/kernel/debug/$FAILTYPE/probability
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echo 100 > /sys/kernel/debug/$FAILTYPE/interval
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echo -1 > /sys/kernel/debug/$FAILTYPE/times
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echo 0 > /sys/kernel/debug/$FAILTYPE/space
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echo 2 > /sys/kernel/debug/$FAILTYPE/verbose
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echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait
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echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-highmem
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echo 10 > /sys/kernel/debug/$FAILTYPE/stacktrace-depth
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trap "echo 0 > /sys/kernel/debug/$FAILTYPE/probability" SIGINT SIGTERM EXIT
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echo "Injecting errors into the module $module... (interrupt to stop)"
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sleep 1000000
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