185848707e
Fix and cleanup example scripts in fault injection documentation. 1. Eliminate broken oops() shell function. 2. Fold failcmd.sh and failmodule.sh into example scripts. It makes the example scripts work independent of current working directory. 3. Set "space" parameter to 0 to start injecting errors immediately. 4. Use /sys/module/<modulename>/sections/.data as upper bound of .text section. Because some module doesn't have .exit.text section. Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
237 lines
6 KiB
Text
237 lines
6 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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- /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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/debug/fail*/interval for such testcases.
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- /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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- /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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- /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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- /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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- /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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- /debug/fail*/require-start:
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- /debug/fail*/require-end:
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- /debug/fail*/reject-start:
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- /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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- /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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- /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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- /debug/failslab/ignore-gfp-wait:
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- /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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- /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 > /debug/$FAILTYPE/task-filter
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echo 10 > /debug/$FAILTYPE/probability
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echo 100 > /debug/$FAILTYPE/interval
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echo -1 > /debug/$FAILTYPE/times
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echo 0 > /debug/$FAILTYPE/space
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echo 2 > /debug/$FAILTYPE/verbose
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echo 1 > /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 > /debug/$FAILTYPE/require-start
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cat /sys/module/$module/sections/.data > /debug/$FAILTYPE/require-end
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echo N > /debug/$FAILTYPE/task-filter
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echo 10 > /debug/$FAILTYPE/probability
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echo 100 > /debug/$FAILTYPE/interval
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echo -1 > /debug/$FAILTYPE/times
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echo 0 > /debug/$FAILTYPE/space
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echo 2 > /debug/$FAILTYPE/verbose
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echo 1 > /debug/$FAILTYPE/ignore-gfp-wait
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echo 1 > /debug/$FAILTYPE/ignore-gfp-highmem
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echo 10 > /debug/$FAILTYPE/stacktrace-depth
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trap "echo 0 > /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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