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-rw-r--r--Documentation/fault-injection/fault-injection.rst453
-rw-r--r--Documentation/fault-injection/index.rst20
-rw-r--r--Documentation/fault-injection/notifier-error-inject.rst98
-rw-r--r--Documentation/fault-injection/nvme-fault-injection.rst178
-rw-r--r--Documentation/fault-injection/provoke-crashes.rst58
5 files changed, 807 insertions, 0 deletions
diff --git a/Documentation/fault-injection/fault-injection.rst b/Documentation/fault-injection/fault-injection.rst
new file mode 100644
index 000000000..47de5006f
--- /dev/null
+++ b/Documentation/fault-injection/fault-injection.rst
@@ -0,0 +1,453 @@
+===========================================
+Fault injection capabilities infrastructure
+===========================================
+
+See also drivers/md/md-faulty.c and "every_nth" module option for scsi_debug.
+
+
+Available fault injection capabilities
+--------------------------------------
+
+- failslab
+
+ injects slab allocation failures. (kmalloc(), kmem_cache_alloc(), ...)
+
+- fail_page_alloc
+
+ injects page allocation failures. (alloc_pages(), get_free_pages(), ...)
+
+- fail_usercopy
+
+ injects failures in user memory access functions. (copy_from_user(), get_user(), ...)
+
+- fail_futex
+
+ injects futex deadlock and uaddr fault errors.
+
+- fail_make_request
+
+ injects disk IO errors on devices permitted by setting
+ /sys/block/<device>/make-it-fail or
+ /sys/block/<device>/<partition>/make-it-fail. (submit_bio_noacct())
+
+- fail_mmc_request
+
+ injects MMC data errors on devices permitted by setting
+ debugfs entries under /sys/kernel/debug/mmc0/fail_mmc_request
+
+- fail_function
+
+ injects error return on specific functions, which are marked by
+ ALLOW_ERROR_INJECTION() macro, by setting debugfs entries
+ under /sys/kernel/debug/fail_function. No boot option supported.
+
+- NVMe fault injection
+
+ inject NVMe status code and retry flag on devices permitted by setting
+ debugfs entries under /sys/kernel/debug/nvme*/fault_inject. The default
+ status code is NVME_SC_INVALID_OPCODE with no retry. The status code and
+ retry flag can be set via the debugfs.
+
+
+Configure fault-injection capabilities behavior
+-----------------------------------------------
+
+debugfs entries
+^^^^^^^^^^^^^^^
+
+fault-inject-debugfs kernel module provides some debugfs entries for runtime
+configuration of fault-injection capabilities.
+
+- /sys/kernel/debug/fail*/probability:
+
+ likelihood of failure injection, in percent.
+
+ Format: <percent>
+
+ Note that one-failure-per-hundred is a very high error rate
+ for some testcases. Consider setting probability=100 and configure
+ /sys/kernel/debug/fail*/interval for such testcases.
+
+- /sys/kernel/debug/fail*/interval:
+
+ specifies the interval between failures, for calls to
+ should_fail() that pass all the other tests.
+
+ Note that if you enable this, by setting interval>1, you will
+ probably want to set probability=100.
+
+- /sys/kernel/debug/fail*/times:
+
+ specifies how many times failures may happen at most. A value of -1
+ means "no limit".
+
+- /sys/kernel/debug/fail*/space:
+
+ specifies an initial resource "budget", decremented by "size"
+ on each call to should_fail(,size). Failure injection is
+ suppressed until "space" reaches zero.
+
+- /sys/kernel/debug/fail*/verbose
+
+ Format: { 0 | 1 | 2 }
+
+ specifies the verbosity of the messages when failure is
+ injected. '0' means no messages; '1' will print only a single
+ log line per failure; '2' will print a call trace too -- useful
+ to debug the problems revealed by fault injection.
+
+- /sys/kernel/debug/fail*/task-filter:
+
+ Format: { 'Y' | 'N' }
+
+ A value of 'N' disables filtering by process (default).
+ Any positive value limits failures to only processes indicated by
+ /proc/<pid>/make-it-fail==1.
+
+- /sys/kernel/debug/fail*/require-start,
+ /sys/kernel/debug/fail*/require-end,
+ /sys/kernel/debug/fail*/reject-start,
+ /sys/kernel/debug/fail*/reject-end:
+
+ specifies the range of virtual addresses tested during
+ stacktrace walking. Failure is injected only if some caller
+ in the walked stacktrace lies within the required range, and
+ none lies within the rejected range.
+ Default required range is [0,ULONG_MAX) (whole of virtual address space).
+ Default rejected range is [0,0).
+
+- /sys/kernel/debug/fail*/stacktrace-depth:
+
+ specifies the maximum stacktrace depth walked during search
+ for a caller within [require-start,require-end) OR
+ [reject-start,reject-end).
+
+- /sys/kernel/debug/fail_page_alloc/ignore-gfp-highmem:
+
+ Format: { 'Y' | 'N' }
+
+ default is 'N', setting it to 'Y' won't inject failures into
+ highmem/user allocations.
+
+- /sys/kernel/debug/failslab/ignore-gfp-wait:
+- /sys/kernel/debug/fail_page_alloc/ignore-gfp-wait:
+
+ Format: { 'Y' | 'N' }
+
+ default is 'N', setting it to 'Y' will inject failures
+ only into non-sleep allocations (GFP_ATOMIC allocations).
+
+- /sys/kernel/debug/fail_page_alloc/min-order:
+
+ specifies the minimum page allocation order to be injected
+ failures.
+
+- /sys/kernel/debug/fail_futex/ignore-private:
+
+ Format: { 'Y' | 'N' }
+
+ default is 'N', setting it to 'Y' will disable failure injections
+ when dealing with private (address space) futexes.
+
+- /sys/kernel/debug/fail_function/inject:
+
+ Format: { 'function-name' | '!function-name' | '' }
+
+ specifies the target function of error injection by name.
+ If the function name leads '!' prefix, given function is
+ removed from injection list. If nothing specified ('')
+ injection list is cleared.
+
+- /sys/kernel/debug/fail_function/injectable:
+
+ (read only) shows error injectable functions and what type of
+ error values can be specified. The error type will be one of
+ below;
+ - NULL: retval must be 0.
+ - ERRNO: retval must be -1 to -MAX_ERRNO (-4096).
+ - ERR_NULL: retval must be 0 or -1 to -MAX_ERRNO (-4096).
+
+- /sys/kernel/debug/fail_function/<function-name>/retval:
+
+ specifies the "error" return value to inject to the given function.
+ This will be created when the user specifies a new injection entry.
+ Note that this file only accepts unsigned values. So, if you want to
+ use a negative errno, you better use 'printf' instead of 'echo', e.g.:
+ $ printf %#x -12 > retval
+
+Boot option
+^^^^^^^^^^^
+
+In order to inject faults while debugfs is not available (early boot time),
+use the boot option::
+
+ failslab=
+ fail_page_alloc=
+ fail_usercopy=
+ fail_make_request=
+ fail_futex=
+ mmc_core.fail_request=<interval>,<probability>,<space>,<times>
+
+proc entries
+^^^^^^^^^^^^
+
+- /proc/<pid>/fail-nth,
+ /proc/self/task/<tid>/fail-nth:
+
+ Write to this file of integer N makes N-th call in the task fail.
+ Read from this file returns a integer value. A value of '0' indicates
+ that the fault setup with a previous write to this file was injected.
+ A positive integer N indicates that the fault wasn't yet injected.
+ Note that this file enables all types of faults (slab, futex, etc).
+ This setting takes precedence over all other generic debugfs settings
+ like probability, interval, times, etc. But per-capability settings
+ (e.g. fail_futex/ignore-private) take precedence over it.
+
+ This feature is intended for systematic testing of faults in a single
+ system call. See an example below.
+
+How to add new fault injection capability
+-----------------------------------------
+
+- #include <linux/fault-inject.h>
+
+- define the fault attributes
+
+ DECLARE_FAULT_ATTR(name);
+
+ Please see the definition of struct fault_attr in fault-inject.h
+ for details.
+
+- provide a way to configure fault attributes
+
+- boot option
+
+ If you need to enable the fault injection capability from boot time, you can
+ provide boot option to configure it. There is a helper function for it:
+
+ setup_fault_attr(attr, str);
+
+- debugfs entries
+
+ failslab, fail_page_alloc, fail_usercopy, and fail_make_request use this way.
+ Helper functions:
+
+ fault_create_debugfs_attr(name, parent, attr);
+
+- module parameters
+
+ If the scope of the fault injection capability is limited to a
+ single kernel module, it is better to provide module parameters to
+ configure the fault attributes.
+
+- add a hook to insert failures
+
+ Upon should_fail() returning true, client code should inject a failure:
+
+ should_fail(attr, size);
+
+Application Examples
+--------------------
+
+- Inject slab allocation failures into module init/exit code::
+
+ #!/bin/bash
+
+ FAILTYPE=failslab
+ echo Y > /sys/kernel/debug/$FAILTYPE/task-filter
+ echo 10 > /sys/kernel/debug/$FAILTYPE/probability
+ echo 100 > /sys/kernel/debug/$FAILTYPE/interval
+ echo -1 > /sys/kernel/debug/$FAILTYPE/times
+ echo 0 > /sys/kernel/debug/$FAILTYPE/space
+ echo 2 > /sys/kernel/debug/$FAILTYPE/verbose
+ echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait
+
+ faulty_system()
+ {
+ bash -c "echo 1 > /proc/self/make-it-fail && exec $*"
+ }
+
+ if [ $# -eq 0 ]
+ then
+ echo "Usage: $0 modulename [ modulename ... ]"
+ exit 1
+ fi
+
+ for m in $*
+ do
+ echo inserting $m...
+ faulty_system modprobe $m
+
+ echo removing $m...
+ faulty_system modprobe -r $m
+ done
+
+------------------------------------------------------------------------------
+
+- Inject page allocation failures only for a specific module::
+
+ #!/bin/bash
+
+ FAILTYPE=fail_page_alloc
+ module=$1
+
+ if [ -z $module ]
+ then
+ echo "Usage: $0 <modulename>"
+ exit 1
+ fi
+
+ modprobe $module
+
+ if [ ! -d /sys/module/$module/sections ]
+ then
+ echo Module $module is not loaded
+ exit 1
+ fi
+
+ cat /sys/module/$module/sections/.text > /sys/kernel/debug/$FAILTYPE/require-start
+ cat /sys/module/$module/sections/.data > /sys/kernel/debug/$FAILTYPE/require-end
+
+ echo N > /sys/kernel/debug/$FAILTYPE/task-filter
+ echo 10 > /sys/kernel/debug/$FAILTYPE/probability
+ echo 100 > /sys/kernel/debug/$FAILTYPE/interval
+ echo -1 > /sys/kernel/debug/$FAILTYPE/times
+ echo 0 > /sys/kernel/debug/$FAILTYPE/space
+ echo 2 > /sys/kernel/debug/$FAILTYPE/verbose
+ echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait
+ echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-highmem
+ echo 10 > /sys/kernel/debug/$FAILTYPE/stacktrace-depth
+
+ trap "echo 0 > /sys/kernel/debug/$FAILTYPE/probability" SIGINT SIGTERM EXIT
+
+ echo "Injecting errors into the module $module... (interrupt to stop)"
+ sleep 1000000
+
+------------------------------------------------------------------------------
+
+- Inject open_ctree error while btrfs mount::
+
+ #!/bin/bash
+
+ rm -f testfile.img
+ dd if=/dev/zero of=testfile.img bs=1M seek=1000 count=1
+ DEVICE=$(losetup --show -f testfile.img)
+ mkfs.btrfs -f $DEVICE
+ mkdir -p tmpmnt
+
+ FAILTYPE=fail_function
+ FAILFUNC=open_ctree
+ echo $FAILFUNC > /sys/kernel/debug/$FAILTYPE/inject
+ printf %#x -12 > /sys/kernel/debug/$FAILTYPE/$FAILFUNC/retval
+ echo N > /sys/kernel/debug/$FAILTYPE/task-filter
+ echo 100 > /sys/kernel/debug/$FAILTYPE/probability
+ echo 0 > /sys/kernel/debug/$FAILTYPE/interval
+ echo -1 > /sys/kernel/debug/$FAILTYPE/times
+ echo 0 > /sys/kernel/debug/$FAILTYPE/space
+ echo 1 > /sys/kernel/debug/$FAILTYPE/verbose
+
+ mount -t btrfs $DEVICE tmpmnt
+ if [ $? -ne 0 ]
+ then
+ echo "SUCCESS!"
+ else
+ echo "FAILED!"
+ umount tmpmnt
+ fi
+
+ echo > /sys/kernel/debug/$FAILTYPE/inject
+
+ rmdir tmpmnt
+ losetup -d $DEVICE
+ rm testfile.img
+
+
+Tool to run command with failslab or fail_page_alloc
+----------------------------------------------------
+In order to make it easier to accomplish the tasks mentioned above, we can use
+tools/testing/fault-injection/failcmd.sh. Please run a command
+"./tools/testing/fault-injection/failcmd.sh --help" for more information and
+see the following examples.
+
+Examples:
+
+Run a command "make -C tools/testing/selftests/ run_tests" with injecting slab
+allocation failure::
+
+ # ./tools/testing/fault-injection/failcmd.sh \
+ -- make -C tools/testing/selftests/ run_tests
+
+Same as above except to specify 100 times failures at most instead of one time
+at most by default::
+
+ # ./tools/testing/fault-injection/failcmd.sh --times=100 \
+ -- make -C tools/testing/selftests/ run_tests
+
+Same as above except to inject page allocation failure instead of slab
+allocation failure::
+
+ # env FAILCMD_TYPE=fail_page_alloc \
+ ./tools/testing/fault-injection/failcmd.sh --times=100 \
+ -- make -C tools/testing/selftests/ run_tests
+
+Systematic faults using fail-nth
+---------------------------------
+
+The following code systematically faults 0-th, 1-st, 2-nd and so on
+capabilities in the socketpair() system call::
+
+ #include <sys/types.h>
+ #include <sys/stat.h>
+ #include <sys/socket.h>
+ #include <sys/syscall.h>
+ #include <fcntl.h>
+ #include <unistd.h>
+ #include <string.h>
+ #include <stdlib.h>
+ #include <stdio.h>
+ #include <errno.h>
+
+ int main()
+ {
+ int i, err, res, fail_nth, fds[2];
+ char buf[128];
+
+ system("echo N > /sys/kernel/debug/failslab/ignore-gfp-wait");
+ sprintf(buf, "/proc/self/task/%ld/fail-nth", syscall(SYS_gettid));
+ fail_nth = open(buf, O_RDWR);
+ for (i = 1;; i++) {
+ sprintf(buf, "%d", i);
+ write(fail_nth, buf, strlen(buf));
+ res = socketpair(AF_LOCAL, SOCK_STREAM, 0, fds);
+ err = errno;
+ pread(fail_nth, buf, sizeof(buf), 0);
+ if (res == 0) {
+ close(fds[0]);
+ close(fds[1]);
+ }
+ printf("%d-th fault %c: res=%d/%d\n", i, atoi(buf) ? 'N' : 'Y',
+ res, err);
+ if (atoi(buf))
+ break;
+ }
+ return 0;
+ }
+
+An example output::
+
+ 1-th fault Y: res=-1/23
+ 2-th fault Y: res=-1/23
+ 3-th fault Y: res=-1/12
+ 4-th fault Y: res=-1/12
+ 5-th fault Y: res=-1/23
+ 6-th fault Y: res=-1/23
+ 7-th fault Y: res=-1/23
+ 8-th fault Y: res=-1/12
+ 9-th fault Y: res=-1/12
+ 10-th fault Y: res=-1/12
+ 11-th fault Y: res=-1/12
+ 12-th fault Y: res=-1/12
+ 13-th fault Y: res=-1/12
+ 14-th fault Y: res=-1/12
+ 15-th fault Y: res=-1/12
+ 16-th fault N: res=0/12
diff --git a/Documentation/fault-injection/index.rst b/Documentation/fault-injection/index.rst
new file mode 100644
index 000000000..8408a8a91
--- /dev/null
+++ b/Documentation/fault-injection/index.rst
@@ -0,0 +1,20 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+fault-injection
+===============
+
+.. toctree::
+ :maxdepth: 1
+
+ fault-injection
+ notifier-error-inject
+ nvme-fault-injection
+ provoke-crashes
+
+.. only:: subproject and html
+
+ Indices
+ =======
+
+ * :ref:`genindex`
diff --git a/Documentation/fault-injection/notifier-error-inject.rst b/Documentation/fault-injection/notifier-error-inject.rst
new file mode 100644
index 000000000..1668b6e48
--- /dev/null
+++ b/Documentation/fault-injection/notifier-error-inject.rst
@@ -0,0 +1,98 @@
+Notifier error injection
+========================
+
+Notifier error injection 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 which is rarely executed. There are kernel
+modules that can be used to test the following notifiers.
+
+ * PM notifier
+ * Memory hotplug notifier
+ * powerpc pSeries reconfig notifier
+ * Netdevice notifier
+
+PM notifier error injection module
+----------------------------------
+This feature is controlled through debugfs interface
+
+ /sys/kernel/debug/notifier-error-inject/pm/actions/<notifier event>/error
+
+Possible PM notifier events to be failed are:
+
+ * PM_HIBERNATION_PREPARE
+ * PM_SUSPEND_PREPARE
+ * PM_RESTORE_PREPARE
+
+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
+
+Memory hotplug notifier error injection module
+----------------------------------------------
+This feature is controlled through debugfs interface
+
+ /sys/kernel/debug/notifier-error-inject/memory/actions/<notifier event>/error
+
+Possible memory notifier events to be failed are:
+
+ * MEM_GOING_ONLINE
+ * MEM_GOING_OFFLINE
+
+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
+
+powerpc pSeries reconfig notifier error injection module
+--------------------------------------------------------
+This feature is controlled through debugfs interface
+
+ /sys/kernel/debug/notifier-error-inject/pSeries-reconfig/actions/<notifier event>/error
+
+Possible pSeries reconfig notifier events to be failed are:
+
+ * PSERIES_RECONFIG_ADD
+ * PSERIES_RECONFIG_REMOVE
+ * PSERIES_DRCONF_MEM_ADD
+ * PSERIES_DRCONF_MEM_REMOVE
+
+Netdevice notifier error injection module
+----------------------------------------------
+This feature is controlled through debugfs interface
+
+ /sys/kernel/debug/notifier-error-inject/netdev/actions/<notifier event>/error
+
+Netdevice notifier events which can be failed are:
+
+ * NETDEV_REGISTER
+ * NETDEV_CHANGEMTU
+ * NETDEV_CHANGENAME
+ * NETDEV_PRE_UP
+ * NETDEV_PRE_TYPE_CHANGE
+ * NETDEV_POST_INIT
+ * NETDEV_PRECHANGEMTU
+ * NETDEV_PRECHANGEUPPER
+ * NETDEV_CHANGEUPPER
+
+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
+
+For more usage examples
+-----------------------
+There are tools/testing/selftests using the notifier error injection features
+for CPU and memory notifiers.
+
+ * tools/testing/selftests/cpu-hotplug/on-off-test.sh
+ * tools/testing/selftests/memory-hotplug/on-off-test.sh
+
+These scripts first do simple online and offline tests and then do fault
+injection tests if notifier error injection module is available.
diff --git a/Documentation/fault-injection/nvme-fault-injection.rst b/Documentation/fault-injection/nvme-fault-injection.rst
new file mode 100644
index 000000000..1d4427890
--- /dev/null
+++ b/Documentation/fault-injection/nvme-fault-injection.rst
@@ -0,0 +1,178 @@
+NVMe Fault Injection
+====================
+Linux's fault injection framework provides a systematic way to support
+error injection via debugfs in the /sys/kernel/debug directory. When
+enabled, the default NVME_SC_INVALID_OPCODE with no retry will be
+injected into the nvme_try_complete_req. Users can change the default status
+code and no retry flag via the debugfs. The list of Generic Command
+Status can be found in include/linux/nvme.h
+
+Following examples show how to inject an error into the nvme.
+
+First, enable CONFIG_FAULT_INJECTION_DEBUG_FS kernel config,
+recompile the kernel. After booting up the kernel, do the
+following.
+
+Example 1: Inject default status code with no retry
+---------------------------------------------------
+
+::
+
+ mount /dev/nvme0n1 /mnt
+ echo 1 > /sys/kernel/debug/nvme0n1/fault_inject/times
+ echo 100 > /sys/kernel/debug/nvme0n1/fault_inject/probability
+ cp a.file /mnt
+
+Expected Result::
+
+ cp: cannot stat ‘/mnt/a.file’: Input/output error
+
+Message from dmesg::
+
+ FAULT_INJECTION: forcing a failure.
+ name fault_inject, interval 1, probability 100, space 0, times 1
+ CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc8+ #2
+ Hardware name: innotek GmbH VirtualBox/VirtualBox,
+ BIOS VirtualBox 12/01/2006
+ Call Trace:
+ <IRQ>
+ dump_stack+0x5c/0x7d
+ should_fail+0x148/0x170
+ nvme_should_fail+0x2f/0x50 [nvme_core]
+ nvme_process_cq+0xe7/0x1d0 [nvme]
+ nvme_irq+0x1e/0x40 [nvme]
+ __handle_irq_event_percpu+0x3a/0x190
+ handle_irq_event_percpu+0x30/0x70
+ handle_irq_event+0x36/0x60
+ handle_fasteoi_irq+0x78/0x120
+ handle_irq+0xa7/0x130
+ ? tick_irq_enter+0xa8/0xc0
+ do_IRQ+0x43/0xc0
+ common_interrupt+0xa2/0xa2
+ </IRQ>
+ RIP: 0010:native_safe_halt+0x2/0x10
+ RSP: 0018:ffffffff82003e90 EFLAGS: 00000246 ORIG_RAX: ffffffffffffffdd
+ RAX: ffffffff817a10c0 RBX: ffffffff82012480 RCX: 0000000000000000
+ RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
+ RBP: 0000000000000000 R08: 000000008e38ce64 R09: 0000000000000000
+ R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff82012480
+ R13: ffffffff82012480 R14: 0000000000000000 R15: 0000000000000000
+ ? __sched_text_end+0x4/0x4
+ default_idle+0x18/0xf0
+ do_idle+0x150/0x1d0
+ cpu_startup_entry+0x6f/0x80
+ start_kernel+0x4c4/0x4e4
+ ? set_init_arg+0x55/0x55
+ secondary_startup_64+0xa5/0xb0
+ print_req_error: I/O error, dev nvme0n1, sector 9240
+ EXT4-fs error (device nvme0n1): ext4_find_entry:1436:
+ inode #2: comm cp: reading directory lblock 0
+
+Example 2: Inject default status code with retry
+------------------------------------------------
+
+::
+
+ mount /dev/nvme0n1 /mnt
+ echo 1 > /sys/kernel/debug/nvme0n1/fault_inject/times
+ echo 100 > /sys/kernel/debug/nvme0n1/fault_inject/probability
+ echo 1 > /sys/kernel/debug/nvme0n1/fault_inject/status
+ echo 0 > /sys/kernel/debug/nvme0n1/fault_inject/dont_retry
+
+ cp a.file /mnt
+
+Expected Result::
+
+ command success without error
+
+Message from dmesg::
+
+ FAULT_INJECTION: forcing a failure.
+ name fault_inject, interval 1, probability 100, space 0, times 1
+ CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.15.0-rc8+ #4
+ Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
+ Call Trace:
+ <IRQ>
+ dump_stack+0x5c/0x7d
+ should_fail+0x148/0x170
+ nvme_should_fail+0x30/0x60 [nvme_core]
+ nvme_loop_queue_response+0x84/0x110 [nvme_loop]
+ nvmet_req_complete+0x11/0x40 [nvmet]
+ nvmet_bio_done+0x28/0x40 [nvmet]
+ blk_update_request+0xb0/0x310
+ blk_mq_end_request+0x18/0x60
+ flush_smp_call_function_queue+0x3d/0xf0
+ smp_call_function_single_interrupt+0x2c/0xc0
+ call_function_single_interrupt+0xa2/0xb0
+ </IRQ>
+ RIP: 0010:native_safe_halt+0x2/0x10
+ RSP: 0018:ffffc9000068bec0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff04
+ RAX: ffffffff817a10c0 RBX: ffff88011a3c9680 RCX: 0000000000000000
+ RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
+ RBP: 0000000000000001 R08: 000000008e38c131 R09: 0000000000000000
+ R10: 0000000000000000 R11: 0000000000000000 R12: ffff88011a3c9680
+ R13: ffff88011a3c9680 R14: 0000000000000000 R15: 0000000000000000
+ ? __sched_text_end+0x4/0x4
+ default_idle+0x18/0xf0
+ do_idle+0x150/0x1d0
+ cpu_startup_entry+0x6f/0x80
+ start_secondary+0x187/0x1e0
+ secondary_startup_64+0xa5/0xb0
+
+Example 3: Inject an error into the 10th admin command
+------------------------------------------------------
+
+::
+
+ echo 100 > /sys/kernel/debug/nvme0/fault_inject/probability
+ echo 10 > /sys/kernel/debug/nvme0/fault_inject/space
+ echo 1 > /sys/kernel/debug/nvme0/fault_inject/times
+ nvme reset /dev/nvme0
+
+Expected Result::
+
+ After NVMe controller reset, the reinitialization may or may not succeed.
+ It depends on which admin command is actually forced to fail.
+
+Message from dmesg::
+
+ nvme nvme0: resetting controller
+ FAULT_INJECTION: forcing a failure.
+ name fault_inject, interval 1, probability 100, space 1, times 1
+ CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.2.0-rc2+ #2
+ Hardware name: MSI MS-7A45/B150M MORTAR ARCTIC (MS-7A45), BIOS 1.50 04/25/2017
+ Call Trace:
+ <IRQ>
+ dump_stack+0x63/0x85
+ should_fail+0x14a/0x170
+ nvme_should_fail+0x38/0x80 [nvme_core]
+ nvme_irq+0x129/0x280 [nvme]
+ ? blk_mq_end_request+0xb3/0x120
+ __handle_irq_event_percpu+0x84/0x1a0
+ handle_irq_event_percpu+0x32/0x80
+ handle_irq_event+0x3b/0x60
+ handle_edge_irq+0x7f/0x1a0
+ handle_irq+0x20/0x30
+ do_IRQ+0x4e/0xe0
+ common_interrupt+0xf/0xf
+ </IRQ>
+ RIP: 0010:cpuidle_enter_state+0xc5/0x460
+ Code: ff e8 8f 5f 86 ff 80 7d c7 00 74 17 9c 58 0f 1f 44 00 00 f6 c4 02 0f 85 69 03 00 00 31 ff e8 62 aa 8c ff fb 66 0f 1f 44 00 00 <45> 85 ed 0f 88 37 03 00 00 4c 8b 45 d0 4c 2b 45 b8 48 ba cf f7 53
+ RSP: 0018:ffffffff88c03dd0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffffdc
+ RAX: ffff9dac25a2ac80 RBX: ffffffff88d53760 RCX: 000000000000001f
+ RDX: 0000000000000000 RSI: 000000002d958403 RDI: 0000000000000000
+ RBP: ffffffff88c03e18 R08: fffffff75e35ffb7 R09: 00000a49a56c0b48
+ R10: ffffffff88c03da0 R11: 0000000000001b0c R12: ffff9dac25a34d00
+ R13: 0000000000000006 R14: 0000000000000006 R15: ffffffff88d53760
+ cpuidle_enter+0x2e/0x40
+ call_cpuidle+0x23/0x40
+ do_idle+0x201/0x280
+ cpu_startup_entry+0x1d/0x20
+ rest_init+0xaa/0xb0
+ arch_call_rest_init+0xe/0x1b
+ start_kernel+0x51c/0x53b
+ x86_64_start_reservations+0x24/0x26
+ x86_64_start_kernel+0x74/0x77
+ secondary_startup_64+0xa4/0xb0
+ nvme nvme0: Could not set queue count (16385)
+ nvme nvme0: IO queues not created
diff --git a/Documentation/fault-injection/provoke-crashes.rst b/Documentation/fault-injection/provoke-crashes.rst
new file mode 100644
index 000000000..18de17354
--- /dev/null
+++ b/Documentation/fault-injection/provoke-crashes.rst
@@ -0,0 +1,58 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============================================================
+Provoking crashes with Linux Kernel Dump Test Module (LKDTM)
+============================================================
+
+The lkdtm module provides an interface to disrupt (and usually crash)
+the kernel at predefined code locations to evaluate the reliability of
+the kernel's exception handling and to test crash dumps obtained using
+different dumping solutions. The module uses KPROBEs to instrument the
+trigger location, but can also trigger the kernel directly without KPROBE
+support via debugfs.
+
+You can select the location of the trigger ("crash point name") and the
+type of action ("crash point type") either through module arguments when
+inserting the module, or through the debugfs interface.
+
+Usage::
+
+ insmod lkdtm.ko [recur_count={>0}] cpoint_name=<> cpoint_type=<>
+ [cpoint_count={>0}]
+
+recur_count
+ Recursion level for the stack overflow test. By default this is
+ dynamically calculated based on kernel configuration, with the
+ goal of being just large enough to exhaust the kernel stack. The
+ value can be seen at `/sys/module/lkdtm/parameters/recur_count`.
+
+cpoint_name
+ Where in the kernel to trigger the action. It can be
+ one of INT_HARDWARE_ENTRY, INT_HW_IRQ_EN, INT_TASKLET_ENTRY,
+ FS_DEVRW, MEM_SWAPOUT, TIMERADD, SCSI_QUEUE_RQ,
+ IDE_CORE_CP, or DIRECT
+
+cpoint_type
+ Indicates the action to be taken on hitting the crash point.
+ These are numerous, and best queried directly from debugfs. Some
+ of the common ones are PANIC, BUG, EXCEPTION, LOOP, and OVERFLOW.
+ See the contents of `/sys/kernel/debug/provoke-crash/DIRECT` for
+ a complete list.
+
+cpoint_count
+ Indicates the number of times the crash point is to be hit
+ before triggering the action. The default is 10 (except for
+ DIRECT, which always fires immediately).
+
+You can also induce failures by mounting debugfs and writing the type to
+<debugfs>/provoke-crash/<crashpoint>. E.g.::
+
+ mount -t debugfs debugfs /sys/kernel/debug
+ echo EXCEPTION > /sys/kernel/debug/provoke-crash/INT_HARDWARE_ENTRY
+
+The special file `DIRECT` will induce the action directly without KPROBE
+instrumentation. This mode is the only one available when the module is
+built for a kernel without KPROBEs support::
+
+ # Instead of having a BUG kill your shell, have it kill "cat":
+ cat <(echo WRITE_RO) >/sys/kernel/debug/provoke-crash/DIRECT