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- .. 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_SUBMIT_BH, MEM_SWAPOUT, TIMERADD, SCSI_QUEUE_RQ, 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
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