2020-10-15 22:45:59 +00:00
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.. SPDX-License-Identifier: GPL-2.0
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2019-06-12 17:52:44 +00:00
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2020-10-15 22:45:59 +00:00
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============================================================
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Provoking crashes with Linux Kernel Dump Test Module (LKDTM)
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============================================================
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2019-06-12 17:52:44 +00:00
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2020-10-15 22:45:59 +00:00
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The lkdtm module provides an interface to disrupt (and usually crash)
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the kernel at predefined code locations to evaluate the reliability of
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the kernel's exception handling and to test crash dumps obtained using
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different dumping solutions. The module uses KPROBEs to instrument the
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trigger location, but can also trigger the kernel directly without KPROBE
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support via debugfs.
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2019-06-12 17:52:44 +00:00
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2020-10-15 22:45:59 +00:00
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You can select the location of the trigger ("crash point name") and the
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type of action ("crash point type") either through module arguments when
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inserting the module, or through the debugfs interface.
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2019-06-12 17:52:44 +00:00
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Usage::
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insmod lkdtm.ko [recur_count={>0}] cpoint_name=<> cpoint_type=<>
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[cpoint_count={>0}]
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recur_count
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Recursion level for the stack overflow test. By default this is
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dynamically calculated based on kernel configuration, with the
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goal of being just large enough to exhaust the kernel stack. The
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value can be seen at `/sys/module/lkdtm/parameters/recur_count`.
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2019-06-12 17:52:44 +00:00
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cpoint_name
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Where in the kernel to trigger the action. It can be
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one of INT_HARDWARE_ENTRY, INT_HW_IRQ_EN, INT_TASKLET_ENTRY,
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2023-05-03 16:29:44 +00:00
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FS_SUBMIT_BH, MEM_SWAPOUT, TIMERADD, SCSI_QUEUE_RQ, or DIRECT.
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2019-06-12 17:52:44 +00:00
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cpoint_type
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Indicates the action to be taken on hitting the crash point.
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2020-10-15 22:45:59 +00:00
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These are numerous, and best queried directly from debugfs. Some
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of the common ones are PANIC, BUG, EXCEPTION, LOOP, and OVERFLOW.
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See the contents of `/sys/kernel/debug/provoke-crash/DIRECT` for
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a complete list.
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2019-06-12 17:52:44 +00:00
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cpoint_count
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Indicates the number of times the crash point is to be hit
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before triggering the action. The default is 10 (except for
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DIRECT, which always fires immediately).
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2019-06-12 17:52:44 +00:00
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You can also induce failures by mounting debugfs and writing the type to
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<debugfs>/provoke-crash/<crashpoint>. E.g.::
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2020-10-15 22:45:59 +00:00
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mount -t debugfs debugfs /sys/kernel/debug
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echo EXCEPTION > /sys/kernel/debug/provoke-crash/INT_HARDWARE_ENTRY
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2020-10-15 22:45:59 +00:00
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The special file `DIRECT` will induce the action directly without KPROBE
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instrumentation. This mode is the only one available when the module is
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built for a kernel without KPROBEs support::
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2019-06-12 17:52:44 +00:00
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2020-10-15 22:45:59 +00:00
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# Instead of having a BUG kill your shell, have it kill "cat":
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cat <(echo WRITE_RO) >/sys/kernel/debug/provoke-crash/DIRECT
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