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58 lines
2.3 KiB
58 lines
2.3 KiB
.. SPDX-License-Identifier: GPL-2.0 |
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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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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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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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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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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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FS_DEVRW, MEM_SWAPOUT, TIMERADD, SCSI_DISPATCH_CMD, |
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IDE_CORE_CP, or DIRECT |
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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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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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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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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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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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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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# 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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