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diff --git a/Documentation/fault-injection/provoke-crashes.rst b/Documentation/fault-injection/provoke-crashes.rst new file mode 100644 index 000000000..1f087e502 --- /dev/null +++ b/Documentation/fault-injection/provoke-crashes.rst @@ -0,0 +1,57 @@ +.. 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 |