path: root/arch/arm/probes/kprobes/test-core.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * arch/arm/kernel/kprobes-test.c
 *
 * Copyright (C) 2011 Jon Medhurst <tixy@yxit.co.uk>.
 */

/*
 * This file contains test code for ARM kprobes.
 *
 * The top level function run_all_tests() executes tests for all of the
 * supported instruction sets: ARM, 16-bit Thumb, and 32-bit Thumb. These tests
 * fall into two categories; run_api_tests() checks basic functionality of the
 * kprobes API, and run_test_cases() is a comprehensive test for kprobes
 * instruction decoding and simulation.
 *
 * run_test_cases() first checks the kprobes decoding table for self consistency
 * (using table_test()) then executes a series of test cases for each of the CPU
 * instruction forms. coverage_start() and coverage_end() are used to verify
 * that these test cases cover all of the possible combinations of instructions
 * described by the kprobes decoding tables.
 *
 * The individual test cases are in kprobes-test-arm.c and kprobes-test-thumb.c
 * which use the macros defined in kprobes-test.h. The rest of this
 * documentation will describe the operation of the framework used by these
 * test cases.
 */

/*
 * TESTING METHODOLOGY
 * -------------------
 *
 * The methodology used to test an ARM instruction 'test_insn' is to use
 * inline assembler like:
 *
 * test_before: nop
 * test_case:	test_insn
 * test_after:	nop
 *
 * When the test case is run a kprobe is placed of each nop. The
 * post-handler of the test_before probe is used to modify the saved CPU
 * register context to that which we require for the test case. The
 * pre-handler of the of the test_after probe saves a copy of the CPU
 * register context. In this way we can execute test_insn with a specific
 * register context and see the results afterwards.
 *
 * To actually test the kprobes instruction emulation we perform the above
 * step a second time but with an additional kprobe on the test_case
 * instruction itself. If the emulation is accurate then the results seen
 * by the test_