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lib/tests: Add randstruct KUnit test
Perform basic validation about layout randomization and initialization tracking when using CONFIG_RANDSTRUCT=y. Tested using: $ ./tools/testing/kunit/kunit.py run \ --kconfig_add CONFIG_RANDSTRUCT_FULL=y \ randstruct [17:22:30] ================= randstruct (2 subtests) ================== [17:22:30] [PASSED] randstruct_layout [17:22:30] [PASSED] randstruct_initializers [17:22:30] =================== [PASSED] randstruct ==================== [17:22:30] ============================================================ [17:22:30] Testing complete. Ran 2 tests: passed: 2 [17:22:30] Elapsed time: 5.091s total, 0.001s configuring, 4.974s building, 0.086s running Adding "--make_option LLVM=1" can be used to test Clang, which also passes. Acked-by: David Gow <[email protected]> Signed-off-by: Kees Cook <[email protected]>
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‎MAINTAINERS

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@@ -12892,6 +12892,7 @@ F: include/linux/overflow.h
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F: include/linux/randomize_kstack.h
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F: include/linux/ucopysize.h
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F: kernel/configs/hardening.config
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F: lib/tests/randstruct_kunit.c
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F: lib/tests/usercopy_kunit.c
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F: mm/usercopy.c
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F: security/Kconfig.hardening

‎lib/Kconfig.debug

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@@ -2863,6 +2863,14 @@ config OVERFLOW_KUNIT_TEST
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If unsure, say N.
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config RANDSTRUCT_KUNIT_TEST
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tristate "Test randstruct structure layout randomization at runtime" if !KUNIT_ALL_TESTS
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depends on KUNIT
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default KUNIT_ALL_TESTS
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help
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Builds unit tests for the checking CONFIG_RANDSTRUCT=y, which
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randomizes structure layouts.
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config STACKINIT_KUNIT_TEST
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tristate "Test level of stack variable initialization" if !KUNIT_ALL_TESTS
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depends on KUNIT

‎lib/tests/Makefile

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@@ -35,6 +35,7 @@ obj-$(CONFIG_MEMCPY_KUNIT_TEST) += memcpy_kunit.o
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CFLAGS_overflow_kunit.o = $(call cc-disable-warning, tautological-constant-out-of-range-compare)
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obj-$(CONFIG_OVERFLOW_KUNIT_TEST) += overflow_kunit.o
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obj-$(CONFIG_PRINTF_KUNIT_TEST) += printf_kunit.o
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obj-$(CONFIG_RANDSTRUCT_KUNIT_TEST) += randstruct_kunit.o
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obj-$(CONFIG_SCANF_KUNIT_TEST) += scanf_kunit.o
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obj-$(CONFIG_SIPHASH_KUNIT_TEST) += siphash_kunit.o
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obj-$(CONFIG_SLUB_KUNIT_TEST) += slub_kunit.o

‎lib/tests/randstruct_kunit.c

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// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Test cases for struct randomization, i.e. CONFIG_RANDSTRUCT=y.
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*
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* For example, see:
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* "Running tests with kunit_tool" at Documentation/dev-tools/kunit/start.rst
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* ./tools/testing/kunit/kunit.py run randstruct [--raw_output] \
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* [--make_option LLVM=1] \
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* --kconfig_add CONFIG_RANDSTRUCT_FULL=y
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*
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <kunit/test.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/string.h>
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#define DO_MANY_MEMBERS(macro, args...) \
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macro(a, args) \
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macro(b, args) \
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macro(c, args) \
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macro(d, args) \
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macro(e, args) \
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macro(f, args) \
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macro(g, args) \
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macro(h, args)
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#define do_enum(x, ignored) MEMBER_NAME_ ## x,
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enum randstruct_member_names {
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DO_MANY_MEMBERS(do_enum)
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MEMBER_NAME_MAX,
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};
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/* Make sure the macros are working: want 8 test members. */
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_Static_assert(MEMBER_NAME_MAX == 8, "Number of test members changed?!");
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/* This is an unsigned long member to match the function pointer size */
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#define unsigned_long_member(x, ignored) unsigned long x;
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struct randstruct_untouched {
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DO_MANY_MEMBERS(unsigned_long_member)
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};
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/* Struct explicitly marked with __randomize_layout. */
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struct randstruct_shuffled {
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DO_MANY_MEMBERS(unsigned_long_member)
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} __randomize_layout;
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#undef unsigned_long_member
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/* Struct implicitly randomized from being all func ptrs. */
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#define func_member(x, ignored) size_t (*x)(int);
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struct randstruct_funcs_untouched {
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DO_MANY_MEMBERS(func_member)
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} __no_randomize_layout;
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struct randstruct_funcs_shuffled {
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DO_MANY_MEMBERS(func_member)
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};
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#undef func_member
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#define func_body(x, ignored) \
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static noinline size_t func_##x(int arg) \
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{ \
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return offsetof(struct randstruct_funcs_untouched, x); \
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}
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DO_MANY_MEMBERS(func_body)
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/* Various mixed types. */
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#define mixed_members \
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bool a; \
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short b; \
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unsigned int c __aligned(16); \
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size_t d; \
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char e; \
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u64 f; \
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union { \
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struct randstruct_shuffled shuffled; \
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uintptr_t g; \
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}; \
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union { \
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void *ptr; \
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char h; \
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};
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struct randstruct_mixed_untouched {
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mixed_members
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};
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struct randstruct_mixed_shuffled {
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mixed_members
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} __randomize_layout;
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#undef mixed_members
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struct contains_randstruct_untouched {
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int before;
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struct randstruct_untouched untouched;
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int after;
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};
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struct contains_randstruct_shuffled {
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int before;
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struct randstruct_shuffled shuffled;
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int after;
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};
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static void randstruct_layout(struct kunit *test)
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{
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int mismatches;
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#define check_mismatch(x, untouched, shuffled) \
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if (offsetof(untouched, x) != offsetof(shuffled, x)) \
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mismatches++; \
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kunit_info(test, #shuffled "::" #x " @ %zu (vs %zu)\n", \
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offsetof(shuffled, x), \
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offsetof(untouched, x)); \
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#define check_pair(outcome, untouched, shuffled) \
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mismatches = 0; \
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DO_MANY_MEMBERS(check_mismatch, untouched, shuffled) \
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kunit_info(test, "Differing " #untouched " vs " #shuffled " member positions: %d\n", \
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mismatches); \
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KUNIT_##outcome##_MSG(test, mismatches, 0, \
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#untouched " vs " #shuffled " layouts: unlucky or broken?\n");
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check_pair(EXPECT_EQ, struct randstruct_untouched, struct randstruct_untouched)
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check_pair(EXPECT_GT, struct randstruct_untouched, struct randstruct_shuffled)
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check_pair(EXPECT_GT, struct randstruct_untouched, struct randstruct_funcs_shuffled)
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check_pair(EXPECT_GT, struct randstruct_funcs_untouched, struct randstruct_funcs_shuffled)
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check_pair(EXPECT_GT, struct randstruct_mixed_untouched, struct randstruct_mixed_shuffled)
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#undef check_pair
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#undef check_mismatch
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}
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#define check_mismatch(x, ignore) \
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KUNIT_EXPECT_EQ_MSG(test, untouched->x, shuffled->x, \
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"Mismatched member value in %s initializer\n", \
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name);
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static void test_check_init(struct kunit *test, const char *name,
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struct randstruct_untouched *untouched,
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struct randstruct_shuffled *shuffled)
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{
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DO_MANY_MEMBERS(check_mismatch)
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}
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static void test_check_mixed_init(struct kunit *test, const char *name,
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struct randstruct_mixed_untouched *untouched,
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struct randstruct_mixed_shuffled *shuffled)
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{
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DO_MANY_MEMBERS(check_mismatch)
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}
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#undef check_mismatch
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#define check_mismatch(x, ignore) \
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KUNIT_EXPECT_EQ_MSG(test, untouched->untouched.x, \
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shuffled->shuffled.x, \
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"Mismatched member value in %s initializer\n", \
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name);
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static void test_check_contained_init(struct kunit *test, const char *name,
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struct contains_randstruct_untouched *untouched,
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struct contains_randstruct_shuffled *shuffled)
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{
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DO_MANY_MEMBERS(check_mismatch)
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}
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#undef check_mismatch
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#define check_mismatch(x, ignore) \
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KUNIT_EXPECT_PTR_EQ_MSG(test, untouched->x, shuffled->x, \
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"Mismatched member value in %s initializer\n", \
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name);
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static void test_check_funcs_init(struct kunit *test, const char *name,
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struct randstruct_funcs_untouched *untouched,
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struct randstruct_funcs_shuffled *shuffled)
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{
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DO_MANY_MEMBERS(check_mismatch)
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}
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#undef check_mismatch
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static void randstruct_initializers(struct kunit *test)
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{
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#define init_members \
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.a = 1, \
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.b = 3, \
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.c = 5, \
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.d = 7, \
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.e = 11, \
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.f = 13, \
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.g = 17, \
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.h = 19,
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struct randstruct_untouched untouched = {
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init_members
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};
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struct randstruct_shuffled shuffled = {
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init_members
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};
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struct randstruct_mixed_untouched mixed_untouched = {
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init_members
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};
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struct randstruct_mixed_shuffled mixed_shuffled = {
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init_members
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};
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struct contains_randstruct_untouched contains_untouched = {
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.untouched = {
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init_members
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},
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};
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struct contains_randstruct_shuffled contains_shuffled = {
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.shuffled = {
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init_members
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},
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};
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#define func_member(x, ignored) \
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.x = func_##x,
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struct randstruct_funcs_untouched funcs_untouched = {
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DO_MANY_MEMBERS(func_member)
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};
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struct randstruct_funcs_shuffled funcs_shuffled = {
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DO_MANY_MEMBERS(func_member)
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};
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test_check_init(test, "named", &untouched, &shuffled);
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test_check_init(test, "unnamed", &untouched,
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&(struct randstruct_shuffled){
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init_members
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});
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test_check_contained_init(test, "named", &contains_untouched, &contains_shuffled);
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test_check_contained_init(test, "unnamed", &contains_untouched,
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&(struct contains_randstruct_shuffled){
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.shuffled = (struct randstruct_shuffled){
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init_members
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},
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});
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test_check_contained_init(test, "named", &contains_untouched, &contains_shuffled);
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test_check_contained_init(test, "unnamed copy", &contains_untouched,
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&(struct contains_randstruct_shuffled){
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/* full struct copy initializer */
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.shuffled = shuffled,
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});
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test_check_mixed_init(test, "named", &mixed_untouched, &mixed_shuffled);
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test_check_mixed_init(test, "unnamed", &mixed_untouched,
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&(struct randstruct_mixed_shuffled){
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init_members
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});
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test_check_funcs_init(test, "named", &funcs_untouched, &funcs_shuffled);
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test_check_funcs_init(test, "unnamed", &funcs_untouched,
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&(struct randstruct_funcs_shuffled){
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DO_MANY_MEMBERS(func_member)
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});
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#undef func_member
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#undef init_members
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}
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static int randstruct_test_init(struct kunit *test)
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{
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if (!IS_ENABLED(CONFIG_RANDSTRUCT))
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kunit_skip(test, "Not built with CONFIG_RANDSTRUCT=y");
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return 0;
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}
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static struct kunit_case randstruct_test_cases[] = {
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KUNIT_CASE(randstruct_layout),
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KUNIT_CASE(randstruct_initializers),
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{}
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};
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static struct kunit_suite randstruct_test_suite = {
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.name = "randstruct",
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.init = randstruct_test_init,
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.test_cases = randstruct_test_cases,
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};
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kunit_test_suites(&randstruct_test_suite);
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MODULE_DESCRIPTION("Test cases for struct randomization");
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MODULE_LICENSE("GPL");

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