text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * Test cases for compiler-based stack variable zeroing via
   * -ftrivial-auto-var-init={zero,pattern} or CONFIG_GCC_PLUGIN_STRUCTLEAK*.
   * For example, see:
   * https://www.kernel.org/doc/html/latest/dev-tools/kunit/kunit-tool.html#configuring-building-and-running-tests
   *	./tools/testing/kunit/kunit.py run stackinit [--raw_output] \
   *		--make_option LLVM=1 \
   *		--kconfig_add CONFIG_INIT_STACK_ALL_ZERO=y
   *
   */
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <kunit/test.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/string.h>
  
  /* Exfiltration buffer. */
  #define MAX_VAR_SIZE	128
  static u8 check_buf[MAX_VAR_SIZE];
  
  /* Character array to trigger stack protector in all functions. */
  #define VAR_BUFFER	 32
  
  /* Volatile mask to convince compiler to copy memory with 0xff. */
  static volatile u8 forced_mask = 0xff;
  
  /* Location and size tracking to validate fill and test are colocated. */
  static void *fill_start, *target_start;
  static size_t fill_size, target_size;
  
  static bool range_contains(char *haystack_start, size_t haystack_size,
  			   char *needle_start, size_t needle_size)
  {
  	if (needle_start >= haystack_start &&
  	    needle_start + needle_size <= haystack_start + haystack_size)
  		return true;
  	return false;
  }
  
  /* Whether the test is expected to fail. */
  #define WANT_SUCCESS				0
  #define XFAIL					1
  
  #define DO_NOTHING_TYPE_SCALAR(var_type)	var_type
  #define DO_NOTHING_TYPE_STRING(var_type)	void
  #define DO_NOTHING_TYPE_STRUCT(var_type)	void
  
  #define DO_NOTHING_RETURN_SCALAR(ptr)		*(ptr)
  #define DO_NOTHING_RETURN_STRING(ptr)		/**/
  #define DO_NOTHING_RETURN_STRUCT(ptr)		/**/
  
  #define DO_NOTHING_CALL_SCALAR(var, name)			\
  		(var) = do_nothing_ ## name(&(var))
  #define DO_NOTHING_CALL_STRING(var, name)			\
  		do_nothing_ ## name(var)
  #define DO_NOTHING_CALL_STRUCT(var, name)			\
  		do_nothing_ ## name(&(var))
  
  #define FETCH_ARG_SCALAR(var)		&var
  #define FETCH_ARG_STRING(var)		var
  #define FETCH_ARG_STRUCT(var)		&var
  
  #define FILL_SIZE_STRING		16
  
  #define INIT_CLONE_SCALAR		/**/
  #define INIT_CLONE_STRING		[FILL_SIZE_STRING]
  #define INIT_CLONE_STRUCT		/**/
  
  #define ZERO_CLONE_SCALAR(zero)		memset(&(zero), 0x00, sizeof(zero))
  #define ZERO_CLONE_STRING(zero)		memset(&(zero), 0x00, sizeof(zero))
  /*
   * For the struct, intentionally poison padding to see if it gets
   * copied out in direct assignments.
   * */
  #define ZERO_CLONE_STRUCT(zero)				\
  	do {						\
  		memset(&(zero), 0xFF, sizeof(zero));	\
  		zero.one = 0;				\
  		zero.two = 0;				\
  		zero.three = 0;				\
  		zero.four = 0;				\
  	} while (0)
  
  #define INIT_SCALAR_none(var_type)	/**/
  #define INIT_SCALAR_zero(var_type)	= 0
  
  #define INIT_STRING_none(var_type)	[FILL_SIZE_STRING] /**/
  #define INIT_STRING_zero(var_type)	[FILL_SIZE_STRING] = { }
  
  #define INIT_STRUCT_none(var_type)	/**/
  #define INIT_STRUCT_zero(var_type)	= { }
  
  
  #define __static_partial		{ .two = 0, }
  #define __static_all			{ .one = 0,			\
  					  .two = 0,			\
  					  .three = 0,			\
  					  .four = 0,			\
  					}
  #define __dynamic_partial		{ .two = arg->two, }
  #define __dynamic_all			{ .one = arg->one,		\
  					  .two = arg->two,		\
  					  .three = arg->three,		\
  					  .four = arg->four,		\
  					}
  #define __runtime_partial		var.two = 0
  #define __runtime_all			var.one = 0;			\
  					var.two = 0;			\
  					var.three = 0;			\
  					var.four = 0
  
  #define INIT_STRUCT_static_partial(var_type)				\
  					= __static_partial
  #define INIT_STRUCT_static_all(var_type)				\
  					= __static_all
  #define INIT_STRUCT_dynamic_partial(var_type)				\
  					= __dynamic_partial
  #define INIT_STRUCT_dynamic_all(var_type)				\
  					= __dynamic_all
  #define INIT_STRUCT_runtime_partial(var_type)				\
  					; __runtime_partial
  #define INIT_STRUCT_runtime_all(var_type)				\
  					; __runtime_all
  
  #define INIT_STRUCT_assigned_static_partial(var_type)			\
  					; var = (var_type)__static_partial
  #define INIT_STRUCT_assigned_static_all(var_type)			\
  					; var = (var_type)__static_all
  #define INIT_STRUCT_assigned_dynamic_partial(var_type)			\
  					; var = (var_type)__dynamic_partial
  #define INIT_STRUCT_assigned_dynamic_all(var_type)			\
  					; var = (var_type)__dynamic_all
  
  #define INIT_STRUCT_assigned_copy(var_type)				\
  					; var = *(arg)
  
  /*
   * @name: unique string name for the test
   * @var_type: type to be tested for zeroing initialization
   * @which: is this a SCALAR, STRING, or STRUCT type?
   * @init_level: what kind of initialization is performed
   * @xfail: is this test expected to fail?
   */
  #define DEFINE_TEST_DRIVER(name, var_type, which, xfail)	\
  /* Returns 0 on success, 1 on failure. */			\
  static noinline void test_ ## name (struct kunit *test)		\
  {								\
  	var_type zero INIT_CLONE_ ## which;			\
  	int ignored;						\
  	u8 sum = 0, i;						\
  								\
  	/* Notice when a new test is larger than expected. */	\
  	BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE);		\
  								\
  	/* Fill clone type with zero for per-field init. */	\
  	ZERO_CLONE_ ## which(zero);				\
  	/* Clear entire check buffer for 0xFF overlap test. */	\
  	memset(check_buf, 0x00, sizeof(check_buf));		\
  	/* Fill stack with 0xFF. */				\
  	ignored = leaf_ ##name((unsigned long)&ignored, 1,	\
  				FETCH_ARG_ ## which(zero));	\
  	/* Verify all bytes overwritten with 0xFF. */		\
  	for (sum = 0, i = 0; i < target_size; i++)		\
  		sum += (check_buf[i] != 0xFF);			\
  	KUNIT_ASSERT_EQ_MSG(test, sum, 0,			\
  			    "leaf fill was not 0xFF!?\n");	\
  	/* Clear entire check buffer for later bit tests. */	\
  	memset(check_buf, 0x00, sizeof(check_buf));		\
  	/* Extract stack-defined variable contents. */		\
  	ignored = leaf_ ##name((unsigned long)&ignored, 0,	\
  				FETCH_ARG_ ## which(zero));	\
  								\
  	/* Validate that compiler lined up fill and target. */	\
  	KUNIT_ASSERT_TRUE_MSG(test,				\
  		range_contains(fill_start, fill_size,		\
  			    target_start, target_size),		\
  		"stack fill missed target!? "			\
  		"(fill %zu wide, target offset by %d)\n",	\
  		fill_size,					\
  		(int)((ssize_t)(uintptr_t)fill_start -		\
  		      (ssize_t)(uintptr_t)target_start));	\
  								\
  	/* Look for any bytes still 0xFF in check region. */	\
  	for (sum = 0, i = 0; i < target_size; i++)		\
  		sum += (check_buf[i] == 0xFF);			\
  								\
  	if (sum != 0 && xfail)					\
  		kunit_skip(test,				\
  			   "XFAIL uninit bytes: %d\n",		\
  			   sum);				\
  	KUNIT_ASSERT_EQ_MSG(test, sum, 0,			\
  		"uninit bytes: %d\n", sum);			\
  }
  #define DEFINE_TEST(name, var_type, which, init_level, xfail)	\
  /* no-op to force compiler into ignoring "uninitialized" vars */\
  static noinline DO_NOTHING_TYPE_ ## which(var_type)		\
  do_nothing_ ## name(var_type *ptr)				\
  {								\
  	/* Will always be true, but compiler doesn't know. */	\
  	if ((unsigned long)ptr > 0x2)				\
  		return DO_NOTHING_RETURN_ ## which(ptr);	\
  	else							\
  		return DO_NOTHING_RETURN_ ## which(ptr + 1);	\
  }								\
  static noinline int leaf_ ## name(unsigned long sp, bool fill,	\
  				  var_type *arg)		\
  {								\
  	char buf[VAR_BUFFER];					\
  	var_type var						\
  		INIT_ ## which ## _ ## init_level(var_type);	\
  								\
  	target_start = &var;					\
  	target_size = sizeof(var);				\
  	/*							\
  	 * Keep this buffer around to make sure we've got a	\
  	 * stack frame of SOME kind...				\
  	 */							\
  	memset(buf, (char)(sp & 0xff), sizeof(buf));		\
  	/* Fill variable with 0xFF. */				\
  	if (fill) {						\
  		fill_start = &var;				\
  		fill_size = sizeof(var);			\
  		memset(fill_start,				\
  		       (char)((sp & 0xff) | forced_mask),	\
  		       fill_size);				\
  	}							\
  								\
  	/* Silence "never initialized" warnings. */		\
  	DO_NOTHING_CALL_ ## which(var, name);			\
  								\
  	/* Exfiltrate "var". */					\
  	memcpy(check_buf, target_start, target_size);		\
  								\
  	return (int)buf[0] | (int)buf[sizeof(buf) - 1];		\
  }								\
  DEFINE_TEST_DRIVER(name, var_type, which, xfail)
  
  /* Structure with no padding. */
  struct test_packed {
  	unsigned long one;
  	unsigned long two;
  	unsigned long three;
  	unsigned long four;
  };
  
  /* Simple structure with padding likely to be covered by compiler. */
  struct test_small_hole {
  	size_t one;
  	char two;
  	/* 3 byte padding hole here. */
  	int three;
  	unsigned long four;
  };
  
  /* Trigger unhandled padding in a structure. */
  struct test_big_hole {
  	u8 one;
  	u8 two;
  	u8 three;
  	/* 61 byte padding hole here. */
  	u8 four __aligned(64);
  } __aligned(64);
  
  struct test_trailing_hole {
  	char *one;
  	char *two;
  	char *three;
  	char four;
  	/* "sizeof(unsigned long) - 1" byte padding hole here. */
  };
  
  /* Test if STRUCTLEAK is clearing structs with __user fields. */
  struct test_user {
  	u8 one;
  	unsigned long two;
  	char __user *three;
  	unsigned long four;
  };
  
  #define ALWAYS_PASS	WANT_SUCCESS
  #define ALWAYS_FAIL	XFAIL
  
  #ifdef CONFIG_INIT_STACK_NONE
  # define USER_PASS	XFAIL
  # define BYREF_PASS	XFAIL
  # define STRONG_PASS	XFAIL
  #elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_USER)
  # define USER_PASS	WANT_SUCCESS
  # define BYREF_PASS	XFAIL
  # define STRONG_PASS	XFAIL
  #elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF)
  # define USER_PASS	WANT_SUCCESS
  # define BYREF_PASS	WANT_SUCCESS
  # define STRONG_PASS	XFAIL
  #else
  # define USER_PASS	WANT_SUCCESS
  # define BYREF_PASS	WANT_SUCCESS
  # define STRONG_PASS	WANT_SUCCESS
  #endif
  
  #define DEFINE_SCALAR_TEST(name, init, xfail)			\
  		DEFINE_TEST(name ## _ ## init, name, SCALAR,	\
  			    init, xfail)
  
  #define DEFINE_SCALAR_TESTS(init, xfail)			\
  		DEFINE_SCALAR_TEST(u8, init, xfail);		\
  		DEFINE_SCALAR_TEST(u16, init, xfail);		\
  		DEFINE_SCALAR_TEST(u32, init, xfail);		\
  		DEFINE_SCALAR_TEST(u64, init, xfail);		\
  		DEFINE_TEST(char_array_ ## init, unsigned char,	\
  			    STRING, init, xfail)
  
  #define DEFINE_STRUCT_TEST(name, init, xfail)			\
  		DEFINE_TEST(name ## _ ## init,			\
  			    struct test_ ## name, STRUCT, init, \
  			    xfail)
  
  #define DEFINE_STRUCT_TESTS(init, xfail)			\
  		DEFINE_STRUCT_TEST(small_hole, init, xfail);	\
  		DEFINE_STRUCT_TEST(big_hole, init, xfail);	\
  		DEFINE_STRUCT_TEST(trailing_hole, init, xfail);	\
  		DEFINE_STRUCT_TEST(packed, init, xfail)
  
  #define DEFINE_STRUCT_INITIALIZER_TESTS(base, xfail)		\
  		DEFINE_STRUCT_TESTS(base ## _ ## partial,	\
  				    xfail);			\
  		DEFINE_STRUCT_TESTS(base ## _ ## all, xfail)
  
  /* These should be fully initialized all the time! */
  DEFINE_SCALAR_TESTS(zero, ALWAYS_PASS);
  DEFINE_STRUCT_TESTS(zero, ALWAYS_PASS);
  /* Struct initializers: padding may be left uninitialized. */
  DEFINE_STRUCT_INITIALIZER_TESTS(static, STRONG_PASS);
  DEFINE_STRUCT_INITIALIZER_TESTS(dynamic, STRONG_PASS);
  DEFINE_STRUCT_INITIALIZER_TESTS(runtime, STRONG_PASS);
  DEFINE_STRUCT_INITIALIZER_TESTS(assigned_static, STRONG_PASS);
  DEFINE_STRUCT_INITIALIZER_TESTS(assigned_dynamic, STRONG_PASS);
  DEFINE_STRUCT_TESTS(assigned_copy, ALWAYS_FAIL);
  /* No initialization without compiler instrumentation. */
  DEFINE_SCALAR_TESTS(none, STRONG_PASS);
  DEFINE_STRUCT_TESTS(none, BYREF_PASS);
  /* Initialization of members with __user attribute. */
  DEFINE_TEST(user, struct test_user, STRUCT, none, USER_PASS);
  
  /*
   * Check two uses through a variable declaration outside either path,
   * which was noticed as a special case in porting earlier stack init
   * compiler logic.
   */
  static int noinline __leaf_switch_none(int path, bool fill)
  {
  	switch (path) {
  		/*
  		 * This is intentionally unreachable. To silence the
  		 * warning, build with -Wno-switch-unreachable
  		 */
  		uint64_t var[10];
  
  	case 1:
  		target_start = &var;
  		target_size = sizeof(var);
  		if (fill) {
  			fill_start = &var;
  			fill_size = sizeof(var);
  
  			memset(fill_start, forced_mask | 0x55, fill_size);
  		}
  		memcpy(check_buf, target_start, target_size);
  		break;
  	case 2:
  		target_start = &var;
  		target_size = sizeof(var);
  		if (fill) {
  			fill_start = &var;
  			fill_size = sizeof(var);
  
  			memset(fill_start, forced_mask | 0xaa, fill_size);
  		}
  		memcpy(check_buf, target_start, target_size);
  		break;
  	default:
  		var[1] = 5;
  		return var[1] & forced_mask;
  	}
  	return 0;
  }
  
  static noinline int leaf_switch_1_none(unsigned long sp, bool fill,
  					      uint64_t *arg)
  {
  	return __leaf_switch_none(1, fill);
  }
  
  static noinline int leaf_switch_2_none(unsigned long sp, bool fill,
  					      uint64_t *arg)
  {
  	return __leaf_switch_none(2, fill);
  }
  
  /*
   * These are expected to fail for most configurations because neither
   * GCC nor Clang have a way to perform initialization of variables in
   * non-code areas (i.e. in a switch statement before the first "case").
   * https://bugs.llvm.org/show_bug.cgi?id=44916
   */
  DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, ALWAYS_FAIL);
  DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, ALWAYS_FAIL);
  
  #define KUNIT_test_scalars(init)			\
  		KUNIT_CASE(test_u8_ ## init),		\
  		KUNIT_CASE(test_u16_ ## init),		\
  		KUNIT_CASE(test_u32_ ## init),		\
  		KUNIT_CASE(test_u64_ ## init),		\
  		KUNIT_CASE(test_char_array_ ## init)
  
  #define KUNIT_test_structs(init)			\
  		KUNIT_CASE(test_small_hole_ ## init),	\
  		KUNIT_CASE(test_big_hole_ ## init),	\
  		KUNIT_CASE(test_trailing_hole_ ## init),\
  		KUNIT_CASE(test_packed_ ## init)	\
  
  static struct kunit_case stackinit_test_cases[] = {
  	/* These are explicitly initialized and should always pass. */
  	KUNIT_test_scalars(zero),
  	KUNIT_test_structs(zero),
  	/* Padding here appears to be accidentally always initialized? */
  	KUNIT_test_structs(dynamic_partial),
  	KUNIT_test_structs(assigned_dynamic_partial),
  	/* Padding initialization depends on compiler behaviors. */
  	KUNIT_test_structs(static_partial),
  	KUNIT_test_structs(static_all),
  	KUNIT_test_structs(dynamic_all),
  	KUNIT_test_structs(runtime_partial),
  	KUNIT_test_structs(runtime_all),
  	KUNIT_test_structs(assigned_static_partial),
  	KUNIT_test_structs(assigned_static_all),
  	KUNIT_test_structs(assigned_dynamic_all),
  	/* Everything fails this since it effectively performs a memcpy(). */
  	KUNIT_test_structs(assigned_copy),
  	/* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
  	KUNIT_test_scalars(none),
  	KUNIT_CASE(test_switch_1_none),
  	KUNIT_CASE(test_switch_2_none),
  	/* STRUCTLEAK_BYREF should cover from here down. */
  	KUNIT_test_structs(none),
  	/* STRUCTLEAK will only cover this. */
  	KUNIT_CASE(test_user),
  	{}
  };
  
  static struct kunit_suite stackinit_test_suite = {
  	.name = "stackinit",
  	.test_cases = stackinit_test_cases,
  };
  
  kunit_test_suites(&stackinit_test_suite);
  
  MODULE_LICENSE("GPL");
  