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![Kees Cook](/assets/img/avatar_default.png)
Add whole-variable assignments of cast static initializers. These appear to currently behave like the direct initializers, but best to check them too. For example: struct test_big_hole var; var = (struct test_big_hole){ .one = arg->one, .two= arg->two, .three = arg->three, .four = arg->four }; Additionally adds a test for whole-object assignment, which is expected to fail since it usually falls back to a memcpy(): var = *arg; Suggested-by: Arnd Bergmann <arnd@arndb.de> Link: https://lore.kernel.org/lkml/CAK8P3a20SEoYCrp3jOK32oZc9OkiPv+1KTjNZ2GxLbHpY4WexQ@mail.gmail.com Cc: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20210723221933.3431999-4-keescook@chromium.org
514 lines
15 KiB
C
514 lines
15 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Test cases for compiler-based stack variable zeroing via
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* -ftrivial-auto-var-init={zero,pattern} or CONFIG_GCC_PLUGIN_STRUCTLEAK*.
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*
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* External build example:
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* clang -O2 -Wall -ftrivial-auto-var-init=pattern \
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* -o test_stackinit test_stackinit.c
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*/
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#ifdef __KERNEL__
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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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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#else
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/* Userspace headers. */
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#include <stdio.h>
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#include <stdint.h>
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#include <string.h>
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#include <stdbool.h>
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#include <errno.h>
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#include <sys/types.h>
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/* Linux kernel-ism stubs for stand-alone userspace build. */
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#define KBUILD_MODNAME "stackinit"
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#define pr_err(fmt, ...) fprintf(stderr, pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_warn(fmt, ...) fprintf(stderr, pr_fmt(fmt), ##__VA_ARGS__)
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#define pr_info(fmt, ...) fprintf(stdout, pr_fmt(fmt), ##__VA_ARGS__)
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#define __init /**/
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#define __exit /**/
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#define __user /**/
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#define noinline __attribute__((__noinline__))
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#define __aligned(x) __attribute__((__aligned__(x)))
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#ifdef __clang__
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# define __compiletime_error(message) /**/
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#else
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# define __compiletime_error(message) __attribute__((__error__(message)))
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#endif
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#define __compiletime_assert(condition, msg, prefix, suffix) \
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do { \
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extern void prefix ## suffix(void) __compiletime_error(msg); \
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if (!(condition)) \
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prefix ## suffix(); \
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} while (0)
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#define _compiletime_assert(condition, msg, prefix, suffix) \
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__compiletime_assert(condition, msg, prefix, suffix)
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#define compiletime_assert(condition, msg) \
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_compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
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#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
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#define BUILD_BUG_ON(condition) \
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BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
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typedef uint8_t u8;
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typedef uint16_t u16;
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typedef uint32_t u32;
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typedef uint64_t u64;
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#define module_init(func) static int (*do_init)(void) = func
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#define module_exit(func) static void (*do_exit)(void) = func
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#define MODULE_LICENSE(str) int main(void) { \
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int rc; \
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/* License: str */ \
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rc = do_init(); \
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if (rc == 0) \
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do_exit(); \
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return rc; \
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}
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#endif /* __KERNEL__ */
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/* Exfiltration buffer. */
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#define MAX_VAR_SIZE 128
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static u8 check_buf[MAX_VAR_SIZE];
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/* Character array to trigger stack protector in all functions. */
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#define VAR_BUFFER 32
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/* Volatile mask to convince compiler to copy memory with 0xff. */
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static volatile u8 forced_mask = 0xff;
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/* Location and size tracking to validate fill and test are colocated. */
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static void *fill_start, *target_start;
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static size_t fill_size, target_size;
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static bool range_contains(char *haystack_start, size_t haystack_size,
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char *needle_start, size_t needle_size)
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{
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if (needle_start >= haystack_start &&
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needle_start + needle_size <= haystack_start + haystack_size)
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return true;
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return false;
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}
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/* Whether the test is expected to fail. */
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#define WANT_SUCCESS 0
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#define XFAIL 1
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#define DO_NOTHING_TYPE_SCALAR(var_type) var_type
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#define DO_NOTHING_TYPE_STRING(var_type) void
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#define DO_NOTHING_TYPE_STRUCT(var_type) void
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#define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr)
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#define DO_NOTHING_RETURN_STRING(ptr) /**/
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#define DO_NOTHING_RETURN_STRUCT(ptr) /**/
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#define DO_NOTHING_CALL_SCALAR(var, name) \
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(var) = do_nothing_ ## name(&(var))
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#define DO_NOTHING_CALL_STRING(var, name) \
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do_nothing_ ## name(var)
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#define DO_NOTHING_CALL_STRUCT(var, name) \
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do_nothing_ ## name(&(var))
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#define FETCH_ARG_SCALAR(var) &var
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#define FETCH_ARG_STRING(var) var
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#define FETCH_ARG_STRUCT(var) &var
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#define FILL_SIZE_STRING 16
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#define INIT_CLONE_SCALAR /**/
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#define INIT_CLONE_STRING [FILL_SIZE_STRING]
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#define INIT_CLONE_STRUCT /**/
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#define ZERO_CLONE_SCALAR(zero) memset(&(zero), 0x00, sizeof(zero))
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#define ZERO_CLONE_STRING(zero) memset(&(zero), 0x00, sizeof(zero))
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/*
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* For the struct, intentionally poison padding to see if it gets
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* copied out in direct assignments.
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* */
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#define ZERO_CLONE_STRUCT(zero) \
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do { \
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memset(&(zero), 0xFF, sizeof(zero)); \
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zero.one = 0; \
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zero.two = 0; \
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zero.three = 0; \
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zero.four = 0; \
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} while (0)
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#define INIT_SCALAR_none(var_type) /**/
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#define INIT_SCALAR_zero(var_type) = 0
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#define INIT_STRING_none(var_type) [FILL_SIZE_STRING] /**/
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#define INIT_STRING_zero(var_type) [FILL_SIZE_STRING] = { }
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#define INIT_STRUCT_none(var_type) /**/
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#define INIT_STRUCT_zero(var_type) = { }
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#define __static_partial { .two = 0, }
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#define __static_all { .one = 0, \
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.two = 0, \
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.three = 0, \
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.four = 0, \
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}
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#define __dynamic_partial { .two = arg->two, }
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#define __dynamic_all { .one = arg->one, \
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.two = arg->two, \
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.three = arg->three, \
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.four = arg->four, \
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}
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#define __runtime_partial var.two = 0
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#define __runtime_all var.one = 0; \
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var.two = 0; \
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var.three = 0; \
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var.four = 0
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#define INIT_STRUCT_static_partial(var_type) \
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= __static_partial
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#define INIT_STRUCT_static_all(var_type) \
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= __static_all
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#define INIT_STRUCT_dynamic_partial(var_type) \
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= __dynamic_partial
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#define INIT_STRUCT_dynamic_all(var_type) \
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= __dynamic_all
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#define INIT_STRUCT_runtime_partial(var_type) \
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; __runtime_partial
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#define INIT_STRUCT_runtime_all(var_type) \
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; __runtime_all
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#define INIT_STRUCT_assigned_static_partial(var_type) \
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; var = (var_type)__static_partial
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#define INIT_STRUCT_assigned_static_all(var_type) \
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; var = (var_type)__static_all
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#define INIT_STRUCT_assigned_dynamic_partial(var_type) \
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; var = (var_type)__dynamic_partial
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#define INIT_STRUCT_assigned_dynamic_all(var_type) \
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; var = (var_type)__dynamic_all
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#define INIT_STRUCT_assigned_copy(var_type) \
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; var = *(arg)
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/*
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* @name: unique string name for the test
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* @var_type: type to be tested for zeroing initialization
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* @which: is this a SCALAR, STRING, or STRUCT type?
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* @init_level: what kind of initialization is performed
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* @xfail: is this test expected to fail?
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*/
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#define DEFINE_TEST_DRIVER(name, var_type, which, xfail) \
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/* Returns 0 on success, 1 on failure. */ \
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static noinline __init int test_ ## name (void) \
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{ \
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var_type zero INIT_CLONE_ ## which; \
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int ignored; \
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u8 sum = 0, i; \
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\
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/* Notice when a new test is larger than expected. */ \
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BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE); \
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\
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/* Fill clone type with zero for per-field init. */ \
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ZERO_CLONE_ ## which(zero); \
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/* Clear entire check buffer for 0xFF overlap test. */ \
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memset(check_buf, 0x00, sizeof(check_buf)); \
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/* Fill stack with 0xFF. */ \
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ignored = leaf_ ##name((unsigned long)&ignored, 1, \
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FETCH_ARG_ ## which(zero)); \
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/* Verify all bytes overwritten with 0xFF. */ \
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for (sum = 0, i = 0; i < target_size; i++) \
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sum += (check_buf[i] != 0xFF); \
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if (sum) { \
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pr_err(#name ": leaf fill was not 0xFF!?\n"); \
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return 1; \
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} \
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/* Clear entire check buffer for later bit tests. */ \
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memset(check_buf, 0x00, sizeof(check_buf)); \
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/* Extract stack-defined variable contents. */ \
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ignored = leaf_ ##name((unsigned long)&ignored, 0, \
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FETCH_ARG_ ## which(zero)); \
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\
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/* Validate that compiler lined up fill and target. */ \
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if (!range_contains(fill_start, fill_size, \
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target_start, target_size)) { \
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pr_err(#name ": stack fill missed target!?\n"); \
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pr_err(#name ": fill %zu wide\n", fill_size); \
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pr_err(#name ": target offset by %d\n", \
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(int)((ssize_t)(uintptr_t)fill_start - \
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(ssize_t)(uintptr_t)target_start)); \
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return 1; \
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} \
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\
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/* Look for any bytes still 0xFF in check region. */ \
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for (sum = 0, i = 0; i < target_size; i++) \
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sum += (check_buf[i] == 0xFF); \
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\
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if (sum == 0) { \
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pr_info(#name " ok\n"); \
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return 0; \
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} else { \
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pr_warn(#name " %sFAIL (uninit bytes: %d)\n", \
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(xfail) ? "X" : "", sum); \
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return (xfail) ? 0 : 1; \
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} \
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}
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#define DEFINE_TEST(name, var_type, which, init_level, xfail) \
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/* no-op to force compiler into ignoring "uninitialized" vars */\
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static noinline __init DO_NOTHING_TYPE_ ## which(var_type) \
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do_nothing_ ## name(var_type *ptr) \
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{ \
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/* Will always be true, but compiler doesn't know. */ \
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if ((unsigned long)ptr > 0x2) \
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return DO_NOTHING_RETURN_ ## which(ptr); \
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else \
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return DO_NOTHING_RETURN_ ## which(ptr + 1); \
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} \
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static noinline __init int leaf_ ## name(unsigned long sp, \
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bool fill, \
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var_type *arg) \
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{ \
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char buf[VAR_BUFFER]; \
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var_type var \
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INIT_ ## which ## _ ## init_level(var_type); \
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\
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target_start = &var; \
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target_size = sizeof(var); \
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/* \
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* Keep this buffer around to make sure we've got a \
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* stack frame of SOME kind... \
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*/ \
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memset(buf, (char)(sp & 0xff), sizeof(buf)); \
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/* Fill variable with 0xFF. */ \
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if (fill) { \
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fill_start = &var; \
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fill_size = sizeof(var); \
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memset(fill_start, \
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(char)((sp & 0xff) | forced_mask), \
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fill_size); \
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} \
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\
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/* Silence "never initialized" warnings. */ \
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DO_NOTHING_CALL_ ## which(var, name); \
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\
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/* Exfiltrate "var". */ \
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memcpy(check_buf, target_start, target_size); \
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\
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return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \
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} \
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DEFINE_TEST_DRIVER(name, var_type, which, xfail)
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/* Structure with no padding. */
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struct test_packed {
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unsigned long one;
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unsigned long two;
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unsigned long three;
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unsigned long four;
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};
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/* Simple structure with padding likely to be covered by compiler. */
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struct test_small_hole {
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size_t one;
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char two;
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/* 3 byte padding hole here. */
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int three;
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unsigned long four;
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};
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/* Trigger unhandled padding in a structure. */
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struct test_big_hole {
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u8 one;
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u8 two;
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u8 three;
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/* 61 byte padding hole here. */
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u8 four __aligned(64);
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} __aligned(64);
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struct test_trailing_hole {
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char *one;
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char *two;
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char *three;
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char four;
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/* "sizeof(unsigned long) - 1" byte padding hole here. */
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};
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/* Test if STRUCTLEAK is clearing structs with __user fields. */
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struct test_user {
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u8 one;
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unsigned long two;
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char __user *three;
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unsigned long four;
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};
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#define DEFINE_SCALAR_TEST(name, init, xfail) \
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DEFINE_TEST(name ## _ ## init, name, SCALAR, \
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init, xfail)
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#define DEFINE_SCALAR_TESTS(init, xfail) \
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DEFINE_SCALAR_TEST(u8, init, xfail); \
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DEFINE_SCALAR_TEST(u16, init, xfail); \
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DEFINE_SCALAR_TEST(u32, init, xfail); \
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DEFINE_SCALAR_TEST(u64, init, xfail); \
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DEFINE_TEST(char_array_ ## init, unsigned char, \
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STRING, init, xfail)
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#define DEFINE_STRUCT_TEST(name, init, xfail) \
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DEFINE_TEST(name ## _ ## init, \
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struct test_ ## name, STRUCT, init, \
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xfail)
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#define DEFINE_STRUCT_TESTS(init, xfail) \
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DEFINE_STRUCT_TEST(small_hole, init, xfail); \
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DEFINE_STRUCT_TEST(big_hole, init, xfail); \
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DEFINE_STRUCT_TEST(trailing_hole, init, xfail); \
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DEFINE_STRUCT_TEST(packed, init, xfail)
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#define DEFINE_STRUCT_INITIALIZER_TESTS(base) \
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DEFINE_STRUCT_TESTS(base ## _ ## partial, \
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WANT_SUCCESS); \
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DEFINE_STRUCT_TESTS(base ## _ ## all, \
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WANT_SUCCESS)
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/* These should be fully initialized all the time! */
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DEFINE_SCALAR_TESTS(zero, WANT_SUCCESS);
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DEFINE_STRUCT_TESTS(zero, WANT_SUCCESS);
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/* Struct initializers: padding may be left uninitialized. */
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DEFINE_STRUCT_INITIALIZER_TESTS(static);
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DEFINE_STRUCT_INITIALIZER_TESTS(dynamic);
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DEFINE_STRUCT_INITIALIZER_TESTS(runtime);
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DEFINE_STRUCT_INITIALIZER_TESTS(assigned_static);
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DEFINE_STRUCT_INITIALIZER_TESTS(assigned_dynamic);
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DEFINE_STRUCT_TESTS(assigned_copy, XFAIL);
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/* No initialization without compiler instrumentation. */
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DEFINE_SCALAR_TESTS(none, WANT_SUCCESS);
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DEFINE_STRUCT_TESTS(none, WANT_SUCCESS);
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/* Initialization of members with __user attribute. */
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DEFINE_TEST(user, struct test_user, STRUCT, none, WANT_SUCCESS);
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/*
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* Check two uses through a variable declaration outside either path,
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* which was noticed as a special case in porting earlier stack init
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* compiler logic.
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*/
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static int noinline __leaf_switch_none(int path, bool fill)
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{
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switch (path) {
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/*
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* This is intentionally unreachable. To silence the
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* warning, build with -Wno-switch-unreachable
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*/
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uint64_t var;
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case 1:
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target_start = &var;
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target_size = sizeof(var);
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if (fill) {
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fill_start = &var;
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fill_size = sizeof(var);
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memset(fill_start, forced_mask | 0x55, fill_size);
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}
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memcpy(check_buf, target_start, target_size);
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break;
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case 2:
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target_start = &var;
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target_size = sizeof(var);
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if (fill) {
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fill_start = &var;
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fill_size = sizeof(var);
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memset(fill_start, forced_mask | 0xaa, fill_size);
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}
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memcpy(check_buf, target_start, target_size);
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break;
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default:
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var = 5;
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return var & forced_mask;
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}
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return 0;
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}
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static noinline __init int leaf_switch_1_none(unsigned long sp, bool fill,
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uint64_t *arg)
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{
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return __leaf_switch_none(1, fill);
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}
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static noinline __init int leaf_switch_2_none(unsigned long sp, bool fill,
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uint64_t *arg)
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{
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return __leaf_switch_none(2, fill);
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}
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/*
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* These are expected to fail for most configurations because neither
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* GCC nor Clang have a way to perform initialization of variables in
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* non-code areas (i.e. in a switch statement before the first "case").
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* https://bugs.llvm.org/show_bug.cgi?id=44916
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*/
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DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, XFAIL);
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DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, XFAIL);
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static int __init test_stackinit_init(void)
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{
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unsigned int failures = 0;
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#define test_scalars(init) do { \
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failures += test_u8_ ## init (); \
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failures += test_u16_ ## init (); \
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failures += test_u32_ ## init (); \
|
|
failures += test_u64_ ## init (); \
|
|
failures += test_char_array_ ## init (); \
|
|
} while (0)
|
|
|
|
#define test_structs(init) do { \
|
|
failures += test_small_hole_ ## init (); \
|
|
failures += test_big_hole_ ## init (); \
|
|
failures += test_trailing_hole_ ## init (); \
|
|
failures += test_packed_ ## init (); \
|
|
} while (0)
|
|
|
|
/* These are explicitly initialized and should always pass. */
|
|
test_scalars(zero);
|
|
test_structs(zero);
|
|
/* Padding here appears to be accidentally always initialized? */
|
|
test_structs(dynamic_partial);
|
|
test_structs(assigned_dynamic_partial);
|
|
/* Padding initialization depends on compiler behaviors. */
|
|
test_structs(static_partial);
|
|
test_structs(static_all);
|
|
test_structs(dynamic_all);
|
|
test_structs(runtime_partial);
|
|
test_structs(runtime_all);
|
|
test_structs(assigned_static_partial);
|
|
test_structs(assigned_static_all);
|
|
test_structs(assigned_dynamic_all);
|
|
/* Everything fails this since it effectively performs a memcpy(). */
|
|
test_structs(assigned_copy);
|
|
|
|
/* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
|
|
test_scalars(none);
|
|
failures += test_switch_1_none();
|
|
failures += test_switch_2_none();
|
|
|
|
/* STRUCTLEAK_BYREF should cover from here down. */
|
|
test_structs(none);
|
|
|
|
/* STRUCTLEAK will only cover this. */
|
|
failures += test_user();
|
|
|
|
if (failures == 0)
|
|
pr_info("all tests passed!\n");
|
|
else
|
|
pr_err("failures: %u\n", failures);
|
|
|
|
return failures ? -EINVAL : 0;
|
|
}
|
|
module_init(test_stackinit_init);
|
|
|
|
static void __exit test_stackinit_exit(void)
|
|
{ }
|
|
module_exit(test_stackinit_exit);
|
|
|
|
MODULE_LICENSE("GPL");
|