1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __ASM_GENERIC_ACCESS_OK_H__
3 #define __ASM_GENERIC_ACCESS_OK_H__
4
5 /*
6 * Checking whether a pointer is valid for user space access.
7 * These definitions work on most architectures, but overrides can
8 * be used where necessary.
9 */
10
11 /*
12 * architectures with compat tasks have a variable TASK_SIZE and should
13 * override this to a constant.
14 */
15 #ifndef TASK_SIZE_MAX
16 #define TASK_SIZE_MAX TASK_SIZE
17 #endif
18
19 #ifndef __access_ok
20 /*
21 * 'size' is a compile-time constant for most callers, so optimize for
22 * this case to turn the check into a single comparison against a constant
23 * limit and catch all possible overflows.
24 * On architectures with separate user address space (m68k, s390, parisc,
25 * sparc64) or those without an MMU, this should always return true.
26 *
27 * This version was originally contributed by Jonas Bonn for the
28 * OpenRISC architecture, and was found to be the most efficient
29 * for constant 'size' and 'limit' values.
30 */
31 static inline int __access_ok(const void __user *ptr, unsigned long size)
32 {
33 unsigned long limit = TASK_SIZE_MAX;
34 unsigned long addr = (unsigned long)ptr;
35
36 if (IS_ENABLED(CONFIG_ALTERNATE_USER_ADDRESS_SPACE) ||
37 !IS_ENABLED(CONFIG_MMU))
38 return true;
39
40 return (size <= limit) && (addr <= (limit - size));
41 }
42 #endif
43
44 #ifndef access_ok
45 #define access_ok(addr, size) likely(__access_ok(addr, size))
46 #endif
47
48 #endif
49
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