1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * vvar.h: Shared vDSO/kernel variable declarations
4 * Copyright (c) 2011 Andy Lutomirski
5 *
6 * A handful of variables are accessible (read-only) from userspace
7 * code in the vsyscall page and the vdso. They are declared here.
8 * Some other file must define them with DEFINE_VVAR.
9 *
10 * In normal kernel code, they are used like any other variable.
11 * In user code, they are accessed through the VVAR macro.
12 *
13 * These variables live in a page of kernel data that has an extra RO
14 * mapping for userspace. Each variable needs a unique offset within
15 * that page; specify that offset with the DECLARE_VVAR macro. (If
16 * you mess up, the linker will catch it.)
17 */
18
19 #ifndef _ASM_X86_VVAR_H
20 #define _ASM_X86_VVAR_H
21
22 #ifdef EMIT_VVAR
23 /*
24 * EMIT_VVAR() is used by the kernel linker script to put vvars in the
25 * right place. Also, it's used by kernel code to import offsets values.
26 */
27 #define DECLARE_VVAR(offset, type, name) \
28 EMIT_VVAR(name, offset)
29 #define DECLARE_VVAR_SINGLE(offset, type, name) \
30 EMIT_VVAR(name, offset)
31
32 #else
33
34 extern char __vvar_page;
35
36 #define DECLARE_VVAR(offset, type, name) \
37 extern type vvar_ ## name[CS_BASES] \
38 __attribute__((visibility("hidden"))); \
39 extern type timens_ ## name[CS_BASES] \
40 __attribute__((visibility("hidden"))); \
41
42 #define DECLARE_VVAR_SINGLE(offset, type, name) \
43 extern type vvar_ ## name \
44 __attribute__((visibility("hidden"))); \
45
46 #define VVAR(name) (vvar_ ## name)
47 #define TIMENS(name) (timens_ ## name)
48
49 #define DEFINE_VVAR(type, name) \
50 type name[CS_BASES] \
51 __attribute__((section(".vvar_" #name), aligned(16))) __visible
52
53 #define DEFINE_VVAR_SINGLE(type, name) \
54 type name \
55 __attribute__((section(".vvar_" #name), aligned(16))) __visible
56
57 #endif
58
59 /* DECLARE_VVAR(offset, type, name) */
60
61 DECLARE_VVAR(128, struct vdso_data, _vdso_data)
62
63 #if !defined(_SINGLE_DATA)
64 #define _SINGLE_DATA
65 DECLARE_VVAR_SINGLE(640, struct vdso_rng_data, _vdso_rng_data)
66 #endif
67
68 #undef DECLARE_VVAR
69 #undef DECLARE_VVAR_SINGLE
70
71 #endif
72
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