Linux 5.7.6
[linux/fpc-iii.git] / arch / x86 / include / asm / vvar.h
blob183e98e49ab943aeaf9e7ecc183c2f383545887d
1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * vvar.h: Shared vDSO/kernel variable declarations
4 * Copyright (c) 2011 Andy Lutomirski
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.
10 * In normal kernel code, they are used like any other variable.
11 * In user code, they are accessed through the VVAR macro.
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.)
19 #ifndef _ASM_X86_VVAR_H
20 #define _ASM_X86_VVAR_H
22 #ifdef EMIT_VVAR
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.
27 #define DECLARE_VVAR(offset, type, name) \
28 EMIT_VVAR(name, offset)
30 #else
32 extern char __vvar_page;
34 #define DECLARE_VVAR(offset, type, name) \
35 extern type vvar_ ## name[CS_BASES] \
36 __attribute__((visibility("hidden"))); \
37 extern type timens_ ## name[CS_BASES] \
38 __attribute__((visibility("hidden"))); \
40 #define VVAR(name) (vvar_ ## name)
41 #define TIMENS(name) (timens_ ## name)
43 #define DEFINE_VVAR(type, name) \
44 type name[CS_BASES] \
45 __attribute__((section(".vvar_" #name), aligned(16))) __visible
47 #endif
49 /* DECLARE_VVAR(offset, type, name) */
51 DECLARE_VVAR(128, struct vdso_data, _vdso_data)
53 #undef DECLARE_VVAR
55 #endif