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 30 #else 31 32 extern char __vvar_page; 33 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"))); \ 39 40 #define VVAR(name) (vvar_ ## name) 41 #define TIMENS(name) (timens_ ## name) 42 43 #define DEFINE_VVAR(type, name) \ 44 type name[CS_BASES] \ 45 __attribute__((section(".vvar_" #name), aligned(16))) __visible 46 47 #endif 48 49 /* DECLARE_VVAR(offset, type, name) */ 50 51 DECLARE_VVAR(128, struct vdso_data, _vdso_data) 52 53 #undef DECLARE_VVAR 54 55 #endif 56