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1 | /* |
2 | * vvar.h: Shared vDSO/kernel variable declarations | |
3 | * Copyright (c) 2011 Andy Lutomirski | |
4 | * Subject to the GNU General Public License, version 2 | |
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 | * | |
9fd67b4e AL |
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.) | |
8c49d9a7 AL |
17 | */ |
18 | ||
7c03156f SS |
19 | #ifndef _ASM_X86_VVAR_H |
20 | #define _ASM_X86_VVAR_H | |
21 | ||
8c49d9a7 AL |
22 | #if defined(__VVAR_KERNEL_LDS) |
23 | ||
24 | /* The kernel linker script defines its own magic to put vvars in the | |
25 | * right place. | |
26 | */ | |
27 | #define DECLARE_VVAR(offset, type, name) \ | |
9fd67b4e | 28 | EMIT_VVAR(name, offset) |
8c49d9a7 AL |
29 | |
30 | #else | |
31 | ||
f40c3300 | 32 | extern char __vvar_page; |
ef721987 SS |
33 | |
34 | #define DECLARE_VVAR(offset, type, name) \ | |
35 | extern type vvar_ ## name __attribute__((visibility("hidden"))); | |
36 | ||
37 | #define VVAR(name) (vvar_ ## name) | |
38 | ||
8c49d9a7 | 39 | #define DEFINE_VVAR(type, name) \ |
9fd67b4e | 40 | type name \ |
28596b6a | 41 | __attribute__((section(".vvar_" #name), aligned(16))) __visible |
8c49d9a7 | 42 | |
8c49d9a7 AL |
43 | #endif |
44 | ||
45 | /* DECLARE_VVAR(offset, type, name) */ | |
46 | ||
8c49d9a7 AL |
47 | DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data) |
48 | ||
49 | #undef DECLARE_VVAR | |
7c03156f SS |
50 | |
51 | #endif |