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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 | * | |
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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.) | |
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17 | */ |
18 | ||
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19 | /* Base address of vvars. This is not ABI. */ |
20 | #define VVAR_ADDRESS (-10*1024*1024 - 4096) | |
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21 | |
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) |
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29 | |
30 | #else | |
31 | ||
32 | #define DECLARE_VVAR(offset, type, name) \ | |
33 | static type const * const vvaraddr_ ## name = \ | |
9fd67b4e | 34 | (void *)(VVAR_ADDRESS + (offset)); |
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35 | |
36 | #define DEFINE_VVAR(type, name) \ | |
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37 | type name \ |
38 | __attribute__((section(".vvar_" #name), aligned(16))) | |
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39 | |
40 | #define VVAR(name) (*vvaraddr_ ## name) | |
41 | ||
42 | #endif | |
43 | ||
44 | /* DECLARE_VVAR(offset, type, name) */ | |
45 | ||
46 | DECLARE_VVAR(0, volatile unsigned long, jiffies) | |
6879eb2d | 47 | DECLARE_VVAR(16, int, vgetcpu_mode) |
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48 | DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data) |
49 | ||
50 | #undef DECLARE_VVAR |