| Andy Lutomirski | 8c49d9a | 2011-05-23 09:31:24 -0400 | [diff] [blame] | 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 | * |
| 13 | * Each of these variables lives in the vsyscall page, and each |
| 14 | * one needs a unique offset within the little piece of the page |
| 15 | * reserved for vvars. Specify that offset in DECLARE_VVAR. |
| 16 | * (There are 896 bytes available. If you mess up, the linker will |
| 17 | * catch it.) |
| 18 | */ |
| 19 | |
| 20 | /* Offset of vars within vsyscall page */ |
| 21 | #define VSYSCALL_VARS_OFFSET (3072 + 128) |
| 22 | |
| 23 | #if defined(__VVAR_KERNEL_LDS) |
| 24 | |
| 25 | /* The kernel linker script defines its own magic to put vvars in the |
| 26 | * right place. |
| 27 | */ |
| 28 | #define DECLARE_VVAR(offset, type, name) \ |
| 29 | EMIT_VVAR(name, VSYSCALL_VARS_OFFSET + offset) |
| 30 | |
| 31 | #else |
| 32 | |
| 33 | #define DECLARE_VVAR(offset, type, name) \ |
| 34 | static type const * const vvaraddr_ ## name = \ |
| 35 | (void *)(VSYSCALL_START + VSYSCALL_VARS_OFFSET + (offset)); |
| 36 | |
| 37 | #define DEFINE_VVAR(type, name) \ |
| 38 | type __vvar_ ## name \ |
| 39 | __attribute__((section(".vsyscall_var_" #name), aligned(16))) |
| 40 | |
| 41 | #define VVAR(name) (*vvaraddr_ ## name) |
| 42 | |
| 43 | #endif |
| 44 | |
| 45 | /* DECLARE_VVAR(offset, type, name) */ |
| 46 | |
| 47 | DECLARE_VVAR(0, volatile unsigned long, jiffies) |
| Andy Lutomirski | 6879eb2 | 2011-06-05 13:50:17 -0400 | [diff] [blame^] | 48 | DECLARE_VVAR(16, int, vgetcpu_mode) |
| Andy Lutomirski | 8c49d9a | 2011-05-23 09:31:24 -0400 | [diff] [blame] | 49 | DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data) |
| 50 | |
| 51 | #undef DECLARE_VVAR |
| 52 | #undef VSYSCALL_VARS_OFFSET |