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 * 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 /* Base address of vvars. This is not ABI. */ 20 #define VVAR_ADDRESS (-10*1024*1024 - 4096) 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) \ 28 EMIT_VVAR(name, offset) 29 30 #else 31 32 #define DECLARE_VVAR(offset, type, name) \ 33 static type const * const vvaraddr_ ## name = \ 34 (void *)(VVAR_ADDRESS + (offset)); 35 36 #define DEFINE_VVAR(type, name) \ 37 type name \ 38 __attribute__((section(".vvar_" #name), aligned(16))) 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) 47 DECLARE_VVAR(16, int, vgetcpu_mode) 48 DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data) 49 50 #undef DECLARE_VVAR 51