| b.liu | e958203 | 2025-04-17 19:18:16 +0800 | [diff] [blame^] | 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 | #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 | extern char __vvar_page; |
| 33 | |
| 34 | #define DECLARE_VVAR(offset, type, name) \ |
| 35 | extern type vvar_ ## name[CS_BASES] \ |
| 36 | __attribute__((visibility("hidden"))); |
| 37 | |
| 38 | #define VVAR(name) (vvar_ ## name) |
| 39 | |
| 40 | #define DEFINE_VVAR(type, name) \ |
| 41 | type name[CS_BASES] \ |
| 42 | __attribute__((section(".vvar_" #name), aligned(16))) __visible |
| 43 | |
| 44 | #endif |
| 45 | |
| 46 | /* DECLARE_VVAR(offset, type, name) */ |
| 47 | |
| 48 | DECLARE_VVAR(128, struct vdso_data, _vdso_data) |
| 49 | |
| 50 | #undef DECLARE_VVAR |
| 51 | |
| 52 | #endif |