1 files changed, 55 insertions, 0 deletions
diff --git a/arch/x86/include/asm/vvar.h b/arch/x86/include/asm/vvar.h
new file mode 100644
index 000000000..183e98e49
--- /dev/null
+++ b/arch/x86/include/asm/vvar.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * vvar.h: Shared vDSO/kernel variable declarations
+ * Copyright (c) 2011 Andy Lutomirski
+ *
+ * A handful of variables are accessible (read-only) from userspace
+ * code in the vsyscall page and the vdso.  They are declared here.
+ * Some other file must define them with DEFINE_VVAR.
+ *
+ * In normal kernel code, they are used like any other variable.
+ * In user code, they are accessed through the VVAR macro.
+ *
+ * These variables live in a page of kernel data that has an extra RO
+ * mapping for userspace.  Each variable needs a unique offset within
+ * that page; specify that offset with the DECLARE_VVAR macro.  (If
+ * you mess up, the linker will catch it.)
+ */
+
+#ifndef _ASM_X86_VVAR_H
+#define _ASM_X86_VVAR_H
+
+#ifdef EMIT_VVAR
+/*
+ * EMIT_VVAR() is used by the kernel linker script to put vvars in the
+ * right place. Also, it's used by kernel code to import offsets values.
+ */
+#define DECLARE_VVAR(offset, type, name) \
+	EMIT_VVAR(name, offset)
+
+#else
+
+extern char __vvar_page;
+
+#define DECLARE_VVAR(offset, type, name)				\
+	extern type vvar_ ## name[CS_BASES]				\
+	__attribute__((visibility("hidden")));				\
+	extern type timens_ ## name[CS_BASES]				\
+	__attribute__((visibility("hidden")));				\
+
+#define VVAR(name) (vvar_ ## name)
+#define TIMENS(name) (timens_ ## name)
+
+#define DEFINE_VVAR(type, name)						\
+	type name[CS_BASES]						\
+	__attribute__((section(".vvar_" #name), aligned(16))) __visible
+
+#endif
+
+/* DECLARE_VVAR(offset, type, name) */
+
+DECLARE_VVAR(128, struct vdso_data, _vdso_data)
+
+#undef DECLARE_VVAR
+
+#endif