1 files changed, 52 insertions, 0 deletions
diff --git a/arch/x86/include/asm/vvar.h b/arch/x86/include/asm/vvar.h
new file mode 100644
index 000000000000..341b3559452b
--- /dev/null
+++ b/arch/x86/include/asm/vvar.h
@@ -0,0 +1,52 @@
+/*
+ * vvar.h: Shared vDSO/kernel variable declarations
+ * Copyright (c) 2011 Andy Lutomirski
+ * Subject to the GNU General Public License, version 2
+ *
+ * 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.
+ *
+ * Each of these variables lives in the vsyscall page, and each
+ * one needs a unique offset within the little piece of the page
+ * reserved for vvars.  Specify that offset in DECLARE_VVAR.
+ * (There are 896 bytes available.  If you mess up, the linker will
+ * catch it.)
+ */
+
+/* Offset of vars within vsyscall page */
+#define VSYSCALL_VARS_OFFSET (3072 + 128)
+
+#if defined(__VVAR_KERNEL_LDS)
+
+/* The kernel linker script defines its own magic to put vvars in the
+ * right place.
+ */
+#define DECLARE_VVAR(offset, type, name) \
+	EMIT_VVAR(name, VSYSCALL_VARS_OFFSET + offset)
+
+#else
+
+#define DECLARE_VVAR(offset, type, name)				\
+	static type const * const vvaraddr_ ## name =			\
+		(void *)(VSYSCALL_START + VSYSCALL_VARS_OFFSET + (offset));
+
+#define DEFINE_VVAR(type, name)						\
+	type __vvar_ ## name						\
+	__attribute__((section(".vsyscall_var_" #name), aligned(16)))
+
+#define VVAR(name) (*vvaraddr_ ## name)
+
+#endif
+
+/* DECLARE_VVAR(offset, type, name) */
+
+DECLARE_VVAR(0, volatile unsigned long, jiffies)
+DECLARE_VVAR(8, int, vgetcpu_mode)
+DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data)
+
+#undef DECLARE_VVAR
+#undef VSYSCALL_VARS_OFFSET