um: implement a x86_64 vDSO
Until now UML had no x86_64 vDSO. So glibc always used the vsyscall page
for gettimeday() and friends. Calls to gettimeday() returned falsely the
host time and confused some programs.
This patch adds a vDSO which turns all __vdso_* calls into a system call
so that UML can trap them.
As glibc still uses the vsyscall page for static binaries this patch
improves the situation only for dynamic binaries.
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/um/sys-x86_64/vdso/vdso.lds.S b/arch/um/sys-x86_64/vdso/vdso.lds.S
new file mode 100644
index 0000000..b96b267
--- /dev/null
+++ b/arch/um/sys-x86_64/vdso/vdso.lds.S
@@ -0,0 +1,32 @@
+/*
+ * Linker script for 64-bit vDSO.
+ * We #include the file to define the layout details.
+ * Here we only choose the prelinked virtual address.
+ *
+ * This file defines the version script giving the user-exported symbols in
+ * the DSO. We can define local symbols here called VDSO* to make their
+ * values visible using the asm-x86/vdso.h macros from the kernel proper.
+ */
+
+#define VDSO_PRELINK 0xffffffffff700000
+#include "vdso-layout.lds.S"
+
+/*
+ * This controls what userland symbols we export from the vDSO.
+ */
+VERSION {
+ LINUX_2.6 {
+ global:
+ clock_gettime;
+ __vdso_clock_gettime;
+ gettimeofday;
+ __vdso_gettimeofday;
+ getcpu;
+ __vdso_getcpu;
+ time;
+ __vdso_time;
+ local: *;
+ };
+}
+
+VDSO64_PRELINK = VDSO_PRELINK;