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>

1 files changed, 10 insertions, 0 deletions

diff --git a/arch/um/sys-x86_64/vdso/checkundef.sh b/arch/um/sys-x86_64/vdso/checkundef.sh
new file mode 100644
index 000000000000..7ee90a9b549d
--- /dev/null
+++ b/arch/um/sys-x86_64/vdso/checkundef.sh
@@ -0,0 +1,10 @@
+#!/bin/sh
+nm="$1"
+file="$2"
+$nm "$file" | grep '^ *U' > /dev/null 2>&1
+if [ $? -eq 1 ]; then
+    exit 0
+else
+    echo "$file: undefined symbols found" >&2
+    exit 1
+fi