elf: Move vDSO setup to rtld (BZ#24967)

This patch moves the vDSO setup from libc to loader code, just after
the vDSO link_map setup.  For static case the initialization
is moved to _dl_non_dynamic_init instead.

Instead of using the mangled pointer, the vDSO data is set as
attribute_relro (on _rtld_global_ro for shared or _dl_vdso_* for
static).  It is read-only even with partial relro.

It fixes BZ#24967 now that the vDSO pointer is setup earlier than
malloc interposition is called.

Also, vDSO calls should not be a problem for static dlopen as
indicated by BZ#20802.  The vDSO pointer would be zero-initialized
and the syscall will be issued instead.

Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu,
arm-linux-gnueabihf, powerpc64le-linux-gnu, powerpc64-linux-gnu,
powerpc-linux-gnu, s390x-linux-gnu, sparc64-linux-gnu, and
sparcv9-linux-gnu.  I also run some tests on mips.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

1 files changed, 2 insertions, 3 deletions

diff --git a/sysdeps/unix/sysv/linux/powerpc/get_timebase_freq.c b/sysdeps/unix/sysv/linux/powerpc/get_timebase_freq.c
index ebd0d2f880..81f7c73f38 100644
--- a/sysdeps/unix/sysv/linux/powerpc/get_timebase_freq.c
+++ b/sysdeps/unix/sysv/linux/powerpc/get_timebase_freq.c
@@ -21,7 +21,7 @@
 
 #include <libc-internal.h>
 #include <not-cancel.h>
-#include <libc-vdso.h>
+#include <sysdep-vdso.h>
 
 static uint64_t
 get_timebase_freq_fallback (void)
@@ -101,8 +101,7 @@ uint64_t
 __get_timebase_freq (void)
 {
   /* The vDSO does not have a fallback mechanism (such calling a syscall).  */
-  __typeof (VDSO_SYMBOL (get_tbfreq)) vdsop = VDSO_SYMBOL (get_tbfreq);
-  PTR_DEMANGLE (vdsop);
+  uint64_t (*vdsop)(void) = GLRO(dl_vdso_get_tbfreq);
   if (vdsop == NULL)
     return get_timebase_freq_fallback ();