Although s390 only enables vDSO for dynamically linked elf binaries
(arch/s390/kernel/vdso.c:217), there is no indication in the code or
associated commit message for why not enable it for statically linked
binaries as well. To double check, I rebuilt a kernel with the
check removed and the vDSO does work for static build for supplied
symbols.
Checked on s390x-linux-gnu and s390-linux-gnu.
[BZ #19767]
* sysdeps/unix/sysv/linux/s390/init-first.c: Remove #ifdef SHARED.
* sysdeps/unix/sysv/linux/s390/libc-vdso.h: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
(ALWAYS_USE_VSYSCALL): Define.
* sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
(ALWAYS_USE_VSYSCALL): Likewise.
This patch adds support for symbol __kernel_getcpu in vDSO,
which is available with kernel 4.5.
Now sched_getcpu is using this symbol if available in mapped vDSO
by defining macro HAVE_GETCPU_VSYSCALL. If not available at runtime,
the former syscall is used.
This patch consolidate the Linux vDSO define and usage across all ports
that uses it. The common vDSO definitions and calling through
{INLINE/INTERNAL}_VSYSCALL macros are moved to a common header
sysdep-vdso.h and vDSO name declaration and prototype is defined
using a common macro.
Also PTR_{MANGLE,DEMANGLE} is added to ports that does not use them
for vDSO calls (aarch64, powerpc, s390, and tile) and thus it will
reflect in code changes. For ports that already implement pointer
mangling/demangling in vDSO system (i386, x32, x86_64) this patch
is mainly a code refactor.
Checked on x32, x86_64, x32, ppc64le, and aarch64.
Adhemerval Zanella
Joseph Myers
Stefan Liebler
Adhemerval Zanella