[PATCH] Enable VDSO for static linking on s390

[Rafael Avila de Espindola]

"Stefan Liebler" <stli@linux.ibm.com> writes:

> Hi Rafael,
>
> can you please resend the patch?

Attached.

> But I have a question: Do I need a special kernel parameter / configuration?

I don't think so, but I don't know if there is something special on s390x.

> When I run it on Intel, I recognize that there is a vdso mapped and
> AT_SYSINFO_EHDR contains the address.

That was already working. What was missing is just glibc using the
loaded vdso.

What I have been using for testing is running the following program with
strace:

#include <time.h>
#include <stdio.h>
int main() {
    struct timespec ts;
    clock_gettime(CLOCK_REALTIME, &ts);
    printf("%ld.%09ld\n", ts.tv_sec, ts.tv_nsec);
    return 0;
}

My expectation is

* If built as shared, no syscall for clock_realtime.
* If built as static with glibc master, there will be a syscall.
* The patch avoids the syscall.

Cheers,
Rafael