Re: [PATCH] Enable VDSO for static linking on s390

[Rafael Avila de Espindola <rafael at espindo dot la>]

Hi Stefan,

Have you had a change to try the patch?

Thanks,
Rafael

"Rafael Avila de Espindola" <rafael@espindo.la> writes:

> "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
>
>
> From ffe4dc79ffd5ffef09a1275208f56ec5686c74a1 Mon Sep 17 00:00:00 2001
> From: =?UTF-8?q?Rafael=20=C3=81vila=20de=20Esp=C3=ADndola?=
>  <rafael@espindo.la>
> Date: Thu, 13 Dec 2018 19:25:34 -0800
> Subject: [PATCH] Enable VDSO for static linking on s390
>
> I don't have access to a s390, so I have not been able to test this.
> ---
>  sysdeps/unix/sysv/linux/s390/init-first.c     | 8 +++-----
>  sysdeps/unix/sysv/linux/s390/libc-vdso.h      | 3 ---
>  sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h | 3 +++
>  sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h | 3 +++
>  4 files changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/sysdeps/unix/sysv/linux/s390/init-first.c b/sysdeps/unix/sysv/linux/s390/init-first.c
> index 3a862309bf..10f47ef346 100644
> --- a/sysdeps/unix/sysv/linux/s390/init-first.c
> +++ b/sysdeps/unix/sysv/linux/s390/init-first.c
> @@ -16,9 +16,8 @@
>     License along with the GNU C Library; if not, see
>     <http://www.gnu.org/licenses/>.  */
>  
> -#ifdef SHARED
> -# include <dl-vdso.h>
> -# include <libc-vdso.h>
> +#include <dl-vdso.h>
> +#include <libc-vdso.h>
>  
>  long int (*VDSO_SYMBOL(gettimeofday)) (struct timeval *, void *)
>     attribute_hidden;
> @@ -54,7 +53,6 @@ _libc_vdso_platform_setup (void)
>    VDSO_SYMBOL (getcpu) = p;
>  }
>  
> -# define VDSO_SETUP _libc_vdso_platform_setup
> -#endif
> +#define VDSO_SETUP _libc_vdso_platform_setup
>  
>  #include <csu/init-first.c>
> diff --git a/sysdeps/unix/sysv/linux/s390/libc-vdso.h b/sysdeps/unix/sysv/linux/s390/libc-vdso.h
> index 664bd15f3d..0d4ecb39a8 100644
> --- a/sysdeps/unix/sysv/linux/s390/libc-vdso.h
> +++ b/sysdeps/unix/sysv/linux/s390/libc-vdso.h
> @@ -20,8 +20,6 @@
>  #ifndef _LIBC_VDSO_H
>  #define _LIBC_VDSO_H
>  
> -#ifdef SHARED
> -
>  #include <sysdep-vdso.h>
>  
>  extern long int (*VDSO_SYMBOL(gettimeofday)) (struct timeval *, void *)
> @@ -33,6 +31,5 @@ extern long int (*VDSO_SYMBOL(clock_getres)) (clockid_t, struct timespec *);
>  
>  extern long int (*VDSO_SYMBOL(getcpu)) (unsigned *, unsigned *, void *)
>     attribute_hidden;
> -#endif
>  
>  #endif /* _LIBC_VDSO_H */
> diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h b/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
> index 0d683a5bcb..cebd4cbfad 100644
> --- a/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
> +++ b/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
> @@ -19,6 +19,9 @@
>  #ifndef _LINUX_S390_SYSDEP_H
>  #define _LINUX_S390_SYSDEP_H
>  
> +/* Always enable vsyscalls on s390-32. */
> +#define ALWAYS_USE_VSYSCALL 1
> +
>  #include <sysdeps/s390/s390-32/sysdep.h>
>  #include <sysdeps/unix/sysdep.h>
>  #include <sysdeps/unix/sysv/linux/sysdep.h>
> diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h b/sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
> index 0414fc5f2c..348f1afb58 100644
> --- a/sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
> +++ b/sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
> @@ -20,6 +20,9 @@
>  #ifndef _LINUX_S390_SYSDEP_H
>  #define _LINUX_S390_SYSDEP_H
>  
> +/* Always enable vsyscalls on s390-64. */
> +#define ALWAYS_USE_VSYSCALL 1
> +
>  #include <sysdeps/s390/s390-64/sysdep.h>
>  #include <sysdeps/unix/sysdep.h>
>  #include <sysdeps/unix/sysv/linux/sysdep.h>
> -- 
> 2.19.2