[PATCH] Linux: Use 32-bit vDSO for clock_gettime, gettimeofday, time (bug 28071)

[Florian Weimer]

* Adhemerval Zanella:

> Using the test (a slight modified one from the bug report):
>
> --
> #include <time.h>
> #include <stdio.h>
> #include <errno.h>
>
> int
> main (void)
> {
>   struct timespec ts;
>   errno = 0;
>   clock_gettime (CLOCK_REALTIME, &ts);
>   printf ("errno = %m (%d)\n", errno);
>   errno = 0;
>   clock_gettime (CLOCK_MONOTONIC, &ts);
>   printf ("errno = %m (%d)\n", errno);
> }
> --
>
> I see no syscall on 5.11 kernel, only a clock_gettime (CLOCK_MONOTONIC)
> on the 4.4 and a clock_gettime_time64 plus a clock_gettime on the 3.10.

This still introduces a severe performance regression on older kernels.
It may well make some exsting 32-bit applications unusable until the
kernel is upgraded.  I'm not sure if this is a good idea.

At least I can see that the clobbering of errno is gone.

Thanks,
Florian