Re: [PATCH 11/12] linux: Consolidate time implementation

[Tulio Magno Quites Machado Filho <tuliom at ascii dot art dot br>]

Adhemerval Zanella <adhemerval.zanella@linaro.org> writes:

> The time syscall has currently 3 possible implementations:
>
>    1. Wire-up __NR_time with a vDSO implementation (currently only x86 and
>       powerpc).
>    2. Wire-up __NR_time (hppa, i686, m68k, microblaze, mips, powerpc,
>       powerpc64, s390, sh4, sparcv9, x86_64).
>    3. Using internal gettimeofday (aarch64, alpha, arm, mips64, mips64-n32,
>       nios2, s390x, sparc64).
>
> This patch consolidates all implementation on Linux generic
> sysdeps/unix/sysv/linux/time.c.  To simplify the code, some changes are
> made:
>
>    * The wire-up with vDSO implementation route external calls directly
>      to vDSO through IFUNC.  To enable it the architecture need to
>      explicit define USE_TIME_VSYSCALL_IFUNC.
>
>    * Also, powerpc and x86 tries to route internal time usages to
>      IFUNC mechanism, which is problematic since powerpc32 and i686 does
>      not really support it.  Instead, all internal calls are routed to
>      a default internal symbol which in turn calls INTERNAL_VSYSCALL.
>
>    * Static linking also uses the fallback mechanism which calls
>      INTERNAL_VSYSCALL, so vDSO is used for this case as well.
>
> The generic implementation issues a syscall as default, calls the
> vDSO if the architecture defines HAVE_TIME_VSYSCALL, and route the external
> calls to iFUNC if the architecture also defines USE_TIME_VSYSCALL_IFUNC.
>
> Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc-linux-gnu,
> powerpc64-linux-gnu, powerpc64le-linux-gnu, and aarch64-linux-gnu.

This patch is causing segmentation faults in powerpc64, e.g.
$ ./testrun.sh ./io/test-utime
Segmentation fault

> diff --git a/sysdeps/unix/sysv/linux/time.c b/sysdeps/unix/sysv/linux/time.c
> index 1978f6d817..93e036fe16 100644
> --- a/sysdeps/unix/sysv/linux/time.c
> +++ b/sysdeps/unix/sysv/linux/time.c
> ...
> +#if HAVE_IFUNC && defined USE_TIME_VSYSCALL_IFUNC
> +/* Route externals calls direct to vDSO and static and internal calls to
> +   fallback implementation (which also might call the vDSO).  */
> +# ifdef SHARED
> +#  define INIT_ARCH()
> +libc_ifunc_redirected (__redirect_time, time,
> +		       get_vdso_symbol (HAVE_TIME_VSYSCALL)
> +		       ?: time_syscall);

Missing VDSO_IFUNC_RET ?

-- 
Tulio Magno