Re: [PATCH v3 2/2] perf bench: Add support for 32-bit systems with 64-bit time_t

[Arnd Bergmann]

On Wed, Sep 22, 2021 at 1:06 AM André Almeida <andrealmeid@xxxxxxxxxxxxx> wrote:
> Às 05:08 de 21/09/21, Arnd Bergmann escreveu:
> > On Tue, Sep 21, 2021 at 12:47 AM André Almeida
> > <andrealmeid@xxxxxxxxxxxxx> wrote:
> >>
> >> #if defined(__i386__) || __TIMESIZE == 32
> >> # define NR_gettime64 __NR_clock_gettime64
> >> #else
> >> # define NR_gettime64 __NR_clock_gettime
> >> #endif
> >>
> >> struct timespec64 {
> >>         long long tv_sec;       /* seconds */
> >>         long long tv_nsec;      /* nanoseconds */
> >> };
> >>
> >> int gettime64(clock_t clockid, struct timespec64 *tv)
> >> {
> >>         return syscall(NR_gettime64, clockid, tv);
> >> }
> >>
> >> Then we can just use &timeout at __NR_futex_time64 for 32bit arch and at
> >> __NR_futex for 64bit arch.
> >
> > This is still broken when you disable CONFIG_COMPAT_32BIT_TIME,
> > which disables all system calls that take time32 arguments.
> >
>
> Oh, I think my point was confusing then. My suggestion was to use only
> the futex entry points that accepts time64, and to always use
> clock_gettime that uses time64, for all platforms. Then it will work if
> we disable CONFIG_COMPAT_32BIT_TIME.

Yes, that would be ok. It does require using at least linux-5.1, but we
perf is already sort-of tied to the kernel version.

        Arnd