Re: [PATCH v5] sysdeps/clock_nanosleep: Use clock_nanosleep_time64 if avaliable

[Alistair Francis <alistair23 at gmail dot com>]

On Thu, Nov 7, 2019 at 11:23 AM Alistair Francis <alistair23@gmail.com> wrote:
>
> On Thu, Nov 7, 2019 at 11:15 AM Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
> >
> >
> >
> > On 07/11/2019 15:11, Alistair Francis wrote:
> > > The clock_nanosleep syscall is not supported on newer 32-bit platforms (such
> > > as RV32). To fix this issue let's use clock_nanosleep_time64 if it is
> > > avaliable.
> > > ---
> > > This was patch was runtime tested with RV32 and RV64
> > > It was build tested using the ./scripts/build-many-glibcs.py script.
> > >
> > > I also ran:
> > > $ make ; make install ; make check
> > > tests on native ARM (32-bit) with the following three confiugrations:
> > >  - 4.19 Kernel and 4.19 Headers
> > >  - 5.2 Kernel and 4.19 Headers
> > >  - 5.2 Kernel and 5.2 Headers
> > > and didn't see any regressions
> > >
> > > v5:
> > >  - Fix clock_nanosleep syscall
> > >  - Rebase on master
> > >
> > > v4:
> > >  - Rebase on master
> > >  - Use __clock_nanosleep to avoid duplicate implementations
> > >  - Fix the error handling when a syscall fails
> > > v2:
> > >  - Explicitly include `#include <kernel-features.h>`
> > >
> > >  include/time.h                            | 20 +++++++
> > >  sysdeps/unix/sysv/linux/clock_nanosleep.c | 66 +++++++++++++++++++++--
> > >  2 files changed, 81 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/include/time.h b/include/time.h
> > > index b3e635395db..03389bda290 100644
> > > --- a/include/time.h
> > > +++ b/include/time.h
> > > @@ -209,6 +209,26 @@ libc_hidden_proto (__difftime64)
> > >
> > >  extern double __difftime (time_t time1, time_t time0);
> > >
> > > +#if __TIMESIZE == 64
> > > +# define __thrd_sleep_time64 thrd_sleep
> >
> > I think it should be on its own patch.
>
> Ok, I'll split this out, as with the other comments.
>
> >
> > > +# define __clock_nanosleep_time64 __clock_nanosleep
> > > +# define __nanosleep_time64 __nanosleep
> >
> > Same as before.
> >
> > > +# define __nanosleep_nocancel_time64 __nanosleep_nocancel
> >
> > There is no need to redirect this inexistent symbol.
> >
> > > +#else
> > > +extern int __thrd_sleep_time64 (const struct __timespec64* time_point,
> > > +                                struct __timespec64* remaining);
> >
> > As before.
> >
> > > +libc_hidden_proto (__thrd_sleep_time64)
> > > +extern int __clock_nanosleep_time64 (clockid_t clock_id,
> > > +                                     int flags, const struct __timespec64 *req,
> > > +                                     struct __timespec64 *rem);
> > > +libc_hidden_proto (__clock_nanosleep_time64)
> > > +extern int __nanosleep_time64 (const struct __timespec64 *requested_time,
> > > +                                struct __timespec64 *remaining);
> >
> > As before.
> >
> > > +libc_hidden_proto (__nanosleep_time64)
> > > +extern int __nanosleep_nocancel_time64 (const struct __timespec64 *requested_time,
> > > +                                        struct __timespec64 *remaining);
> > > +libc_hidden_proto (__nanosleep_nocancel_time64)
> >
> > As before.
> >
> > > +#endif
> > >
> > >  /* Use in the clock_* functions.  Size of the field representing the
> > >     actual clock ID.  */
> > > diff --git a/sysdeps/unix/sysv/linux/clock_nanosleep.c b/sysdeps/unix/sysv/linux/clock_nanosleep.c
> > > index f3c6fd2d5f7..7212dcf9c6d 100644
> > > --- a/sysdeps/unix/sysv/linux/clock_nanosleep.c
> > > +++ b/sysdeps/unix/sysv/linux/clock_nanosleep.c
> > > @@ -16,6 +16,7 @@
> > >     <https://www.gnu.org/licenses/>.  */
> > >
> > >  #include <time.h>
> > > +#include <kernel-features.h>
> > >  #include <errno.h>
> > >
> > >  #include <sysdep-cancel.h>
> > > @@ -26,9 +27,11 @@
> > >  /* We can simply use the syscall.  The CPU clocks are not supported
> > >     with this function.  */
> > >  int
> > > -__clock_nanosleep (clockid_t clock_id, int flags, const struct timespec *req,
> > > -                struct timespec *rem)
> > > +__clock_nanosleep_time64 (clockid_t clock_id, int flags, const struct __timespec64 *req,
> > > +                          struct __timespec64 *rem)
> > >  {
> > > +  int r;
> > > +
> > >    if (clock_id == CLOCK_THREAD_CPUTIME_ID)
> > >      return EINVAL;
> > >    if (clock_id == CLOCK_PROCESS_CPUTIME_ID)
> >
> > Ok.
> >
> > > @@ -37,11 +40,64 @@ __clock_nanosleep (clockid_t clock_id, int flags, const struct timespec *req,
> > >    /* If the call is interrupted by a signal handler or encounters an error,
> > >       it returns a positive value similar to errno.  */
> > >    INTERNAL_SYSCALL_DECL (err);
> > > -  int r = INTERNAL_SYSCALL_CANCEL (clock_nanosleep, err, clock_id, flags,
> > > -                                req, rem);
> > > +
> > > +#ifdef __ASSUME_TIME64_SYSCALLS
> > > +# ifndef __NR_clock_nanosleep_time64
> > > +#  define __NR_clock_nanosleep_time64 __NR_clock_nanosleep
> > > +# endif
> > > +  r = INTERNAL_SYSCALL_CANCEL (clock_nanosleep_time64, err, clock_id,
> > > +                               flags, req, rem);
> >
> > Ok.
> >
> > > +#else
> > > +# ifdef __NR_clock_nanosleep_time64
> > > +  r = INTERNAL_SYSCALL_CANCEL (clock_nanosleep_time64, err, clock_id,
> > > +                               flags, req, rem);
> > > +
> > > +  if (r == 0 || errno != ENOSYS)
> > > +    {
> > > +      return (INTERNAL_SYSCALL_ERROR_P (r, err)
> > > +              ? INTERNAL_SYSCALL_ERRNO (r, err) : 0);
> > > +    }
> >
> > Ok.
> >
> > > +# endif /* __NR_clock_nanosleep_time64 */
> > > +  struct timespec ts32, tr32;
> > > +
> > > +  if (! in_time_t_range (req->tv_sec))
> > > +    {
> > > +      __set_errno (EOVERFLOW);
> > > +      return -1;
> > > +    }
> > > +
> > > +  ts32 = valid_timespec64_to_timespec (*req);
> > > +  r =  INTERNAL_SYSCALL_CANCEL (clock_nanosleep, err, clock_id, flags,
> > > +                                &ts32, &tr32);
> > > +
> > > +  if ((r == 0 || errno != ENOSYS) && rem)
> > > +    *rem = valid_timespec_to_timespec64 (tr32);
> >
> > I think we can assume __NR_nanosleep here.
>
> I'm not sure what you mean
>
> >
> > > +#endif /* __ASSUME_TIME64_SYSCALLS */
> > > +
> > >    return (INTERNAL_SYSCALL_ERROR_P (r, err)
> > > -       ? INTERNAL_SYSCALL_ERRNO (r, err) : 0);
> > > +          ? INTERNAL_SYSCALL_ERRNO (r, err) : 0);
> > >  }
> >
> > This is just replacing a tab with spaces, I don't think it is really required.
>
> It's the only tab in the file. I was cleaning up the indentation while
> touching everything else. I can drop it though.
>
> >
> > > +
> > > +#if __TIMESIZE != 64
> > > +int
> > > +__clock_nanosleep (clockid_t clock_id, int flags, const struct timespec *req,
> > > +                   struct timespec *rem)
> > > +{
> > > +  int r;
> > > +  struct __timespec64 treq64, trem64;
> > > +
> > > +  treq64 = valid_timespec_to_timespec64 (*req);
> > > +  r = __clock_nanosleep_time64 (clock_id, flags, &treq64, &trem64);
> > > +
> > > +  if (r == 0 || errno != ENOSYS)
> > > +    {
> > > +      if (rem)
> > > +        *rem = valid_timespec64_to_timespec (trem64);
> >
> > Wouldn't we copy uninitialised data for EINVAL/ENOTSUPP/EFAULT?
>
> This I'm not sure about. Should we only set it if we don't fail?

Yeah, it will have invalid data for EFAULT [1].

Should it only be set on success or is there some combination of
errors where we set it as well?

1: https://elixir.bootlin.com/linux/v5.4-rc5/source/kernel/time/hrtimer.c#L1854

>
> Alistair
>
> >
> > > +    }
> > > +
> > > +  return r;
> > > +}
> > > +#endif
> > >  libc_hidden_def (__clock_nanosleep)
> > >  versioned_symbol (libc, __clock_nanosleep, clock_nanosleep, GLIBC_2_17);
> > >  /* clock_nanosleep moved to libc in version 2.17;
> > >
> >
> > Ok