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

[Alistair Francis <alistair23 at gmail dot com>]

On Fri, Nov 8, 2019 at 8:56 AM Alistair Francis <alistair23@gmail.com> wrote:
>
> On Fri, Nov 8, 2019 at 4:54 AM Lukasz Majewski <lukma@denx.de> wrote:
> >
> > Hi Alistair,
> >
> > Please find my comments regarding checking of NULL pointers.
> >
> > > 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
> > > +# define __clock_nanosleep_time64 __clock_nanosleep
> > > +# define __nanosleep_time64 __nanosleep
> > > +# define __nanosleep_nocancel_time64 __nanosleep_nocancel
> > > +#else
> > > +extern int __thrd_sleep_time64 (const struct __timespec64*
> > > time_point,
> > > +                                struct __timespec64* remaining);
> > > +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);
> > > +libc_hidden_proto (__nanosleep_time64)
> > > +extern int __nanosleep_nocancel_time64 (const struct __timespec64
> > > *requested_time,
> > > +                                        struct __timespec64
> > > *remaining); +libc_hidden_proto (__nanosleep_nocancel_time64)
> > > +#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)
> > > @@ -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);
> > > +#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);
> > > +    }
> > > +# 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);
> >
> > Here we don't need to check req == NULL, as we will go into this piece
> > of code only for 32 bit systems (and kernel < 5.1) with glibc's local
> > copy of struct __timespec64.
> >
> > > +  r =  INTERNAL_SYSCALL_CANCEL (clock_nanosleep, err, clock_id,
> > > flags,
> > > +                                &ts32, &tr32);
> > > +
> > > +  if ((r == 0 || errno != ENOSYS) && rem)
> > > +    *rem = valid_timespec_to_timespec64 (tr32);
> > > +#endif /* __ASSUME_TIME64_SYSCALLS */
> > > +
> > >    return (INTERNAL_SYSCALL_ERROR_P (r, err)
> > > -       ? INTERNAL_SYSCALL_ERRNO (r, err) : 0);
> > > +          ? INTERNAL_SYSCALL_ERRNO (r, err) : 0);
> > >  }
> > > +
> > > +#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);
> >
> > The above line would cause regression. Please find below explanation:
> >
> > The check on *rqtp (in Linux kernel's clock_nanosleep syscall handling):
> > https://elixir.bootlin.com/linux/v5.4-rc5/source/kernel/time/posix-timers.c#L1220
> >
> > When compiling test program with clock_nanosleep() passing *request [1]
> > as NULL [3] - the clock_nanosleep returns 14, which corresponds to
> > #define EFAULT 14 [2] (which matches [1]).
> >
> > Hence we should have following code in [*]:
> >
> > if (req == NULL)
> >   {
> >     __set_errno(EFAULT)
> >     returm 1;
> >   }
> >
> >
> > Otherwise we will break in glibc before we enter the clock_nanosleep
> > syscall (which would then return with proper error code).
>
> I think you are right. I have updated the patch.

As Joseph mentioned in another thread, glibc doesn't check for NULL
pointers, so I have removed this.

Alistair

>
> Alistair
>
> >
> >
> > Links:
> > [1] - http://man7.org/linux/man-pages/man2/clock_nanosleep.2.html
> > [2] - cpp -dM /usr/include/errno.h | grep 'define E' | sort -n -k 3
> > [3] - test program:
> >
> > int main(int argc, char **argv)
> > {
> >   int result;
> >
> >   result = clock_nanosleep(CLOCK_REALTIME, 0 /* relative */,
> >     NULL, NULL);
> >
> >   if (result)
> >     printf("clock_nanosleep: %d\n", result);
> >
> >   return 0;
> > }
> >
> > > +  r = __clock_nanosleep_time64 (clock_id, flags, &treq64, &trem64);
> > > +
> > > +  if (r == 0 || errno != ENOSYS)
> > > +    {
> > > +      if (rem)
> > > +        *rem = valid_timespec64_to_timespec (trem64);
> > > +    }
> > > +
> > > +  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;
> >
> >
> >
> >
> > Best regards,
> >
> > Lukasz Majewski
> >
> > --
> >
> > DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> > HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> > Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de