Re: [PATCH 4/6] linux: Use 32-bit time_t for itimerval

[Lukasz Majewski <lukma at denx dot de>]

Hi Alistair,

Maybe it would be good to rewrite the subject line to also reflect the
introduction of __[gs]etitimer64 ?

> The Linux kernel expects itimerval to use a 32-bit time_t, even on
> archs with a 64-bit time_t (like RV32). To address this let's convert
> itimerval to/from 32-bit and 64-bit to ensure the kernel always gets
> a 32-bit time_t.
> 
> This means that all 32-bit architectures with a 64-bit time_t will be
> able to use this generic implementation.
> 
> This code is based on similar code in alpha, but adjusted to pass the
> 32-bit time_t to the kernel.
> 
> We can't directly call the __getitimer/__setitimer functions as they
> expect a struct itimerval but we need to pass in a struct itimerval32.

Please update this patch series to also include information about
build/run testing.

For example:

Build-tests:
./src/scripts/build-many-glibcs.py glibcs


> ---
>  include/time.h                                | 12 +++
>  .../linux/generic/wordsize-32/getitimer.c     | 54 +++++++++++++
>  .../linux/generic/wordsize-32/setitimer.c     | 77
> +++++++++++++++++++ .../linux/generic/wordsize-32/tv32-compat.h   |
> 35 +++++++++ 4 files changed, 178 insertions(+)
>  create mode 100644
> sysdeps/unix/sysv/linux/generic/wordsize-32/getitimer.c create mode

The same issue as pointed out in patch 6/6. The path
sysdeps/unix/sysv/linux/generic/wordsize-32 is NOT searched by ARMv7
(ARM32) for files to be built.

I've removed getitimer, getrusage and setitimer from
./sysdeps/unix/syscalls.list, so they are NOT auto generated wrappers
anymore, but this doesn't help.

It seems like for RV32 some extra paths are added...

I've dug to the @sysnames@ variable set in configure in the source of glibc.
I'm wondering how RV32 modifies it (and how it differs from ARM32)?


> 100644 sysdeps/unix/sysv/linux/generic/wordsize-32/setitimer.c create
> mode 100644 sysdeps/unix/sysv/linux/generic/wordsize-32/tv32-compat.h
> 
> diff --git a/include/time.h b/include/time.h
> index 898ff0fb2d..e1d80b4190 100644
> --- a/include/time.h
> +++ b/include/time.h
> @@ -6,6 +6,7 @@
>  # include <bits/types/locale_t.h>
>  # include <stdbool.h>
>  # include <time/mktime-internal.h>
> +# include <sys/time.h>
>  # include <endian.h>
>  # include <time-clockid.h>
>  
> @@ -118,6 +119,17 @@ struct __itimerval64
>  };
>  #endif
>  
> +#if __TIMESIZE == 64
> +# define __getitimer64 __getitimer
> +# define __setitimer64 __setitimer
> +#else
> +extern int __getitimer64 (enum __itimer_which __which,
> +                          struct __itimerval64 *__value);

Please add here:
libc_hidden_proto (__getitimer64)

> +extern int __setitimer64 (enum __itimer_which __which,
> +                          const struct __itimerval64 *__restrict
> __new,
> +                          struct __itimerval64 *__restrict __old);

Please add here:
libc_hidden_proto (__setitimer64)

> +#endif
> +
>  #if __TIMESIZE == 64
>  # define __ctime64 ctime
>  #else
> diff --git a/sysdeps/unix/sysv/linux/generic/wordsize-32/getitimer.c
> b/sysdeps/unix/sysv/linux/generic/wordsize-32/getitimer.c new file
> mode 100644 index 0000000000..28a3e31126
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/generic/wordsize-32/getitimer.c
> @@ -0,0 +1,54 @@
> +/* getitimer -- Get the state of an interval timer.  Linux/tv32
> version.
> +   Copyright (C) 2020 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be
> useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <time.h>
> +#include <sys/time.h>
> +#include <sysdep.h>
> +#include <tv32-compat.h>
> +
> +int
> +__getitimer64 (__itimer_which_t which, struct __itimerval64
> *curr_value) +{
> +  struct __itimerval32 curr_value_32;
> +  if (INLINE_SYSCALL_CALL (getitimer, which, &curr_value_32) == -1)
> +    return -1;
> +
> +  /* Write all fields of 'curr_value' regardless of overflow.  */
> +  curr_value->it_interval
> +    = valid_timeval32_to_timeval64 (curr_value_32.it_interval);
> +  curr_value->it_value
> +    = valid_timeval32_to_timeval64 (curr_value_32.it_value);
> +  return 0;
> +}
> +
> +
> +#if __TIMESIZE != 64

Please add here:
libc_hidden_def (__gettimer64)

Rationale:

Before we introduce the Y2038 support (with -D_TIME_BITS=64) the
__gettimer64 shall be hidden (to avoid resolving it via PLT).

> +int
> +__getitimer (__itimer_which_t which, struct itimerval *curr_value)
> +{
> +  struct __itimerval64 val64;
> +
> +  val64.it_interval
> +    = valid_timeval_to_timeval64 (curr_value->it_interval);
> +  val64.it_value
> +    = valid_timeval_to_timeval64 (curr_value->it_value);
> +
> +  return __getitimer64 (which, &val64);
> +}

Ok. As we expect 32 bit values - there is no need for checking (and 64
<-> 32 conversions will be OK).

> +#endif
> +weak_alias (__getitimer, getitimer)
> diff --git a/sysdeps/unix/sysv/linux/generic/wordsize-32/setitimer.c
> b/sysdeps/unix/sysv/linux/generic/wordsize-32/setitimer.c new file
> mode 100644 index 0000000000..fabc7f2c0c
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/generic/wordsize-32/setitimer.c
> @@ -0,0 +1,77 @@
> +/* setitimer -- Set the state of an interval timer.  Linux/tv32
> version.
> +   Copyright (C) 2020 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be
> useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <time.h>
> +#include <sys/time.h>
> +#include <sysdep.h>
> +#include <tv32-compat.h>
> +
> +int
> +__setitimer64 (__itimer_which_t which,
> +               const struct __itimerval64 *restrict new_value,
> +               struct __itimerval64 *restrict old_value)
> +{
> +  struct __itimerval32 new_value_32;
> +  new_value_32.it_interval
> +    = valid_timeval64_to_timeval32 (new_value->it_interval);
> +  new_value_32.it_value
> +    = valid_timeval64_to_timeval32 (new_value->it_value);
> +
> +  if (old_value == NULL)
> +    return INLINE_SYSCALL_CALL (setitimer, which, &new_value_32,
> NULL); +

The above code is correct of course.

However, I've used another approach for timerfd_settime (IMHO a bit
more concise):
https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/timerfd_settime.c;h=164b4e860acb6a365a3890f30e2eac364a518c22;hb=eae22432723b877354291aca4dbbfde5891dad59#l49

> +  struct __itimerval32 old_value_32;
> +  if (INLINE_SYSCALL_CALL (setitimer, which, &new_value_32,
> &old_value_32) == -1)
> +    return -1;
> +
> +  /* Write all fields of 'old_value' regardless of overflow.  */
> +  old_value->it_interval
> +     = valid_timeval32_to_timeval64 (old_value_32.it_interval);
> +  old_value->it_value
> +     = valid_timeval32_to_timeval64 (old_value_32.it_value);
> +  return 0;
> +}
> +
> +#if __TIMESIZE != 64

Please add here:
libc_hidden_def (__settimer64)

> +int
> +__setitimer (__itimer_which_t which,
> +             const struct itimerval *restrict new_value,
> +             struct itimerval *restrict old_value)
> +{
> +  int ret;
> +  struct __itimerval64 new64, old64;
> +
> +  new64.it_interval
> +    = valid_timeval_to_timeval64 (new_value->it_interval);
> +  new64.it_value
> +    = valid_timeval_to_timeval64 (new_value->it_value);
> +
> +  ret = __setitimer64 (which, &new64, &old64);

I think that here we shall also consider the NULL pointer for old_value
(as stated in http://man7.org/linux/man-pages/man2/setitimer.2.html)

ret = __setitimer64 (which, &new64, old_value ? &old64 : NULL);

> +
> +  if (ret != 0)
> +    return ret;
> +
> +  old_value->it_interval
> +    = valid_timeval64_to_timeval (old64.it_interval);
> +  old_value->it_value
> +    = valid_timeval64_to_timeval (old64.it_value);
> +

Maybe it would be better to change this code to:

if (ret == 0 && old_value)
  {
    old_value->it_interval
      = valid_timeval64_to_timeval (old64.it_interval);
    old_value->it_value
      = valid_timeval64_to_timeval (old64.it_value);
  }

return ret

Please find the timerfd_settime as a reference:
https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/timerfd_settime.c;h=164b4e860acb6a365a3890f30e2eac364a518c22;hb=eae22432723b877354291aca4dbbfde5891dad59#l77

> +  return ret;
> +}
> +#endif
> +weak_alias (__setitimer, setitimer)
> diff --git
> a/sysdeps/unix/sysv/linux/generic/wordsize-32/tv32-compat.h
> b/sysdeps/unix/sysv/linux/generic/wordsize-32/tv32-compat.h new file
> mode 100644 index 0000000000..4eb6f216ea --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/generic/wordsize-32/tv32-compat.h
> @@ -0,0 +1,35 @@
> +/* Compatibility definitions for `struct timeval' with 32-bit time_t.
> +   Copyright (C) 2020 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be
> useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#ifndef _TV32_COMPAT_H
> +#define _TV32_COMPAT_H 1
> +
> +#include <features.h>
> +
> +#include <bits/types.h>
> +#include <bits/types/time_t.h>
> +#include <bits/types/struct_timeval.h>
> +
> +/* Structures containing 'struct timeval' with 32-bit time_t.  */
> +struct __itimerval32
> +{
> +  struct __timeval32 it_interval;
> +  struct __timeval32 it_value;
> +};

I do guess that here (with the introduction of tv32-compat.h) we do
follow what is done for alpha port?

> +
> +#endif /* tv32-compat.h */




Best regards,

Lukasz Majewski

--

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