Re: [RFC v6 04/23] linux: Use 32-bit time_t for itimerval

[Lukasz Majewski <lukma at denx dot de>]

Hi Alistair,

> 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 bsaed 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.
> ---
>  .../linux/generic/wordsize-32/getitimer.c     | 42 +++++++++++++++
>  .../linux/generic/wordsize-32/setitimer.c     | 53
> +++++++++++++++++++ .../linux/generic/wordsize-32/tv32-compat.h   |
> 35 ++++++++++++ 3 files changed, 130 insertions(+)
>  create mode 100644
> sysdeps/unix/sysv/linux/generic/wordsize-32/getitimer.c create mode
> 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/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..b279acbc2e
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/generic/wordsize-32/getitimer.c
> @@ -0,0 +1,42 @@
> +/* getitimer -- Get the state of an interval timer.  Linux/RV32/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 <sys/time.h>
> +#include <sysdep.h>
> +#include <tv32-compat.h>
> +
> +int
> +__getitimer (__itimer_which_t which, struct itimerval *curr_value)
> +{
> +#if __TIMESIZE == 64
> +  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_timeval_long_to_timeval64 (curr_value_32.it_interval);
> +  curr_value->it_value
> +    = valid_timeval_long_to_timeval64 (curr_value_32.it_value);
> +  return 0;
> +#else
> +  return INLINE_SYSCALL_CALL (getitimer, which, curr_value);
> +#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..807683ccae
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/generic/wordsize-32/setitimer.c
> @@ -0,0 +1,53 @@
> +/* getitimer -- Get the state of an interval timer.  Linux/RV32/tv32
> version.

Please update the header info. I suppose you refer to setitimer here.

> +   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 <sys/time.h>
> +#include <sysdep.h>
> +#include <tv32-compat.h>
> +
> +int
> +__setitimer (__itimer_which_t which,
> +             const struct itimerval *restrict new_value,
> +             struct itimerval *restrict old_value)
> +{
> +#if __TIMESIZE == 64

I think that Y2038 safe systems with __WORDSIZE == 32 && __TIMESIZE ==
32 (for now?) also could reuse this work.

To allow it this syscall wrapper shall be converted (written) in the
same way as e.g:

./sysdeps/unix/sysv/linux/clock_settime.c

(the same issue is with getitimer).

Then only redirection when __USE_TIME_BITS64 is set are needed to use
__setitimer64/__getitimer64 on Y2038 safe systems.

> +  struct itimerval32 new_value_32;
> +  new_value_32.it_interval
> +    = valid_timeval64_to_timeval_long (new_value->it_interval);
> +  new_value_32.it_value
> +    = valid_timeval64_to_timeval_long (new_value->it_value);
> +
> +  if (old_value == NULL)
> +    return INLINE_SYSCALL_CALL (setitimer, which, &new_value_32,
> NULL); +
> +  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_timeval_long_to_timeval64 (old_value_32.it_interval);
> +  old_value->it_value
> +     = valid_timeval_long_to_timeval64 (old_value_32.it_value);
> +  return 0;
> +#else
> +  return INLINE_SYSCALL_CALL (setitimer, which, new_value,
> old_value); +#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..aa960a6632 --- /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 __timeval_long it_interval;
> +  struct __timeval_long it_value;
> +};
> +
> +#endif /* tv32-compat.h */


Best regards,

Lukasz Majewski

--

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