Re: [RFC v6 07/23] RISC-V: Use 64-bit time_t and off_t for RV32 and RV64

Vineet Gupta
2020-02-12T00:14:19Z

Hi Alistair,

On 1/12/20 2:33 AM, Alistair Francis wrote:
> Using the original glibc headers under bits/ let's make small
> modifications to use 64-bit time_t and off_t for both RV32 and RV64.
>
> For the typesizes.h, here are justifications for the changes from the
> generic version (based on Arnd's very helpful feedback):
> - All the !__USE_FILE_OFFSET64 types (__off_t, __ino_t, __rlim_t, ...) are
> changed to match the 64-bit replacements.
>
> - __time_t is defined to 64 bit, but no __time64_t is added. This makes sense
> as we don't have the time64 support for other 32-bit architectures yet, and
> it will be easy to change when that happens.
>
> - __suseconds_t is 64-bit. This matches what we use the kerne ABI for the
> few drivers that are relying on 'struct timeval' input arguments in
> ioctl, as well as the adjtimex system call. It means that timeval has to
> be defined without the padding, unlike timespec, which needs padding.
> ---
> .../unix/sysv/linux/riscv/bits/environments.h | 85 ++++++++++++++++++
> sysdeps/unix/sysv/linux/riscv/bits/time64.h | 36 ++++++++
> sysdeps/unix/sysv/linux/riscv/bits/timesize.h | 22 +++++
> .../unix/sysv/linux/riscv/bits/typesizes.h | 90 +++++++++++++++++++
> sysdeps/unix/sysv/linux/riscv/kernel_stat.h | 23 +++++
> 5 files changed, 256 insertions(+)
> create mode 100644 sysdeps/unix/sysv/linux/riscv/bits/environments.h
> create mode 100644 sysdeps/unix/sysv/linux/riscv/bits/time64.h
> create mode 100644 sysdeps/unix/sysv/linux/riscv/bits/timesize.h
> create mode 100644 sysdeps/unix/sysv/linux/riscv/bits/typesizes.h
> create mode 100644 sysdeps/unix/sysv/linux/riscv/kernel_stat.h
>
> diff --git a/sysdeps/unix/sysv/linux/riscv/bits/environments.h b/sysdeps/unix/sysv/linux/riscv/bits/environments.h
> new file mode 100644
> index 0000000000..8d401d1976
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/riscv/bits/environments.h
> @@ -0,0 +1,85 @@
> +/* Copyright (C) 1999-2020 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 _UNISTD_H
> +# error "Never include this file directly. Use <unistd.h> instead"
> +#endif
> +
> +#include <bits/wordsize.h>
> +
> +/* This header should define the following symbols under the described
> + situations. A value `1' means that the model is always supported,
> + `-1' means it is never supported. Undefined means it cannot be
> + statically decided.
> +
> + _POSIX_V7_ILP32_OFF32 32bit int, long, pointers, and off_t type
> + _POSIX_V7_ILP32_OFFBIG 32bit int, long, and pointers and larger off_t type
> +
> + _POSIX_V7_LP64_OFF32 64bit long and pointers and 32bit off_t type
> + _POSIX_V7_LPBIG_OFFBIG 64bit long and pointers and large off_t type
> +
> + The macros _POSIX_V6_ILP32_OFF32, _POSIX_V6_ILP32_OFFBIG,
> + _POSIX_V6_LP64_OFF32, _POSIX_V6_LPBIG_OFFBIG, _XBS5_ILP32_OFF32,
> + _XBS5_ILP32_OFFBIG, _XBS5_LP64_OFF32, and _XBS5_LPBIG_OFFBIG were
> + used in previous versions of the Unix standard and are available
> + only for compatibility.
> +*/
> +
> +#if __WORDSIZE == 64
> +
> +/* We can never provide environments with 32-bit wide pointers. */
> +# define _POSIX_V7_ILP32_OFF32 -1
> +# define _POSIX_V7_ILP32_OFFBIG -1
> +# define _POSIX_V6_ILP32_OFF32 -1
> +# define _POSIX_V6_ILP32_OFFBIG -1
> +# define _XBS5_ILP32_OFF32 -1
> +# define _XBS5_ILP32_OFFBIG -1
> +/* We also have no use (for now) for an environment with bigger pointers
> + and offsets. */
> +# define _POSIX_V7_LPBIG_OFFBIG -1
> +# define _POSIX_V6_LPBIG_OFFBIG -1
> +# define _XBS5_LPBIG_OFFBIG -1
> +
> +/* By default we have 64-bit wide `long int', pointers and `off_t'. */
> +# define _POSIX_V7_LP64_OFF64 1
> +# define _POSIX_V6_LP64_OFF64 1
> +# define _XBS5_LP64_OFF64 1
> +
> +#else /* __WORDSIZE == 32 */
> +
> +/* RISC-V requires 64-bit off_t
> + # undef _POSIX_V7_ILP32_OFF32
> + # undef _POSIX_V6_ILP32_OFF32
> + # undef _XBS5_ILP32_OFF32
> + */
> +
> +# define _POSIX_V7_ILP32_OFFBIG 1
> +# define _POSIX_V6_ILP32_OFFBIG 1
> +# define _XBS5_ILP32_OFFBIG 1
> +
> +/* We can never provide environments with 64-bit wide pointers. */
> +# define _POSIX_V7_LP64_OFF64 -1
> +# define _POSIX_V7_LPBIG_OFFBIG -1
> +# define _POSIX_V6_LP64_OFF64 -1
> +# define _POSIX_V6_LPBIG_OFFBIG -1
> +# define _XBS5_LP64_OFF64 -1
> +# define _XBS5_LPBIG_OFFBIG -1
> +
> +/* CFLAGS. */
> +#define __ILP32_OFFBIG_CFLAGS "-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64"
> +
> +#endif /* __WORDSIZE == 32 */
> diff --git a/sysdeps/unix/sysv/linux/riscv/bits/time64.h b/sysdeps/unix/sysv/linux/riscv/bits/time64.h
> new file mode 100644
> index 0000000000..cc21b45ef1
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/riscv/bits/time64.h
> @@ -0,0 +1,36 @@
> +/* bits/time64.h -- underlying types for __time64_t. Generic version.
> + Copyright (C) 2018-2020 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 _BITS_TYPES_H
> +# error "Never include <bits/time64.h> directly; use <sys/types.h> instead."
> +#endif
> +
> +#ifndef _BITS_TIME64_H
> +#define _BITS_TIME64_H 1
> +
> +/* Define __TIME64_T_TYPE so that it is always a 64-bit type. */
> +
> +#if __WORDSIZE == 64
> +/* If we already have 64-bit time type then use it. */
> +# define __TIME64_T_TYPE __TIME_T_TYPE
> +#else
> +/* Define a 64-bit time type alongsize the 32-bit one. */
> +# define __TIME64_T_TYPE __SQUAD_TYPE
> +#endif
> +
> +#endif /* bits/time64.h */
> diff --git a/sysdeps/unix/sysv/linux/riscv/bits/timesize.h b/sysdeps/unix/sysv/linux/riscv/bits/timesize.h
> new file mode 100644
> index 0000000000..afb5d86b2b
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/riscv/bits/timesize.h
> @@ -0,0 +1,22 @@
> +/* Bit size of the time_t type at glibc build time, general case.
> + Copyright (C) 2018-2020 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 <bits/wordsize.h>
> +
> +/* RV32 and RV64 both use 64-bit time_t */
> +#define __TIMESIZE 64
> diff --git a/sysdeps/unix/sysv/linux/riscv/bits/typesizes.h b/sysdeps/unix/sysv/linux/riscv/bits/typesizes.h
> new file mode 100644
> index 0000000000..0da3bdeb5d
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/riscv/bits/typesizes.h

I was hoping newer arches could simply use the asm-generic one ?

> +/* Tell the libc code that off_t and off64_t are actually the same type
> + for all ABI purposes, even if possibly expressed as different base types
> + for C type-checking purposes. */
> +# define __OFF_T_MATCHES_OFF64_T 1

This is orthogonal to time_t but since we are on topic of newer ports, how are you
doing this. The asm-generic uapi defines

typedef __kernel_long_t __kernel_off_t;

and types.h defines

typedef __kernel_off_t off_t;

And I presume long on RV32 is 32-bits

> +
> +/* Same for ino_t and ino64_t. */
> +# define __INO_T_MATCHES_INO64_T 1

> +
> +/* And for rlim_t and rlim64_t. */
> +# define __RLIM_T_MATCHES_RLIM64_T 1
> +
> +/* And for fsblkcnt_t and fsfilcnt_t */
> +# define __STATFS_MATCHES_STATFS64 1
> +
> +/* And for fsblkcnt_t, fsblkcnt64_t, fsfilcnt_t and fsfilcnt64_t. */
> +# define __STATFS_MATCHES_STATFS64 1
> +
> +/* Define these as RV32 requires 64-bit syscall. */
> +#if __riscv_xlen == 32
> +#define __ASSUME_TIME64_SYSCALLS 1

From the POV of newer arches needing 64-bit time_t support, this need not be
forced as it is set automatically for kernel >= 5.1

> +#define __ASSUME_RLIM64_SYSCALLS 1

Is this used anywhere ?

Thx,
-Vineet