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

Alistair Francis
2020-02-12T00:22:10Z

On Tue, Feb 11, 2020 at 4:14 PM Vineet Gupta <vineetg76@gmail.com> wrote:
>
> Hi Alistair,

Hi Vineet,

>
> 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 ?

We need to specify that RV32 uses a 64-bit time_t. The generic ones
don't do that for 32-bit arches.

>
> > +/* 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

Can you point me to the code? Last time I looked the kernel used the
64-bit versions for the syscalls on RV32.

>
> > +
> > +/* 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

Ah, I think you are right about this and we don't need to define it.

>
> > +#define __ASSUME_RLIM64_SYSCALLS 1
>
> Is this used anywhere ?

Apparently not, I have removed it.

Alistair

>
> Thx,
> -Vineet