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

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Hi Arnd, Joseph,

> On Thu, Feb 20, 2020 at 1:46 AM Joseph Myers
> <joseph@xxxxxxxxxxxxxxxx> wrote:
> >
> > On Thu, 20 Feb 2020, Vineet Gupta wrote:
> >  
> > > The first 4 will need more work as sym aliasing like
> > >       strong_alias (__xstat64, __xstat)
> > >
> > > will be needed in those ARM files (which in turn use i386).  
> >
> > The situation for Arm is fundamentally different from that for ARC.
> >
> > For ARC, you only need a single public stat structure (using 64-bit
> > times and offsets).
> >
> > For Arm, a third public stat structure will need to be added
> > alongside the existing two, initially used internally in
> > 64-bit-time stat functions that aren't exported from glibc,
> > eventually to be used with _TIME_BITS=64 with the 64-bit-time stat
> > interfaces exported once all the _TIME_BITS=64 interfaces are
> > ready.  
> But surely that structure layout would be the same on ARM and ARC
> as well as all other 32-bit architectures with _TIME_BITS=64, right?

For ARM32 stat case (current):

./io/stat.c -> __xstat -> ./sysdeps/unix/sysv/linux/xstat64.c
and then struct stat64 buf is filled by the kernel.

The generic idea (which requires converting
./sysdeps/unix/sysv/linux/xstat64.c) would be to use statx always in
glibc instead of stat* syscalls (as it is done in

To do that we do need in-glibc internal new type - namely struct

which would have always:

__time64_t st_atime; (and st_mtime, st_ctime).

instead of 

__time_t st_atime;

and also introduce __cp_stat64_time64_statx along with __cp_stat64_statx

as struct statx inherently support 64 bit time via struct
statx_timestamp even on 32 bit archs.

IMHO using statx as widely as possible in glibc is the easiest way to
convert stat* and friends functions to support Y2038.

> What's wrong with having a single implementation for the most
> recent set of stat syscalls, with the older variants being only
> compiled for architectures that need them to support _TIME_BITS=32
> and/or _FILE_OFFSET_BITS=32?
>         Arnd

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@xxxxxxx

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