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

Arnd Bergmann
2020-02-20T16:08:31Z

On Thu, Feb 20, 2020 at 4:42 PM Lukasz Majewski <lukma@denx.de> wrote:
> > On Thu, Feb 20, 2020 at 2:15 PM Lukasz Majewski <lukma@denx.de> wrote:

>
> I do see two approaches here:
>
> 1. In glibc:
>
> When -D_TIME_BITS=64 is set - redirections are enabled for syscall
> wrappers; for example __clock_settime64 is used instead of
> __clock_settime (e.g. sysdeps/unix/sysv/linux/clock_settime).
>
> The latter is guarded by #ifdef __TIMESIZE != 64 so we could change
> mechanically that __clock_settime returns -1 and sets errno to -ENOTSUPP

What I meant is to remove the __clock_settime function from the
library entirely to cause a link failure. I suppose replacing most
"__TIMESIZE != 64" with '0' would do that. Ideally I'd just set
__TIMESIZE to 64, but doing that would make the ABI incompatible
with mainline glibc.

> 2. In kernel - return -ENOTSUPP when clock_settime syscall instead of
> clock_settime64 is invoked.

We already have that with CONFIG_COMPAT_32BIT_TIME, but
at the moment I think that still breaks glibc's usage of __NR_futex,
and a compile-time error is always better than a runtime error,
as it's easier to catch them reliably

Arnd