linux-kernel - Re: [PATCH] riscv: add asm/unistd.h UAPI header

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Date:   Thu, 8 Nov 2018 11:38:22 +0100
From:   David Abdurachmanov <david.abdurachmanov@...il.com>
To:     Palmer Dabbelt <palmer@...ive.com>
Cc:     Arnd Bergmann <arnd@...db.de>, aou@...s.berkeley.edu,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Marcin Juszkiewicz <marcin.juszkiewicz@...aro.org>,
        Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH] riscv: add asm/unistd.h UAPI header

On Thu, Nov 8, 2018 at 3:10 AM Palmer Dabbelt <palmer@...ive.com> wrote:
>
> On Wed, 07 Nov 2018 13:09:39 PST (-0800), Arnd Bergmann wrote:
> > On Wed, Nov 7, 2018 at 7:30 PM David Abdurachmanov
> > <david.abdurachmanov@...il.com> wrote:
> >> On Wed, Nov 7, 2018 at 1:08 AM Palmer Dabbelt <palmer@...ive.com> wrote:
> >> > On Mon, 05 Nov 2018 12:56:15 PST (-0800), Arnd Bergmann wrote:
> >
> >> > The target is still the next glibc release (Feb 1st) for a stable RV32I ABI.
> >> > That's progressing well, with one last blocking issue related to some of our
> >> > floating-point emulation routines before we can submit the port.  This should
> >> > give us ample time to line up the ABIs correctly so everything works.
> >> >
> >> > So I think the correct answer here is to drop __ARCH_WANT_STAT64 from RISC-V.
> >> >
> >>
> >> Then if you agree I could do and send v2:
> >>
> >> +#ifdef __LP64__
> >> +#define __ARCH_WANT_NEW_STAT
> >> +#endif /* __LP64__ */
> >
> > Looks good to me.
>
> This is a bit pedantic, but I'm not sure what the right answer is here:
> "-march=rv64gc -mabi=ilp32d" will not define __LP64__, but will define
> "__riscv_xlen == 64".  I actually don't know enough about how an rv64gc/ilp32d
> ABI would work to answer this: would we have "long long" all over our syscalls?
>
> Probably not worth worrying about for now, as we'll have to go audit all of
> these if we ever end up with an ilp32 ABI.  So just go for it and we'll throw
> this on the pile to deal with later :)

GCC will not allow "-march=rv64gc -mabi=ilp32d":

    cc1: error: ABI requires -march=rv32

I see that arch/riscv/include/uapi/asm/elf.h already use __riscv_xlen so to be
consistent I will use it too (but I like __LP64__ more as it is well
known macro).

Looking at other UAPI headers I see that include/uapi/linux/rseq.h is using
__LP64__ macro. This header is installed on riscv.