Re: [PATCH v2] RISC-V: Don't use a global include guard for uapi/asm/syscalls.h

[Palmer Dabbelt]

On Mon, 06 Aug 2018 14:00:53 PDT (-0700), rdunlap@xxxxxxxxxxxxx wrote:
> On 08/06/2018 01:42 PM, Palmer Dabbelt wrote:
> > This file is expected to be included multiple times in the same file in
> > order to allow the __SYSCALL macro to generate system call tables.  With
> > a global include guard we end up missing __NR_riscv_flush_icache in the
> > syscall table, which results in icache flushes that escape the vDSO call
> > to not actually do anything.
> >
> > The fix is to move to per-#define include guards, which allows the
> > system call tables to actually be populated.  Thanks to Macrus Comstedt
> > for finding and fixing the bug!
> >
> > I also went ahead and fixed the SPDX header to use a //-style comment,
> > which I've been told is the canonical way to do it.
> >
> > Cc: Marcus Comstedt <marcus@xxxxxxxx>
> > Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxx>
> > ---
> >  arch/riscv/include/asm/unistd.h        |  5 +++++
> >  arch/riscv/include/uapi/asm/syscalls.h | 15 +++++++++------
> >  2 files changed, 14 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/unistd.h b/arch/riscv/include/asm/unistd.h
> > index 080fb28061de..508be1780323 100644
> > --- a/arch/riscv/include/asm/unistd.h
> > +++ b/arch/riscv/include/asm/unistd.h
> > @@ -11,6 +11,11 @@
> >   *   GNU General Public License for more details.
> >   */
> >
> > +/*
> > + * There is explicitly no include guard here because this file is expected to
>
> to .. be .. included

Thanks.  I'm not going to spin a v3 unless there's more feedback, but I'll 
include it in the PR.

> > + * included multiple times.  See uapi/asm/syscalls.h for more info.
> > + */
> > +
> >  #define __ARCH_WANT_SYS_CLONE
> >  #include <uapi/asm/unistd.h>
> >  #include <uapi/asm/syscalls.h>
> > diff --git a/arch/riscv/include/uapi/asm/syscalls.h b/arch/riscv/include/uapi/asm/syscalls.h
> > index 818655b0d535..690beb002d1d 100644
> > --- a/arch/riscv/include/uapi/asm/syscalls.h
> > +++ b/arch/riscv/include/uapi/asm/syscalls.h
> > @@ -1,10 +1,13 @@
> > -/* SPDX-License-Identifier: GPL-2.0 */
> > +// SPDX-License-Identifier: GPL-2.0
> >  /*
> > - * Copyright (C) 2017 SiFive
> > + * Copyright (C) 2017-2018 SiFive
> >   */
> >
> > -#ifndef _ASM__UAPI__SYSCALLS_H
> > -#define _ASM__UAPI__SYSCALLS_H
> > +/*
> > + * There is explicitly no include guard here because this file is expected to
> > + * be included multiple times in order to define the syscall macros via
>
> like that one :)
>
> > + * __SYSCALL.
> > + */
> >
> >  /*
> >   * Allows the instruction cache to be flushed from userspace.  Despite RISC-V