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From: Peter Maydell <peter.maydell@linaro.org>
Date: Tue, 4 Oct 2016 13:42:50 -0700
Message-ID: <CAFEAcA8CSHofEUMxwtcUvShQ70ORqrDpxYfqLADGQP-CSO6USQ@mail.gmail.com>
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Subject: Re: [Qemu-devel] [PATCH 4/4] linux-user: Fix fadvise64() syscall
 support for Mips32
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To: Aleksandar Markovic <aleksandar.markovic@rt-rk.com>
Cc: QEMU Developers <qemu-devel@nongnu.org>, Riku Voipio <riku.voipio@iki.fi>, Laurent Vivier <laurent@vivier.eu>, Aurelien Jarno <aurelien@aurel32.net>, Yongbok Kim <Yongbok.Kim@imgtec.com>, Leon Alrae <leon.alrae@imgtec.com>, Petar Jovanovic <petar.jovanovic@imgtec.com>, Miodrag Dinic <miodrag.dinic@imgtec.com>, aleksandar.rikalo@imgtec.com, Aleksandar Markovic <aleksandar.markovic@imgtec.com>

On 4 October 2016 at 11:05, Aleksandar Markovic
<aleksandar.markovic@rt-rk.com> wrote:
> From: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
>
> By looking at the file arch/mips/kernel/sys.S in Linux kernel,

There doesn't appear to be a file by that name:
http://lxr.free-electrons.com/source/arch/mips/kernel/

> it can be deduced that, for Mips32 platform, syscall
> corresponding to number _NR_fadvise64 translates to kernel
> function sys_fadvise64_64, and that argument layout is as
> follows:
>           0             32 0             32
>          +----------------+----------------+
>   (arg1) |       fd       |     __pad      | (arg2)
>          +----------------+----------------+
>   (arg3) |             buffer              | (arg4)
>          +----------------+----------------+
>   (arg5) |               len               | (arg6)
>          +----------------+----------------+
>   (arg7) |     advise     |    not used    | (arg8)
>          +----------------+----------------+
>
> This can be deduced from glibc code as well, and relevant commits
> in linux kernel and glibc.
>
> Mips32 uniqness is that it does not define _NR_fadvise64_64,
> however its fadvise64 implemantation is identical to
> fadvise64_64 impleanentation on most other platforms.
>
> This patch also fixes the failure LTP test posix_fadvise03, if
> executed on Qemu-emulated Mips32 platform (user mode).

We could alternatively fix this by having
#define TARGET_NR_fadvise64_64 (TARGET_NR_Linux + 254)
in linux-user/mips/syscall_nr.h rather than
#define TARGET_NR_fadvise64 (TARGET_NR_Linux + 254)

right?

thanks
-- PMM