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From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Wed, 24 Apr 2019 16:27:43 +0200
Message-ID: <CAJfpegsgfRdN9oAfmFZtr0cDnjdkikCKv_TTvNLLorHr22ERLw@mail.gmail.com>
Subject: Re: [PATCH] fuse: Add ioctl flag for x32 compat ioctl
To:     Ian Abbott <abbotti@mev.co.uk>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
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On Wed, Apr 24, 2019 at 4:14 PM Ian Abbott <abbotti@mev.co.uk> wrote:
>
> Currently, a CUSE server running on a 64-bit kernel can tell when an
> ioctl request comes from a process running a 32-bit ABI, but cannot tell
> whether the requesting process is using legacy IA32 emulation or x32
> ABI.  In particular, the server does not know the size of the client
> process's `time_t` type.
>
> For 64-bit kernels, the `FUSE_IOCTL_COMPAT` and `FUSE_IOCTL_32BIT` flags
> are currently set in the ioctl input request (`struct fuse_ioctl_in`
> member `flags`) for a 32-bit requesting process.  This patch defines a
> new flag `FUSE_IOCTL_COMPAT_X32` and sets it if the 32-bit requesting
> process is using the x32 ABI.  This allows the server process to
> distinguish between requests from requesting client processes using IA32
> emulation or the x32 ABI and so infer the size of the client process's
> `time_t` type and any other IA32/x32 differences.

Thanks, applied.

Miklos