From: Greg Kurz <groug@kaod.org>
To: Christian Schoenebeck <qemu_oss@crudebyte.com>
Cc: qemu-devel@nongnu.org, qemu-stable@nongnu.org,
Keno Fischer <keno@juliacomputing.com>,
Michael Roitzsch <reactorcontrol@icloud.com>,
Will Cohen <wwcohen@gmail.com>,
Akihiko Odaki <akihiko.odaki@gmail.com>
Subject: Re: [PATCH 3/5] 9pfs: fix wrong encoding of rdev field in Rgetattr on macOS
Date: Thu, 21 Apr 2022 12:31:29 +0200 [thread overview]
Message-ID: <20220421123129.2f04c9d3@bahia> (raw)
In-Reply-To: <8971800.MWpjzubbLj@silver>
On Thu, 21 Apr 2022 12:25:23 +0200
Christian Schoenebeck <qemu_oss@crudebyte.com> wrote:
> On Donnerstag, 21. April 2022 09:30:56 CEST Greg Kurz wrote:
> > On Tue, 19 Apr 2022 13:41:15 +0200
> >
> > Christian Schoenebeck <qemu_oss@crudebyte.com> wrote:
> > > The 'rdev' field in 9p reponse 'Rgetattr' is of type dev_t,
> > > which is actually a system dependant type and therefore both the
> > > size and encoding of dev_t differ between macOS and Linux.
> > >
> > > So far we have sent 'rdev' to guest in host's dev_t format as-is,
> > > which caused devices to appear with wrong device numbers on
> > > guests running on macOS hosts, eventually leading to various
> > > misbehaviours on guest in conjunction with device files.
> > >
> > > This patch fixes this issue by converting the device number from
> > > host's dev_t format to Linux dev_t format. As 9p request
> > > 'Tgettattr' is exclusive to protocol version 9p2000.L, it should
> > > be fair to assume that 'rdev' field is assumed to be in Linux dev_t
> > > format by client as well.
> >
> > For the sake of accuracy : this is converting the host's dev_t to glibc's
> > format (MMMM_Mmmm_mmmM_MMmm, 64 bits) actually, which is compatible with
> > linux's format (mmmM_MMmm, 32 bits), as described in <bits/sysmacros.h>.
>
> You want me to put this to the commit log?
>
Maybe closer to the code that does the actual magic...
> > > Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
> > > ---
> > >
> > > hw/9pfs/9p.c | 37 ++++++++++++++++++++++++++++++++++++-
> > > 1 file changed, 36 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> > > index 225f31fc31..d953035e1c 100644
> > > --- a/hw/9pfs/9p.c
> > > +++ b/hw/9pfs/9p.c
> > > @@ -1318,6 +1318,41 @@ static int32_t stat_to_iounit(const V9fsPDU *pdu,
> > > const struct stat *stbuf)>
> > > return blksize_to_iounit(pdu, stbuf->st_blksize);
> > >
> > > }
> > >
> > > +#if !defined(CONFIG_LINUX)
> > > +
> > > +/*
> > > + * Generates a Linux device number (a.k.a. dev_t) for given device major
> > > + * and minor numbers.
... here ^^.
> > > + */
> > > +static uint64_t makedev_dotl(uint32_t dev_major, uint32_t dev_minor)
> > > +{
> > > + uint64_t dev;
> > > +
> > > + // from glibc sysmacros.h:
> > > + dev = (((uint64_t) (dev_major & 0x00000fffu)) << 8);
> > > + dev |= (((uint64_t) (dev_major & 0xfffff000u)) << 32);
> > > + dev |= (((uint64_t) (dev_minor & 0x000000ffu)) << 0);
> > > + dev |= (((uint64_t) (dev_minor & 0xffffff00u)) << 12);
> > > + return dev;
> > > +}
> > > +
> > > +#endif
> > > +
> > > +/*
> > > + * Converts given device number from host's device number format to Linux
> > > + * device number format. As both the size of type dev_t and encoding of
> > > + * dev_t is system dependant, we have to convert them for Linux guests if
> > > + * host is not running Linux.
> > > + */
> > > +static uint64_t host_dev_to_dotl_dev(dev_t dev)
> > > +{
> > > +#ifdef CONFIG_LINUX
> > > + return dev;
> > > +#else
> > > + return makedev_dotl(major(dev), minor(dev));
> > > +#endif
> > > +}
> > > +
> >
> > It is a bit unfortunate to inflate 9p.c, which is large enough, with
> > glue code. Even if they are only used here, I'd personally put them
> > in 9p-util.h. No big deal.
>
> Makes sense, I'll move it.
>
> > Reviewed-by: Greg Kurz <groug@kaod.org>
>
> Thanks!
>
> > > static int stat_to_v9stat_dotl(V9fsPDU *pdu, const struct stat *stbuf,
> > >
> > > V9fsStatDotl *v9lstat)
> > >
> > > {
> > >
> > > @@ -1327,7 +1362,7 @@ static int stat_to_v9stat_dotl(V9fsPDU *pdu, const
> > > struct stat *stbuf,>
> > > v9lstat->st_nlink = stbuf->st_nlink;
> > > v9lstat->st_uid = stbuf->st_uid;
> > > v9lstat->st_gid = stbuf->st_gid;
> > >
> > > - v9lstat->st_rdev = stbuf->st_rdev;
> > > + v9lstat->st_rdev = host_dev_to_dotl_dev(stbuf->st_rdev);
> > >
> > > v9lstat->st_size = stbuf->st_size;
> > > v9lstat->st_blksize = stat_to_iounit(pdu, stbuf);
> > > v9lstat->st_blocks = stbuf->st_blocks;
>
>
next prev parent reply other threads:[~2022-04-21 10:58 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-19 12:07 [PATCH 0/5] 9pfs: macOS host fixes Christian Schoenebeck
2022-04-19 11:40 ` [PATCH 1/5] 9pfs: fix qemu_mknodat(S_IFREG) on macOS Christian Schoenebeck
2022-04-19 13:44 ` Will Cohen
2022-04-20 2:03 ` Akihiko Odaki
2022-04-20 8:40 ` Greg Kurz
2022-04-20 9:38 ` Christian Schoenebeck
2022-04-19 11:41 ` [PATCH 2/5] 9pfs: fix qemu_mknodat(S_IFSOCK) " Christian Schoenebeck
2022-04-19 13:46 ` Will Cohen
2022-04-20 9:09 ` Greg Kurz
2022-04-20 10:28 ` Christian Schoenebeck
2022-04-20 12:08 ` Greg Kurz
2022-04-20 12:10 ` Greg Kurz
2022-04-20 12:41 ` Christian Schoenebeck
2022-04-19 11:41 ` [PATCH 3/5] 9pfs: fix wrong encoding of rdev field in Rgetattr " Christian Schoenebeck
2022-04-21 7:30 ` Greg Kurz
2022-04-21 10:25 ` Christian Schoenebeck
2022-04-21 10:31 ` Greg Kurz [this message]
2022-04-19 11:41 ` [PATCH 4/5] 9pfs: fix wrong errno being sent to Linux client on macOS host Christian Schoenebeck
2022-04-21 10:48 ` Greg Kurz
2022-04-21 11:13 ` Christian Schoenebeck
2022-04-21 11:46 ` Greg Kurz
2022-04-21 12:20 ` Christian Schoenebeck
2022-04-19 11:43 ` [PATCH 5/5] 9pfs: fix removing non-existent POSIX ACL xattr " Christian Schoenebeck
2022-04-21 8:26 ` Greg Kurz
2022-04-21 10:55 ` Christian Schoenebeck
2022-04-21 12:26 ` Greg Kurz
2022-04-21 13:03 ` Christian Schoenebeck
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