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 09:30:56 +0200 [thread overview]
Message-ID: <20220421093056.5ab1e7ed@bahia> (raw)
In-Reply-To: <9db9268aac4eb87e1471ab8240109c7c29be3bef.1650370027.git.qemu_oss@crudebyte.com>
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>.
> 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.
> + */
> +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.
Reviewed-by: Greg Kurz <groug@kaod.org>
> 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 7:46 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 [this message]
2022-04-21 10:25 ` Christian Schoenebeck
2022-04-21 10:31 ` Greg Kurz
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220421093056.5ab1e7ed@bahia \
--to=groug@kaod.org \
--cc=akihiko.odaki@gmail.com \
--cc=keno@juliacomputing.com \
--cc=qemu-devel@nongnu.org \
--cc=qemu-stable@nongnu.org \
--cc=qemu_oss@crudebyte.com \
--cc=reactorcontrol@icloud.com \
--cc=wwcohen@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).