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Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on m
From: |
Greg Kurz |
Subject: |
Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host |
Date: |
Fri, 29 Apr 2022 14:44:55 +0200 |
On Fri, 29 Apr 2022 19:28:39 +0800
Bin Meng <bmeng.cn@gmail.com> wrote:
> On Fri, Apr 29, 2022 at 7:16 PM Christian Schoenebeck
> <qemu_oss@crudebyte.com> wrote:
> >
> > Linux and macOS only share some errno definitions with equal macro
> > name and value. In fact most mappings for errno are completely
> > different on the two systems.
> >
> > This patch converts some important errno values from macOS host to
> > corresponding Linux errno values before eventually sending such error
> > codes along with 'Rlerror' replies (if 9p2000.L is used that is). Not
> > having translated errnos before violated the 9p2000.L protocol spec,
> > which says:
> >
> > "
> > size[4] Rlerror tag[2] ecode[4]
> >
> > ... ecode is a numerical Linux errno.
> > "
> >
> > https://github.com/chaos/diod/wiki/protocol#lerror----return-error-code
> >
> > This patch fixes a bunch of misbehaviours when running a Linux client
> > on macOS host. For instance this patch fixes:
> >
> > mount -t 9p -o posixacl ...
> >
> > on Linux guest if security_mode=mapped was used for 9p server, which
> > refused to mount successfully, because macOS returned ENOATTR==93
> > when client tried to retrieve POSIX ACL xattrs, because errno 93
> > is defined as EPROTONOSUPPORT==93 on Linux, so Linux client believed
> > that xattrs were not supported by filesystem on host in general.
>
> This issue looks exact the same issue we were trying to fix when
> supporting 9p on Windows host,
>
> What we did is like this:
> http://patchwork.ozlabs.org/project/qemu-devel/patch/20220425142705.2099270-10-bmeng.cn@gmail.com/
>
> But we had some questions in mind (see the commit message of our
> patch, and below)
>
> >
> > Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
> > Link: https://lore.kernel.org/qemu-devel/20220421124835.3e664669@bahia/
> > Reviewed-by: Greg Kurz <groug@kaod.org>
> > ---
> > hw/9pfs/9p-util.h | 30 ++++++++++++++++++++++++++++++
> > hw/9pfs/9p.c | 2 ++
> > 2 files changed, 32 insertions(+)
> >
> > diff --git a/hw/9pfs/9p-util.h b/hw/9pfs/9p-util.h
> > index 2cc9a5dbfb..c3526144c9 100644
> > --- a/hw/9pfs/9p-util.h
> > +++ b/hw/9pfs/9p-util.h
> > @@ -58,6 +58,36 @@ static inline uint64_t host_dev_to_dotl_dev(dev_t dev)
> > #endif
> > }
> >
> > +/* Translates errno from host -> Linux if needed */
> > +static inline int errno_to_dotl(int err) {
> > +#if defined(CONFIG_LINUX)
> > + /* nothing to translate (Linux -> Linux) */
> > +#elif defined(CONFIG_DARWIN)
> > + /*
> > + * translation mandatory for macOS hosts
> > + *
> > + * FIXME: Only most important errnos translated here yet, this should
> > be
> > + * extended to as many errnos being translated as possible in future.
> > + */
> > + if (err == ENAMETOOLONG) {
> > + err = 36; /* ==ENAMETOOLONG on Linux */
> > + } else if (err == ENOTEMPTY) {
> > + err = 39; /* ==ENOTEMPTY on Linux */
> > + } else if (err == ELOOP) {
> > + err = 40; /* ==ELOOP on Linux */
> > + } else if (err == ENOATTR) {
> > + err = 61; /* ==ENODATA on Linux */
> > + } else if (err == ENOTSUP) {
> > + err = 95; /* ==EOPNOTSUPP on Linux */
> > + } else if (err == EOPNOTSUPP) {
> > + err = 95; /* ==EOPNOTSUPP on Linux */
> > + }
>
> What happens if a macOS guest is running on QEMU from a macOS host?
> Here all macOS errnos are translated to the Linux errnos. Will macOS
> be happy?
>
The 9p2000.L protocol is tailored for a linux client. As mentioned in
the changelog, the spec explicitly mentions 'numerical linux errno'.
A macOS client should thus convert back errno in a Rlerror message
to a macOS errno.
> > +#else
> > +#error Missing errno translation to Linux for this host system
> > +#endif
> > + return err;
> > +}
> > +
> > #ifdef CONFIG_DARWIN
> > #define qemu_fgetxattr(...) fgetxattr(__VA_ARGS__, 0, 0)
> > #define qemu_lgetxattr(...) getxattr(__VA_ARGS__, 0, XATTR_NOFOLLOW)
> > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> > index 4a296a0b94..0cd0c14c2a 100644
> > --- a/hw/9pfs/9p.c
> > +++ b/hw/9pfs/9p.c
> > @@ -1054,6 +1054,8 @@ static void coroutine_fn pdu_complete(V9fsPDU *pdu,
> > ssize_t len)
> > }
> > len += ret;
> > id = P9_RERROR;
> > + } else {
> > + err = errno_to_dotl(err);
> > }
> >
> > ret = pdu_marshal(pdu, len, "d", err);
> > --
>
> Regards,
> Bin
- [PATCH v5 1/6] 9pfs: fix qemu_mknodat(S_IFREG) on macOS, (continued)
[PATCH v5 3/6] 9pfs: fix wrong encoding of rdev field in Rgetattr on macOS, Christian Schoenebeck, 2022/04/29
[PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host, Christian Schoenebeck, 2022/04/29
- Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host, Bin Meng, 2022/04/29
- Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host,
Greg Kurz <=
- Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host, Christian Schoenebeck, 2022/04/29
- Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host, Greg Kurz, 2022/04/29
- Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host, Bin Meng, 2022/04/29
- Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host, Greg Kurz, 2022/04/29
- Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host, Christian Schoenebeck, 2022/04/29
- Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host, Bin Meng, 2022/04/29
- Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host, Christian Schoenebeck, 2022/04/29
- Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host, Bin Meng, 2022/04/29
[PATCH v5 5/6] 9pfs: fix removing non-existent POSIX ACL xattr on macOS host, Christian Schoenebeck, 2022/04/29
[PATCH v5 6/6] 9pfs: fix qemu_mknodat() to always return -1 on error on macOS host, Christian Schoenebeck, 2022/04/29