On Fri, 29 Apr 2022 19:28:39 +0800 Bin Meng <bmeng...@gmail.com> wrote:
> On Fri, Apr 29, 2022 at 7:16 PM Christian Schoenebeck > <qemu_...@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...@gmail.com/ > > But we had some questions in mind (see the commit message of our > patch, and below) > > > > > Signed-off-by: Christian Schoenebeck <qemu_...@crudebyte.com> > > Link: https://lore.kernel.org/qemu-devel/20220421124835.3e664669@bahia/ > > Reviewed-by: Greg Kurz <gr...@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
