On Thu, 21 Apr 2022 13:13:08 +0200 Christian Schoenebeck <qemu_...@crudebyte.com> wrote:
> On Donnerstag, 21. April 2022 12:48:35 CEST Greg Kurz wrote: > > On Tue, 19 Apr 2022 13:41:59 +0200 > > > > 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 Tlerror replies (if 9p2000.L is used that is), which > > > fixes a bunch of misbehaviours when running a Linux client on macOS > > > host. > > > > This even fixes an actual protocol violation : > > > > lerror -- return error code > > > > size[4] Rlerror tag[2] ecode[4] > > > > lerror replaces the reply message used in a successful call. ecode is a > > numerical Linux errno. > > ^^^^^^^^^^^^^^^^^^^^^ > > > > Taken from > > https://github.com/chaos/diod/wiki/protocol#lerror----return-error-code > > Again, something to add to the commit log? > IMHO a protocol violation is important enough to be mentioned but I'll leave it to you. > > > 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. > > > > > > Signed-off-by: Christian Schoenebeck <qemu_...@crudebyte.com> > > > --- > > > > > > hw/9pfs/9p.c | 27 +++++++++++++++++++++++++++ > > > 1 file changed, 27 insertions(+) > > > > > > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c > > > index d953035e1c..becc41cbfd 100644 > > > --- a/hw/9pfs/9p.c > > > +++ b/hw/9pfs/9p.c > > > @@ -57,6 +57,31 @@ enum { > > > > > > P9ARRAY_DEFINE_TYPE(V9fsPath, v9fs_path_free); > > > > > > +/* Translates errno from host -> Linux if needed */ > > > +static int errno_to_dotl(int err) { > > > +#if defined(CONFIG_LINUX) > > > + /* nothing to translate (Linux -> Linux) */ > > > +#elif defined(CONFIG_DARWIN) > > > + /* translation mandatory for macOS hosts */ > > > + 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 */ > > > + } > > > > I'm assuming you have audited all errnos, right ? Just to be sure > > that this won't bite anymore. > > Depends on what you mean with "all". Like I wrote in the commit log, for now > I > translated in this patch those errnos that I identified as important, and > those are audited by me of course (checked the man pages for what errors are > expected as result from calls on Linux vs. macOS side and looked up numeric > values from header files on both sides, tests). > I was pretty sure you'd have done that at least :-) > However if you rather mean really all errnos that were ever defined on Linux > and macOS, then the answer is no. That would probably quite some work, and > I'm > not sure if you could just try to translate them dry, i.e. by just looking at > the headers or something. > But yes I was rather meaning the full errno set. > So yes, your concern is justified. The question is, should this all be > translated right now already, or would it be OK to address this minimum set > of > errno translation for now (especially for qemu-stable) and then later address > the rest? > My concern is about the maintenance burden of investigating future implementations of this issue, so I'd say it is mostly up to you as the principal maintainer. Maybe leave a FIXME comment in the code that the list of translated errnos isn't exhaustive at least ? > On the long term you would probably import the Linux errno header file into > the code base, then prefix the individual macros with something like > DOTL_ENODATA, etc. and then use those macros for translating the errnos > instead of using literal numerics, maybe using GCC's designated array > initializers then. > This would make sense indeed since 9p2000.L explicitly mentions the numerical linux errnos. > > > +#else > > > +#error Missing errno translation to Linux for this host system > > > +#endif > > > + return err; > > > +} > > > + > > > > As with the other patch, I'd rather move this magic to 9p-util.h . > > Makes sense. There is indeed already too much utility code piled up in 9p.c. > > > > static ssize_t pdu_marshal(V9fsPDU *pdu, size_t offset, const char *fmt, > > > ...) { > > > > > > ssize_t ret; > > > > > > @@ -1054,6 +1079,8 @@ 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); > >