On Montag, 7. Februar 2022 23:40:19 CET Will Cohen wrote:
> From: Keno Fischer <k...@juliacomputing.com>
>
> Signed-off-by: Keno Fischer <k...@juliacomputing.com>
> Signed-off-by: Michael Roitzsch <reactorcont...@icloud.com>
>
> Because XATTR_SIZE_MAX is not defined on Darwin,
> create a cross-platform P9_XATTR_SIZE_MAX instead.
>
> [Will Cohen: - Adjust coding style
> - Lower XATTR_SIZE_MAX to 64k
> - Add explanatory context related to XATTR_SIZE_MAX]
> [Fabian Franz: - Move XATTR_SIZE_MAX reference from 9p.c to
> P9_XATTR_SIZE_MAX in 9p.h]
> Signed-off-by: Will Cohen <wwco...@gmail.com>
> Signed-off-by: Fabian Franz <fabianfranz....@gmail.com>
> ---
> hw/9pfs/9p.c | 2 +-
> hw/9pfs/9p.h | 11 +++++++++++
> 2 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> index 14e84c3bcf..7405352c37 100644
> --- a/hw/9pfs/9p.c
> +++ b/hw/9pfs/9p.c
> @@ -3949,7 +3949,7 @@ static void coroutine_fn v9fs_xattrcreate(void
> *opaque) rflags |= XATTR_REPLACE;
> }
>
> - if (size > XATTR_SIZE_MAX) {
> + if (size > P9_XATTR_SIZE_MAX) {
> err = -E2BIG;
> goto out_nofid;
> }
> diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
> index 1567b67841..6a1856b4dc 100644
> --- a/hw/9pfs/9p.h
> +++ b/hw/9pfs/9p.h
> @@ -479,4 +479,15 @@ struct V9fsTransport {
> void (*push_and_notify)(V9fsPDU *pdu);
> };
>
> +/*
> + * Darwin doesn't seem to define a maximum xattr size in its user
> + * space header, so manually configure it across platforms as 64k.
> + *
> + * Having no limit at all can lead to QEMU crashing during large g_malloc()
> + * calls. Because QEMU does not currently support macOS guests, the below
> + * preliminary solution only works due to its being a reflection of the
> limit of
> + * Linux guests.
> + */
> +#define P9_XATTR_SIZE_MAX 65536
It would be cleaner in a way like this:
#if defined(XATTR_SIZE_MAX)
/* Linux */
#define P9_XATTR_SIZE_MAX XATTR_SIZE_MAX
#elif defined(CONFIG_DARWIN)
/* darwin comment goes here */
#define P9_XATTR_SIZE_MAX 65536
#else
#error Missing definition for P9_XATTR_SIZE_MAX for this host system
#endif
Sorry, I haven't noticed that before. You actually had that wrapped into some
ifdefs in v2 before:
#if defined(CONFIG_DARWIN) && !defined(XATTR_SIZE_MAX)
...
#endif
> +
> #endif
