@@ -46,6 +46,21 @@ int xencall_close(xencall_handle *xcall);
/*
* Call hypercalls with varying numbers of arguments.
+ *
+ * On success the return value of the hypercall is the return value of
+ * the xencall function. On error these functions set errno and
+ * return -1.
+ *
+ * The errno values will be either:
+ * - The Xen hypercall error return (from xen/include/public/errno.h)
+ * translated into the corresponding local value for that POSIX error.
+ * - An errno value produced by the OS driver or the library
+ * implementation. Such values may be defined by POSIX or by the OS.
+ *
+ * Note that under some circumstances it will not be possible to tell
+ * whether an error came from Xen or from the OS/library.
+ *
+ * These functions never log.
*/
int xencall0(xencall_handle *xcall, unsigned int op);
int xencall1(xencall_handle *xcall, unsigned int op,
This behaviour has been confirmed by inspection on: - Linux - NetBSD & FreeBSD (NB: hcall->retval is the hypercall return value only for values >= 0. For negative values the underlying privcmd driver translates the value from Xen to {Net,Free}BSD errno space and returns it as the result of the ioctl, which becomes ret=-1/errno=EFOO in userspace) - MiniOS (which takes care of errno in this library) Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Acked-by: Wei Liu <wei.liu2@citrix.com> Acked-by: Ian Jackson <ian.jackson@eu.citrix.com> Acked-by: Roger Pau Monné <roger.pau@citrix.com> Cc: Roger Pau Monné <roger.pau@citrix.com> --- v7: Noted NetBSD behaviour v6: New patch --- tools/libs/call/include/xencall.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+)