On Thu, Oct 15, 2015 at 12:24:39PM +0100, David Vrabel wrote: > On 15/10/15 12:18, Mikko Rapeli wrote: > > On Thu, Oct 15, 2015 at 11:29:12AM +0100, David Vrabel wrote: > >> On 15/10/15 06:56, Mikko Rapeli wrote: > >>> xen/interface/xen.h is not exported from kernel headers so remove the > >>> dependency and provide needed defines for domid_t and xen_pfn_t if they > >>> are not already defined by some other e.g. Xen specific headers. > >>> > >>> Suggested by Andrew Cooper <andrew.coop...@citrix.com> on lkml message > >>> <5569f9c9.8000...@citrix.com>. > >>> > >>> The ifdef for ARM is ugly but did not find better solutions for it. > >>> > >>> Fixes userspace compilation error: > >>> > >>> xen/privcmd.h:38:31: fatal error: xen/interface/xen.h: No such file or > >>> directory > >> [...] > >>> --- a/include/uapi/xen/privcmd.h > >>> +++ b/include/uapi/xen/privcmd.h > >>> @@ -35,7 +35,19 @@ > >>> > >>> #include <linux/types.h> > >>> #include <linux/compiler.h> > >>> -#include <xen/interface/xen.h> > >>> + > >>> +/* Might be defined by Xen specific headers, but if not */ > >>> +#ifndef domid_t > >>> +typedef __u16 domid_t; > >>> +#endif /* domid_t */ > >> > >> As the kbuild bot points out, this does not work since the existence of > >> a typedef cannot be checked with #ifdef. > > > > Yeah, this hack doesn't cut it. Sorry. Tried to implement these changes: > > http://www.spinics.net/lists/linux-api/msg11048.html > > > >> I'm not really sure what problem you're trying to solve. A user space > >> program making use of this interface gets the domid_t and xen_pfn_t etc > >> typedefs from the headers provided as part of the libxenctrl library. > > > > I'm trying to make sure that kernel headers in userspace compile with > > minimal > > dependencies which are gcc and libc. > > > > For me it is clear by now that many Linux API's and ABI's like Xen parts do > > not live in the uapi header files and instead there's a separate userspace > > library with needed headers and defines which have embedded copies of > > the needed API and ABI definitions, like header files. > > > > So how could this file be changed so that it compiles in userspace without > > definitions from libxenctrl? > > I don't think anything needs to be changed. > > Instead I would make your compilation check of this header dependent on > the existence of the xen/interface/xen.h header. Or you may exclude the > check of this header entirely.
There are not many headers in uapi which require additional userspace headers to compile (I'm not saying that uapi headers represent the full API's/ABI's, it's clear they don't). If there are ~700 headers and just a single one needs an exception and additional dependencies, I would try to make it work without the dependency. I just need some advice and guidance from maintainers how to do this. Or we should start tracking these userspace library dependencies too, at least at linux-headers package levels in distributions. This might be a good idea anyway, but then we might as well move headers like this directly to the userspace library and out of include/uapi. Both would solve the non-compiling uapi header problem. > > I guess I could copy the needed definitions for domid_t and xen_pfn_t from > > xen/interface/xen.h of libxenctrl. That I should have done to begin with > > instead of trying to hack something on my own. > > I do not want definitions duplicated/copied from the hypervisor ABI > headers. This causes problems when support for new architectures is > added (for example). Understood. -Mikko > David -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
