Re: [UNIKRAFT PATCH 6/7] lib/vfscore: Expose max fds to sysconf

[Simon Kuenzer <simon.kuenzer@xxxxxxxxx>]

Hey,

I noticed that this commit breaks compiling posix-sysinfo with nolibc 
because _SC_OPEN_MAX is undefined. I guess it is defined with newlib or 
musl, unfortunately not with nolibc but should have been added with this 
patch. We are currently using posix-sysinfo with nolibc for binary 
compatibility use cases where we try to populate the Linux system call 
ABI with a slim kernel libc (nolibc).
@Clupu or @Cristian: Can you review and push a fix that I am going to send?

Thanks,

Simon

On 05.05.20 20:19, Costin Lupu wrote:
> Thanks for adding this, Cristi!
> I'll upstream this now and we shall skip it from the v2.
>
> Reviewed-by: Costin Lupu <costin.lupu@xxxxxxxxx>
>
> On 5/2/20 6:13 PM, Cristian Banu wrote:
> > Expose FDTABLE_MAX_FILES from vfscore as the return value of
> > sysconf(_SC_OPEN_MAX) if CONFIG_LIBVFSCORE is enabled.
> >
> > This allows language runtimes to inspect the number of active
> > fds (e.g. for tests).
> >
> > Signed-off-by: Cristian Banu <cristb@xxxxxxxxx>
> > ---
> >   lib/posix-sysinfo/sysinfo.c        | 10 ++++++++++
> >   lib/vfscore/fd.c                   |  2 --
> >   lib/vfscore/include/vfscore/file.h |  3 +++
> >   3 files changed, 13 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/posix-sysinfo/sysinfo.c b/lib/posix-sysinfo/sysinfo.c
> > index 7bcfc8b..075f320 100644
> > --- a/lib/posix-sysinfo/sysinfo.c
> > +++ b/lib/posix-sysinfo/sysinfo.c
> > @@ -43,6 +43,11 @@
> >   #include <sys/sysinfo.h>
> >   #include <uk/syscall.h>
> >   
> > +#if CONFIG_LIBVFSCORE
> > +/* For FDTABLE_MAX_FILES. */
> > +#include <vfscore/file.h>
> > +#endif
> > +
> >   static struct utsname utsname = {
> >         .sysname        = "Unikraft",
> >         .nodename       = "unikraft",
> > @@ -85,6 +90,11 @@ long sysconf(int name)
> >         if (name == _SC_PAGESIZE)
> >                 return __PAGE_SIZE;
> >   
> > +#if CONFIG_LIBVFSCORE
> > +       if (name == _SC_OPEN_MAX)
> > +               return FDTABLE_MAX_FILES;
> > +#endif
> > +
> >         return 0;
> >   }
> >   
> > diff --git a/lib/vfscore/fd.c b/lib/vfscore/fd.c
> > index 684ea50..956846f 100644
> > --- a/lib/vfscore/fd.c
> > +++ b/lib/vfscore/fd.c
> > @@ -42,8 +42,6 @@
> >   #include <errno.h>
> >   #include <uk/ctors.h>
> >   
> > -#define FDTABLE_MAX_FILES 1024
> > -
> >   void init_stdio(void);
> >   
> >   struct fdtable {
> > diff --git a/lib/vfscore/include/vfscore/file.h 
> > b/lib/vfscore/include/vfscore/file.h
> > index be23974..ec45a08 100644
> > --- a/lib/vfscore/include/vfscore/file.h
> > +++ b/lib/vfscore/include/vfscore/file.h
> > @@ -80,6 +80,9 @@ int fdrop(struct vfscore_file* fp);
> >   
> >   #define FOF_OFFSET  0x0800    /* Use the offset in uio argument */
> >   
> > +/* Used from posix-sysinfo to determine sysconf(_SC_OPEN_MAX). */
> > +#define FDTABLE_MAX_FILES 1024
> > +
> >   #ifdef __cplusplus
> >   }
> >   #endif