On Thu, Jul 24, 2014 at 12:52:26PM -0400, Dave Reisner wrote:
> On Wed, Jul 23, 2014 at 07:39:02PM +0200, Andreas Henriksson wrote:
> > The "linux only" check for pivot_root seems to suffer from
> > a cut-n-paste problem from the earlier switch_root part.
> >
> > Signed-off-by: Andreas Henriksson <andreas@xxxxxxxx>
> > ---
> > configure.ac | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/configure.ac b/configure.ac
> > index db53dff..aae2456 100644
> > --- a/configure.ac
> > +++ b/configure.ac
> > @@ -1193,7 +1193,7 @@ AC_ARG_ENABLE([pivot_root],
> > [], [UL_DEFAULT_ENABLE([pivot_root], [check])]
> > )
> > UL_BUILD_INIT([pivot_root])
> > -UL_REQUIRES_LINUX([switch_root])
> > +UL_REQUIRES_LINUX([pivot_root])
>
> Is this really correct? Seems to me like the check should simply be
> removed.
It's definitely better to check that the system is Linux before you
start to check for something more complicated. There is logical "and"
between all UL_REQUIRES_*, so the first unsuccessful check disabled
the rest.
> In sys-utils/pivot_root.c, we have the following:
>
> #define pivot_root(new_root,put_old) syscall(SYS_pivot_root,new_root,put_old)
>
> So, the subsequent check for the syscall seems like the only necessary
> check needed. As is, I think that u-l now fails to build in places where
> the pivot_root wrapper doesn't exist in the libc, but the syscall exists
> (does such a platform even exist?).
There is no glibc wrapper at all, in code we always call the syscall
and in configure.ac we check for SYS_pivot_root sycall on Linux.
Nowhere we care about libc.
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
http://karelzak.blogspot.com
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