Re: [Xen-devel] [PATCH] tools/pygrub: do not override pygrub with a symbolic link

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-04-22 at 13:26 +0100, Christoph Egger wrote:
> On 22.04.13 13:58, Ian Campbell wrote:
> > On Mon, 2013-04-22 at 12:50 +0100, Christoph Egger wrote:
> >> tools/pygrub: Do not override pygrub with a symbolic link if $(BINDIR)
> >> and $(PRIVATE_BINDIR) are the same.
> > 
> > More properly this is "fix the if condition we use to decide when to
> > create the symlink", since it is already the intention to not override
> > if they are the same  but the condition is written wrong since it
> > includes DESTDIR on one side but not the other, which defeats the check.
> > 
> > FWIW I would niuke the DESTDIR on the left rather than adding it on the
> > right, it might even fit on one line then?
> 
> Does not work. See comment below.

OK, that makes sense I guess.

> >> Signed-off-by: Christoph Egger <chegger@xxxxxxxxx>
> >> diff --git a/tools/pygrub/Makefile b/tools/pygrub/Makefile
> >> index 039f7f7..c3b34d7 100644
> >> --- a/tools/pygrub/Makefile
> >> +++ b/tools/pygrub/Makefile
> >> @@ -15,8 +15,8 @@ install: all
> >>            --install-scripts=$(PRIVATE_BINDIR) --force
> >>    $(INSTALL_DIR) $(DESTDIR)/var/run/xend/boot
> >>    set -e; if [ "`readlink -f $(DESTDIR)/$(BINDIR)`" != \
> >> -               "`readlink -f $(PRIVATE_BINDIR)`" ]; then \
> >> -      ln -sf $(PRIVATE_BINDIR)/pygrub $(DESTDIR)/$(BINDIR); \
> >> +               "`readlink -f $(DESTDIR)/$(PRIVATE_BINDIR)`" ]; then \
> >> +      ln -sf $(DESTDIR)/$(PRIVATE_BINDIR)/pygrub $(DESTDIR)/$(BINDIR); \
> > 
> > I don't think this change to the first path passed to ln is correct
> > since this will become the content of the symlink, which doesn't want to
> > include DESTDIR.
> 
> What actually happens when $(BINDIR) and $(PRIVATE_BINDIR) are equal
> is that the pygrub python script does not exist. pygrub is a symbolic
> link to a file that doesn't exist instead.
> 
> With this patch you will actually install the pygrub python script
> rather a symbolic link.

The code inside the if shouldn't even be run in the case you are trying
to fix.

But you have broken the case where BINDIR and PRIVATE_BINDIR differ
because /usr/bin/pygrub will be a symlink
to /tmp/destdir.XYZ/usr/lib/xen/bin/pygrub and not
to /usr/lib/xen/bin/pygrub.

Ian.


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