Date: Fri, 22 Apr 2005 18:18:29 -0400 From: Tom Rhodes <trhodes@FreeBSD.org> To: freebsd-arch@FreeBSD.org Subject: Re: libpthread version bump Message-ID: <20050422181829.1e0221ce@mobile.pittgoth.com> In-Reply-To: <20050422173033.33890323@mobile.pittgoth.com> References: <Pine.GSO.4.43.0504221701470.24214-100000@sea.ntplx.net> <200504221429.20458.peter@wemm.org> <20050422173033.33890323@mobile.pittgoth.com>
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On Fri, 22 Apr 2005 17:30:33 -0400
Tom Rhodes <trhodes@freebsd.org> wrote:
> On Fri, 22 Apr 2005 14:29:19 -0700
> Peter Wemm <peter@wemm.org> wrote:
>
> > On Friday 22 April 2005 02:03 pm, Daniel Eischen wrote:
> > > On Fri, 22 Apr 2005, Peter Wemm wrote:
> > > > The only other idea that springs to mind is to use dlsym() to test
> > > > for the symbol, but that has its own serious problems. If the
> > > > pragma weak stuff works, then I'd be happy with that.
> > > >
> > > > The only gotcha is that we still have to test for the possibility
> > > > that the *base syscalls return EINVAL.. This will happen for
> > > > booting old kernel.old files, and I'm not sure that current is
> > > > quite robust enough yet that people aren't going to want to be able
> > > > to rewind a few months.
> > > >
> > > > So, the options are:
> > > > 1) test for have_gsbase using weak (or dlsym).
> > > > 2) As previously suggested, add implemenations to libc.so.5 and
> > > > pick them up via a fresh compat5x. We can add an implementation to
> > > > libc.so.5. Since they wouldn't be used on 5.x, there is no risk of
> > > > breaking anything. The functions would only do something when
> > > > running the libc.so.5 library with a 5.x application on 6.x.
> > > >
> > > > I have a slight preference for #2, but that would mean adding two
> > > > tiny (but otherwise unused) libc.so functions very late in the
> > > > cycle. If re@ would allow it, I'd like that. But the #pragma weak
> > > > option also works for me.
> > > >
> > > > #2 can also make it a little easier to run 5.x i386 binaries on
> > > > amd64 - we could kill of most of those nasty ifdefs.
> > > >
> > > > #1 would end up something like:
> > > > #pragma weak i386_set_gsbase
> > > > #pragma weak i386_get_gsbase
> > > > static void (*have_get_gsbase)(void) = i386_get_gsbase;
> > > > static void (*have_set_gsbase)(void *) = i386_set_gsbase;
> > > > if (have_i386_get_gsbase == NULL || have_get_gsbase() == -1) {
> > > > use_ldt();
> > > > } else {
> > > > use_gsbase();
> > > > }
> > > > I think that is sufficient to test if the symbols are present and
> > > > test if they work at runtime...
> > >
> > > I worked up a quick patch. It compiles, but it will be some time
> > > before I can try it.
> > >
> > > http://people.freebsd.org/~deischen/kse/libpthread.diffs
> >
> > I think this will work. If somebody would like to try this, I think it
> > would be a good thing. (rebuild libpthread.so.0, and run a 5.x
> > threaded binary that would normally have the undefined symbols)
>
> Hey! I have one of those! And I would like to use it. Building
> now! :)
And it works. Yay. Thanks Dan.
--
Tom Rhodes
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