Date: Fri, 22 Apr 2005 17:03:59 -0400 (EDT) From: Daniel Eischen <deischen@freebsd.org> To: Peter Wemm <peter@wemm.org> Cc: freebsd-arch@freebsd.org Subject: Re: libpthread version bump Message-ID: <Pine.GSO.4.43.0504221701470.24214-100000@sea.ntplx.net> In-Reply-To: <200504221357.31957.peter@wemm.org>
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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
--
DE
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