Date: Thu, 15 Feb 2001 09:04:45 -0700 From: Warner Losh <imp@harmony.village.org> To: arch@FreeBSD.ORG Subject: Re: The whole libc thing. Message-ID: <200102151604.f1FG4jW62156@harmony.village.org> In-Reply-To: Your message of "Thu, 15 Feb 2001 02:03:53 MST." <200102150903.f1F93rW62243@harmony.village.org> References: <200102150903.f1F93rW62243@harmony.village.org>
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In message <200102150903.f1F93rW62243@harmony.village.org> Warner Losh writes:
: Green's solution of stealing a pointer and using that to "grow" FILE.
: This would allow old binaris to keep working at the cost of binary
: compatibility. There's a few extra indirections in this case, you'll
: likely not be able to measure that performance loss. But it will work
: with the case above and most of the others we threw at it.
I've become convinced that the old FILE layout is what we need to do.
Step 1:
Back out to Feb 10.
Step 2:
Apply Green's and Daniel's changes (Green to get the new
layout, Daniel's for thread locking). These two changes
are in my tree right now.
Step 3:
Introduce __stdin, __stdout, and __stderr into libc.so.3,
libc.so.4 and libc.so.5. WE can do this in the building of
libc.so via a trick that Tor Egge sent me (he did it to
libc.so.3):
--- /usr/obj/usr/src/gnu/usr.bin/binutils/ld/ldscripts/elf_i386.xs Sun Feb 4 00:23:05 2001
+++ /tmp/tegge1 Thu Feb 15 05:46:01 2001
@@ -62,6 +62,9 @@
.data :
{
*(.data)
+ __stdin = __sF;
+ __stdout = __sF +0x58 ;
+ __stderr = __sF +0xB0 ;
*(.gnu.linkonce.d*)
CONSTRUCTORS
}
Or, alternatively, I think that we could do this with a small
amount of assembler on each platform that we support (i386,
pc98 and alpha). I'm not sure how to do this, but something
like the following might work on i386:
.set __stdin, __sF
.set __stdout, __sF + 0x58
.set __stderr, __sF + 0xB0
Step 4:
Create compat libraries for libc.so.4 and libc.so.3.
Encourage people to upgrade to these. This is the hard part
and the weak part of my plan.
Step 5: <in a while, assuming that 3 and 4 work>
Bump the major version of libc and start using something like
peter's change.
I think that this will work. But need to make sure that we have no
cases where newer libraries are using __sF and that breaking things.
I'll try to put together a table to convince myself and others that
this path will work. Steps 1 and 2 are known to work.
Warner
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