From: Richard Henderson <rth@cygnus.com>
To: law@cygnus.com
Cc: m9305357@bohm.anu.edu.au, egcs@cygnus.com
Subject: Re: Shared C++ libs on i386-pc-solaris2.5.1
Date: Thu, 11 Sep 1997 13:20:00 -0000 [thread overview]
Message-ID: <199709111955.MAA20955@rtl.cygnus.com> (raw)
In-Reply-To: <4912.873994065@hurl.cygnus.com>
> On some systems (PAs running hpux), you can't have a text/readonly data
> item which is initialized to the address of another item.
>
> ie
>
> .word foo
>
> isn't valid if it's going into the text or readonly data section.
This is not the case on an i386 ELF system.
In the main application there is a nasty hack called .dynbss which the
linker creates to hold all of the variable references. So the symbols
are really at constant addresses, and have their contents filled in at
run time. (It is odeious and breaks when symbol sizes (read arrays)
change.)
A shared library, on the other hand, is tagged with DT_TEXTREL which
tells the loader that it should temporarily remap everything read-write.
Thus, while outputting read-only data that contains relocactions should
be avoided (because of the mprotect penalty), it does function correctly.
All this is if course how things are _supposed_ to work. If you've got
a broken loader on some system...
r~
next prev parent reply other threads:[~1997-09-11 13:20 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <199709100139.SAA07609@cygnus.com>
1997-09-09 19:54 ` James Macnicol
1997-09-10 22:37 ` James Macnicol
1997-09-11 10:01 ` Jeffrey A Law
1997-09-11 13:20 ` Richard Henderson [this message]
1997-09-07 5:42 James Macnicol
1997-09-07 10:11 ` H.J. Lu
[not found] <34096EF5.5768EC4F@student.anu.edu.au>
1997-09-04 15:05 ` Jim Wilson
1997-09-04 16:55 ` Jeffrey A Law
-- strict thread matches above, loose matches on Subject: below --
1997-08-31 2:07 egcs 970828 and X11 on linux/x86 H.J. Lu
1997-08-31 13:17 ` Shared C++ libs on i386-pc-solaris2.5.1 James Macnicol
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