SVR3 shared libs and copying of data section

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2 total messages Started by Thomas Wolfram Thu, 07 Jan 1993 01:04

#2620

Author: Thomas Wolfram
Date: Thu, 07 Jan 1993 01:04

20 lines
1076 bytes

Hi,
on SVR3 all processes linked with a shared library get their
own copy of the data section of the (target) shared library.
Does somebody know how that copying is realized?

Is it realized by "Copy-on-write", I mean that a page of the
data section is only copyed if another process want to write
to it like with SysV-fork(2)?
Or is it realized by copying the whole data section for the
process?

Thank you for any hints,
Thomas

PS: I'm about to create SVR3 shared libraries for XFree86 1.2 and
    must decide fastly about a implementation question.
    (I've two different versions yet.)
-- 
Thomas Wolfram, thomas@aeon.in-berlin.de
EANTC, TU Berlin, wolf@prz.tu-berlin.de, +49 030 31421294

Re: SVR3 shared libs and copying of data section

#2621

Author: DaviD W. Sanderson
Date: Thu, 07 Jan 1993 04:37

14 lines
1069 bytes

In article <C0GLMt.9p@aeon.in-berlin.de> thomas@aeon.in-berlin.de (Thomas Wolfram) writes:
>on SVR3 all processes linked with a shared library get their
>own copy of the data section of the (target) shared library.
>Is it realized by "Copy-on-write"?

Yes, it's a page-level copy-on-write.  It's just like what happens with
the regular data section of a child process after a fork() - the child
only gets its own copy of the data pages it modifies.

>PS: I'm about to create SVR3 shared libraries for XFree86 1.2

My sympathies.

DaviD W. Sanderson (dws@ssec.wisc.edu)

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