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sybperl-l Archive

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From: "Stepan, Jamison" <Jamison dot Stepan at state dot mn dot us>
Subject: RE: Linking ctlib-linux-elf-dynamic on RedHat 5.1
Date: Aug 24 1998 1:33PM

This is great work Ted!

If it's something this simple, would is be worth pestering Sybase to do a
recompile of the libraries for glibc?

Would they even do it?

Jamison

> -----Original Message-----
> From:	Ted Law [SMTP:tedlaw@cibcwg.com]
> Sent:	Sunday, August 23, 1998 4:38 AM
> To:	SybPerl Discussion List
> Cc:	mpeppler@mbay.net; tedlaw@cibcwg.com
> Subject:	Linking ctlib-linux-elf-dynamic on RedHat 5.1
> 
> After hours of machine level debugging, I finally figured out what's
> going on.  The symtom was that DBD::Sybase and Sybperl will work when
> running from bash but not from zsh, whether it was linked dynamically or
> statically.  It turned out to be just a smoke screen.  The real problem
> is that ctlib-linux-elf-dynamic was compiled with a definition of struct
> sigaction that is different from the one compiled into glibc 6 used in
> RedHat 5.1.
> 
> The offsets for sa_mask, sa_flags, and sa_restorer were 4, 132, 136,
> respectively in glibc.  But ctlib-linux-elf-dynamic assumed 4, 8, 12.
> So when sigaction is called with a non-null value for old_act, glibc
> actually overwrites part of the stack.  Then, when the overwritten part
> is used as an address to write to,  a SEG fault occurs.  The reason why
> it would work when running from bash was that the incorrect address
> happens to fall into the unprotected gap between two shared libraries.
> 
> A workaround would be to write a wrapper for all struct sigaction
> related routines to bridge the two sides.  But I don't know how to do
> that.  Would some one please take this on?
> 
> Ted Law