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 for linux-um@lists.infradead.org; Thu, 04 Mar 2021 07:47:38 +0000
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Subject: Re: linux uml segfault
From: Johannes Berg <johannes@sipsolutions.net>
Date: Thu, 04 Mar 2021 08:47:20 +0100
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To: Hajime Tazaki <thehajime@gmail.com>
Cc: rrs@debian.org, anton.ivanov@kot-begemot.co.uk, chris.obbard@collabora.com, linux-um@lists.infradead.org, 983379@bugs.debian.org

On Thu, 2021-03-04 at 14:38 +0900, Hajime Tazaki wrote:

> > Now, I don't know how to fix it (short of changing your nsswitch
> > configuration) - maybe we could somehow rename sem_init()? Or maybe we
> > can somehow give the kernel binary a lower symbol resolution than the
> > libc/libpthread.
> 
> objcopy (from binutils) can localize symbols (i.e., objcopy -L
> sem_init $orig_file $new_file).  It also does renaming symbols.  But
> not sure this is the ideal solution.

Yes, we started thinking about it but it was too late at night when I
replied ...

I think there's basically a way to have an external list of symbols to
export, for symbol versioning, that we could/should use to basically not
export any of the kernel symbols out to libs.

> How does UML handle symbol conflicts between userspace code and Linux
> kernel (like this case sem_init) ?  AFAIK, libnl has a same symbol as
> Linux kernel (genlmsg_put) and others can possibly do as well.

I fear it doesn't?

johannes


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