linux-kernel - Re: [PATCH 1/4] exec: Change uselib(2) IS

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Message-ID: <87sgfwuoi3.fsf@x220.int.ebiederm.org>
Date:   Tue, 19 May 2020 06:56:36 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Andreas Schwab <schwab@...ux-m68k.org>
Cc:     Christian Brauner <christian.brauner@...ntu.com>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Eric Biggers <ebiggers3@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] exec: Change uselib(2) IS_SREG() failure to EACCES

Andreas Schwab <schwab@...ux-m68k.org> writes:

> On Mai 18 2020, Eric W. Biederman wrote:
>
>> If it was only libc4 and libc5 that used the uselib system call then it
>> can probably be removed after enough time.
>
> Only libc4 used it, libc5 was already ELF.

binfmt_elf.c supports uselib.  In a very a.out ish way.  Do you know if
that support was ever used?

If we are truly talking a.out only we should be able to make uselib
conditional on a.out support in the kernel which is strongly mostly
disabled at this point.

I am wondering if there are source trees for libc4 or libc5 around
anywhere that we can look at to see how usage of uselib evolved.

Eric