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From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no>
To: freebsd-arch@freebsd.org
Subject: COMPAT_32BIT oddness in rtld-elf (was: Re: /usr/lib/private)
References: <86zjrut4an.fsf@nine.des.no>
Date: Sat, 07 Sep 2013 13:48:13 +0200
In-Reply-To: <86zjrut4an.fsf@nine.des.no> ("Dag-Erling =?utf-8?Q?Sm=C3=B8r?=
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 "Tue, 03 Sep 2013 15:37:04 +0200")
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I'm having trouble understanding this code in libexec/rtld-elf/rtld.c:

static void *
path_enumerate(const char *path, path_enum_proc callback, void *arg)
{
#ifdef COMPAT_32BIT
    const char *trans;
#endif
    if (path =3D=3D NULL)
	return (NULL);

    path +=3D strspn(path, ":;");
    while (*path !=3D '\0') {
	size_t len;
	char  *res;

	len =3D strcspn(path, ":;");
#ifdef COMPAT_32BIT
	trans =3D lm_findn(NULL, path, len);
	if (trans)
	    res =3D callback(trans, strlen(trans), arg);
	else
#endif
	res =3D callback(path, len, arg);

	if (res !=3D NULL)
	    return (res);

	path +=3D len;
	path +=3D strspn(path, ":;");
    }

    return (NULL);
}

This function is used to traverse paths, such as rtld's built-in search
path, LD_LIBRARY_PATH, an Elf object's rpath, etc.  As far as I can
tell, the result of this is that *in the COMPAT_32BIT case only* it is
possible to list one directory as replacing another in libmap.conf.  In
other words, we could have this in libmap32.conf:

/lib                    /lib32
/usr/lib                /usr/lib32
/usr/lib/private        /usr/lib32/private

instead of hardcoding a different standard search path in rtld.h.

What I don't understand is why this functionality is only available in
the COMPAT_32BIT case.  It seems universally useful to me.

DES
--=20
Dag-Erling Sm=C3=B8rgrav - des@des.no