COMPAT_32BIT oddness in rtld-elf (was: Re: /usr/lib/private)
John Baldwin
jhb at freebsd.org
Mon Sep 9 17:46:05 UTC 2013
On Saturday, September 07, 2013 7:48:13 am Dag-Erling Smørgrav wrote:
> 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 == NULL)
> return (NULL);
>
> path += strspn(path, ":;");
> while (*path != '\0') {
> size_t len;
> char *res;
>
> len = strcspn(path, ":;");
> #ifdef COMPAT_32BIT
> trans = lm_findn(NULL, path, len);
> if (trans)
> res = callback(trans, strlen(trans), arg);
> else
> #endif
> res = callback(path, len, arg);
>
> if (res != NULL)
> return (res);
>
> path += len;
> path += 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.
I think it would be fine to make it universally available. You should talk to
Doug Ambrisko. He has patches to extend libmap support to key off OS-version,
etc. and might already make the directory case universal.
--
John Baldwin
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