misc/186435: [patch] Allow for an alternative run-time loader

[Yuri]

>Number:         186435
>Category:       misc
>Synopsis:       [patch] Allow for an alternative run-time loader
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          change-request
>Submitter-Id:   current-users
>Arrival-Date:   Mon Feb 03 23:40:01 UTC 2014
>Closed-Date:
>Last-Modified:
>Originator:     Yuri
>Release:        9.2
>Organization:
n/a
>Environment:
>Description:
Synopsys:
This is a simple patch to run-time loader, which allows other parts of the process to load objects dynamically.

What this patch does:
This patch makes r_debug and related symbols in the ld-elf.so.1 run-time loader public.

Detailed description:
Currently, only r_debug_symbol is public out of all debugger-related symbols in ld-elf.so. This is done so that debuggers can add a breakpoint on it to get notified of changes in the set of loaded shared libraries. This is sufficient when ld-elf.so is the only one who loads objects.

Now imagine the situation when an application wants to load its own ELF objects in its own way, still having the benefit of using the debug info. Such application would need to have access to the list of objects maintained by ld-elf.so. r_debug variable contains this list.

Such application would necessarily be system specific, and would have to have the knowledge of some inner workings of ld-elf.so. But, in my opinion, this is a legitimate use and should be allowed. Therefore I am suggesting this patch. Except r_debug, it adds related lock object and functions to the list of publics, because they are needed to avoid race conditions.

This is, of course, not a mainstream way to do things, but nevertheless it should be allowed.
This is also a minor patch, and it can't possibly hurt anything else.

--begin patch--
--- libexec/rtld-elf/Symbol.map  (revision 260894)
+++ libexec/rtld-elf/Symbol.map  (working copy)
@@ -15,6 +15,11 @@
     dlinfo;
     dl_iterate_phdr;
     r_debug_state;
+    r_debug;
+    rtld_bind_lock;
+    rlock_acquire;
+    wlock_acquire;
+    lock_release;
     __tls_get_addr;
 };

--end patch--

>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
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