From 1659238a0ca2744d18f4b9a3c77ed1e224510e11 Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Fri, 15 May 2020 11:58:01 +0000
Subject: [PATCH] Implement RTLD_DEEPBIND.

PR:	246462
Tested by:	Martin Birgmeier <d8zNeCFG@aon.at>
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D24841
---
 include/dlfcn.h         | 2 ++
 lib/libc/gen/dlopen.3   | 5 ++++-
 libexec/rtld-elf/rtld.c | 4 ++++
 libexec/rtld-elf/rtld.h | 1 +
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/dlfcn.h b/include/dlfcn.h
index 76a7fa02ed74..f219879b8fa5 100644
--- a/include/dlfcn.h
+++ b/include/dlfcn.h
@@ -47,6 +47,8 @@
 #define	RTLD_TRACE	0x200	/* Trace loaded objects and exit. */
 #define	RTLD_NODELETE	0x01000	/* Do not remove members. */
 #define	RTLD_NOLOAD	0x02000	/* Do not load if not already loaded. */
+#define	RTLD_DEEPBIND	0x04000	/* Put symbols from the dso ahead of
+				   the global list */
 
 /*
  * Request arguments for dlinfo().
diff --git a/lib/libc/gen/dlopen.3 b/lib/libc/gen/dlopen.3
index 169a657b3952..8bafb0897fd9 100644
--- a/lib/libc/gen/dlopen.3
+++ b/lib/libc/gen/dlopen.3
@@ -32,7 +32,7 @@
 .\" @(#) dlopen.3 1.6 90/01/31 SMI
 .\" $FreeBSD$
 .\"
-.Dd January 2, 2019
+.Dd May 14, 2020
 .Dt DLOPEN 3
 .Os
 .Sh NAME
@@ -162,6 +162,9 @@ the process address space, otherwise
 is returned.
 Other mode flags may be specified, which will be applied for promotion
 for the found object.
+.It Dv RTLD_DEEPBIND
+Symbols from the loaded library are put before global symbols when
+resolving symbolic references originated from the library.
 .El
 .Pp
 If
diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
index 4b26aefb5240..c4c17c2d3a8a 100644
--- a/libexec/rtld-elf/rtld.c
+++ b/libexec/rtld-elf/rtld.c
@@ -3366,6 +3366,8 @@ rtld_dlopen(const char *name, int fd, int mode)
 	    lo_flags |= RTLD_LO_NODELETE;
     if (mode & RTLD_NOLOAD)
 	    lo_flags |= RTLD_LO_NOLOAD;
+    if (mode & RTLD_DEEPBIND)
+	    lo_flags |= RTLD_LO_DEEPBIND;
     if (ld_tracing != NULL)
 	    lo_flags |= RTLD_LO_TRACE | RTLD_LO_IGNSTLS;
 
@@ -3417,6 +3419,8 @@ dlopen_object(const char *name, int fd, Obj_Entry *refobj, int lo_flags,
 	if (globallist_next(old_obj_tail) != NULL) {
 	    /* We loaded something new. */
 	    assert(globallist_next(old_obj_tail) == obj);
+	    if ((lo_flags & RTLD_LO_DEEPBIND) != 0)
+		obj->symbolic = true;
 	    result = 0;
 	    if ((lo_flags & (RTLD_LO_EARLY | RTLD_LO_IGNSTLS)) == 0 &&
 	      obj->static_tls && !allocate_tls_offset(obj)) {
diff --git a/libexec/rtld-elf/rtld.h b/libexec/rtld-elf/rtld.h
index 7812ebb15390..c7bbc4e46e51 100644
--- a/libexec/rtld-elf/rtld.h
+++ b/libexec/rtld-elf/rtld.h
@@ -309,6 +309,7 @@ TAILQ_HEAD(obj_entry_q, Struct_Obj_Entry);
 #define	RTLD_LO_EARLY	0x20	/* Do not call ctors, postpone it to the
 				   initialization during the image start. */
 #define	RTLD_LO_IGNSTLS 0x40	/* Do not allocate static TLS */
+#define	RTLD_LO_DEEPBIND 0x80	/* Force symbolic for this object */
 
 /*
  * Symbol cache entry used during relocation to avoid multiple lookups