From c77c434149959e135ba21d1dd8a78a408fef2489 Mon Sep 17 00:00:00 2001
From: Pavel Chupin <pavel.v.chupin@intel.com>
Date: Wed, 31 Oct 2012 13:55:51 +0400
Subject: [PATCH] Adjust symbol lookup for DT_SYMBOLIC case

According ELF spec re. DT_SYMBOLIC:
This element's presence in a shared object library alters the dynamic
linker's symbol resolution algorithm for references within the library.
Instead of starting a symbol search with the executable file, the
dynamic linker starts from the shared object itself. If the shared
object fails to supply the referenced symbol, the dynamic linker then
searches the executable file and other shared objects as usual.

This change implements the last part.

Change-Id: Iae95d53d455313a4306f11733941bcd3596ac85f
Signed-off-by: Pavel Chupin <pavel.v.chupin@intel.com>
---
 linker/linker.cpp | 76 +++++++++++++++++++++++++++++++++--------------
 1 file changed, 53 insertions(+), 23 deletions(-)
 mode change 100644 => 100755 linker/linker.cpp

diff --git a/linker/linker.cpp b/linker/linker.cpp
old mode 100644
new mode 100755
index 9e4138e15..8bb989a4b
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -425,38 +425,68 @@ soinfo_do_lookup(soinfo *si, const char *name, soinfo **lsi,
     Elf32_Sym *s = NULL;
     int i;
 
-    if (si != NULL) {
+    if (si != NULL && somain != NULL) {
 
         /*
-         * If this object was built with symbolic relocations disabled, the
-         * first place to look to resolve external references is the main
-         * executable.
+         * Local scope is executable scope. Just start looking into it right away
+         * for the shortcut.
          */
 
-        if (!si->has_DT_SYMBOLIC) {
-            DEBUG("%5d %s: looking up %s in executable %s\n",
-                  pid, si->name, name, somain->name);
-            s = soinfo_elf_lookup(somain, elf_hash, name);
+        if (si == somain) {
+            s = soinfo_elf_lookup(si, elf_hash, name);
             if (s != NULL) {
-                *lsi = somain;
+                *lsi = si;
                 goto done;
             }
-        }
+        } else {
+            /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */
 
-        /* Look for symbols in the local scope (the object who is
-         * searching). This happens with C++ templates on i386 for some
-         * reason.
-         *
-         * Notes on weak symbols:
-         * The ELF specs are ambiguous about treatment of weak definitions in
-         * dynamic linking.  Some systems return the first definition found
-         * and some the first non-weak definition.   This is system dependent.
-         * Here we return the first definition found for simplicity.  */
+            /*
+             * If this object was built with symbolic relocations disabled, the
+             * first place to look to resolve external references is the main
+             * executable.
+             */
 
-        s = soinfo_elf_lookup(si, elf_hash, name);
-        if (s != NULL) {
-            *lsi = si;
-            goto done;
+            if (!si->has_DT_SYMBOLIC) {
+                DEBUG("%5d %s: looking up %s in executable %s\n",
+                      pid, si->name, name, somain->name);
+                s = soinfo_elf_lookup(somain, elf_hash, name);
+                if (s != NULL) {
+                    *lsi = somain;
+                    goto done;
+                }
+            }
+
+            /* Look for symbols in the local scope (the object who is
+             * searching). This happens with C++ templates on i386 for some
+             * reason.
+             *
+             * Notes on weak symbols:
+             * The ELF specs are ambiguous about treatment of weak definitions in
+             * dynamic linking.  Some systems return the first definition found
+             * and some the first non-weak definition.   This is system dependent.
+             * Here we return the first definition found for simplicity.  */
+
+            s = soinfo_elf_lookup(si, elf_hash, name);
+            if (s != NULL) {
+                *lsi = si;
+                goto done;
+            }
+
+            /*
+             * If this object was built with -Bsymbolic and symbol is not found
+             * in the local scope, try to find the symbol in the main executable.
+             */
+
+            if (si->has_DT_SYMBOLIC) {
+                DEBUG("%5d %s: looking up %s in executable %s after local scope\n",
+                      pid, si->name, name, somain->name);
+                s = soinfo_elf_lookup(somain, elf_hash, name);
+                if (s != NULL) {
+                    *lsi = somain;
+                    goto done;
+                }
+            }
         }
     }