From 118897f0303fac8e9dc14c3600444ff9abcaa683 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Wed, 16 Jan 2013 23:41:19 +0100
Subject: =?UTF-8?q?Add=20=E2=80=98--remove-needed=E2=80=99=20option?=
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This allows removing the specified DT_NEEDED entries from the dynamic
section.

Closes #4.
---
 README          | 11 ++++++++++-
 src/patchelf.cc | 44 ++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/README b/README
index e2ec1e2..fbdbcf5 100644
--- a/README
+++ b/README
@@ -19,10 +19,17 @@ libraries.  In particular, it can do the following:
   an RPATH "/lib:/usr/lib:/foo/lib", and libfoo.so can only be found
   in /foo/lib, then the new RPATH will be "/foo/lib".
 
+* Remove declared dependencies on dynamic libraries (DT_NEEDED
+  entries):
+
+  $ patchelf --remove-needed libfoo.so.1 my-program
+
+  This option can be given multiple times.
+
 
 AUTHOR
 
-Copyright 2004-2009 Eelco Dolstra <e.dolstra@tudelft.nl>.
+Copyright 2004-2013 Eelco Dolstra <eelco.dolstra@logicblox.com>.
 
 
 LICENSE
@@ -62,6 +69,8 @@ RELEASE HISTORY
 * Rewrite section indices in symbol tables. This for instance allows
   gdb to show proper backtraces.
 
+* Added `--remove-needed' option.
+
 0.6 (November 7, 2011):
 
 * Hacky support for executables created by the Gold linker.
diff --git a/src/patchelf.cc b/src/patchelf.cc
index 694b2f8..82a4bf1 100644
--- a/src/patchelf.cc
+++ b/src/patchelf.cc
@@ -1,5 +1,6 @@
 #include <string>
 #include <vector>
+#include <set>
 #include <map>
 #include <algorithm>
 
@@ -149,6 +150,8 @@ public:
 
     void modifyRPath(RPathOp op, string newRPath);
 
+    void removeNeeded(set<string> libs);
+
 private:
 
     /* Convert an integer in big or little endian representation (as
@@ -924,7 +927,7 @@ void ElfFile<ElfFileParamNames>::modifyRPath(RPathOp op, string newRPath)
             rpath = strTab + rdi(dyn->d_un.d_val);
         }
         else if (rdi(dyn->d_tag) == DT_NEEDED)
-	  neededLibs.push_back(string(strTab + rdi(dyn->d_un.d_val)));
+            neededLibs.push_back(string(strTab + rdi(dyn->d_un.d_val)));
     }
 
     if (op == rpPrint) {
@@ -1048,6 +1051,37 @@ void ElfFile<ElfFileParamNames>::modifyRPath(RPathOp op, string newRPath)
 }
 
 
+template<ElfFileParams>
+void ElfFile<ElfFileParamNames>::removeNeeded(set<string> libs)
+{
+    if (libs.empty()) return;
+
+    Elf_Shdr & shdrDynamic = findSection(".dynamic");
+    Elf_Shdr & shdrDynStr = findSection(".dynstr");
+    char * strTab = (char *) contents + rdi(shdrDynStr.sh_offset);
+
+    Elf_Dyn * dyn = (Elf_Dyn *) (contents + rdi(shdrDynamic.sh_offset));
+    Elf_Dyn * last = dyn;
+    for ( ; rdi(dyn->d_tag) != DT_NULL; dyn++) {
+        if (rdi(dyn->d_tag) == DT_NEEDED) {
+            char * name = strTab + rdi(dyn->d_un.d_val);
+            if (libs.find(name) != libs.end()) {
+                debug("removing DT_NEEDED entry `%s'\n", name);
+                changed = true;
+            } else {
+                debug("keeping DT_NEEDED entry `%s'\n", name);
+                *last++ = *dyn;
+            }
+        } else
+            *last++ = *dyn;
+    }
+
+    memset(last, 0, sizeof(Elf_Dyn) * (dyn - last));
+
+    debug("%d", dyn - last);
+}
+
+
 static bool printInterpreter = false;
 static string newInterpreter;
 
@@ -1055,6 +1089,7 @@ static bool shrinkRPath = false;
 static bool setRPath = false;
 static bool printRPath = false;
 static string newRPath;
+static set<string> neededLibsToRemove;
 
 
 template<class ElfFile>
@@ -1062,7 +1097,6 @@ static void patchElf2(ElfFile & elfFile, mode_t fileMode)
 {
     elfFile.parse();
 
-
     if (printInterpreter)
         printf("%s\n", elfFile.getInterpreter().c_str());
 
@@ -1077,6 +1111,7 @@ static void patchElf2(ElfFile & elfFile, mode_t fileMode)
     else if (setRPath)
         elfFile.modifyRPath(elfFile.rpSet, newRPath);
 
+    elfFile.removeNeeded(neededLibsToRemove);
 
     if (elfFile.isChanged()){
         elfFile.rewriteSections();
@@ -1128,6 +1163,7 @@ void showHelp(const string & progName)
   [--shrink-rpath]\n\
   [--print-rpath]\n\
   [--force-rpath]\n\
+  [--remove-needed LIBRARY]\n\
   [--debug]\n\
   [--version]\n\
   FILENAME\n", progName.c_str());
@@ -1178,6 +1214,10 @@ int main(int argc, char * * argv)
                added. */
             forceRPath = true;
         }
+        else if (arg == "--remove-needed") {
+            if (++i == argc) error("missing argument");
+            neededLibsToRemove.insert(argv[i]);
+        }
         else if (arg == "--debug") {
             debugMode = true;
         }
-- 
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