add --update-rpath to change between RPATH and RUNPATH

patchelf.1

@@ -79,6 +79,10 @@ the "/foo/lib" reference instead of the "/tmp" entry.
 .IP --print-rpath
 Prints the DT_RUNPATH or DT_RPATH for an executable or library.
 
+.IP --update-rpath
+Updates the DR_RPATH to a DT_RUNTPATH or vice versa if "--force-rpath" is given
+too.
+
 .IP --force-rpath
 Forces the use of the obsolete DT_RPATH in the file instead of
 DT_RUNPATH. By default DT_RPATH is converted to DT_RUNPATH.

src/patchelf.cc

@@ -1601,6 +1601,7 @@ void ElfFile<ElfFileParamNames>::modifyRPath(RPathOp op,
             newRPath = temp;
             break;
         }
+        case rpUpdate: { break; } /* just update the RPATH to RUNPATH or vice versa */
         case rpSet: { break; } /* new rpath was provied as input to this function */
     }
 
@@ -1616,6 +1617,10 @@ void ElfFile<ElfFileParamNames>::modifyRPath(RPathOp op,
         changed = true;
     }
 
+    if (op == rpUpdate) {
+        return;
+    }
+
     if (rpath && rpath == newRPath) {
         return;
     }
@@ -2306,6 +2311,7 @@ static std::vector<std::string> allowedRpathPrefixes;
 static bool removeRPath = false;
 static bool setRPath = false;
 static bool addRPath = false;
+static bool updateRPath = false;
 static bool addDebugTag = false;
 static bool renameDynamicSymbols = false;
 static bool printRPath = false;
@@ -2361,6 +2367,8 @@ static void patchElf2(ElfFile && elfFile, const FileContents & fileContents, con
         elfFile.modifyRPath(elfFile.rpSet, {}, newRPath);
     else if (addRPath)
         elfFile.modifyRPath(elfFile.rpAdd, {}, newRPath);
+    else if (updateRPath)
+        elfFile.modifyRPath(elfFile.rpUpdate, {}, "");
 
     if (printNeeded) elfFile.printNeededLibs();
 
@@ -2430,6 +2438,7 @@ static void showHelp(const std::string & progName)
   [--allowed-rpath-prefixes PREFIXES]\t\tWith '--shrink-rpath', reject rpath entries not starting with the allowed prefix\n\
   [--print-rpath]\n\
   [--force-rpath]\n\
+  [--update-rpath]\n\
   [--add-needed LIBRARY]\n\
   [--remove-needed LIBRARY]\n\
   [--replace-needed LIBRARY NEW_LIBRARY]\n\
@@ -2493,6 +2502,9 @@ static int mainWrapped(int argc, char * * argv)
         else if (arg == "--remove-rpath") {
             removeRPath = true;
         }
+        else if (arg == "--update-rpath") {
+            updateRPath = true;
+        }
         else if (arg == "--shrink-rpath") {
             shrinkRPath = true;
         }

src/patchelf.h

@@ -149,7 +149,7 @@ class ElfFile
 
     void setInterpreter(const std::string & newInterpreter);
 
-    typedef enum { rpPrint, rpShrink, rpSet, rpAdd, rpRemove } RPathOp;
+    typedef enum { rpPrint, rpUpdate, rpShrink, rpSet, rpAdd, rpRemove } RPathOp;
 
     void modifyRPath(RPathOp op, const std::vector<std::string> & allowedRpathPrefixes, std::string newRPath);
     std::string shrinkRPath(char* rpath, std::vector<std::string> &neededLibs, const std::vector<std::string> & allowedRpathPrefixes);

tests/update-rpath.sh

@@ -0,0 +1,36 @@
+#! /bin/sh -e
+SCRATCH=scratch/$(basename "$0" .sh)
+OBJDUMP=${OBJDUMP:-objdump}
+
+rm -rf "${SCRATCH}"
+mkdir -p "${SCRATCH}"
+
+SCRATCHFILE=${SCRATCH}/libfoo.so
+cp libfoo.so "$SCRATCHFILE"
+
+doit() {
+    set +x
+    ../src/patchelf "$@" "$SCRATCHFILE"
+    set -x
+}
+
+expect() {
+    out=$("$OBJDUMP" -x "$SCRATCHFILE" | grep PATH || true)
+
+    for i in $out; do
+        if [ "$i" != "$1" ]; then
+            echo "Expected '$*' but got '$out'"
+            exit 1
+        fi
+        shift
+    done
+}
+
+doit --remove-rpath
+expect ""
+doit --set-rpath foo
+expect RUNPATH foo
+doit --update-rpath --force-rpath 
+expect RPATH foo
+doit --update-rpath
+expect RUNPATH foo