Add -add-rpath-and-shrink operation

The core issue is that `--shrink-rpath` doesn't free up space filled
with `X` by `--add-rpath`, so using a combination of `--add-rpath` &
`--shrink-rpath` on a virtual env will blow up shared libraries and
cause them to segfault when loaded by Python at some point.

Author: Maximilian Bosch

src/patchelf.cc

@@ -1477,8 +1477,13 @@ std::string ElfFile<ElfFileParamNames>::shrinkRPath(char* rpath, std::vector<std
     std::vector<bool> neededLibFound(neededLibs.size(), false);
 
     std::string newRPath = "";
+    std::set<std::string> componentsConsidered;
 
     for (auto & dirName : splitColonDelimitedString(rpath)) {
+        if (componentsConsidered.find(dirName) != componentsConsidered.end()) {
+            continue;
+        }
+        componentsConsidered.insert(dirName);
 
         /* Non-absolute entries are allowed (e.g., the special
            "$ORIGIN" hack). */
@@ -1617,6 +1622,14 @@ void ElfFile<ElfFileParamNames>::modifyRPath(RPathOp op,
             break;
         }
         case rpSet: { break; } /* new rpath was provied as input to this function */
+        case rpShrinkAndAdd: {
+            auto temp = std::string(rpath ? rpath : "");
+            appendRPath(temp, newRPath);
+            newRPath = temp;
+            char * newRPathCStr = const_cast<char *>(newRPath.c_str());
+            newRPath = shrinkRPath(newRPathCStr, neededLibs, allowedRpathPrefixes);
+            break;
+        }
     }
 
     if (!forceRPath && dynRPath && !dynRunPath) { /* convert DT_RPATH to DT_RUNPATH */
@@ -2419,7 +2432,9 @@ static void patchElf2(ElfFile && elfFile, const FileContents & fileContents, con
     else if (setExecstack)
         elfFile.modifyExecstack(ElfFile::ExecstackMode::set);
 
-    if (shrinkRPath)
+    if (shrinkRPath && addRPath)
+        elfFile.modifyRPath(elfFile.rpShrinkAndAdd, allowedRpathPrefixes, newRPath);
+    else if (shrinkRPath)
         elfFile.modifyRPath(elfFile.rpShrink, allowedRpathPrefixes, "");
     else if (removeRPath)
         elfFile.modifyRPath(elfFile.rpRemove, {}, "");
@@ -2567,6 +2582,12 @@ static int mainWrapped(int argc, char * * argv)
             if (++i == argc) error("missing argument");
             allowedRpathPrefixes = splitColonDelimitedString(argv[i]);
         }
+        else if (arg == "--add-rpath-and-shrink") {
+            if (++i == argc) error("missing argument");
+            addRPath = true;
+            newRPath = resolveArgument(argv[i]);
+            shrinkRPath = true;
+        }
         else if (arg == "--set-rpath") {
             if (++i == argc) error("missing argument");
             setRPath = 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, rpShrink, rpSet, rpAdd, rpRemove, rpShrinkAndAdd } 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);