elf: handle new DT_RUNPATH

This patch enhances dynamic linker to resolve dependent objects that rely on DT_RUNPATH entry to specify directories to search for. Some ELFs have both DT_RUNPATH and DT_RPATH in which case our linker disregards the latter per specification. For details read slide "Finding shared libraries at run time" under http://man7.org/training/download/shlib_dynlinker_slides.pdf. Fixes #1039 Signed-off-by: Waldemar Kozaczuk <[email protected]> Message-Id: <[email protected]>
cloudius-systems · May 19, 2019 · 31926c3 · 31926c3
1 parent b3aef65
commit 31926c3
Show file tree

Hide file tree

Showing 2 changed files with 13 additions and 3 deletions.
diff --git a/core/elf.cc b/core/elf.cc
@@ -932,8 +932,17 @@ static std::string dirname(std::string path)
 void object::load_needed(std::vector<std::shared_ptr<object>>& loaded_objects)
 {
     std::vector<std::string> rpath;
-    if (dynamic_exists(DT_RPATH)) {
-        std::string rpath_str = dynamic_str(DT_RPATH);
+
+    std::string rpath_str;
+    // Prefer newer DT_RUNPATH
+    if (dynamic_exists(DT_RUNPATH)) {
+        rpath_str = dynamic_str(DT_RUNPATH);
+    // Otherwise fall back to older DT_RPATH
+    } else if (dynamic_exists(DT_RPATH)) {
+        rpath_str = dynamic_str(DT_RPATH);
+    }
+
+    if (!rpath_str.empty()) {
         boost::replace_all(rpath_str, "$ORIGIN", dirname(_pathname));
         boost::split(rpath, rpath_str, boost::is_any_of(":"));
     }

diff --git a/include/osv/elf.hh b/include/osv/elf.hh
@@ -167,7 +167,7 @@ enum {
     DT_INIT = 12, // d_ptr Address of the initialization function.
     DT_FINI = 13, // d_ptr Address of the termination function.
     DT_SONAME = 14, // d_val The string table offset of the name of this shared object.
-    DT_RPATH = 15, // d_val The string table offset of a shared library search path string.
+    DT_RPATH = 15, // d_val The string table offset of a shared library search path string (deprecated)
     DT_SYMBOLIC = 16, // ignored The presence of this dynamic table entry modifies the
       // symbol resolution algorithm for references within the
       // library. Symbols defined within the library are used to
@@ -191,6 +191,7 @@ enum {
     DT_FINI_ARRAY = 26, // d_ptr Pointer to an array of pointers to termination functions.
     DT_INIT_ARRAYSZ = 27, // d_val Size, in bytes, of the array of initialization functions.
     DT_FINI_ARRAYSZ = 28, // d_val Size, in bytes, of the array of termination functions.
+    DT_RUNPATH = 29, // d_val The string table offset of a shared library search path string.
     DT_FLAGS = 30, // value is various flags, bits from DF_*.
     DT_FLAGS_1 = 0x6ffffffb, // value is various flags, bits from DF_1_*.
     DT_LOOS = 0x60000000, // Defines a range of dynamic table tags that are reserved for