Allow clients to specify search order of DynamicLibraries.

Summary: Different JITs and other clients of LLVM may have different needs in how symbol resolution should occur.

Reviewers: v.g.vassilev, lhames, karies

Reviewed By: v.g.vassilev

Subscribers: pcanal, llvm-commits

Differential Revision: https://reviews.llvm.org/D33529

llvm-svn: 307849

1 files changed, 32 insertions, 11 deletions

diff --git a/llvm/lib/Support/DynamicLibrary.cpp b/llvm/lib/Support/DynamicLibrary.cpp
index 9398789..d842211 100644
--- a/llvm/lib/Support/DynamicLibrary.cpp
+++ b/llvm/lib/Support/DynamicLibrary.cpp
@@ -14,6 +14,7 @@
 #include "llvm/Support/DynamicLibrary.h"
 #include "llvm-c/Support.h"
 #include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/Config/config.h"
 #include "llvm/Support/ManagedStatic.h"
@@ -73,19 +74,37 @@ public:
     return true;
   }
 
-  void *Lookup(const char *Symbol) {
-    // Process handle gets first try.
+  void *LibLookup(const char *Symbol, DynamicLibrary::SearchOrdering Order) {
+    if (Order & SO_LoadOrder) {
+      for (void *Handle : Handles) {
+        if (void *Ptr = DLSym(Handle, Symbol))
+          return Ptr;
+      }
+    } else {
+      for (void *Handle : llvm::reverse(Handles)) {
+        if (void *Ptr = DLSym(Handle, Symbol))
+          return Ptr;
+      }
+    }
+    return nullptr;
+  }
+
+  void *Lookup(const char *Symbol, DynamicLibrary::SearchOrdering Order) {
+    assert(!((Order & SO_LoadedFirst) && (Order & SO_LoadedLast)) &&
+           "Invalid Ordering");
+
+    if (!Process || (Order & SO_LoadedFirst)) {
+      if (void *Ptr = LibLookup(Symbol, Order))
+        return Ptr;
+    }
     if (Process) {
+      // Use OS facilities to search the current binary and all loaded libs.
       if (void *Ptr = DLSym(Process, Symbol))
         return Ptr;
-#ifndef NDEBUG
-      for (void *Handle : Handles)
-        assert(!DLSym(Handle, Symbol) && "Symbol exists in non process handle");
-#endif
-    } else {
-      // Iterate in reverse, so newer libraries/symbols override older.
-      for (auto &&I = Handles.rbegin(), E = Handles.rend(); I != E; ++I) {
-        if (void *Ptr = DLSym(*I, Symbol))
+
+      // Search any libs that might have been skipped because of RTLD_LOCAL.
+      if (Order & SO_LoadedLast) {
+        if (void *Ptr = LibLookup(Symbol, Order))
           return Ptr;
       }
     }
@@ -113,6 +132,8 @@ static llvm::ManagedStatic<llvm::sys::SmartMutex<true>> SymbolsMutex;
 #endif
 
 char DynamicLibrary::Invalid;
+DynamicLibrary::SearchOrdering DynamicLibrary::SearchOrder =
+    DynamicLibrary::SO_Linker;
 
 namespace llvm {
 void *SearchForAddressOfSpecialSymbol(const char *SymbolName) {
@@ -170,7 +191,7 @@ void *DynamicLibrary::SearchForAddressOfSymbol(const char *SymbolName) {
 
     // Now search the libraries.
     if (OpenedHandles.isConstructed()) {
-      if (void *Ptr = OpenedHandles->Lookup(SymbolName))
+      if (void *Ptr = OpenedHandles->Lookup(SymbolName, SearchOrder))
         return Ptr;
     }
   }