Lookup functions in the binding table directly (#1337)

instead of making multiple redundant copies of it. Copying and making a map out of the table incurs a significant overhead.
dyninst · Dec 15, 2022 · 42612b4 · 42612b4
1 parent 3937542
commit 42612b4
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Showing 3 changed files with 29 additions and 28 deletions.
diff --git a/dyninstAPI/src/unix.C b/dyninstAPI/src/unix.C
@@ -743,45 +743,21 @@ func_instance *block_instance::callee() {
 
    // get the relocation information for this image
    Symtab *sym = obj()->parse_img()->getObject();
-   std::vector<relocationEntry> fbt;
-   if (!sym->getFuncBindingTable(fbt)) {
-      return NULL;
-   }
-
-
-   /**
-    * Object files and static binaries will not have a function binding table
-    * because the function binding table holds relocations used by the dynamic
-    * linker
-    */
-   if (!fbt.size() && !sym->isStaticBinary() &&
-           sym->getObjectType() != obj_RelocatableFile ) 
-   {
-      fprintf(stderr, "%s[%d]:  WARN:  zero func bindings\n", FILE__, __LINE__);
-   }
-
-   std::map<Address, std::string> pltFuncs;
-   obj()->parse_img()->getPltFuncs(pltFuncs);
-
    // find the target address in the list of relocationEntries
-   if (pltFuncs.find(target_addr) != pltFuncs.end()) {
+   relocationEntry function_binding;
+   if(sym->findPltEntryByTarget(target_addr, function_binding)) {
 	  Address base_addr = obj()->codeBase();
-      for (u_int i=0; i < fbt.size(); i++) {
-         if (fbt[i].target_addr() == target_addr) 
-         {
             // check to see if this function has been bound yet...if the
             // PLT entry for this function has been modified by the runtime
             // linker
             func_instance *target_pdf = 0;
-            if (proc()->hasBeenBound(fbt[i], target_pdf, base_addr)) {
+      if (proc()->hasBeenBound(function_binding, target_pdf, base_addr)) {
                updateCallTarget(target_pdf);
                obj()->setCalleeName(this, target_pdf->symTabName());
                obj()->setCallee(this, target_pdf);
                return target_pdf;
             }
-         }
-      }
-      return callee(pltFuncs[target_addr]);
+      return callee(function_binding.name());
    } else {
 	   /*
 	    * Sometimes, the PLT address and the CFG target aren't the same

diff --git a/symtabAPI/h/Symtab.h b/symtabAPI/h/Symtab.h
@@ -219,6 +219,7 @@ class SYMTAB_EXPORT Symtab : public LookupInterface,
 
    // Relocation entries
    bool getFuncBindingTable(std::vector<relocationEntry> &fbt) const;
+   bool findPltEntryByTarget(Address target_address, relocationEntry &result) const;
    bool updateFuncBindingTable(Offset stub_addr, Offset plt_addr);
 
    /**************************************

diff --git a/symtabAPI/src/Symtab.C b/symtabAPI/src/Symtab.C
@@ -1548,6 +1548,30 @@ SYMTAB_EXPORT bool Symtab::getFuncBindingTable(std::vector<relocationEntry> &fbt
    return true;
 }
 
+SYMTAB_EXPORT bool Symtab::findPltEntryByTarget(const Address target_address, relocationEntry &result) const
+{
+    /**
+     * Object files and static binaries will not have a function binding table
+     * because the function binding table holds relocations used by the dynamic
+     * linker
+     */
+    if(relocation_table_.empty() && !isStaticBinary() &&
+       getObjectType() != obj_RelocatableFile)
+    {
+        fprintf(stderr, "%s[%d]:  WARN:  zero func bindings\n", FILE__, __LINE__);
+    }
+
+    auto it = std::find_if(relocation_table_.cbegin(), relocation_table_.cend(),
+                           [=](const relocationEntry& entry) {
+                               return entry.target_addr() == target_address;
+                           });
+    if(it == relocation_table_.cend())
+        return false;
+
+    result = *it;
+    return true;
+}
+
 SYMTAB_EXPORT bool Symtab::updateFuncBindingTable(Offset stub_addr, Offset plt_addr)
 {
     int stub_idx = -1, plt_idx = -1;