diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp
index 33ae89538d5645552d32de40a8d0b9c3974ef343..4e368aadf62a557fcd1438001783bec4c3051861 100644
--- a/lld/ELF/SyntheticSections.cpp
+++ b/lld/ELF/SyntheticSections.cpp
@@ -4070,13 +4070,11 @@ void AdltSection<ELFT>::finalizeContents() {
     ADLT_HASH_TYPE_GNU_HASH,        // .stringHashType
     getBlobStartOffset(),           // .blobStart
     estimateBlobSize(),             // .blobSize
-    0,                              // .overallMappedSize
+    0,                              // .overallMappedSize, known on writeTo
     {0, 0},                         // .relaDynSegs, filled in writeTo
     {0, 0},                         // .relaPltSegs, filled in writeTo
   };
 
-  // TODO: estimate and fill overallMappedSize
-
   buildSonameIndex();
   linkInternalDtNeeded();
   extractInitFiniArray();
@@ -4133,6 +4131,15 @@ void AdltSection<ELFT>::extractInitFiniArray() {
   }
 }
 
+template <typename ELFT>
+size_t AdltSection<ELFT>::estimateOverallMappedSize() {
+  size_t totalMemsz = 0;
+  for (PhdrEntry* ph : mainPart->phdrs)
+    if (ph->p_type == PT_LOAD)
+      totalMemsz += ph->p_memsz;
+  return totalMemsz;
+}
+
 template <typename ELFT>
 typename AdltSection<ELFT>::CommonData
 AdltSection<ELFT>::makeCommonData() {
@@ -4265,6 +4272,12 @@ adlt_blob_array_t AdltSection<ELFT>::writeDtNeeded(
   return writeArray(buff, offset, needIndexes);
 }
 
+template <typename ELFT>
+void AdltSection<ELFT>::finalizeOnWrite() {
+  // require Writer::setPhdrs previously been called
+  header.overallMappedSize = estimateOverallMappedSize();
+}
+
 template <typename ELFT>
 void AdltSection<ELFT>::writeTo(uint8_t* buf) {
   // TODO: take care of endianness, use write32 / write64 etc.
@@ -4277,6 +4290,8 @@ void AdltSection<ELFT>::writeTo(uint8_t* buf) {
     psods.push_back(psod);
   }
 
+  finalizeOnWrite();
+
   // serialize blob data
   {
     uint8_t* const blobBuf = buf + header.blobStart;
diff --git a/lld/ELF/SyntheticSections.h b/lld/ELF/SyntheticSections.h
index c69b95704406e06fcdcad81c394021cff0bcc911..a93ff052cfe362624439003531fc2b36047ff3cb 100644
--- a/lld/ELF/SyntheticSections.h
+++ b/lld/ELF/SyntheticSections.h
@@ -1282,15 +1282,16 @@ private:
   void buildSonameIndex();
   void linkInternalDtNeeded();
   void extractInitFiniArray();
+  size_t estimateOverallMappedSize();
+  Elf64_Xword calculateHash(StringRef str) const;
 
   CommonData makeCommonData();
   SoData makeSoData(const SharedFileExtended<ELFT>*);
-
-  Elf64_Xword calculateHash(StringRef str) const;
   adlt_psod_t serialize(const SoData&) const;
-
   size_t estimateBlobSize() const;
 
+  void finalizeOnWrite();
+
   template <typename T, unsigned N>
   adlt_blob_array_t writeArray(uint8_t* buff, size_t offset,
                                const SmallVector<T, N>& data);