Index: ELF/LinkerScript.h
===================================================================
--- ELF/LinkerScript.h
+++ ELF/LinkerScript.h
@@ -230,7 +230,7 @@
   uint64_t getDot() { return Dot; }
   void discard(ArrayRef<InputSection *> V);
 
-  ExprValue getSymbolValue(StringRef Name, const Twine &Loc);
+  ExprValue getSymbolValue(StringRef Name, const Twine &Loc, bool CanUseDot);
 
   void fabricateDefaultCommands();
   void addOrphanSections(OutputSectionFactory &Factory);
Index: ELF/LinkerScript.cpp
===================================================================
--- ELF/LinkerScript.cpp
+++ ELF/LinkerScript.cpp
@@ -402,7 +402,8 @@
       // is given, input sections are aligned to that value, whether the
       // given value is larger or smaller than the original section alignment.
       if (Sec->SubalignExpr) {
-        uint32_t Subalign = Sec->SubalignExpr().getValue();
+        uint32_t Subalign =
+            std::max((uint64_t)1, Sec->SubalignExpr().getValue());
         for (InputSectionBase *S : V)
           S->Alignment = Subalign;
       }
@@ -873,9 +874,10 @@
   return false;
 }
 
-ExprValue LinkerScript::getSymbolValue(StringRef Name, const Twine &Loc) {
+ExprValue LinkerScript::getSymbolValue(StringRef Name, const Twine &Loc,
+                                       bool CanUseDot) {
   if (Name == ".") {
-    if (Ctx)
+    if (CanUseDot)
       return {Ctx->OutSec, false, Dot - Ctx->OutSec->Addr, Loc};
     error(Loc + ": unable to get location counter value");
     return 0;
Index: ELF/ScriptLexer.h
===================================================================
--- ELF/ScriptLexer.h
+++ ELF/ScriptLexer.h
@@ -38,6 +38,7 @@
   std::vector<MemoryBufferRef> MBs;
   std::vector<StringRef> Tokens;
   bool InExpr = false;
+  bool CanUseDot = false;
   size_t Pos = 0;
 
 private:
Index: ELF/ScriptParser.cpp
===================================================================
--- ELF/ScriptParser.cpp
+++ ELF/ScriptParser.cpp
@@ -31,6 +31,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/SaveAndRestore.h"
 #include <cassert>
 #include <limits>
 #include <vector>
@@ -258,6 +259,7 @@
     } else if (Tok == "SEARCH_DIR") {
       readSearchDir();
     } else if (Tok == "SECTIONS") {
+      SaveAndRestore<bool> R(CanUseDot, true);
       readSections();
     } else if (Tok == "VERSION") {
       readVersion();
@@ -654,8 +656,11 @@
     Cmd->LMAExpr = readParenExpr();
   if (consume("ALIGN"))
     Cmd->AlignExpr = readParenExpr();
-  if (consume("SUBALIGN"))
+  if (consume("SUBALIGN")) {
+    // SUBALIGN expression must be constant, so can't use Dot.
+    SaveAndRestore<bool> R(CanUseDot, false);
     Cmd->SubalignExpr = readParenExpr();
+  }
 
   // Parse constraints.
   if (consume("ONLY_IF_RO"))
@@ -756,7 +761,10 @@
   Expr E = readExpr();
   if (Op == "+=") {
     std::string Loc = getCurrentLocation();
-    E = [=] { return add(Script->getSymbolValue(Name, Loc), E()); };
+    bool DotAvailable = CanUseDot;
+    E = [=] {
+      return add(Script->getSymbolValue(Name, Loc, DotAvailable), E());
+    };
   }
   return make<SymbolAssignment>(Name, E, getCurrentLocation());
 }
@@ -1056,8 +1064,9 @@
     return [=] { return elf::getHeaderSize(); };
 
   // Tok is the dot.
+  bool DotAvailable = CanUseDot;
   if (Tok == ".")
-    return [=] { return Script->getSymbolValue(Tok, Location); };
+    return [=] { return Script->getSymbolValue(Tok, Location, DotAvailable); };
 
   // Tok is a literal number.
   if (Optional<uint64_t> Val = parseInt(Tok))
@@ -1067,7 +1076,7 @@
   if (!isValidCIdentifier(Tok))
     setError("malformed number: " + Tok);
   Script->ReferencedSymbols.push_back(Tok);
-  return [=] { return Script->getSymbolValue(Tok, Location); };
+  return [=] { return Script->getSymbolValue(Tok, Location, DotAvailable); };
 }
 
 Expr ScriptParser::readTernary(Expr Cond) {