[PATCH] D33629: [ELF] Use late evaluation for ALIGN in expression

[Petr Hosek via Phabricator via llvm-commits]

phosek created this revision.
phosek added a project: lld.
Herald added a subscriber: emaste.

While the following expression is handled fine:

  PROVIDE_HIDDEN(newsym = oldsym + address);

The following expression triggers an error because the expression
is evaluated as absolute:

  PROVIDE_HIDDEN(newsym = ALIGN(oldsym, CONSTANT(MAXPAGESIZE)) + address);

To avoid this error, we use late evaluation for ALIGN by making the
alignment an attribute of the expression itself.


Repository:
  rL LLVM

https://reviews.llvm.org/D33629

Files:
  ELF/LinkerScript.cpp
  ELF/LinkerScript.h
  ELF/ScriptParser.cpp
  test/ELF/linkerscript/align.s
  test/ELF/linkerscript/symbol-reserved.s


Index: test/ELF/linkerscript/symbol-reserved.s
===================================================================
--- test/ELF/linkerscript/symbol-reserved.s
+++ test/ELF/linkerscript/symbol-reserved.s
@@ -11,6 +11,12 @@
 
 # SHARED: 0000000000000005 .dynsym 00000000 .hidden newsym
 
+# RUN: echo "PROVIDE_HIDDEN(newsym = ALIGN(__ehdr_start, CONSTANT(MAXPAGESIZE)) + 5);" > %t.script
+# RUN: ld.lld -o %t1 %t.script %t
+# RUN: llvm-objdump -t %t1 | FileCheck --check-prefix=ALIGNED %s
+
+# ALIGNED: 0000000000200005 .text 00000000 .hidden newsym
+
 .global _start
 _start:
   lea newsym(%rip),%rax
Index: test/ELF/linkerscript/align.s
===================================================================
--- test/ELF/linkerscript/align.s
+++ test/ELF/linkerscript/align.s
@@ -64,7 +64,7 @@
 # SYMBOLS-NEXT: 0000000000010000         *ABS*           00000000 __code_base__
 # SYMBOLS-NEXT: 0000000000001000         *ABS*           00000000 VAR
 # SYMBOLS-NEXT: 0000000000011000         .bbb            00000000 __start_bbb
-# SYMBOLS-NEXT: 0000000000012000         *ABS*           00000000 __end_bbb
+# SYMBOLS-NEXT: 0000000000012000         .bbb            00000000 __end_bbb
 
 .global _start
 _start:
Index: ELF/ScriptParser.cpp
===================================================================
--- ELF/ScriptParser.cpp
+++ ELF/ScriptParser.cpp
@@ -859,7 +859,11 @@
     expect(",");
     Expr E2 = readExpr();
     expect(")");
-    return [=] { return alignTo(E().getValue(), E2().getValue()); };
+    return [=] {
+      ExprValue V = E();
+      V.Align = E2().getValue();
+      return V;
+    };
   }
   if (Tok == "ALIGNOF") {
     StringRef Name = readParenLiteral();
Index: ELF/LinkerScript.h
===================================================================
--- ELF/LinkerScript.h
+++ ELF/LinkerScript.h
@@ -41,9 +41,12 @@
   SectionBase *Sec;
   uint64_t Val;
   bool ForceAbsolute;
+  uint64_t Align;
 
+  ExprValue(SectionBase *Sec, bool ForceAbsolute, uint64_t Val, uint64_t Align)
+      : Sec(Sec), Val(Val), ForceAbsolute(ForceAbsolute), Align(Align) {}
   ExprValue(SectionBase *Sec, bool ForceAbsolute, uint64_t Val)
-      : Sec(Sec), Val(Val), ForceAbsolute(ForceAbsolute) {}
+      : Sec(Sec), Val(Val), ForceAbsolute(ForceAbsolute), Align(1) {}
   ExprValue(SectionBase *Sec, uint64_t Val) : ExprValue(Sec, false, Val) {}
   ExprValue(uint64_t Val) : ExprValue(nullptr, Val) {}
   bool isAbsolute() const { return ForceAbsolute || Sec == nullptr; }
Index: ELF/LinkerScript.cpp
===================================================================
--- ELF/LinkerScript.cpp
+++ ELF/LinkerScript.cpp
@@ -52,11 +52,12 @@
 uint64_t ExprValue::getValue() const {
   if (Sec) {
     if (Sec->getOutputSection())
-      return Sec->getOffset(Val) + Sec->getOutputSection()->Addr;
+      return alignTo(Sec->getOffset(Val) + Sec->getOutputSection()->Addr,
+                     Align);
     error("unable to evaluate expression: input section " + Sec->Name +
           " has no output section assigned");
   }
-  return Val;
+  return alignTo(Val, Align);
 }
 
 uint64_t ExprValue::getSecAddr() const {
@@ -143,7 +144,7 @@
   } else {
     Sym->Section = V.Sec;
     if (Sym->Section->Flags & SHF_ALLOC)
-      Sym->Value = V.Val;
+      Sym->Value = alignTo(V.Val, V.Align);
     else
       Sym->Value = V.getValue();
   }


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