[lld] r302107 - Fix accounting of tbss.

[Rafael Espindola via llvm-commits]

Author: rafael
Date: Wed May  3 22:00:27 2017
New Revision: 302107

URL: http://llvm.org/viewvc/llvm-project?rev=302107&view=rev
Log:
Fix accounting of tbss.

We were correctly computing the size contribution of a .tbss input
section (it is none), but we were incorrectly considering the
alignment of the output section: it was advancing Dot instead of
ThreadBssOffset.

As far as I can tell this was always wrong in our linkerscript
implementation, but that became more visible now that the code is
shared with the non linker script case.

Modified:
    lld/trunk/ELF/LinkerScript.cpp
    lld/trunk/ELF/LinkerScript.h
    lld/trunk/test/ELF/tls-offset.s

Modified: lld/trunk/ELF/LinkerScript.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.cpp?rev=302107&r1=302106&r2=302107&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.cpp (original)
+++ lld/trunk/ELF/LinkerScript.cpp Wed May  3 22:00:27 2017
@@ -495,17 +495,22 @@ void LinkerScript::addOrphanSections(Out
   }
 }
 
-static bool isTbss(OutputSection *Sec) {
-  return (Sec->Flags & SHF_TLS) && Sec->Type == SHT_NOBITS;
+uint64_t LinkerScript::advance(uint64_t Size, unsigned Align) {
+  bool IsTbss = (CurOutSec->Flags & SHF_TLS) && CurOutSec->Type == SHT_NOBITS;
+  uint64_t Start = IsTbss ? Dot + ThreadBssOffset : Dot;
+  Start = alignTo(Start, Align);
+  uint64_t End = Start + Size;
+
+  if (IsTbss)
+    ThreadBssOffset = End - Dot;
+  else
+    Dot = End;
+  return End;
 }
 
 void LinkerScript::output(InputSection *S) {
-  bool IsTbss = isTbss(CurOutSec);
-
-  uint64_t Pos = IsTbss ? Dot + ThreadBssOffset : Dot;
-  Pos = alignTo(Pos, S->Alignment);
-  S->OutSecOff = Pos - CurOutSec->Addr;
-  Pos += S->getSize();
+  uint64_t Pos = advance(S->getSize(), S->Alignment);
+  S->OutSecOff = Pos - S->getSize() - CurOutSec->Addr;
 
   // Update output section size after adding each section. This is so that
   // SIZEOF works correctly in the case below:
@@ -524,11 +529,6 @@ void LinkerScript::output(InputSection *
             " bytes");
     }
   }
-
-  if (IsTbss)
-    ThreadBssOffset = Pos - Dot;
-  else
-    Dot = Pos;
 }
 
 void LinkerScript::switchTo(OutputSection *Sec) {
@@ -536,9 +536,7 @@ void LinkerScript::switchTo(OutputSectio
     return;
 
   CurOutSec = Sec;
-
-  Dot = alignTo(Dot, CurOutSec->Alignment);
-  CurOutSec->Addr = isTbss(CurOutSec) ? Dot + ThreadBssOffset : Dot;
+  CurOutSec->Addr = advance(0, CurOutSec->Alignment);
 
   // If neither AT nor AT> is specified for an allocatable section, the linker
   // will set the LMA such that the difference between VMA and LMA for the

Modified: lld/trunk/ELF/LinkerScript.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.h?rev=302107&r1=302106&r2=302107&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.h (original)
+++ lld/trunk/ELF/LinkerScript.h Wed May  3 22:00:27 2017
@@ -228,6 +228,7 @@ protected:
   MemoryRegion *findMemoryRegion(OutputSectionCommand *Cmd);
 
   void switchTo(OutputSection *Sec);
+  uint64_t advance(uint64_t Size, unsigned Align);
   void output(InputSection *Sec);
   void process(BaseCommand &Base);
 

Modified: lld/trunk/test/ELF/tls-offset.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/tls-offset.s?rev=302107&r1=302106&r2=302107&view=diff
==============================================================================
--- lld/trunk/test/ELF/tls-offset.s (original)
+++ lld/trunk/test/ELF/tls-offset.s Wed May  3 22:00:27 2017
@@ -10,7 +10,7 @@
 // RUN:   .tbss : { *(.tbss) } \
 // RUN:   .data.rel.ro : { *(.data.rel.ro) } \
 // RUN: }" > %t.script
-        // RUN: ld.lld -T %t.script %t -o %tout2
+// RUN: ld.lld -T %t.script %t -o %tout2
 // RUN: echo SCRIPT
 // RUN: llvm-readobj -s %tout2 | FileCheck %s
         .global _start
@@ -61,6 +61,6 @@ _start:
 // CHECK-NEXT:   SHF_ALLOC
 // CHECK-NEXT:   SHF_WRITE
 // CHECK-NEXT: ]
-// CHECK-NEXT: Address: 0x202010
-// CHECK-NEXT: Offset: 0x2010
+// CHECK-NEXT: Address: 0x202004
+// CHECK-NEXT: Offset: 0x2004
 // CHECK-NEXT: Size: 4