[lld] r251454 - [elf2] Don't allocate VA space for TLS NOBITS sections.

[Michael J. Spencer via llvm-commits]

Author: mspencer
Date: Tue Oct 27 16:22:54 2015
New Revision: 251454

URL: http://llvm.org/viewvc/llvm-project?rev=251454&view=rev
Log:
[elf2] Don't allocate VA space for TLS NOBITS sections.

Differential Revision: http://reviews.llvm.org/D13838

Added:
    lld/trunk/test/elf2/tls.s
Modified:
    lld/trunk/ELF/Writer.cpp

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=251454&r1=251453&r2=251454&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Tue Oct 27 16:22:54 2015
@@ -611,6 +611,15 @@ static uint32_t toPhdrFlags(uint64_t Fla
   return Ret;
 }
 
+template <class ELFT>
+static bool consumesVirtualAddressSpace(OutputSectionBase<ELFT> *Sec) {
+  return (Sec->getFlags() & SHF_ALLOC) &&
+         // Don't allocate VA space for TLS NOBITS sections. The PT_TLS PHDR is
+         // responsible for allocating space for them, not the PT_LOAD that
+         // contains the TLS initialization image.
+         !((Sec->getFlags() & SHF_TLS) && Sec->getType() == SHT_NOBITS);
+}
+
 // Visits all sections to create PHDRs and to assign incremental,
 // non-overlapping addresses to output sections.
 template <class ELFT> void Writer<ELFT>::assignAddresses() {
@@ -659,7 +668,7 @@ template <class ELFT> void Writer<ELFT>:
       }
     }
 
-    if (Sec->getFlags() & SHF_ALLOC) {
+    if (consumesVirtualAddressSpace<ELFT>(Sec)) {
       VA = RoundUpToAlignment(VA, Sec->getAlign());
       Sec->setVA(VA);
       VA += Sec->getSize();

Added: lld/trunk/test/elf2/tls.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/tls.s?rev=251454&view=auto
==============================================================================
--- lld/trunk/test/elf2/tls.s (added)
+++ lld/trunk/test/elf2/tls.s Tue Oct 27 16:22:54 2015
@@ -0,0 +1,93 @@
+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+// RUN: ld.lld2 %t -o %tout
+// RUN: llvm-readobj -sections -program-headers %tout | FileCheck %s
+
+.global _start
+_start:
+
+	.section	.tbss,"awT", at nobits
+	.long	0
+
+	.section	.tdata,"awT", at progbits
+	.long	1
+
+	.section	.thread_bss,"awT", at nobits
+	.long	0
+
+	.section	.thread_data,"awT", at progbits
+	.long	2
+
+// CHECK:          Name: .tdata
+// CHECK-NEXT:     Type: SHT_PROGBITS
+// CHECK-NEXT:     Flags [
+// CHECK-NEXT:       SHF_ALLOC
+// CHECK-NEXT:       SHF_TLS
+// CHECK-NEXT:       SHF_WRITE
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address:
+// CHECK-NEXT:     Offset:
+// CHECK-NEXT:     Size: 4
+// CHECK-NEXT:     Link:
+// CHECK-NEXT:     Info:
+// CHECK-NEXT:     AddressAlignment:
+// CHECK-NEXT:     EntrySize:
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Section {
+// CHECK-NEXT:     Index:
+// CHECK-NEXT:     Name: .thread_data
+// CHECK-NEXT:     Type: SHT_PROGBITS
+// CHECK-NEXT:     Flags [
+// CHECK-NEXT:       SHF_ALLOC
+// CHECK-NEXT:       SHF_TLS
+// CHECK-NEXT:       SHF_WRITE
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address:
+// CHECK-NEXT:     Offset:
+// CHECK-NEXT:     Size: 4
+// CHECK-NEXT:     Link:
+// CHECK-NEXT:     Info:
+// CHECK-NEXT:     AddressAlignment:
+// CHECK-NEXT:     EntrySize:
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Section {
+// CHECK-NEXT:     Index:
+// CHECK-NEXT:     Name: .tbss
+// CHECK-NEXT:     Type: SHT_NOBITS
+// CHECK-NEXT:     Flags [
+// CHECK-NEXT:       SHF_ALLOC
+// CHECK-NEXT:       SHF_TLS
+// CHECK-NEXT:       SHF_WRITE
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address:
+// CHECK-NEXT:     Offset:
+// CHECK-NEXT:     Size: 4
+// CHECK-NEXT:     Link:
+// CHECK-NEXT:     Info:
+// CHECK-NEXT:     AddressAlignment:
+// CHECK-NEXT:     EntrySize:
+// CHECK-NEXT:   }
+// CHECK-NEXT:   Section {
+// CHECK-NEXT:     Index:
+// CHECK-NEXT:     Name: .thread_bss
+// CHECK-NEXT:     Type: SHT_NOBITS
+// CHECK-NEXT:     Flags [
+// CHECK-NEXT:       SHF_ALLOC
+// CHECK-NEXT:       SHF_TLS
+// CHECK-NEXT:       SHF_WRITE
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Address:
+// CHECK-NEXT:     Offset:
+// CHECK-NEXT:     Size: 4
+
+// Check that the TLS NOBITS sections weren't added to the R/W PT_LOAD's size.
+
+// CHECK:      ProgramHeaders [
+// CHECK:          Type: PT_LOAD
+// CHECK:          Type: PT_LOAD
+// CHECK:          FileSize: 8
+// CHECK-NEXT:     MemSize: 8
+// CHECK-NEXT:     Flags [
+// CHECK-NEXT:       PF_R
+// CHECK-NEXT:       PF_W
+// CHECK-NEXT:     ]