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

[ruiu]

ELF/Writer.cpp

629–633 ↗

(On Diff #37659)

Factor out as a function.

[• rafael]

I am OK with the test update.
Just make sure Rui is OK with the refactoring he asked for.

test/elf2/tls.s

83 ↗

(On Diff #37659)

Make this check a tiny bit stronger. You know which PT_LOAD this is, so you can do

CHECK: PT_LOAD
CHECK: PT_LOAD
// CHECK: PT_LOAD
....

To make sure you skip the RO and RW segments.

[ruiu]

Are you still working on this?

lld/trunk/ELF/Writer.cpp

static uint32_t toPhdrFlags(uint64_t Flags) {
   uint32_t Ret = PF_R;
   if (Flags & SHF_WRITE)
     Ret |= PF_W;
   if (Flags & SHF_EXECINSTR)
     Ret |= PF_X;
   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() {
   uintX_t VA = getVAStart() + sizeof(Elf_Ehdr);
   uintX_t FileOff = sizeof(Elf_Ehdr);
 
   // Calculate and reserve the space for the program header first so that
   // the first section can start right after the program header.
if (Sec->getSize()) {
           VA = RoundUpToAlignment(VA, Target->getPageSize());
           FileOff = RoundUpToAlignment(FileOff, Target->getPageSize());
           Elf_Phdr *PH = &Phdrs[++PhdrIdx];
           setPhdr(PH, PT_LOAD, Flags, FileOff, VA, 0, Target->getPageSize());
         }
       }
     }
 
-    if (Sec->getFlags() & SHF_ALLOC) {
+    if (consumesVirtualAddressSpace<ELFT>(Sec)) {
       VA = RoundUpToAlignment(VA, Sec->getAlign());
       Sec->setVA(VA);
       VA += Sec->getSize();
     }
     FileOff = RoundUpToAlignment(FileOff, Sec->getAlign());
     Sec->setFileOffset(FileOff);
     if (Sec->getType() != SHT_NOBITS)
       FileOff += Sec->getSize();

lld/trunk/test/elf2/tls.s

+// 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",@nobits
+  .long 0
+
+  .section  .tdata,"awT",@progbits
+  .long 1
+
+  .section  .thread_bss,"awT",@nobits
+  .long 0
+
+  .section  .thread_data,"awT",@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:     ]