Don't include NOBITS TLS in PT_LOAD.
They don't count for the memory or file size, so this is mostly just a simplification. The only noticeable difference should be fewer empty program headers. llvm-svn: 260465
This commit is contained in:
Rafael Espindola
parent
82f68a88b5
commit
ef762f2639
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@ -1184,8 +1184,16 @@ void Writer<ELFT>::addStartStopSymbols(OutputSectionBase<ELFT> *Sec) {
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Symtab.addSynthetic(Stop, *Sec, Sec->getSize());
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}
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template <class ELFT> static bool needsPhdr(OutputSectionBase<ELFT> *Sec) {
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return Sec->getFlags() & SHF_ALLOC;
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template <class ELFT> static bool needsPtLoad(OutputSectionBase<ELFT> *Sec) {
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if (!(Sec->getFlags() & SHF_ALLOC))
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return false;
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// Don't allocate VA space for TLS NOBITS sections. The PT_TLS PHDR is
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// responsible for allocating space for them, not the PT_LOAD that
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// contains the TLS initialization image.
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if (Sec->getFlags() & SHF_TLS && Sec->getType() == SHT_NOBITS)
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return false;
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return true;
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}
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static uint32_t toPhdrFlags(uint64_t Flags) {
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@ -1241,9 +1249,18 @@ template <class ELFT> void Writer<ELFT>::createPhdrs() {
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Phdr TlsHdr(PT_TLS, PF_R);
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Phdr RelRo(PT_GNU_RELRO, PF_R);
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for (OutputSectionBase<ELFT> *Sec : OutputSections) {
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if (!needsPhdr<ELFT>(Sec))
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if (!(Sec->getFlags() & SHF_ALLOC))
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break;
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// If we meet TLS section then we create TLS header
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// and put all TLS sections inside for futher use when
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// assign addresses.
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if (Sec->getFlags() & SHF_TLS)
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AddSec(TlsHdr, Sec);
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if (!needsPtLoad<ELFT>(Sec))
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continue;
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// If flags changed then we want new load segment.
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uintX_t NewFlags = toPhdrFlags(Sec->getFlags());
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if (Flags != NewFlags) {
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@ -1252,14 +1269,6 @@ template <class ELFT> void Writer<ELFT>::createPhdrs() {
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Load = AddHdr(LoadType, NewFlags);
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Flags = NewFlags;
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}
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// If we meet TLS section then we create TLS header
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// and put all TLS sections inside for futher use when
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// assign addresses.
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if (Sec->getFlags() & SHF_TLS) {
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AddSec(TlsHdr, Sec);
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if (Sec->getType() == SHT_NOBITS)
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continue;
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}
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AddSec(*Load, Sec);
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@ -1307,18 +1316,15 @@ template <class ELFT> void Writer<ELFT>::assignAddresses() {
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SmallPtrSet<OutputSectionBase<ELFT> *, 4> PageAlign;
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for (const Phdr &P : Phdrs) {
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if (P.H.p_type == PT_GNU_RELRO) {
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// Find the first section after PT_GNU_RELRO. If it is in a PT_LOAD
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// and is not tls, we have to align it to a page. We don't have to
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// align tls since TLS NOBITS takes no space.
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// Find the first section after PT_GNU_RELRO. If it is in a PT_LOAD we
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// have to align it to a page.
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auto I = std::find(OutputSections.begin(), OutputSections.end(), P.Last);
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++I;
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if (I != OutputSections.end() && needsPhdr(*I) &&
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!((*I)->getFlags() & SHF_TLS))
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if (I != OutputSections.end() && needsPtLoad(*I))
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PageAlign.insert(*I);
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}
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// FIXME: why create empty PT_LOAD?
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if (P.H.p_type == PT_LOAD && P.First)
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if (P.H.p_type == PT_LOAD)
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PageAlign.insert(P.First);
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}
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@ -1337,21 +1343,15 @@ template <class ELFT> void Writer<ELFT>::assignAddresses() {
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FileOff += Sec->getSize();
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// We only assign VAs to allocated sections.
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if (needsPhdr<ELFT>(Sec)) {
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// Don't allocate VA space for TLS NOBITS sections. The PT_TLS PHDR is
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// responsible for allocating space for them, not the PT_LOAD that
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// contains the TLS initialization image.
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bool IsTls = Sec->getFlags() & SHF_TLS;
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if (IsTls && Sec->getType() == SHT_NOBITS) {
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if (needsPtLoad<ELFT>(Sec)) {
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VA = alignTo(VA, Align);
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Sec->setVA(VA);
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VA += Sec->getSize();
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} else if (Sec->getFlags() & SHF_TLS && Sec->getType() == SHT_NOBITS) {
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uintX_t TVA = VA + ThreadBssOffset;
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TVA = alignTo(TVA, Align);
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Sec->setVA(TVA);
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ThreadBssOffset = TVA - VA + Sec->getSize();
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} else {
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VA = alignTo(VA, Align);
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Sec->setVA(VA);
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VA += Sec->getSize();
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}
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}
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}
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@ -0,0 +1,78 @@
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// REQUIRES: x86
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// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
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// RUN: ld.lld %t -o %tout
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// RUN: llvm-readobj -program-headers %tout | FileCheck %s
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.global _start
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_start:
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retq
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.section .tbss,"awT",@nobits
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.zero 4
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// FIXME: Test that we don't create unecessary empty PT_LOAD and PT_GNU_RELRO
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// for the .tbss section.
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// CHECK: ProgramHeaders [
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// CHECK-NEXT: ProgramHeader {
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// CHECK-NEXT: Type: PT_PHDR (0x6)
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// CHECK-NEXT: Offset: 0x40
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// CHECK-NEXT: VirtualAddress: 0x10040
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// CHECK-NEXT: PhysicalAddress: 0x10040
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// CHECK-NEXT: FileSize: 280
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// CHECK-NEXT: MemSize: 280
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// CHECK-NEXT: Flags [ (0x4)
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// CHECK-NEXT: PF_R (0x4)
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// CHECK-NEXT: ]
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// CHECK-NEXT: Alignment: 8
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// CHECK-NEXT: }
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// CHECK-NEXT: ProgramHeader {
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// CHECK-NEXT: Type: PT_LOAD (0x1)
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// CHECK-NEXT: Offset: 0x0
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// CHECK-NEXT: VirtualAddress: 0x10000
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// CHECK-NEXT: PhysicalAddress: 0x10000
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// CHECK-NEXT: FileSize: 344
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// CHECK-NEXT: MemSize: 344
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// CHECK-NEXT: Flags [ (0x4)
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// CHECK-NEXT: PF_R (0x4)
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// CHECK-NEXT: ]
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// CHECK-NEXT: Alignment: 4096
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// CHECK-NEXT: }
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// CHECK-NEXT: ProgramHeader {
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// CHECK-NEXT: Type: PT_LOAD (0x1)
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// CHECK-NEXT: Offset: 0x1000
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// CHECK-NEXT: VirtualAddress: 0x11000
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// CHECK-NEXT: PhysicalAddress: 0x11000
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// CHECK-NEXT: FileSize: 1
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// CHECK-NEXT: MemSize: 1
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// CHECK-NEXT: Flags [ (0x5)
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// CHECK-NEXT: PF_R (0x4)
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// CHECK-NEXT: PF_X (0x1)
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// CHECK-NEXT: ]
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// CHECK-NEXT: Alignment: 4096
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// CHECK-NEXT: }
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// CHECK-NEXT: ProgramHeader {
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// CHECK-NEXT: Type: PT_TLS (0x7)
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// CHECK-NEXT: Offset: 0x1001
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// CHECK-NEXT: VirtualAddress: 0x11001
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// CHECK-NEXT: PhysicalAddress: 0x11001
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// CHECK-NEXT: FileSize: 0
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// CHECK-NEXT: MemSize: 4
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// CHECK-NEXT: Flags [ (0x4)
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// CHECK-NEXT: PF_R (0x4)
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// CHECK-NEXT: ]
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// CHECK-NEXT: Alignment: 1
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// CHECK-NEXT: }
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// CHECK-NEXT: ProgramHeader {
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// CHECK-NEXT: Type: PT_GNU_STACK (0x6474E551)
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// CHECK-NEXT: Offset: 0x0
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// CHECK-NEXT: VirtualAddress: 0x0
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// CHECK-NEXT: PhysicalAddress: 0x0
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// CHECK-NEXT: FileSize: 0
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// CHECK-NEXT: MemSize: 0
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// CHECK-NEXT: Flags [ (0x6)
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// CHECK-NEXT: PF_R (0x4)
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// CHECK-NEXT: PF_W (0x2)
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// CHECK-NEXT: ]
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// CHECK-NEXT: Alignment: 0
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// CHECK-NEXT: }
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// CHECK-NEXT: ]
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