[lld] r327248 - For most Targets the _GLOBAL_OFFSET_TABLE_ symbol is expected to be at
Peter Smith via llvm-commits
llvm-commits at lists.llvm.org
Sun Mar 11 13:58:19 PDT 2018
Author: psmith
Date: Sun Mar 11 13:58:18 2018
New Revision: 327248
URL: http://llvm.org/viewvc/llvm-project?rev=327248&view=rev
Log:
For most Targets the _GLOBAL_OFFSET_TABLE_ symbol is expected to be at
the start of the .got.plt section so that _GLOBAL_OFFSET_TABLE_[0] =
reserved value that is by convention the address of the dynamic section.
Previously we had defined _GLOBAL_OFFSET_TABLE_ as either the start or end
of the .got section with the intention that the .got.plt section would
follow the .got. However this does not always hold with the current
default section ordering so _GLOBAL_OFFSET_TABLE_[0] may not be consistent
with the reserved first entry of the .got.plt.
X86, X86_64, Arm and AArch64 will use the .got.plt. Mips and Power use .got
Fixes PR36555
Differential Revision: https://reviews.llvm.org/D44259
Modified:
lld/trunk/ELF/Arch/Mips.cpp
lld/trunk/ELF/Arch/PPC.cpp
lld/trunk/ELF/Arch/X86.cpp
lld/trunk/ELF/Arch/X86_64.cpp
lld/trunk/ELF/SyntheticSections.cpp
lld/trunk/ELF/SyntheticSections.h
lld/trunk/ELF/Target.h
lld/trunk/ELF/Writer.cpp
lld/trunk/test/ELF/arm-got-relative.s
lld/trunk/test/ELF/dynamic-got.s
lld/trunk/test/ELF/global-offset-table-position-aarch64.s
lld/trunk/test/ELF/global-offset-table-position-arm.s
lld/trunk/test/ELF/global-offset-table-position-i386.s
lld/trunk/test/ELF/global-offset-table-position.s
lld/trunk/test/ELF/global_offset_table_shared.s
lld/trunk/test/ELF/got32x-i386.s
lld/trunk/test/ELF/i386-gotpc.s
Modified: lld/trunk/ELF/Arch/Mips.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Arch/Mips.cpp?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/ELF/Arch/Mips.cpp (original)
+++ lld/trunk/ELF/Arch/Mips.cpp Sun Mar 11 13:58:18 2018
@@ -50,6 +50,7 @@ template <class ELFT> MIPS<ELFT>::MIPS()
DefaultMaxPageSize = 65536;
GotEntrySize = sizeof(typename ELFT::uint);
GotPltEntrySize = sizeof(typename ELFT::uint);
+ GotBaseSymInGotPlt = false;
PltEntrySize = 16;
PltHeaderSize = 32;
CopyRel = R_MIPS_COPY;
Modified: lld/trunk/ELF/Arch/PPC.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Arch/PPC.cpp?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/ELF/Arch/PPC.cpp (original)
+++ lld/trunk/ELF/Arch/PPC.cpp Sun Mar 11 13:58:18 2018
@@ -21,13 +21,18 @@ using namespace lld::elf;
namespace {
class PPC final : public TargetInfo {
public:
- PPC() { GotBaseSymOff = 0x8000; }
+ PPC();
void relocateOne(uint8_t *Loc, RelType Type, uint64_t Val) const override;
RelExpr getRelExpr(RelType Type, const Symbol &S,
const uint8_t *Loc) const override;
};
} // namespace
+PPC::PPC() {
+ GotBaseSymOff = 0x8000;
+ GotBaseSymInGotPlt = false;
+}
+
RelExpr PPC::getRelExpr(RelType Type, const Symbol &S,
const uint8_t *Loc) const {
switch (Type) {
Modified: lld/trunk/ELF/Arch/X86.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Arch/X86.cpp?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/ELF/Arch/X86.cpp (original)
+++ lld/trunk/ELF/Arch/X86.cpp Sun Mar 11 13:58:18 2018
@@ -46,7 +46,6 @@ public:
} // namespace
X86::X86() {
- GotBaseSymOff = -1;
CopyRel = R_386_COPY;
GotRel = R_386_GLOB_DAT;
PltRel = R_386_JUMP_SLOT;
Modified: lld/trunk/ELF/Arch/X86_64.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Arch/X86_64.cpp?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/ELF/Arch/X86_64.cpp (original)
+++ lld/trunk/ELF/Arch/X86_64.cpp Sun Mar 11 13:58:18 2018
@@ -51,7 +51,6 @@ private:
} // namespace
template <class ELFT> X86_64<ELFT>::X86_64() {
- GotBaseSymOff = -1;
CopyRel = R_X86_64_COPY;
GotRel = R_X86_64_GLOB_DAT;
PltRel = R_X86_64_JUMP_SLOT;
Modified: lld/trunk/ELF/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.cpp?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.cpp (original)
+++ lld/trunk/ELF/SyntheticSections.cpp Sun Mar 11 13:58:18 2018
@@ -626,8 +626,9 @@ void GotSection::finalizeContents() { Si
bool GotSection::empty() const {
// We need to emit a GOT even if it's empty if there's a relocation that is
// relative to GOT(such as GOTOFFREL) or there's a symbol that points to a GOT
- // (i.e. _GLOBAL_OFFSET_TABLE_).
- return NumEntries == 0 && !HasGotOffRel && !ElfSym::GlobalOffsetTable;
+ // (i.e. _GLOBAL_OFFSET_TABLE_) that the target defines relative to the .got.
+ return NumEntries == 0 && !HasGotOffRel &&
+ !(ElfSym::GlobalOffsetTable && !Target->GotBaseSymInGotPlt);
}
void GotSection::writeTo(uint8_t *Buf) {
@@ -898,6 +899,14 @@ void GotPltSection::writeTo(uint8_t *Buf
}
}
+bool GotPltSection::empty() const {
+ // We need to emit a GOT.PLT even if it's empty if there's a symbol that
+ // references the _GLOBAL_OFFSET_TABLE_ and the Target defines the symbol
+ // relative to the .got.plt section.
+ return Entries.empty() &&
+ !(ElfSym::GlobalOffsetTable && Target->GotBaseSymInGotPlt);
+}
+
// On ARM the IgotPltSection is part of the GotSection, on other Targets it is
// part of the .got.plt
IgotPltSection::IgotPltSection()
Modified: lld/trunk/ELF/SyntheticSections.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.h?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.h (original)
+++ lld/trunk/ELF/SyntheticSections.h Sun Mar 11 13:58:18 2018
@@ -269,7 +269,7 @@ public:
void addEntry(Symbol &Sym);
size_t getSize() const override;
void writeTo(uint8_t *Buf) override;
- bool empty() const override { return Entries.empty(); }
+ bool empty() const override;
private:
std::vector<const Symbol *> Entries;
Modified: lld/trunk/ELF/Target.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Target.h?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/ELF/Target.h (original)
+++ lld/trunk/ELF/Target.h Sun Mar 11 13:58:18 2018
@@ -71,9 +71,10 @@ public:
uint64_t getImageBase();
- // Offset of _GLOBAL_OFFSET_TABLE_ from base of .got section. Use -1 for
- // end of .got
+ // Offset of _GLOBAL_OFFSET_TABLE_ from base of .got or .got.plt section.
uint64_t GotBaseSymOff = 0;
+ // True if _GLOBAL_OFFSET_TABLE_ is relative to .got.plt, false if .got.
+ bool GotBaseSymInGotPlt = true;
// On systems with range extensions we place collections of Thunks at
// regular spacings that enable the majority of branches reach the Thunks.
Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Sun Mar 11 13:58:18 2018
@@ -868,11 +868,12 @@ void Writer<ELFT>::forEachRelSec(std::fu
// defining these symbols explicitly in the linker script.
template <class ELFT> void Writer<ELFT>::setReservedSymbolSections() {
if (ElfSym::GlobalOffsetTable) {
- // The _GLOBAL_OFFSET_TABLE_ symbol is defined by target convention to
- // be at some offset from the base of the .got section, usually 0 or the end
- // of the .got
- InputSection *GotSection = InX::MipsGot ? cast<InputSection>(InX::MipsGot)
- : cast<InputSection>(InX::Got);
+ // The _GLOBAL_OFFSET_TABLE_ symbol is defined by target convention usually
+ // to the start of the .got or .got.plt section.
+ InputSection *GotSection = InX::GotPlt;
+ if (!Target->GotBaseSymInGotPlt)
+ GotSection = InX::MipsGot ? cast<InputSection>(InX::MipsGot)
+ : cast<InputSection>(InX::Got);
ElfSym::GlobalOffsetTable->Section = GotSection;
}
Modified: lld/trunk/test/ELF/arm-got-relative.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/arm-got-relative.s?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/test/ELF/arm-got-relative.s (original)
+++ lld/trunk/test/ELF/arm-got-relative.s Sun Mar 11 13:58:18 2018
@@ -28,17 +28,17 @@ function:
bx lr
// CHECK: Dynamic Relocations {
-// CHECK-NEXT: 0x2048 R_ARM_GLOB_DAT function 0x0
+// CHECK-NEXT: 0x3048 R_ARM_GLOB_DAT function 0x0
// CHECK: Name: _GLOBAL_OFFSET_TABLE_
-// CHECK-NEXT: Value: 0x2048
+// CHECK-NEXT: Value: 0x2000
// CHECK-NEXT: Size:
// CHECK-NEXT: Binding: Local
// CHECK-NEXT: Type: None
// CHECK-NEXT: Other [
// CHECK-NEXT: STV_HIDDEN
// CHECK-NEXT: ]
-// CHECK-NEXT: Section: .got
+// CHECK-NEXT: Section: .got.plt
// CODE: Disassembly of section .text:
// CODE-NEXT: _start:
@@ -47,7 +47,7 @@ function:
// CODE-NEXT: 1008: 03 00 8f e0 add r0, pc, r3
// CODE-NEXT: 100c: 1e ff 2f e1 bx lr
// CODE:$d.1:
-// (_GLOBAL_OFFSET_TABLE_ = 0x2048) - (0x1008 + 8) 0x1038
-// CODE-NEXT: 1010: 38 10 00 00
+// (_GLOBAL_OFFSET_TABLE_ = 0x2000) - (0x1008 + 8) = 0xff0
+// CODE-NEXT: 1010: f0 0f 00 00
// (Got(function) - GotBase = 0x0
// CODE-NEXT: 1014: 00 00 00 00
Modified: lld/trunk/test/ELF/dynamic-got.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/dynamic-got.s?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/test/ELF/dynamic-got.s (original)
+++ lld/trunk/test/ELF/dynamic-got.s Sun Mar 11 13:58:18 2018
@@ -3,6 +3,23 @@
// RUN: ld.lld --hash-style=sysv %t.o -o %t.so -shared
// RUN: llvm-readobj -s -l -section-data -r %t.so | FileCheck %s
+// CHECK: Name: .got.plt
+// CHECK-NEXT: Type: SHT_PROGBITS
+// CHECK-NEXT: Flags [
+// CHECK-NEXT: SHF_ALLOC
+// CHECK-NEXT: SHF_WRITE
+// CHECK-NEXT: ]
+// CHECK-NEXT: Address:
+// CHECK-NEXT: Offset:
+// CHECK-NEXT: Size:
+// CHECK-NEXT: Link:
+// CHECK-NEXT: Info:
+// CHECK-NEXT: AddressAlignment:
+// CHECK-NEXT: EntrySize:
+// CHECK-NEXT: SectionData (
+// CHECK-NEXT: 0000: 00300000 00000000 00000000
+// CHECK-NEXT: )
+
// CHECK: Name: .got
// CHECK-NEXT: Type: SHT_PROGBITS
// CHECK-NEXT: Flags [
@@ -17,19 +34,19 @@
// CHECK-NEXT: AddressAlignment:
// CHECK-NEXT: EntrySize:
// CHECK-NEXT: SectionData (
-// CHECK-NEXT: 0000: 00200000 |
+// CHECK-NEXT: 0000: 00300000
// CHECK-NEXT: )
// CHECK: Relocations [
// CHECK-NEXT: Section ({{.*}}) .rel.dyn {
-// CHECK-NEXT: 0x2050 R_386_RELATIVE - 0x0
+// CHECK-NEXT: 0x3050 R_386_RELATIVE - 0x0
// CHECK-NEXT: }
// CHECK-NEXT: ]
// CHECK: Type: PT_DYNAMIC
-// CHECK-NEXT: Offset: 0x2000
-// CHECK-NEXT: VirtualAddress: 0x2000
-// CHECK-NEXT: PhysicalAddress: 0x2000
+// CHECK-NEXT: Offset: 0x3000
+// CHECK-NEXT: VirtualAddress: 0x3000
+// CHECK-NEXT: PhysicalAddress: 0x3000
calll .L0$pb
.L0$pb:
Modified: lld/trunk/test/ELF/global-offset-table-position-aarch64.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/global-offset-table-position-aarch64.s?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/test/ELF/global-offset-table-position-aarch64.s (original)
+++ lld/trunk/test/ELF/global-offset-table-position-aarch64.s Sun Mar 11 13:58:18 2018
@@ -20,11 +20,11 @@ _start:
.long _GLOBAL_OFFSET_TABLE_ - .
// CHECK: Name: _GLOBAL_OFFSET_TABLE_ (11)
-// CHECK-NEXT: Value: 0x30090
+// CHECK-NEXT: Value: 0x20008
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Local (0x0)
// CHECK-NEXT: Type: None (0x0)
// CHECK-NEXT: Other [ (0x2)
// CHECK-NEXT: STV_HIDDEN (0x2)
// CHECK-NEXT: ]
-// CHECK-NEXT: Section: .got
+// CHECK-NEXT: Section: .got.plt
Modified: lld/trunk/test/ELF/global-offset-table-position-arm.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/global-offset-table-position-arm.s?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/test/ELF/global-offset-table-position-arm.s (original)
+++ lld/trunk/test/ELF/global-offset-table-position-arm.s Sun Mar 11 13:58:18 2018
@@ -3,7 +3,8 @@
// RUN: llvm-readobj -t %t2 | FileCheck %s
// REQUIRES: arm
-// The ARM _GLOBAL_OFFSET_TABLE_ should be defined at the start of the .got
+// The ARM _GLOBAL_OFFSET_TABLE_ should be defined at the start of the
+// .got.plt section.
.globl a
.type a,%object
.comm a,4,4
@@ -25,11 +26,11 @@ _start:
.data
// CHECK: Name: _GLOBAL_OFFSET_TABLE_
-// CHECK-NEXT: Value: 0x3068
+// CHECK-NEXT: Value: 0x2000
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Local
// CHECK-NEXT: Type: None
// CHECK-NEXT: Other [ (0x2)
// CHECK-NEXT: STV_HIDDEN (0x2)
// CHECK-NEXT: ]
-// CHECK-NEXT: Section: .got
+// CHECK-NEXT: Section: .got.plt
Modified: lld/trunk/test/ELF/global-offset-table-position-i386.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/global-offset-table-position-i386.s?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/test/ELF/global-offset-table-position-i386.s (original)
+++ lld/trunk/test/ELF/global-offset-table-position-i386.s Sun Mar 11 13:58:18 2018
@@ -3,7 +3,8 @@
// RUN: llvm-readobj -t %t2 | FileCheck %s
// REQUIRES: x86
-// The X86 _GLOBAL_OFFSET_TABLE_ is defined at the end of the .got section.
+// The X86 _GLOBAL_OFFSET_TABLE_ is defined at the start of the .got.plt
+// section.
.globl a
.type a, at object
.comm a,4,4
@@ -21,11 +22,11 @@ addl $_GLOBAL_OFFSET_TABLE_, %eax
calll f at PLT
// CHECK: Name: _GLOBAL_OFFSET_TABLE_ (1)
-// CHECK-NEXT: Value: 0x306C
+// CHECK-NEXT: Value: 0x2000
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Local (0x0)
// CHECK-NEXT: Type: None (0x0)
// CHECK-NEXT: Other [ (0x2)
// CHECK-NEXT: STV_HIDDEN (0x2)
// CHECK-NEXT: ]
-// CHECK-NEXT: Section: .got (0xA)
+// CHECK-NEXT: Section: .got.plt
Modified: lld/trunk/test/ELF/global-offset-table-position.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/global-offset-table-position.s?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/test/ELF/global-offset-table-position.s (original)
+++ lld/trunk/test/ELF/global-offset-table-position.s Sun Mar 11 13:58:18 2018
@@ -3,7 +3,8 @@
// RUN: llvm-readobj -t %t2 | FileCheck %s
// REQUIRES: x86
-// The X86_64 _GLOBAL_OFFSET_TABLE_ is defined at the end of the .got section.
+// The X86_64 _GLOBAL_OFFSET_TABLE_ is defined at the start of the .got.plt
+// section.
.globl a
.type a, at object
.comm a,4,4
@@ -21,11 +22,11 @@ callq f at PLT
.long _GLOBAL_OFFSET_TABLE_ - .
// CHECK: Name: _GLOBAL_OFFSET_TABLE_
-// CHECK-NEXT: Value: 0x30D8
+// CHECK-NEXT: Value: 0x2008
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Local
// CHECK-NEXT: Type: None (0x0)
// CHECK-NEXT: Other [
// CHECK-NEXT: STV_HIDDEN
// CHECK-NEXT: ]
-// CHECK-NEXT: Section: .got
+// CHECK-NEXT: Section: .got.plt
Modified: lld/trunk/test/ELF/global_offset_table_shared.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/global_offset_table_shared.s?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/test/ELF/global_offset_table_shared.s (original)
+++ lld/trunk/test/ELF/global_offset_table_shared.s Sun Mar 11 13:58:18 2018
@@ -4,11 +4,11 @@
.long _GLOBAL_OFFSET_TABLE_ - .
// CHECK: Name: _GLOBAL_OFFSET_TABLE_
-// CHECK-NEXT: Value: 0x2060
+// CHECK-NEXT: Value: 0x2000
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Local
// CHECK-NEXT: Type: None
// CHECK-NEXT: Other [ (0x2)
// CHECK-NEXT: STV_HIDDEN (0x2)
// CHECK-NEXT: ]
-// CHECK-NEXT: Section: .got
+// CHECK-NEXT: Section: .got.plt
Modified: lld/trunk/test/ELF/got32x-i386.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/got32x-i386.s?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/test/ELF/got32x-i386.s (original)
+++ lld/trunk/test/ELF/got32x-i386.s Sun Mar 11 13:58:18 2018
@@ -33,13 +33,13 @@
## 73728 == 0x12000 == ADDR(.got)
# CHECK: _start:
-# CHECK-NEXT: 11001: 8b 05 {{.*}} movl 73728, %eax
-# CHECK-NEXT: 11007: 8b 1d {{.*}} movl 73728, %ebx
+# CHECK-NEXT: 11001: 8b 05 {{.*}} movl 77824, %eax
+# CHECK-NEXT: 11007: 8b 1d {{.*}} movl 77824, %ebx
# CHECK-NEXT: 1100d: 8b 80 {{.*}} movl -4(%eax), %eax
# CHECK-NEXT: 11013: 8b 83 {{.*}} movl -4(%ebx), %eax
# CHECK: Sections:
# CHECK: Name Size Address
-# CHECK: .got 00000004 0000000000012000
+# CHECK: .got 00000004 0000000000013000
# RUN: not ld.lld %S/Inputs/i386-got32x-baseless.elf -o %t1 -pie 2>&1 | \
# RUN: FileCheck %s --check-prefix=ERR
Modified: lld/trunk/test/ELF/i386-gotpc.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/i386-gotpc.s?rev=327248&r1=327247&r2=327248&view=diff
==============================================================================
--- lld/trunk/test/ELF/i386-gotpc.s (original)
+++ lld/trunk/test/ELF/i386-gotpc.s Sun Mar 11 13:58:18 2018
@@ -6,15 +6,23 @@
movl $_GLOBAL_OFFSET_TABLE_, %eax
+// CHECK: Name: .got.plt
+// CHECK-NEXT: Type: SHT_PROGBITS
+// CHECK-NEXT: Flags [
+// CHECK-NEXT: SHF_ALLOC
+// CHECK-NEXT: SHF_WRITE
+// CHECK-NEXT: ]
+// CHECK-NEXT: Address: 0x2000
+
// CHECK: Name: .got
// CHECK-NEXT: Type: SHT_PROGBITS
// CHECK-NEXT: Flags [
// CHECK-NEXT: SHF_ALLOC
// CHECK-NEXT: SHF_WRITE
// CHECK-NEXT: ]
-// CHECK-NEXT: Address: 0x2030
+// CHECK-NEXT: Address: 0x3030
// DISASM: Disassembly of section .text:
// DISASM-NEXT: .text:
-// DISASM-NEXT: 1000: {{.*}} movl $4144, %eax
-// 0x2030 - 0x1000 = 4144
+// DISASM-NEXT: 1000: {{.*}} movl $8240, %eax
+// 0x3030 - 0x1000 = 0x2030
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