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[LLD][ELF][AArch64] Mark .plt and .iplt with PURECODE flag #134798

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Merged
merged 6 commits into from
Apr 17, 2025
Merged

[LLD][ELF][AArch64] Mark .plt and .iplt with PURECODE flag #134798

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f8e78ec
[LLD][ELF][AArch64] Mark .plt and .iplt with PURECODE flag
Il-Capitano Mar 24, 2025
4fe2ab7
Move EM_AARCH64 check to be alphabetically ordered
Il-Capitano Apr 8, 2025
9cc56c4
Add test to make sure .plt and .iplt will end up in XO segment
Il-Capitano Apr 10, 2025
d373afc
Try to fix windows CI failure
Il-Capitano Apr 10, 2025
add7b16
Actually fix test
Il-Capitano Apr 10, 2025
aea7cfa
Convert tests to use llvm-readelf
Il-Capitano Apr 13, 2025
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10 changes: 10 additions & 0 deletions lld/ELF/SyntheticSections.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2594,6 +2594,11 @@ PltSection::PltSection(Ctx &ctx)
: SyntheticSection(ctx, ".plt", SHT_PROGBITS, SHF_ALLOC | SHF_EXECINSTR,
16),
headerSize(ctx.target->pltHeaderSize) {
// On AArch64, PLT entries only do loads from the .got.plt section, so the
// .plt section can be marked with the SHF_AARCH64_PURECODE section flag.
if (ctx.arg.emachine == EM_AARCH64)
this->flags |= SHF_AARCH64_PURECODE;

// On PowerPC, this section contains lazy symbol resolvers.
if (ctx.arg.emachine == EM_PPC64) {
name = ".glink";
Expand Down Expand Up @@ -2654,6 +2659,11 @@ void PltSection::addSymbols() {
IpltSection::IpltSection(Ctx &ctx)
: SyntheticSection(ctx, ".iplt", SHT_PROGBITS, SHF_ALLOC | SHF_EXECINSTR,
16) {
// On AArch64, PLT entries only do loads from the .got.plt section, so the
// .iplt section can be marked with the SHF_AARCH64_PURECODE section flag.
if (ctx.arg.emachine == EM_AARCH64)
this->flags |= SHF_AARCH64_PURECODE;

if (ctx.arg.emachine == EM_PPC || ctx.arg.emachine == EM_PPC64) {
name = ".glink";
addralign = 4;
Expand Down
35 changes: 35 additions & 0 deletions lld/test/ELF/aarch64-execute-only-plt.s
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Original file line number Diff line number Diff line change
@@ -0,0 +1,35 @@
// REQUIRES: aarch64

// RUN: llvm-mc -filetype=obj -triple=aarch64-linux-gnu %s -o %t.o
// RUN: llvm-mc -filetype=obj -triple=aarch64-linux-gnu %S/Inputs/plt-aarch64.s -o %t2.o
// RUN: ld.lld -shared %t2.o -soname=t2.so -o %t2.so
// RUN: ld.lld %t.o %t2.so -o %t
// RUN: llvm-readelf -S -l %t | FileCheck %s

// CHECK-LABEL: Section Headers:
// CHECK: .text PROGBITS 00000000002102a0 0002a0 000010 00 AXy 0 0 4
// CHECK: .plt PROGBITS 00000000002102b0 0002b0 000030 00 AXy 0 0 16
// CHECK: .iplt PROGBITS 00000000002102e0 0002e0 000010 00 AXy 0 0 16

// CHECK-LABEL: Program Headers:
// CHECK: PHDR
// CHECK-NEXT: LOAD
// CHECK-NEXT: LOAD 0x0002a0 0x00000000002102a0 0x00000000002102a0 0x000050 0x000050 E 0x10000

// CHECK-LABEL: Section to Segment mapping:
/// Index should match the index of the LOAD segment above.
// CHECK: 02 .text .plt .iplt

.global bar

.section .text,"axy",@progbits,unique,0
.global _start
_start:
bl foo
bl bar
ret

.globl foo
.type foo STT_GNU_IFUNC
foo:
ret
36 changes: 19 additions & 17 deletions lld/test/ELF/aarch64-gnu-ifunc-plt.s
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Original file line number Diff line number Diff line change
Expand Up @@ -5,32 +5,34 @@
// RUN: ld.lld --hash-style=sysv %t.so %t.o -o %tout
// RUN: llvm-objdump --no-print-imm-hex -d --no-show-raw-insn %tout | FileCheck %s --check-prefix=DISASM
// RUN: llvm-objdump -s %tout | FileCheck %s --check-prefix=GOTPLT
// RUN: llvm-readobj --dynamic-table -r %tout | FileCheck %s
// RUN: llvm-readelf -S --dynamic-table -r %tout | FileCheck %s

// RUN: llvm-mc -filetype=obj -triple=aarch64_be %S/Inputs/shared2.s -o %t1.be.o
// RUN: ld.lld %t1.be.o --shared --soname=t.so -o %t.be.so
// RUN: llvm-mc -filetype=obj -triple=aarch64_be %s -o %t.be.o
// RUN: ld.lld --hash-style=sysv %t.be.so %t.be.o -o %t.be
// RUN: llvm-objdump --no-print-imm-hex -d --no-show-raw-insn %t.be | FileCheck %s --check-prefix=DISASM
// RUN: llvm-objdump -s %t.be | FileCheck %s --check-prefix=GOTPLT_BE
// RUN: llvm-readobj --dynamic-table -r %t.be | FileCheck %s
// RUN: llvm-readelf -S --dynamic-table -r %t.be | FileCheck %s

// Check that the PLTRELSZ tag does not include the IRELATIVE relocations
// CHECK: DynamicSection [
// CHECK: 0x0000000000000008 RELASZ 48 (bytes)
// CHECK: 0x0000000000000002 PLTRELSZ 48 (bytes)
// CHECK-LABEL: Section Headers:
/// Name Type Address Off Size ES Flg Lk Inf Al
// CHECK: .iplt PROGBITS 0000000000210330 000330 000020 00 AXy 0 0 16

// Check that the IRELATIVE relocations are after the JUMP_SLOT in the plt
// CHECK: Relocations [
// CHECK-NEXT: Section (4) .rela.dyn {
// CHECK-NEXT: 0x230468 R_AARCH64_IRELATIVE - 0x2102D8
// CHECK-NEXT: 0x230470 R_AARCH64_IRELATIVE - 0x2102DC
// CHECK-NEXT: }
// CHECK-NEXT: Section (5) .rela.plt {
// CHECK-NEXT: 0x230458 R_AARCH64_JUMP_SLOT bar2 0x0
// CHECK-NEXT: 0x230460 R_AARCH64_JUMP_SLOT zed2 0x0
// CHECK-NEXT: }
// CHECK-NEXT: ]
/// Check that the PLTRELSZ tag does not include the IRELATIVE relocations
// CHECK-LABEL: Dynamic section at offset 0x350 contains 15 entries:
// CHECK: 0x0000000000000008 (RELASZ) 48 (bytes)
// CHECK: 0x0000000000000002 (PLTRELSZ) 48 (bytes)

/// Check that the IRELATIVE relocations are after the JUMP_SLOT in the plt
// CHECK-LABEL: Relocation section '.rela.dyn' at offset 0x278 contains 2 entries:
// CHECK-NEXT: Offset Info Type Symbol's Value Symbol's Name + Addend
// CHECK-NEXT: 0000000000230468 0000000000000408 R_AARCH64_IRELATIVE 2102d8
// CHECK-NEXT: 0000000000230470 0000000000000408 R_AARCH64_IRELATIVE 2102dc
// CHECK-LABEL: Relocation section '.rela.plt' at offset 0x2a8 contains 2 entries:
// CHECK-NEXT: Offset Info Type Symbol's Value Symbol's Name + Addend
// CHECK-NEXT: 0000000000230458 0000000100000402 R_AARCH64_JUMP_SLOT 0000000000000000 bar2 + 0
// CHECK-NEXT: 0000000000230460 0000000200000402 R_AARCH64_JUMP_SLOT 0000000000000000 zed2 + 0

// Check that .got.plt entries point back to PLT header
// GOTPLT: Contents of section .got.plt:
Expand Down
103 changes: 26 additions & 77 deletions lld/test/ELF/aarch64-plt.s
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Original file line number Diff line number Diff line change
Expand Up @@ -4,52 +4,26 @@
// RUN: ld.lld -shared %t2.o -soname=t2.so -o %t2.so
// RUN: ld.lld -shared %t.o %t2.so -o %t.so
// RUN: ld.lld %t.o %t2.so -o %t.exe
// RUN: llvm-readobj -S -r %t.so | FileCheck --check-prefix=CHECKDSO %s
// RUN: llvm-readelf -S -r %t.so | FileCheck --check-prefix=CHECKDSO %s
// RUN: llvm-objdump -s --section=.got.plt %t.so | FileCheck --check-prefix=DUMPDSO %s
// RUN: llvm-objdump -d --no-show-raw-insn --print-imm-hex %t.so | FileCheck --check-prefix=DISASMDSO %s
// RUN: llvm-readobj -S -r %t.exe | FileCheck --check-prefix=CHECKEXE %s
// RUN: llvm-readelf -S -r %t.exe | FileCheck --check-prefix=CHECKEXE %s
// RUN: llvm-objdump -s --section=.got.plt %t.exe | FileCheck --check-prefix=DUMPEXE %s
// RUN: llvm-objdump -d --no-show-raw-insn --print-imm-hex %t.exe | FileCheck --check-prefix=DISASMEXE %s

// CHECKDSO: Name: .plt
// CHECKDSO-NEXT: Type: SHT_PROGBITS
// CHECKDSO-NEXT: Flags [
// CHECKDSO-NEXT: SHF_ALLOC
// CHECKDSO-NEXT: SHF_EXECINSTR
// CHECKDSO-NEXT: ]
// CHECKDSO-NEXT: Address: 0x10340
// CHECKDSO-NEXT: Offset:
// CHECKDSO-NEXT: Size: 80
// CHECKDSO-NEXT: Link:
// CHECKDSO-NEXT: Info:
// CHECKDSO-NEXT: AddressAlignment: 16

// CHECKDSO: Name: .got.plt
// CHECKDSO-NEXT: Type: SHT_PROGBITS
// CHECKDSO-NEXT: Flags [
// CHECKDSO-NEXT: SHF_ALLOC
// CHECKDSO-NEXT: SHF_WRITE
// CHECKDSO-NEXT: ]
// CHECKDSO-NEXT: Address: 0x30450
// CHECKDSO-NEXT: Offset:
// CHECKDSO-NEXT: Size: 48
// CHECKDSO-NEXT: Link:
// CHECKDSO-NEXT: Info:
// CHECKDSO-NEXT: AddressAlignment: 8

// CHECKDSO: Relocations [
// CHECKDSO-NEXT: Section ({{.*}}) .rela.plt {

// &(.got.plt[3]) = 0x30450 + 3 * 8 = 0x30468
// CHECKDSO-NEXT: 0x30468 R_AARCH64_JUMP_SLOT foo

// &(.got.plt[4]) = 0x30450 + 4 * 8 = 0x30470
// CHECKDSO-NEXT: 0x30470 R_AARCH64_JUMP_SLOT bar

// &(.got.plt[5]) = 0x30000 + 5 * 8 = 0x30470
// CHECKDSO-NEXT: 0x30478 R_AARCH64_JUMP_SLOT weak
// CHECKDSO-NEXT: }
// CHECKDSO-NEXT: ]
// CHECKDSO-LABEL: Section Headers:
/// Name Type Address Off Size ES Flg Lk Inf Al
// CHECKDSO: .plt PROGBITS 0000000000010340 000340 000050 00 AXy 0 0 16
// CHECKDSO: .got.plt PROGBITS 0000000000030450 000450 000030 00 WA 0 0 8

// CHECKDSO-LABEL: Relocation section '.rela.plt' at offset 0x2e8 contains 3 entries:
// CHECKDSO-NEXT: Offset Info Type Symbol's Value Symbol's Name + Addend
/// &(.got.plt[3]) = 0x30450 + 3 * 8 = 0x30468
// CHECKDSO-NEXT: 0000000000030468 0000000400000402 R_AARCH64_JUMP_SLOT 000000000001033c foo + 0
/// &(.got.plt[4]) = 0x30450 + 4 * 8 = 0x30470
// CHECKDSO-NEXT: 0000000000030470 0000000100000402 R_AARCH64_JUMP_SLOT 0000000000000000 bar + 0
/// &(.got.plt[5]) = 0x30000 + 5 * 8 = 0x30478
// CHECKDSO-NEXT: 0000000000030478 0000000200000402 R_AARCH64_JUMP_SLOT 0000000000000000 weak + 0

// DUMPDSO: Contents of section .got.plt:
// .got.plt[0..2] = 0 (reserved)
Expand Down Expand Up @@ -106,42 +80,17 @@
// DISASMDSO-NEXT: 10388: add x16, x16, #0x478
// DISASMDSO-NEXT: 1038c: br x17

// CHECKEXE: Name: .plt
// CHECKEXE-NEXT: Type: SHT_PROGBITS
// CHECKEXE-NEXT: Flags [
// CHECKEXE-NEXT: SHF_ALLOC
// CHECKEXE-NEXT: SHF_EXECINSTR
// CHECKEXE-NEXT: ]
// CHECKEXE-NEXT: Address: 0x2102E0
// CHECKEXE-NEXT: Offset:
// CHECKEXE-NEXT: Size: 64
// CHECKEXE-NEXT: Link:
// CHECKEXE-NEXT: Info:
// CHECKEXE-NEXT: AddressAlignment: 16

// CHECKEXE: Name: .got.plt
// CHECKEXE-NEXT: Type: SHT_PROGBITS
// CHECKEXE-NEXT: Flags [
// CHECKEXE-NEXT: SHF_ALLOC
// CHECKEXE-NEXT: SHF_WRITE
// CHECKEXE-NEXT: ]
// CHECKEXE-NEXT: Address: 0x2303F0
// CHECKEXE-NEXT: Offset:
// CHECKEXE-NEXT: Size: 40
// CHECKEXE-NEXT: Link:
// CHECKEXE-NEXT: Info:
// CHECKEXE-NEXT: AddressAlignment: 8

// CHECKEXE: Relocations [
// CHECKEXE-NEXT: Section ({{.*}}) .rela.plt {

// &(.got.plt[3]) = 0x2303f0 + 3 * 8 = 0x230408
// CHECKEXE-NEXT: 0x230408 R_AARCH64_JUMP_SLOT bar 0x0

// &(.got.plt[4]) = 0x2303f0 + 4 * 8 = 0x230410
// CHECKEXE-NEXT: 0x230410 R_AARCH64_JUMP_SLOT weak 0x0
// CHECKEXE-NEXT: }
// CHECKEXE-NEXT: ]
// CHECKEXE-LABEL: Section Headers:
/// Name Type Address Off Size ES Flg Lk Inf Al
// CHECKEXE: .plt PROGBITS 00000000002102e0 0002e0 000040 00 AXy 0 0 16
// CHECKEXE: .got.plt PROGBITS 00000000002303f0 0003f0 000028 00 WA 0 0 8

// CHECKEXE-LABEL: Relocation section '.rela.plt' at offset 0x298 contains 2 entries:
// CHECKEXE-NEXT: Offset Info Type Symbol's Value Symbol's Name + Addend
/// &(.got.plt[3]) = 0x2303f0 + 3 * 8 = 0x230408
// CHECKEXE-NEXT: 0000000000230408 0000000100000402 R_AARCH64_JUMP_SLOT 0000000000000000 bar + 0
/// &(.got.plt[4]) = 0x2303f0 + 4 * 8 = 0x230410
// CHECKEXE-NEXT: 0000000000230410 0000000200000402 R_AARCH64_JUMP_SLOT 0000000000000000 weak + 0

// DUMPEXE: Contents of section .got.plt:
// .got.plt[0..2] = 0 (reserved)
Expand Down