[AArch64] Add support for SHF_AARCH64_PURECODE ELF section flag (1/3) by Il-Capitano · Pull Request #125687 · llvm/llvm-project

Il-Capitano · 2025-02-04T14:09:31Z

Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304

The general implementation follows the existing one for ARM targets. Generating object files with the SHF_AARCH64_PURECODE flag set is enabled by the +execute-only target feature.

Related PRs:

Clang: [Clang][AArch64] Add support for SHF_AARCH64_PURECODE ELF section flag (2/3) #125688
LLD: [LLD][ELF][AArch64] Add support for SHF_AARCH64_PURECODE ELF section flag (3/3) #125689

Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304 The general implementation follows the existing one for ARM targets. Generating object files with the `SHF_AARCH64_PURECODE` flag set is enabled by the `+execute-only` target feature.

llvmbot · 2025-02-04T14:10:05Z

@llvm/pr-subscribers-objectyaml
@llvm/pr-subscribers-llvm-binary-utilities

@llvm/pr-subscribers-mc

Author: Csanád Hajdú (Il-Capitano)

Changes

Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304

The general implementation follows the existing one for ARM targets. Generating object files with the SHF_AARCH64_PURECODE flag set is enabled by the +execute-only target feature.

Full diff: https://github.com/llvm/llvm-project/pull/125687.diff

18 Files Affected:

(modified) llvm/include/llvm/BinaryFormat/ELF.h (+4-1)
(modified) llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (+8-5)
(modified) llvm/lib/MC/MCParser/ELFAsmParser.cpp (+5-2)
(modified) llvm/lib/MC/MCSectionELF.cpp (+3)
(modified) llvm/lib/ObjectYAML/ELFYAML.cpp (+3)
(modified) llvm/lib/Target/AArch64/AArch64Features.td (+5)
(modified) llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp (+26)
(modified) llvm/lib/Target/AArch64/AArch64TargetObjectFile.h (+6)
(modified) llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp (+16-1)
(modified) llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h (+2)
(modified) llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp (+18)
(added) llvm/test/CodeGen/AArch64/execute-only-section.ll (+21)
(added) llvm/test/MC/ELF/AArch64/execute-only-populated-text-section.s (+27)
(added) llvm/test/MC/ELF/AArch64/execute-only-section.s (+43)
(added) llvm/test/MC/ELF/AArch64/execute-only-text-section-data.s (+27)
(modified) llvm/test/MC/ELF/section-flags-unknown.s (+3)
(modified) llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll (+25)
(modified) llvm/tools/llvm-readobj/ELFDumper.cpp (+8)

diff --git a/llvm/include/llvm/BinaryFormat/ELF.h b/llvm/include/llvm/BinaryFormat/ELF.h
index 8853c4a88b0b59..a5979d029a9eaf 100644
--- a/llvm/include/llvm/BinaryFormat/ELF.h
+++ b/llvm/include/llvm/BinaryFormat/ELF.h
@@ -1300,7 +1300,10 @@ enum : unsigned {
   SHF_MIPS_STRING = 0x80000000,
 
   // Make code section unreadable when in execute-only mode
-  SHF_ARM_PURECODE = 0x20000000
+  SHF_ARM_PURECODE = 0x20000000,
+
+  // Section contains only program instructions and no program data.
+  SHF_AARCH64_PURECODE = 0x20000000
 };
 
 // Section Group Flags
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 3c2c7c8c9fed69..6cfebca9a4d576 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -547,7 +547,7 @@ static unsigned getELFSectionType(StringRef Name, SectionKind K) {
   return ELF::SHT_PROGBITS;
 }
 
-static unsigned getELFSectionFlags(SectionKind K) {
+static unsigned getELFSectionFlags(SectionKind K, const Triple &T) {
   unsigned Flags = 0;
 
   if (!K.isMetadata() && !K.isExclude())
@@ -559,9 +559,12 @@ static unsigned getELFSectionFlags(SectionKind K) {
   if (K.isText())
     Flags |= ELF::SHF_EXECINSTR;
 
-  if (K.isExecuteOnly())
+  if ((T.isARM() || T.isThumb()) && K.isExecuteOnly())
     Flags |= ELF::SHF_ARM_PURECODE;
 
+  if (T.isAArch64() && K.isExecuteOnly())
+    Flags |= ELF::SHF_AARCH64_PURECODE;
+
   if (K.isWriteable())
     Flags |= ELF::SHF_WRITE;
 
@@ -840,7 +843,7 @@ static MCSection *selectExplicitSectionGlobal(const GlobalObject *GO,
   // Infer section flags from the section name if we can.
   Kind = getELFKindForNamedSection(SectionName, Kind);
 
-  unsigned Flags = getELFSectionFlags(Kind);
+  unsigned Flags = getELFSectionFlags(Kind, TM.getTargetTriple());
   auto [Group, IsComdat, ExtraFlags] = getGlobalObjectInfo(GO, TM);
   Flags |= ExtraFlags;
 
@@ -947,7 +950,7 @@ static MCSection *selectELFSectionForGlobal(
 
 MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
-  unsigned Flags = getELFSectionFlags(Kind);
+  unsigned Flags = getELFSectionFlags(Kind, TM.getTargetTriple());
 
   // If we have -ffunction-section or -fdata-section then we should emit the
   // global value to a uniqued section specifically for it.
@@ -967,7 +970,7 @@ MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
 MCSection *TargetLoweringObjectFileELF::getUniqueSectionForFunction(
     const Function &F, const TargetMachine &TM) const {
   SectionKind Kind = SectionKind::getText();
-  unsigned Flags = getELFSectionFlags(Kind);
+  unsigned Flags = getELFSectionFlags(Kind, TM.getTargetTriple());
   // If the function's section names is pre-determined via pragma or a
   // section attribute, call selectExplicitSectionGlobal.
   if (F.hasSection())
diff --git a/llvm/lib/MC/MCParser/ELFAsmParser.cpp b/llvm/lib/MC/MCParser/ELFAsmParser.cpp
index b58210b3c268e9..99b13c68a9966c 100644
--- a/llvm/lib/MC/MCParser/ELFAsmParser.cpp
+++ b/llvm/lib/MC/MCParser/ELFAsmParser.cpp
@@ -328,9 +328,12 @@ static unsigned parseSectionFlags(const Triple &TT, StringRef flagsStr,
       flags |= ELF::XCORE_SHF_DP_SECTION;
       break;
     case 'y':
-      if (!(TT.isARM() || TT.isThumb()))
+      if (TT.isARM() || TT.isThumb())
+        flags |= ELF::SHF_ARM_PURECODE;
+      else if (TT.isAArch64())
+        flags |= ELF::SHF_AARCH64_PURECODE;
+      else
         return -1U;
-      flags |= ELF::SHF_ARM_PURECODE;
       break;
     case 's':
       if (TT.getArch() != Triple::hexagon)
diff --git a/llvm/lib/MC/MCSectionELF.cpp b/llvm/lib/MC/MCSectionELF.cpp
index 25e62b70b5e2a0..72a959b1c92082 100644
--- a/llvm/lib/MC/MCSectionELF.cpp
+++ b/llvm/lib/MC/MCSectionELF.cpp
@@ -118,6 +118,9 @@ void MCSectionELF::printSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
   } else if (T.isARM() || T.isThumb()) {
     if (Flags & ELF::SHF_ARM_PURECODE)
       OS << 'y';
+  } else if (T.isAArch64()) {
+    if (Flags & ELF::SHF_AARCH64_PURECODE)
+      OS << 'y';
   } else if (Arch == Triple::hexagon) {
     if (Flags & ELF::SHF_HEX_GPREL)
       OS << 's';
diff --git a/llvm/lib/ObjectYAML/ELFYAML.cpp b/llvm/lib/ObjectYAML/ELFYAML.cpp
index 539834fc8d4dbf..05e4d85b2ea5d2 100644
--- a/llvm/lib/ObjectYAML/ELFYAML.cpp
+++ b/llvm/lib/ObjectYAML/ELFYAML.cpp
@@ -803,6 +803,9 @@ void ScalarBitSetTraits<ELFYAML::ELF_SHF>::bitset(IO &IO,
     break;
   }
   switch (Object->getMachine()) {
+  case ELF::EM_AARCH64:
+    BCase(SHF_AARCH64_PURECODE);
+    break;
   case ELF::EM_ARM:
     BCase(SHF_ARM_PURECODE);
     break;
diff --git a/llvm/lib/Target/AArch64/AArch64Features.td b/llvm/lib/Target/AArch64/AArch64Features.td
index 20db70ee38572f..7c95ba662938d9 100644
--- a/llvm/lib/Target/AArch64/AArch64Features.td
+++ b/llvm/lib/Target/AArch64/AArch64Features.td
@@ -635,6 +635,11 @@ def FeatureStrictAlign : SubtargetFeature<"strict-align",
                                           "Disallow all unaligned memory "
                                           "access">;
 
+def FeatureExecuteOnly : SubtargetFeature<"execute-only",
+                                          "GenExecuteOnly", "true",
+                                          "Enable the generation of "
+                                          "execute only code.">;
+
 foreach i = {1-7,9-15,18,20-28} in
     def FeatureReserveX#i : SubtargetFeature<"reserve-x"#i, "ReserveXRegister["#i#"]", "true",
                                              "Reserve X"#i#", making it unavailable "
diff --git a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
index 8729fd4b802c8e..434ae32502d484 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
@@ -148,3 +148,29 @@ MCSymbol *AArch64_MachoTargetObjectFile::getAuthPtrSlotSymbol(
   return getAuthPtrSlotSymbolHelper(getContext(), TM, MMI, MachOMMI, RawSym,
                                     Key, Discriminator);
 }
+
+static bool isExecuteOnlyFunction(const GlobalObject *GO, SectionKind Kind,
+                                  const TargetMachine &TM) {
+  if (const Function *F = dyn_cast<Function>(GO))
+    if (TM.getSubtarget<AArch64Subtarget>(*F).genExecuteOnly() && Kind.isText())
+      return true;
+  return false;
+}
+
+MCSection *AArch64_ELFTargetObjectFile::getExplicitSectionGlobal(
+    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
+  // Set execute-only access for the explicit section
+  if (isExecuteOnlyFunction(GO, Kind, TM))
+    Kind = SectionKind::getExecuteOnly();
+
+  return TargetLoweringObjectFileELF::getExplicitSectionGlobal(GO, Kind, TM);
+}
+
+MCSection *AArch64_ELFTargetObjectFile::SelectSectionForGlobal(
+    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
+  // Set execute-only access for the explicit section
+  if (isExecuteOnlyFunction(GO, Kind, TM))
+    Kind = SectionKind::getExecuteOnly();
+
+  return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, Kind, TM);
+}
diff --git a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
index 0c822ac84f200c..3e9cd51b742a29 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
+++ b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
@@ -39,6 +39,12 @@ class AArch64_ELFTargetObjectFile : public TargetLoweringObjectFileELF {
   void emitPersonalityValueImpl(MCStreamer &Streamer, const DataLayout &DL,
                                 const MCSymbol *Sym,
                                 const MachineModuleInfo *MMI) const override;
+
+  MCSection *getExplicitSectionGlobal(const GlobalObject *GO, SectionKind Kind,
+                                      const TargetMachine &TM) const override;
+
+  MCSection *SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind,
+                                    const TargetMachine &TM) const override;
 };
 
 /// AArch64_MachoTargetObjectFile - This TLOF implementation is used for Darwin.
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index a6edcf125782b2..284278e34f8b4d 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -262,6 +262,10 @@ bool AArch64TTIImpl::isMultiversionedFunction(const Function &F) const {
   return F.hasFnAttribute("fmv-features");
 }
 
+const FeatureBitset AArch64TTIImpl::InlineInverseFeatures = {
+    AArch64::FeatureExecuteOnly,
+};
+
 bool AArch64TTIImpl::areInlineCompatible(const Function *Caller,
                                          const Function *Callee) const {
   SMEAttrs CallerAttrs(*Caller), CalleeAttrs(*Callee);
@@ -284,7 +288,18 @@ bool AArch64TTIImpl::areInlineCompatible(const Function *Caller,
       return false;
   }
 
-  return BaseT::areInlineCompatible(Caller, Callee);
+  const TargetMachine &TM = getTLI()->getTargetMachine();
+  const FeatureBitset &CallerBits =
+      TM.getSubtargetImpl(*Caller)->getFeatureBits();
+  const FeatureBitset &CalleeBits =
+      TM.getSubtargetImpl(*Callee)->getFeatureBits();
+  // Adjust the feature bitsets by inverting some of the bits. This is needed
+  // for target features that represent restrictions rather than capabilities,
+  // for example "+execute-only".
+  FeatureBitset EffectiveCallerBits = CallerBits ^ InlineInverseFeatures;
+  FeatureBitset EffectiveCalleeBits = CalleeBits ^ InlineInverseFeatures;
+
+  return (EffectiveCallerBits & EffectiveCalleeBits) == EffectiveCalleeBits;
 }
 
 bool AArch64TTIImpl::areTypesABICompatible(
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
index b65e3c7a1ab20e..481cb5511a331b 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
@@ -48,6 +48,8 @@ class AArch64TTIImpl : public BasicTTIImplBase<AArch64TTIImpl> {
   const AArch64Subtarget *ST;
   const AArch64TargetLowering *TLI;
 
+  static const FeatureBitset InlineInverseFeatures;
+
   const AArch64Subtarget *getST() const { return ST; }
   const AArch64TargetLowering *getTLI() const { return TLI; }
 
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
index 6b5c5f36cbd4b2..d29d383bc23127 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
@@ -27,6 +27,7 @@
 #include "llvm/MC/MCELFStreamer.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSubtargetInfo.h"
@@ -504,6 +505,23 @@ void AArch64TargetELFStreamer::finish() {
     }
   }
 
+  // The mix of execute-only and non-execute-only at link time is
+  // non-execute-only. To avoid the empty implicitly created .text
+  // section from making the whole .text section non-execute-only, we
+  // mark it execute-only if it is empty and there is at least one
+  // execute-only section in the object.
+  if (any_of(Asm, [](const MCSection &Sec) {
+        return cast<MCSectionELF>(Sec).getFlags() & ELF::SHF_AARCH64_PURECODE;
+      })) {
+    auto *Text =
+        static_cast<MCSectionELF *>(Ctx.getObjectFileInfo()->getTextSection());
+    for (auto &F : *Text)
+      if (auto *DF = dyn_cast<MCDataFragment>(&F))
+        if (!DF->getContents().empty())
+          return;
+    Text->setFlags(Text->getFlags() | ELF::SHF_AARCH64_PURECODE);
+  }
+
   MCSectionELF *MemtagSec = nullptr;
   for (const MCSymbol &Symbol : Asm.symbols()) {
     const auto &Sym = cast<MCSymbolELF>(Symbol);
diff --git a/llvm/test/CodeGen/AArch64/execute-only-section.ll b/llvm/test/CodeGen/AArch64/execute-only-section.ll
new file mode 100644
index 00000000000000..15a270b07975e6
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/execute-only-section.ll
@@ -0,0 +1,21 @@
+; RUN: llc -mtriple=aarch64 -mattr=+execute-only %s -o - | FileCheck %s
+
+; CHECK:     .section .text,"axy",@progbits,unique,0
+; CHECK-NOT: .section
+; CHECK-NOT: .text
+; CHECK:     .globl test_SectionForGlobal
+; CHECK:     .type test_SectionForGlobal,@function
+define void @test_SectionForGlobal() {
+entry:
+  ret void
+}
+
+; CHECK:     .section .test,"axy",@progbits
+; CHECK-NOT: .section
+; CHECK-NOT: .text
+; CHECK:     .globl test_ExplicitSectionForGlobal
+; CHECK:     .type test_ExplicitSectionForGlobal,@function
+define void @test_ExplicitSectionForGlobal() section ".test" {
+entry:
+  ret void
+}
diff --git a/llvm/test/MC/ELF/AArch64/execute-only-populated-text-section.s b/llvm/test/MC/ELF/AArch64/execute-only-populated-text-section.s
new file mode 100644
index 00000000000000..b0ba8a18d52b38
--- /dev/null
+++ b/llvm/test/MC/ELF/AArch64/execute-only-populated-text-section.s
@@ -0,0 +1,27 @@
+// RUN: llvm-mc -filetype=obj -triple aarch64-unknown-linux-gnu %s -o - \
+// RUN: | llvm-readobj -S --symbols - | FileCheck %s
+
+        .text
+        ret
+
+        .section        .text.foo,"axy"
+        ret
+
+// CHECK:      Section {
+// CHECK:        Name: .text
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x6)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:      }
+
+// CHECK:      Section {
+// CHECK:        Name: .text.foo
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x20000006)
+// CHECK-NEXT:     SHF_AARCH64_PURECODE (0x20000000)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:      }
diff --git a/llvm/test/MC/ELF/AArch64/execute-only-section.s b/llvm/test/MC/ELF/AArch64/execute-only-section.s
new file mode 100644
index 00000000000000..6fd596376711d6
--- /dev/null
+++ b/llvm/test/MC/ELF/AArch64/execute-only-section.s
@@ -0,0 +1,43 @@
+// RUN: llvm-mc -filetype=obj -triple aarch64-unknown-linux-gnu %s -o - \
+// RUN: | llvm-readobj -S --symbols - | FileCheck %s
+
+        .section        .text,"axy",@progbits,unique,0
+        .globl  foo
+        .p2align  2
+        .type   foo,@function
+foo:
+        .cfi_startproc
+        ret
+.Lfunc_end0:
+        .size   foo, .Lfunc_end0-foo
+        .cfi_endproc
+
+        .section        ".note.GNU-stack","",@progbits
+
+
+// CHECK:      Section {
+// CHECK:        Name: .text
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x20000006)
+// CHECK-NEXT:     SHF_AARCH64_PURECODE (0x20000000)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:        Size: 0
+// CHECK:      }
+
+// CHECK:      Section {
+// CHECK:        Name: .text
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x20000006)
+// CHECK-NEXT:     SHF_AARCH64_PURECODE (0x20000000)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:        Size: 2
+// CHECK:      }
+
+// CHECK: Symbol {
+// CHECK:   Name: foo
+// CHECK:   Section: .text (0x3)
+// CHECK: }
diff --git a/llvm/test/MC/ELF/AArch64/execute-only-text-section-data.s b/llvm/test/MC/ELF/AArch64/execute-only-text-section-data.s
new file mode 100644
index 00000000000000..22bcffae67d0eb
--- /dev/null
+++ b/llvm/test/MC/ELF/AArch64/execute-only-text-section-data.s
@@ -0,0 +1,27 @@
+// RUN: llvm-mc -filetype=obj -triple aarch64-unknown-linux-gnu %s -o - \
+// RUN: | llvm-readobj -S --symbols - | FileCheck %s
+
+        .text
+        .ascii "test"
+
+        .section        .text.foo,"axy"
+        ret
+
+// CHECK:      Section {
+// CHECK:        Name: .text
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x6)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:      }
+
+// CHECK:      Section {
+// CHECK:        Name: .text.foo
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x20000006)
+// CHECK-NEXT:     SHF_AARCH64_PURECODE (0x20000000)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:      }
diff --git a/llvm/test/MC/ELF/section-flags-unknown.s b/llvm/test/MC/ELF/section-flags-unknown.s
index 90c9185e8bfb10..b172403e34556c 100644
--- a/llvm/test/MC/ELF/section-flags-unknown.s
+++ b/llvm/test/MC/ELF/section-flags-unknown.s
@@ -14,5 +14,8 @@
 # CHECK: {{.*}}.s:[[# @LINE+1]]:30: error: unknown flag
 .section SHF_ARM_PURECODE,"y",@progbits
 
+# CHECK: {{.*}}.s:[[# @LINE+1]]:34: error: unknown flag
+.section SHF_AARCH64_PURECODE,"y",@progbits
+
 # CHECK: {{.*}}.s:[[# @LINE+1]]:30: error: unknown flag
 .section SHF_X86_64_LARGE,"l",@progbits
diff --git a/llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll b/llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll
index 636f3c6600f8d4..433a9c7bdd23b0 100644
--- a/llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll
+++ b/llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll
@@ -27,6 +27,14 @@ entry:
 ; CHECK: call i32 @bar()
 }
 
+define i32 @quux() #3 {
+entry:
+  %call = call i32 (...) @baz()
+  ret i32 %call
+; CHECK-LABEL: quux
+; CHECK: call i32 (...) @baz()
+}
+
 define i32 @strict_align() #2 {
 entry:
   %call = call i32 @foo()
@@ -35,6 +43,23 @@ entry:
 ; CHECK: call i32 (...) @baz()
 }
 
+define i32 @execute_only1() #3 {
+entry:
+  %call = call i32 @foo()
+  ret i32 %call
+; CHECK-LABEL: execute_only1
+; CHECK: call i32 @foo()
+}
+
+define i32 @execute_only2() #0 {
+entry:
+  %call = call i32 @quux()
+  ret i32 %call
+; CHECK-LABEL: execute_only2
+; CHECK: call i32 (...) @baz()
+}
+
 attributes #0 = { "target-cpu"="generic" "target-features"="+crc,+neon" }
 attributes #1 = { "target-cpu"="generic" "target-features"="+crc,+neon,+crypto" }
 attributes #2 = { "target-cpu"="generic" "target-features"="+crc,+neon,+strict-align" }
+attributes #3 = { "target-cpu"="generic" "target-features"="+crc,+neon,+execute-only" }
diff --git a/llvm/tools/llvm-readobj/ELFDumper.cpp b/llvm/tools/llvm-readobj/ELFDumper.cpp
index bfca65aad52b44..78aaf79a61c468 100644
--- a/llvm/tools/llvm-readobj/ELFDumper.cpp
+++ b/llvm/tools/llvm-readobj/ELFDumper.cpp
@@ -1337,6 +1337,10 @@ const EnumEntry<unsigned> ElfXCoreSectionFlags[] = {
   ENUM_ENT(XCORE_SHF_DP_SECTION, "")
 };
 
+const EnumEntry<unsigned> ElfAArch64SectionFlags[] = {
+    ENUM_ENT(SHF_AARCH64_PURECODE, "y"),
+};
+
 const EnumEntry<unsigned> ElfARMSectionFlags[] = {
   ENUM_ENT(SHF_ARM_PURECODE, "y")
 };
@@ -1375,6 +1379,10 @@ getSectionFlagsForTarget(unsigned EOSAbi, unsigned EMachine) {
     break;
   }
   switch (EMachine) {
+  case EM_AARCH64:
+    Ret.insert(Ret.end(), std::begin(ElfAArch64SectionFlags),
+               std::end(ElfAArch64SectionFlags));
+    break;
   case EM_ARM:
     Ret.insert(Ret.end(), std::begin(ElfARMSectionFlags),
                std::end(ElfARMSectionFlags));

llvmbot · 2025-02-04T14:10:05Z

@llvm/pr-subscribers-backend-aarch64

Author: Csanád Hajdú (Il-Capitano)

Changes

Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304

The general implementation follows the existing one for ARM targets. Generating object files with the SHF_AARCH64_PURECODE flag set is enabled by the +execute-only target feature.

Full diff: https://github.com/llvm/llvm-project/pull/125687.diff

18 Files Affected:

(modified) llvm/include/llvm/BinaryFormat/ELF.h (+4-1)
(modified) llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (+8-5)
(modified) llvm/lib/MC/MCParser/ELFAsmParser.cpp (+5-2)
(modified) llvm/lib/MC/MCSectionELF.cpp (+3)
(modified) llvm/lib/ObjectYAML/ELFYAML.cpp (+3)
(modified) llvm/lib/Target/AArch64/AArch64Features.td (+5)
(modified) llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp (+26)
(modified) llvm/lib/Target/AArch64/AArch64TargetObjectFile.h (+6)
(modified) llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp (+16-1)
(modified) llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h (+2)
(modified) llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp (+18)
(added) llvm/test/CodeGen/AArch64/execute-only-section.ll (+21)
(added) llvm/test/MC/ELF/AArch64/execute-only-populated-text-section.s (+27)
(added) llvm/test/MC/ELF/AArch64/execute-only-section.s (+43)
(added) llvm/test/MC/ELF/AArch64/execute-only-text-section-data.s (+27)
(modified) llvm/test/MC/ELF/section-flags-unknown.s (+3)
(modified) llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll (+25)
(modified) llvm/tools/llvm-readobj/ELFDumper.cpp (+8)

diff --git a/llvm/include/llvm/BinaryFormat/ELF.h b/llvm/include/llvm/BinaryFormat/ELF.h
index 8853c4a88b0b593..a5979d029a9eafd 100644
--- a/llvm/include/llvm/BinaryFormat/ELF.h
+++ b/llvm/include/llvm/BinaryFormat/ELF.h
@@ -1300,7 +1300,10 @@ enum : unsigned {
   SHF_MIPS_STRING = 0x80000000,
 
   // Make code section unreadable when in execute-only mode
-  SHF_ARM_PURECODE = 0x20000000
+  SHF_ARM_PURECODE = 0x20000000,
+
+  // Section contains only program instructions and no program data.
+  SHF_AARCH64_PURECODE = 0x20000000
 };
 
 // Section Group Flags
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 3c2c7c8c9fed69a..6cfebca9a4d576e 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -547,7 +547,7 @@ static unsigned getELFSectionType(StringRef Name, SectionKind K) {
   return ELF::SHT_PROGBITS;
 }
 
-static unsigned getELFSectionFlags(SectionKind K) {
+static unsigned getELFSectionFlags(SectionKind K, const Triple &T) {
   unsigned Flags = 0;
 
   if (!K.isMetadata() && !K.isExclude())
@@ -559,9 +559,12 @@ static unsigned getELFSectionFlags(SectionKind K) {
   if (K.isText())
     Flags |= ELF::SHF_EXECINSTR;
 
-  if (K.isExecuteOnly())
+  if ((T.isARM() || T.isThumb()) && K.isExecuteOnly())
     Flags |= ELF::SHF_ARM_PURECODE;
 
+  if (T.isAArch64() && K.isExecuteOnly())
+    Flags |= ELF::SHF_AARCH64_PURECODE;
+
   if (K.isWriteable())
     Flags |= ELF::SHF_WRITE;
 
@@ -840,7 +843,7 @@ static MCSection *selectExplicitSectionGlobal(const GlobalObject *GO,
   // Infer section flags from the section name if we can.
   Kind = getELFKindForNamedSection(SectionName, Kind);
 
-  unsigned Flags = getELFSectionFlags(Kind);
+  unsigned Flags = getELFSectionFlags(Kind, TM.getTargetTriple());
   auto [Group, IsComdat, ExtraFlags] = getGlobalObjectInfo(GO, TM);
   Flags |= ExtraFlags;
 
@@ -947,7 +950,7 @@ static MCSection *selectELFSectionForGlobal(
 
 MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
-  unsigned Flags = getELFSectionFlags(Kind);
+  unsigned Flags = getELFSectionFlags(Kind, TM.getTargetTriple());
 
   // If we have -ffunction-section or -fdata-section then we should emit the
   // global value to a uniqued section specifically for it.
@@ -967,7 +970,7 @@ MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
 MCSection *TargetLoweringObjectFileELF::getUniqueSectionForFunction(
     const Function &F, const TargetMachine &TM) const {
   SectionKind Kind = SectionKind::getText();
-  unsigned Flags = getELFSectionFlags(Kind);
+  unsigned Flags = getELFSectionFlags(Kind, TM.getTargetTriple());
   // If the function's section names is pre-determined via pragma or a
   // section attribute, call selectExplicitSectionGlobal.
   if (F.hasSection())
diff --git a/llvm/lib/MC/MCParser/ELFAsmParser.cpp b/llvm/lib/MC/MCParser/ELFAsmParser.cpp
index b58210b3c268e99..99b13c68a9966c7 100644
--- a/llvm/lib/MC/MCParser/ELFAsmParser.cpp
+++ b/llvm/lib/MC/MCParser/ELFAsmParser.cpp
@@ -328,9 +328,12 @@ static unsigned parseSectionFlags(const Triple &TT, StringRef flagsStr,
       flags |= ELF::XCORE_SHF_DP_SECTION;
       break;
     case 'y':
-      if (!(TT.isARM() || TT.isThumb()))
+      if (TT.isARM() || TT.isThumb())
+        flags |= ELF::SHF_ARM_PURECODE;
+      else if (TT.isAArch64())
+        flags |= ELF::SHF_AARCH64_PURECODE;
+      else
         return -1U;
-      flags |= ELF::SHF_ARM_PURECODE;
       break;
     case 's':
       if (TT.getArch() != Triple::hexagon)
diff --git a/llvm/lib/MC/MCSectionELF.cpp b/llvm/lib/MC/MCSectionELF.cpp
index 25e62b70b5e2a0c..72a959b1c920825 100644
--- a/llvm/lib/MC/MCSectionELF.cpp
+++ b/llvm/lib/MC/MCSectionELF.cpp
@@ -118,6 +118,9 @@ void MCSectionELF::printSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
   } else if (T.isARM() || T.isThumb()) {
     if (Flags & ELF::SHF_ARM_PURECODE)
       OS << 'y';
+  } else if (T.isAArch64()) {
+    if (Flags & ELF::SHF_AARCH64_PURECODE)
+      OS << 'y';
   } else if (Arch == Triple::hexagon) {
     if (Flags & ELF::SHF_HEX_GPREL)
       OS << 's';
diff --git a/llvm/lib/ObjectYAML/ELFYAML.cpp b/llvm/lib/ObjectYAML/ELFYAML.cpp
index 539834fc8d4dbfe..05e4d85b2ea5d24 100644
--- a/llvm/lib/ObjectYAML/ELFYAML.cpp
+++ b/llvm/lib/ObjectYAML/ELFYAML.cpp
@@ -803,6 +803,9 @@ void ScalarBitSetTraits<ELFYAML::ELF_SHF>::bitset(IO &IO,
     break;
   }
   switch (Object->getMachine()) {
+  case ELF::EM_AARCH64:
+    BCase(SHF_AARCH64_PURECODE);
+    break;
   case ELF::EM_ARM:
     BCase(SHF_ARM_PURECODE);
     break;
diff --git a/llvm/lib/Target/AArch64/AArch64Features.td b/llvm/lib/Target/AArch64/AArch64Features.td
index 20db70ee38572f2..7c95ba662938d9f 100644
--- a/llvm/lib/Target/AArch64/AArch64Features.td
+++ b/llvm/lib/Target/AArch64/AArch64Features.td
@@ -635,6 +635,11 @@ def FeatureStrictAlign : SubtargetFeature<"strict-align",
                                           "Disallow all unaligned memory "
                                           "access">;
 
+def FeatureExecuteOnly : SubtargetFeature<"execute-only",
+                                          "GenExecuteOnly", "true",
+                                          "Enable the generation of "
+                                          "execute only code.">;
+
 foreach i = {1-7,9-15,18,20-28} in
     def FeatureReserveX#i : SubtargetFeature<"reserve-x"#i, "ReserveXRegister["#i#"]", "true",
                                              "Reserve X"#i#", making it unavailable "
diff --git a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
index 8729fd4b802c8eb..434ae32502d484b 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
@@ -148,3 +148,29 @@ MCSymbol *AArch64_MachoTargetObjectFile::getAuthPtrSlotSymbol(
   return getAuthPtrSlotSymbolHelper(getContext(), TM, MMI, MachOMMI, RawSym,
                                     Key, Discriminator);
 }
+
+static bool isExecuteOnlyFunction(const GlobalObject *GO, SectionKind Kind,
+                                  const TargetMachine &TM) {
+  if (const Function *F = dyn_cast<Function>(GO))
+    if (TM.getSubtarget<AArch64Subtarget>(*F).genExecuteOnly() && Kind.isText())
+      return true;
+  return false;
+}
+
+MCSection *AArch64_ELFTargetObjectFile::getExplicitSectionGlobal(
+    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
+  // Set execute-only access for the explicit section
+  if (isExecuteOnlyFunction(GO, Kind, TM))
+    Kind = SectionKind::getExecuteOnly();
+
+  return TargetLoweringObjectFileELF::getExplicitSectionGlobal(GO, Kind, TM);
+}
+
+MCSection *AArch64_ELFTargetObjectFile::SelectSectionForGlobal(
+    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
+  // Set execute-only access for the explicit section
+  if (isExecuteOnlyFunction(GO, Kind, TM))
+    Kind = SectionKind::getExecuteOnly();
+
+  return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, Kind, TM);
+}
diff --git a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
index 0c822ac84f200c7..3e9cd51b742a29c 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
+++ b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
@@ -39,6 +39,12 @@ class AArch64_ELFTargetObjectFile : public TargetLoweringObjectFileELF {
   void emitPersonalityValueImpl(MCStreamer &Streamer, const DataLayout &DL,
                                 const MCSymbol *Sym,
                                 const MachineModuleInfo *MMI) const override;
+
+  MCSection *getExplicitSectionGlobal(const GlobalObject *GO, SectionKind Kind,
+                                      const TargetMachine &TM) const override;
+
+  MCSection *SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind,
+                                    const TargetMachine &TM) const override;
 };
 
 /// AArch64_MachoTargetObjectFile - This TLOF implementation is used for Darwin.
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index a6edcf125782b2c..284278e34f8b4d0 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -262,6 +262,10 @@ bool AArch64TTIImpl::isMultiversionedFunction(const Function &F) const {
   return F.hasFnAttribute("fmv-features");
 }
 
+const FeatureBitset AArch64TTIImpl::InlineInverseFeatures = {
+    AArch64::FeatureExecuteOnly,
+};
+
 bool AArch64TTIImpl::areInlineCompatible(const Function *Caller,
                                          const Function *Callee) const {
   SMEAttrs CallerAttrs(*Caller), CalleeAttrs(*Callee);
@@ -284,7 +288,18 @@ bool AArch64TTIImpl::areInlineCompatible(const Function *Caller,
       return false;
   }
 
-  return BaseT::areInlineCompatible(Caller, Callee);
+  const TargetMachine &TM = getTLI()->getTargetMachine();
+  const FeatureBitset &CallerBits =
+      TM.getSubtargetImpl(*Caller)->getFeatureBits();
+  const FeatureBitset &CalleeBits =
+      TM.getSubtargetImpl(*Callee)->getFeatureBits();
+  // Adjust the feature bitsets by inverting some of the bits. This is needed
+  // for target features that represent restrictions rather than capabilities,
+  // for example "+execute-only".
+  FeatureBitset EffectiveCallerBits = CallerBits ^ InlineInverseFeatures;
+  FeatureBitset EffectiveCalleeBits = CalleeBits ^ InlineInverseFeatures;
+
+  return (EffectiveCallerBits & EffectiveCalleeBits) == EffectiveCalleeBits;
 }
 
 bool AArch64TTIImpl::areTypesABICompatible(
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
index b65e3c7a1ab20e5..481cb5511a331b7 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
@@ -48,6 +48,8 @@ class AArch64TTIImpl : public BasicTTIImplBase<AArch64TTIImpl> {
   const AArch64Subtarget *ST;
   const AArch64TargetLowering *TLI;
 
+  static const FeatureBitset InlineInverseFeatures;
+
   const AArch64Subtarget *getST() const { return ST; }
   const AArch64TargetLowering *getTLI() const { return TLI; }
 
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
index 6b5c5f36cbd4b27..d29d383bc231277 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
@@ -27,6 +27,7 @@
 #include "llvm/MC/MCELFStreamer.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSubtargetInfo.h"
@@ -504,6 +505,23 @@ void AArch64TargetELFStreamer::finish() {
     }
   }
 
+  // The mix of execute-only and non-execute-only at link time is
+  // non-execute-only. To avoid the empty implicitly created .text
+  // section from making the whole .text section non-execute-only, we
+  // mark it execute-only if it is empty and there is at least one
+  // execute-only section in the object.
+  if (any_of(Asm, [](const MCSection &Sec) {
+        return cast<MCSectionELF>(Sec).getFlags() & ELF::SHF_AARCH64_PURECODE;
+      })) {
+    auto *Text =
+        static_cast<MCSectionELF *>(Ctx.getObjectFileInfo()->getTextSection());
+    for (auto &F : *Text)
+      if (auto *DF = dyn_cast<MCDataFragment>(&F))
+        if (!DF->getContents().empty())
+          return;
+    Text->setFlags(Text->getFlags() | ELF::SHF_AARCH64_PURECODE);
+  }
+
   MCSectionELF *MemtagSec = nullptr;
   for (const MCSymbol &Symbol : Asm.symbols()) {
     const auto &Sym = cast<MCSymbolELF>(Symbol);
diff --git a/llvm/test/CodeGen/AArch64/execute-only-section.ll b/llvm/test/CodeGen/AArch64/execute-only-section.ll
new file mode 100644
index 000000000000000..15a270b07975e69
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/execute-only-section.ll
@@ -0,0 +1,21 @@
+; RUN: llc -mtriple=aarch64 -mattr=+execute-only %s -o - | FileCheck %s
+
+; CHECK:     .section .text,"axy",@progbits,unique,0
+; CHECK-NOT: .section
+; CHECK-NOT: .text
+; CHECK:     .globl test_SectionForGlobal
+; CHECK:     .type test_SectionForGlobal,@function
+define void @test_SectionForGlobal() {
+entry:
+  ret void
+}
+
+; CHECK:     .section .test,"axy",@progbits
+; CHECK-NOT: .section
+; CHECK-NOT: .text
+; CHECK:     .globl test_ExplicitSectionForGlobal
+; CHECK:     .type test_ExplicitSectionForGlobal,@function
+define void @test_ExplicitSectionForGlobal() section ".test" {
+entry:
+  ret void
+}
diff --git a/llvm/test/MC/ELF/AArch64/execute-only-populated-text-section.s b/llvm/test/MC/ELF/AArch64/execute-only-populated-text-section.s
new file mode 100644
index 000000000000000..b0ba8a18d52b386
--- /dev/null
+++ b/llvm/test/MC/ELF/AArch64/execute-only-populated-text-section.s
@@ -0,0 +1,27 @@
+// RUN: llvm-mc -filetype=obj -triple aarch64-unknown-linux-gnu %s -o - \
+// RUN: | llvm-readobj -S --symbols - | FileCheck %s
+
+        .text
+        ret
+
+        .section        .text.foo,"axy"
+        ret
+
+// CHECK:      Section {
+// CHECK:        Name: .text
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x6)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:      }
+
+// CHECK:      Section {
+// CHECK:        Name: .text.foo
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x20000006)
+// CHECK-NEXT:     SHF_AARCH64_PURECODE (0x20000000)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:      }
diff --git a/llvm/test/MC/ELF/AArch64/execute-only-section.s b/llvm/test/MC/ELF/AArch64/execute-only-section.s
new file mode 100644
index 000000000000000..6fd596376711d6a
--- /dev/null
+++ b/llvm/test/MC/ELF/AArch64/execute-only-section.s
@@ -0,0 +1,43 @@
+// RUN: llvm-mc -filetype=obj -triple aarch64-unknown-linux-gnu %s -o - \
+// RUN: | llvm-readobj -S --symbols - | FileCheck %s
+
+        .section        .text,"axy",@progbits,unique,0
+        .globl  foo
+        .p2align  2
+        .type   foo,@function
+foo:
+        .cfi_startproc
+        ret
+.Lfunc_end0:
+        .size   foo, .Lfunc_end0-foo
+        .cfi_endproc
+
+        .section        ".note.GNU-stack","",@progbits
+
+
+// CHECK:      Section {
+// CHECK:        Name: .text
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x20000006)
+// CHECK-NEXT:     SHF_AARCH64_PURECODE (0x20000000)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:        Size: 0
+// CHECK:      }
+
+// CHECK:      Section {
+// CHECK:        Name: .text
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x20000006)
+// CHECK-NEXT:     SHF_AARCH64_PURECODE (0x20000000)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:        Size: 2
+// CHECK:      }
+
+// CHECK: Symbol {
+// CHECK:   Name: foo
+// CHECK:   Section: .text (0x3)
+// CHECK: }
diff --git a/llvm/test/MC/ELF/AArch64/execute-only-text-section-data.s b/llvm/test/MC/ELF/AArch64/execute-only-text-section-data.s
new file mode 100644
index 000000000000000..22bcffae67d0eb2
--- /dev/null
+++ b/llvm/test/MC/ELF/AArch64/execute-only-text-section-data.s
@@ -0,0 +1,27 @@
+// RUN: llvm-mc -filetype=obj -triple aarch64-unknown-linux-gnu %s -o - \
+// RUN: | llvm-readobj -S --symbols - | FileCheck %s
+
+        .text
+        .ascii "test"
+
+        .section        .text.foo,"axy"
+        ret
+
+// CHECK:      Section {
+// CHECK:        Name: .text
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x6)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:      }
+
+// CHECK:      Section {
+// CHECK:        Name: .text.foo
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x20000006)
+// CHECK-NEXT:     SHF_AARCH64_PURECODE (0x20000000)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:      }
diff --git a/llvm/test/MC/ELF/section-flags-unknown.s b/llvm/test/MC/ELF/section-flags-unknown.s
index 90c9185e8bfb108..b172403e34556ca 100644
--- a/llvm/test/MC/ELF/section-flags-unknown.s
+++ b/llvm/test/MC/ELF/section-flags-unknown.s
@@ -14,5 +14,8 @@
 # CHECK: {{.*}}.s:[[# @LINE+1]]:30: error: unknown flag
 .section SHF_ARM_PURECODE,"y",@progbits
 
+# CHECK: {{.*}}.s:[[# @LINE+1]]:34: error: unknown flag
+.section SHF_AARCH64_PURECODE,"y",@progbits
+
 # CHECK: {{.*}}.s:[[# @LINE+1]]:30: error: unknown flag
 .section SHF_X86_64_LARGE,"l",@progbits
diff --git a/llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll b/llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll
index 636f3c6600f8d4c..433a9c7bdd23b01 100644
--- a/llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll
+++ b/llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll
@@ -27,6 +27,14 @@ entry:
 ; CHECK: call i32 @bar()
 }
 
+define i32 @quux() #3 {
+entry:
+  %call = call i32 (...) @baz()
+  ret i32 %call
+; CHECK-LABEL: quux
+; CHECK: call i32 (...) @baz()
+}
+
 define i32 @strict_align() #2 {
 entry:
   %call = call i32 @foo()
@@ -35,6 +43,23 @@ entry:
 ; CHECK: call i32 (...) @baz()
 }
 
+define i32 @execute_only1() #3 {
+entry:
+  %call = call i32 @foo()
+  ret i32 %call
+; CHECK-LABEL: execute_only1
+; CHECK: call i32 @foo()
+}
+
+define i32 @execute_only2() #0 {
+entry:
+  %call = call i32 @quux()
+  ret i32 %call
+; CHECK-LABEL: execute_only2
+; CHECK: call i32 (...) @baz()
+}
+
 attributes #0 = { "target-cpu"="generic" "target-features"="+crc,+neon" }
 attributes #1 = { "target-cpu"="generic" "target-features"="+crc,+neon,+crypto" }
 attributes #2 = { "target-cpu"="generic" "target-features"="+crc,+neon,+strict-align" }
+attributes #3 = { "target-cpu"="generic" "target-features"="+crc,+neon,+execute-only" }
diff --git a/llvm/tools/llvm-readobj/ELFDumper.cpp b/llvm/tools/llvm-readobj/ELFDumper.cpp
index bfca65aad52b443..78aaf79a61c468e 100644
--- a/llvm/tools/llvm-readobj/ELFDumper.cpp
+++ b/llvm/tools/llvm-readobj/ELFDumper.cpp
@@ -1337,6 +1337,10 @@ const EnumEntry<unsigned> ElfXCoreSectionFlags[] = {
   ENUM_ENT(XCORE_SHF_DP_SECTION, "")
 };
 
+const EnumEntry<unsigned> ElfAArch64SectionFlags[] = {
+    ENUM_ENT(SHF_AARCH64_PURECODE, "y"),
+};
+
 const EnumEntry<unsigned> ElfARMSectionFlags[] = {
   ENUM_ENT(SHF_ARM_PURECODE, "y")
 };
@@ -1375,6 +1379,10 @@ getSectionFlagsForTarget(unsigned EOSAbi, unsigned EMachine) {
     break;
   }
   switch (EMachine) {
+  case EM_AARCH64:
+    Ret.insert(Ret.end(), std::begin(ElfAArch64SectionFlags),
+               std::end(ElfAArch64SectionFlags));
+    break;
   case EM_ARM:
     Ret.insert(Ret.end(), std::begin(ElfARMSectionFlags),
                std::end(ElfARMSectionFlags));

llvmbot · 2025-02-04T14:10:05Z

@llvm/pr-subscribers-llvm-transforms

Author: Csanád Hajdú (Il-Capitano)

Changes

Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304

The general implementation follows the existing one for ARM targets. Generating object files with the SHF_AARCH64_PURECODE flag set is enabled by the +execute-only target feature.

Full diff: https://github.com/llvm/llvm-project/pull/125687.diff

18 Files Affected:

(modified) llvm/include/llvm/BinaryFormat/ELF.h (+4-1)
(modified) llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (+8-5)
(modified) llvm/lib/MC/MCParser/ELFAsmParser.cpp (+5-2)
(modified) llvm/lib/MC/MCSectionELF.cpp (+3)
(modified) llvm/lib/ObjectYAML/ELFYAML.cpp (+3)
(modified) llvm/lib/Target/AArch64/AArch64Features.td (+5)
(modified) llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp (+26)
(modified) llvm/lib/Target/AArch64/AArch64TargetObjectFile.h (+6)
(modified) llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp (+16-1)
(modified) llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h (+2)
(modified) llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp (+18)
(added) llvm/test/CodeGen/AArch64/execute-only-section.ll (+21)
(added) llvm/test/MC/ELF/AArch64/execute-only-populated-text-section.s (+27)
(added) llvm/test/MC/ELF/AArch64/execute-only-section.s (+43)
(added) llvm/test/MC/ELF/AArch64/execute-only-text-section-data.s (+27)
(modified) llvm/test/MC/ELF/section-flags-unknown.s (+3)
(modified) llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll (+25)
(modified) llvm/tools/llvm-readobj/ELFDumper.cpp (+8)

diff --git a/llvm/include/llvm/BinaryFormat/ELF.h b/llvm/include/llvm/BinaryFormat/ELF.h
index 8853c4a88b0b59..a5979d029a9eaf 100644
--- a/llvm/include/llvm/BinaryFormat/ELF.h
+++ b/llvm/include/llvm/BinaryFormat/ELF.h
@@ -1300,7 +1300,10 @@ enum : unsigned {
   SHF_MIPS_STRING = 0x80000000,
 
   // Make code section unreadable when in execute-only mode
-  SHF_ARM_PURECODE = 0x20000000
+  SHF_ARM_PURECODE = 0x20000000,
+
+  // Section contains only program instructions and no program data.
+  SHF_AARCH64_PURECODE = 0x20000000
 };
 
 // Section Group Flags
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 3c2c7c8c9fed69..6cfebca9a4d576 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -547,7 +547,7 @@ static unsigned getELFSectionType(StringRef Name, SectionKind K) {
   return ELF::SHT_PROGBITS;
 }
 
-static unsigned getELFSectionFlags(SectionKind K) {
+static unsigned getELFSectionFlags(SectionKind K, const Triple &T) {
   unsigned Flags = 0;
 
   if (!K.isMetadata() && !K.isExclude())
@@ -559,9 +559,12 @@ static unsigned getELFSectionFlags(SectionKind K) {
   if (K.isText())
     Flags |= ELF::SHF_EXECINSTR;
 
-  if (K.isExecuteOnly())
+  if ((T.isARM() || T.isThumb()) && K.isExecuteOnly())
     Flags |= ELF::SHF_ARM_PURECODE;
 
+  if (T.isAArch64() && K.isExecuteOnly())
+    Flags |= ELF::SHF_AARCH64_PURECODE;
+
   if (K.isWriteable())
     Flags |= ELF::SHF_WRITE;
 
@@ -840,7 +843,7 @@ static MCSection *selectExplicitSectionGlobal(const GlobalObject *GO,
   // Infer section flags from the section name if we can.
   Kind = getELFKindForNamedSection(SectionName, Kind);
 
-  unsigned Flags = getELFSectionFlags(Kind);
+  unsigned Flags = getELFSectionFlags(Kind, TM.getTargetTriple());
   auto [Group, IsComdat, ExtraFlags] = getGlobalObjectInfo(GO, TM);
   Flags |= ExtraFlags;
 
@@ -947,7 +950,7 @@ static MCSection *selectELFSectionForGlobal(
 
 MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
-  unsigned Flags = getELFSectionFlags(Kind);
+  unsigned Flags = getELFSectionFlags(Kind, TM.getTargetTriple());
 
   // If we have -ffunction-section or -fdata-section then we should emit the
   // global value to a uniqued section specifically for it.
@@ -967,7 +970,7 @@ MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
 MCSection *TargetLoweringObjectFileELF::getUniqueSectionForFunction(
     const Function &F, const TargetMachine &TM) const {
   SectionKind Kind = SectionKind::getText();
-  unsigned Flags = getELFSectionFlags(Kind);
+  unsigned Flags = getELFSectionFlags(Kind, TM.getTargetTriple());
   // If the function's section names is pre-determined via pragma or a
   // section attribute, call selectExplicitSectionGlobal.
   if (F.hasSection())
diff --git a/llvm/lib/MC/MCParser/ELFAsmParser.cpp b/llvm/lib/MC/MCParser/ELFAsmParser.cpp
index b58210b3c268e9..99b13c68a9966c 100644
--- a/llvm/lib/MC/MCParser/ELFAsmParser.cpp
+++ b/llvm/lib/MC/MCParser/ELFAsmParser.cpp
@@ -328,9 +328,12 @@ static unsigned parseSectionFlags(const Triple &TT, StringRef flagsStr,
       flags |= ELF::XCORE_SHF_DP_SECTION;
       break;
     case 'y':
-      if (!(TT.isARM() || TT.isThumb()))
+      if (TT.isARM() || TT.isThumb())
+        flags |= ELF::SHF_ARM_PURECODE;
+      else if (TT.isAArch64())
+        flags |= ELF::SHF_AARCH64_PURECODE;
+      else
         return -1U;
-      flags |= ELF::SHF_ARM_PURECODE;
       break;
     case 's':
       if (TT.getArch() != Triple::hexagon)
diff --git a/llvm/lib/MC/MCSectionELF.cpp b/llvm/lib/MC/MCSectionELF.cpp
index 25e62b70b5e2a0..72a959b1c92082 100644
--- a/llvm/lib/MC/MCSectionELF.cpp
+++ b/llvm/lib/MC/MCSectionELF.cpp
@@ -118,6 +118,9 @@ void MCSectionELF::printSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
   } else if (T.isARM() || T.isThumb()) {
     if (Flags & ELF::SHF_ARM_PURECODE)
       OS << 'y';
+  } else if (T.isAArch64()) {
+    if (Flags & ELF::SHF_AARCH64_PURECODE)
+      OS << 'y';
   } else if (Arch == Triple::hexagon) {
     if (Flags & ELF::SHF_HEX_GPREL)
       OS << 's';
diff --git a/llvm/lib/ObjectYAML/ELFYAML.cpp b/llvm/lib/ObjectYAML/ELFYAML.cpp
index 539834fc8d4dbf..05e4d85b2ea5d2 100644
--- a/llvm/lib/ObjectYAML/ELFYAML.cpp
+++ b/llvm/lib/ObjectYAML/ELFYAML.cpp
@@ -803,6 +803,9 @@ void ScalarBitSetTraits<ELFYAML::ELF_SHF>::bitset(IO &IO,
     break;
   }
   switch (Object->getMachine()) {
+  case ELF::EM_AARCH64:
+    BCase(SHF_AARCH64_PURECODE);
+    break;
   case ELF::EM_ARM:
     BCase(SHF_ARM_PURECODE);
     break;
diff --git a/llvm/lib/Target/AArch64/AArch64Features.td b/llvm/lib/Target/AArch64/AArch64Features.td
index 20db70ee38572f..7c95ba662938d9 100644
--- a/llvm/lib/Target/AArch64/AArch64Features.td
+++ b/llvm/lib/Target/AArch64/AArch64Features.td
@@ -635,6 +635,11 @@ def FeatureStrictAlign : SubtargetFeature<"strict-align",
                                           "Disallow all unaligned memory "
                                           "access">;
 
+def FeatureExecuteOnly : SubtargetFeature<"execute-only",
+                                          "GenExecuteOnly", "true",
+                                          "Enable the generation of "
+                                          "execute only code.">;
+
 foreach i = {1-7,9-15,18,20-28} in
     def FeatureReserveX#i : SubtargetFeature<"reserve-x"#i, "ReserveXRegister["#i#"]", "true",
                                              "Reserve X"#i#", making it unavailable "
diff --git a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
index 8729fd4b802c8e..434ae32502d484 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp
@@ -148,3 +148,29 @@ MCSymbol *AArch64_MachoTargetObjectFile::getAuthPtrSlotSymbol(
   return getAuthPtrSlotSymbolHelper(getContext(), TM, MMI, MachOMMI, RawSym,
                                     Key, Discriminator);
 }
+
+static bool isExecuteOnlyFunction(const GlobalObject *GO, SectionKind Kind,
+                                  const TargetMachine &TM) {
+  if (const Function *F = dyn_cast<Function>(GO))
+    if (TM.getSubtarget<AArch64Subtarget>(*F).genExecuteOnly() && Kind.isText())
+      return true;
+  return false;
+}
+
+MCSection *AArch64_ELFTargetObjectFile::getExplicitSectionGlobal(
+    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
+  // Set execute-only access for the explicit section
+  if (isExecuteOnlyFunction(GO, Kind, TM))
+    Kind = SectionKind::getExecuteOnly();
+
+  return TargetLoweringObjectFileELF::getExplicitSectionGlobal(GO, Kind, TM);
+}
+
+MCSection *AArch64_ELFTargetObjectFile::SelectSectionForGlobal(
+    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
+  // Set execute-only access for the explicit section
+  if (isExecuteOnlyFunction(GO, Kind, TM))
+    Kind = SectionKind::getExecuteOnly();
+
+  return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, Kind, TM);
+}
diff --git a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
index 0c822ac84f200c..3e9cd51b742a29 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
+++ b/llvm/lib/Target/AArch64/AArch64TargetObjectFile.h
@@ -39,6 +39,12 @@ class AArch64_ELFTargetObjectFile : public TargetLoweringObjectFileELF {
   void emitPersonalityValueImpl(MCStreamer &Streamer, const DataLayout &DL,
                                 const MCSymbol *Sym,
                                 const MachineModuleInfo *MMI) const override;
+
+  MCSection *getExplicitSectionGlobal(const GlobalObject *GO, SectionKind Kind,
+                                      const TargetMachine &TM) const override;
+
+  MCSection *SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind,
+                                    const TargetMachine &TM) const override;
 };
 
 /// AArch64_MachoTargetObjectFile - This TLOF implementation is used for Darwin.
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index a6edcf125782b2..284278e34f8b4d 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -262,6 +262,10 @@ bool AArch64TTIImpl::isMultiversionedFunction(const Function &F) const {
   return F.hasFnAttribute("fmv-features");
 }
 
+const FeatureBitset AArch64TTIImpl::InlineInverseFeatures = {
+    AArch64::FeatureExecuteOnly,
+};
+
 bool AArch64TTIImpl::areInlineCompatible(const Function *Caller,
                                          const Function *Callee) const {
   SMEAttrs CallerAttrs(*Caller), CalleeAttrs(*Callee);
@@ -284,7 +288,18 @@ bool AArch64TTIImpl::areInlineCompatible(const Function *Caller,
       return false;
   }
 
-  return BaseT::areInlineCompatible(Caller, Callee);
+  const TargetMachine &TM = getTLI()->getTargetMachine();
+  const FeatureBitset &CallerBits =
+      TM.getSubtargetImpl(*Caller)->getFeatureBits();
+  const FeatureBitset &CalleeBits =
+      TM.getSubtargetImpl(*Callee)->getFeatureBits();
+  // Adjust the feature bitsets by inverting some of the bits. This is needed
+  // for target features that represent restrictions rather than capabilities,
+  // for example "+execute-only".
+  FeatureBitset EffectiveCallerBits = CallerBits ^ InlineInverseFeatures;
+  FeatureBitset EffectiveCalleeBits = CalleeBits ^ InlineInverseFeatures;
+
+  return (EffectiveCallerBits & EffectiveCalleeBits) == EffectiveCalleeBits;
 }
 
 bool AArch64TTIImpl::areTypesABICompatible(
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
index b65e3c7a1ab20e..481cb5511a331b 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
@@ -48,6 +48,8 @@ class AArch64TTIImpl : public BasicTTIImplBase<AArch64TTIImpl> {
   const AArch64Subtarget *ST;
   const AArch64TargetLowering *TLI;
 
+  static const FeatureBitset InlineInverseFeatures;
+
   const AArch64Subtarget *getST() const { return ST; }
   const AArch64TargetLowering *getTLI() const { return TLI; }
 
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
index 6b5c5f36cbd4b2..d29d383bc23127 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
@@ -27,6 +27,7 @@
 #include "llvm/MC/MCELFStreamer.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSubtargetInfo.h"
@@ -504,6 +505,23 @@ void AArch64TargetELFStreamer::finish() {
     }
   }
 
+  // The mix of execute-only and non-execute-only at link time is
+  // non-execute-only. To avoid the empty implicitly created .text
+  // section from making the whole .text section non-execute-only, we
+  // mark it execute-only if it is empty and there is at least one
+  // execute-only section in the object.
+  if (any_of(Asm, [](const MCSection &Sec) {
+        return cast<MCSectionELF>(Sec).getFlags() & ELF::SHF_AARCH64_PURECODE;
+      })) {
+    auto *Text =
+        static_cast<MCSectionELF *>(Ctx.getObjectFileInfo()->getTextSection());
+    for (auto &F : *Text)
+      if (auto *DF = dyn_cast<MCDataFragment>(&F))
+        if (!DF->getContents().empty())
+          return;
+    Text->setFlags(Text->getFlags() | ELF::SHF_AARCH64_PURECODE);
+  }
+
   MCSectionELF *MemtagSec = nullptr;
   for (const MCSymbol &Symbol : Asm.symbols()) {
     const auto &Sym = cast<MCSymbolELF>(Symbol);
diff --git a/llvm/test/CodeGen/AArch64/execute-only-section.ll b/llvm/test/CodeGen/AArch64/execute-only-section.ll
new file mode 100644
index 00000000000000..15a270b07975e6
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/execute-only-section.ll
@@ -0,0 +1,21 @@
+; RUN: llc -mtriple=aarch64 -mattr=+execute-only %s -o - | FileCheck %s
+
+; CHECK:     .section .text,"axy",@progbits,unique,0
+; CHECK-NOT: .section
+; CHECK-NOT: .text
+; CHECK:     .globl test_SectionForGlobal
+; CHECK:     .type test_SectionForGlobal,@function
+define void @test_SectionForGlobal() {
+entry:
+  ret void
+}
+
+; CHECK:     .section .test,"axy",@progbits
+; CHECK-NOT: .section
+; CHECK-NOT: .text
+; CHECK:     .globl test_ExplicitSectionForGlobal
+; CHECK:     .type test_ExplicitSectionForGlobal,@function
+define void @test_ExplicitSectionForGlobal() section ".test" {
+entry:
+  ret void
+}
diff --git a/llvm/test/MC/ELF/AArch64/execute-only-populated-text-section.s b/llvm/test/MC/ELF/AArch64/execute-only-populated-text-section.s
new file mode 100644
index 00000000000000..b0ba8a18d52b38
--- /dev/null
+++ b/llvm/test/MC/ELF/AArch64/execute-only-populated-text-section.s
@@ -0,0 +1,27 @@
+// RUN: llvm-mc -filetype=obj -triple aarch64-unknown-linux-gnu %s -o - \
+// RUN: | llvm-readobj -S --symbols - | FileCheck %s
+
+        .text
+        ret
+
+        .section        .text.foo,"axy"
+        ret
+
+// CHECK:      Section {
+// CHECK:        Name: .text
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x6)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:      }
+
+// CHECK:      Section {
+// CHECK:        Name: .text.foo
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x20000006)
+// CHECK-NEXT:     SHF_AARCH64_PURECODE (0x20000000)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:      }
diff --git a/llvm/test/MC/ELF/AArch64/execute-only-section.s b/llvm/test/MC/ELF/AArch64/execute-only-section.s
new file mode 100644
index 00000000000000..6fd596376711d6
--- /dev/null
+++ b/llvm/test/MC/ELF/AArch64/execute-only-section.s
@@ -0,0 +1,43 @@
+// RUN: llvm-mc -filetype=obj -triple aarch64-unknown-linux-gnu %s -o - \
+// RUN: | llvm-readobj -S --symbols - | FileCheck %s
+
+        .section        .text,"axy",@progbits,unique,0
+        .globl  foo
+        .p2align  2
+        .type   foo,@function
+foo:
+        .cfi_startproc
+        ret
+.Lfunc_end0:
+        .size   foo, .Lfunc_end0-foo
+        .cfi_endproc
+
+        .section        ".note.GNU-stack","",@progbits
+
+
+// CHECK:      Section {
+// CHECK:        Name: .text
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x20000006)
+// CHECK-NEXT:     SHF_AARCH64_PURECODE (0x20000000)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:        Size: 0
+// CHECK:      }
+
+// CHECK:      Section {
+// CHECK:        Name: .text
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x20000006)
+// CHECK-NEXT:     SHF_AARCH64_PURECODE (0x20000000)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:        Size: 2
+// CHECK:      }
+
+// CHECK: Symbol {
+// CHECK:   Name: foo
+// CHECK:   Section: .text (0x3)
+// CHECK: }
diff --git a/llvm/test/MC/ELF/AArch64/execute-only-text-section-data.s b/llvm/test/MC/ELF/AArch64/execute-only-text-section-data.s
new file mode 100644
index 00000000000000..22bcffae67d0eb
--- /dev/null
+++ b/llvm/test/MC/ELF/AArch64/execute-only-text-section-data.s
@@ -0,0 +1,27 @@
+// RUN: llvm-mc -filetype=obj -triple aarch64-unknown-linux-gnu %s -o - \
+// RUN: | llvm-readobj -S --symbols - | FileCheck %s
+
+        .text
+        .ascii "test"
+
+        .section        .text.foo,"axy"
+        ret
+
+// CHECK:      Section {
+// CHECK:        Name: .text
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x6)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:      }
+
+// CHECK:      Section {
+// CHECK:        Name: .text.foo
+// CHECK-NEXT:   Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT:   Flags [ (0x20000006)
+// CHECK-NEXT:     SHF_AARCH64_PURECODE (0x20000000)
+// CHECK-NEXT:     SHF_ALLOC (0x2)
+// CHECK-NEXT:     SHF_EXECINSTR (0x4)
+// CHECK-NEXT:   ]
+// CHECK:      }
diff --git a/llvm/test/MC/ELF/section-flags-unknown.s b/llvm/test/MC/ELF/section-flags-unknown.s
index 90c9185e8bfb10..b172403e34556c 100644
--- a/llvm/test/MC/ELF/section-flags-unknown.s
+++ b/llvm/test/MC/ELF/section-flags-unknown.s
@@ -14,5 +14,8 @@
 # CHECK: {{.*}}.s:[[# @LINE+1]]:30: error: unknown flag
 .section SHF_ARM_PURECODE,"y",@progbits
 
+# CHECK: {{.*}}.s:[[# @LINE+1]]:34: error: unknown flag
+.section SHF_AARCH64_PURECODE,"y",@progbits
+
 # CHECK: {{.*}}.s:[[# @LINE+1]]:30: error: unknown flag
 .section SHF_X86_64_LARGE,"l",@progbits
diff --git a/llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll b/llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll
index 636f3c6600f8d4..433a9c7bdd23b0 100644
--- a/llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll
+++ b/llvm/test/Transforms/Inline/AArch64/inline-target-attr.ll
@@ -27,6 +27,14 @@ entry:
 ; CHECK: call i32 @bar()
 }
 
+define i32 @quux() #3 {
+entry:
+  %call = call i32 (...) @baz()
+  ret i32 %call
+; CHECK-LABEL: quux
+; CHECK: call i32 (...) @baz()
+}
+
 define i32 @strict_align() #2 {
 entry:
   %call = call i32 @foo()
@@ -35,6 +43,23 @@ entry:
 ; CHECK: call i32 (...) @baz()
 }
 
+define i32 @execute_only1() #3 {
+entry:
+  %call = call i32 @foo()
+  ret i32 %call
+; CHECK-LABEL: execute_only1
+; CHECK: call i32 @foo()
+}
+
+define i32 @execute_only2() #0 {
+entry:
+  %call = call i32 @quux()
+  ret i32 %call
+; CHECK-LABEL: execute_only2
+; CHECK: call i32 (...) @baz()
+}
+
 attributes #0 = { "target-cpu"="generic" "target-features"="+crc,+neon" }
 attributes #1 = { "target-cpu"="generic" "target-features"="+crc,+neon,+crypto" }
 attributes #2 = { "target-cpu"="generic" "target-features"="+crc,+neon,+strict-align" }
+attributes #3 = { "target-cpu"="generic" "target-features"="+crc,+neon,+execute-only" }
diff --git a/llvm/tools/llvm-readobj/ELFDumper.cpp b/llvm/tools/llvm-readobj/ELFDumper.cpp
index bfca65aad52b44..78aaf79a61c468 100644
--- a/llvm/tools/llvm-readobj/ELFDumper.cpp
+++ b/llvm/tools/llvm-readobj/ELFDumper.cpp
@@ -1337,6 +1337,10 @@ const EnumEntry<unsigned> ElfXCoreSectionFlags[] = {
   ENUM_ENT(XCORE_SHF_DP_SECTION, "")
 };
 
+const EnumEntry<unsigned> ElfAArch64SectionFlags[] = {
+    ENUM_ENT(SHF_AARCH64_PURECODE, "y"),
+};
+
 const EnumEntry<unsigned> ElfARMSectionFlags[] = {
   ENUM_ENT(SHF_ARM_PURECODE, "y")
 };
@@ -1375,6 +1379,10 @@ getSectionFlagsForTarget(unsigned EOSAbi, unsigned EMachine) {
     break;
   }
   switch (EMachine) {
+  case EM_AARCH64:
+    Ret.insert(Ret.end(), std::begin(ElfAArch64SectionFlags),
+               std::end(ElfAArch64SectionFlags));
+    break;
   case EM_ARM:
     Ret.insert(Ret.end(), std::begin(ElfARMSectionFlags),
                std::end(ElfARMSectionFlags));

Il-Capitano · 2025-02-04T14:18:22Z

CC @DanielKristofKiss

paulwalker-arm

Other than a minor formatting request the PR looks good to me, being consistent with the ARM/THUMB implementation.

That said, this is not my area so please given other reviewers (I'm tagging in @smithp35 who has more experience in this area) a day or so to chip in before merging the PR.

github-actions · 2025-02-12T09:49:25Z

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff 83ff9d4a34b1e579dd809759d13b70b8837f0cde bcb5275221591da01303f6f2e368be4d3679ce0e --extensions h,cpp -- llvm/include/llvm/BinaryFormat/ELF.h llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp llvm/lib/MC/MCParser/ELFAsmParser.cpp llvm/lib/MC/MCSectionELF.cpp llvm/lib/ObjectYAML/ELFYAML.cpp llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp llvm/lib/Target/AArch64/AArch64TargetObjectFile.h llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp llvm/tools/llvm-readobj/ELFDumper.cpp

View the diff from clang-format here.

diff --git a/llvm/tools/llvm-readobj/ELFDumper.cpp b/llvm/tools/llvm-readobj/ELFDumper.cpp
index a484a897b8..f569dcf2c6 100644
--- a/llvm/tools/llvm-readobj/ELFDumper.cpp
+++ b/llvm/tools/llvm-readobj/ELFDumper.cpp
@@ -1338,8 +1338,7 @@ const EnumEntry<unsigned> ElfXCoreSectionFlags[] = {
 };
 
 const EnumEntry<unsigned> ElfAArch64SectionFlags[] = {
-  ENUM_ENT(SHF_AARCH64_PURECODE, "y")
-};
+    ENUM_ENT(SHF_AARCH64_PURECODE, "y")};
 
 const EnumEntry<unsigned> ElfARMSectionFlags[] = {
   ENUM_ENT(SHF_ARM_PURECODE, "y")

smithp35 · 2025-02-12T15:33:47Z

No objections from me. I've left a few small comments, but nothing significant. I've checked the implementation against the existing ARM backend.

Il-Capitano · 2025-02-12T15:48:16Z

@smithp35 I can't see any comments made by you. Are you sure you saved/published them?

smithp35 · 2025-02-12T16:10:41Z

@smithp35 I can't see any comments made by you. Are you sure you saved/published them?

Thanks for pointing it out. Looks like I've got a few pending.

smithp35

Publish pending comments!

jh7370

Tool code and tests LGTM. I haven't reviewed other aspects.

I think this is ready to be merged. Do you have commit access?

Il-Capitano · 2025-02-13T10:56:51Z

Thanks for the review!

I think this is ready to be merged. Do you have commit access?

No, I don't.

jh7370 · 2025-02-13T11:05:48Z

Thanks for the review!

I think this is ready to be merged. Do you have commit access?

No, I don't.

Okay, I'll give this a day before merging, to give other reviewers a final chance to look it over.

…llvm#125687) Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304 The general implementation follows the existing one for ARM targets. Generating object files with the `SHF_AARCH64_PURECODE` flag set is enabled by the `+execute-only` target feature. Related PRs: * Clang: llvm#125688 * LLD: llvm#125689

…flag (3/3) (#125689) Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304 The general implementation follows the existing one for ARM targets. The output section only has the `SHF_AARCH64_PURECODE` flag set if all input sections have it set. Related PRs: * LLVM: #125687 * Clang: #125688

…LF section flag (3/3) (#125689) Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304 The general implementation follows the existing one for ARM targets. The output section only has the `SHF_AARCH64_PURECODE` flag set if all input sections have it set. Related PRs: * LLVM: llvm/llvm-project#125687 * Clang: llvm/llvm-project#125688

…llvm#125687) Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304 The general implementation follows the existing one for ARM targets. Generating object files with the `SHF_AARCH64_PURECODE` flag set is enabled by the `+execute-only` target feature. Related PRs: * Clang: llvm#125688 * LLD: llvm#125689

…g (2/3) (#125688) Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304 The general implementation follows the existing one for ARM targets. Simlarly to ARM targets, generating object files with the `SHF_AARCH64_PURECODE` flag set is enabled by the `-mexecute-only`/`-mpure-code` driver flag. Related PRs: * LLVM: #125687 * LLD: #125689

…section flag (2/3) (#125688) Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304 The general implementation follows the existing one for ARM targets. Simlarly to ARM targets, generating object files with the `SHF_AARCH64_PURECODE` flag set is enabled by the `-mexecute-only`/`-mpure-code` driver flag. Related PRs: * LLVM: llvm/llvm-project#125687 * LLD: llvm/llvm-project#125689

Support for execute-only code generation (llvm#125687) introduced a bug in the case where the memtag sanitizer is used in a module containing a mix of execute-only and non-execute-only functions. The bug is caused by using `return` instead of `break` to short-circuit a loop, which meant that the rest of the function dealing with memtag sanitizer logic wasn't run.

#133084) Support for execute-only code generation (#125687) introduced a bug in the case where the memtag sanitizer is used in a module containing a mix of execute-only and non-execute-only functions. The bug is caused by using `return` instead of `break` to short-circuit a loop, which meant that the rest of the function dealing with memtag sanitizer logic wasn't run.

…flag (3/3) (#125689) Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304 The general implementation follows the existing one for ARM targets. The output section only has the `SHF_AARCH64_PURECODE` flag set if all input sections have it set. Related PRs: * LLVM: llvm/llvm-project#125687 * Clang: llvm/llvm-project#125688

…g (2/3) (#125688) Add support for the new SHF_AARCH64_PURECODE ELF section flag: ARM-software/abi-aa#304 The general implementation follows the existing one for ARM targets. Simlarly to ARM targets, generating object files with the `SHF_AARCH64_PURECODE` flag set is enabled by the `-mexecute-only`/`-mpure-code` driver flag. Related PRs: * LLVM: llvm/llvm-project#125687 * LLD: llvm/llvm-project#125689

llvmbot added backend:AArch64 llvm:mc Machine (object) code objectyaml llvm:transforms llvm:binary-utilities labels Feb 4, 2025

This was referenced Feb 4, 2025

[Clang][AArch64] Add support for SHF_AARCH64_PURECODE ELF section flag (2/3) #125688

Merged

[LLD][ELF][AArch64] Add support for SHF_AARCH64_PURECODE ELF section flag (3/3) #125689

Merged

Il-Capitano commented Feb 4, 2025

View reviewed changes

Comment thread llvm/include/llvm/BinaryFormat/ELF.h

Address review feedback from llvm#125689

f528eb7

Il-Capitano force-pushed the aarch64-execute-only-llvm branch from de215fd to f528eb7 Compare February 7, 2025 09:08

DanielKristofKiss requested review from davemgreen, jh7370 and paulwalker-arm February 7, 2025 12:45

paulwalker-arm approved these changes Feb 11, 2025

View reviewed changes

Comment thread llvm/tools/llvm-readobj/ELFDumper.cpp Outdated

jh7370 reviewed Feb 12, 2025

View reviewed changes

Comment thread llvm/tools/llvm-readobj/ELFDumper.cpp

Il-Capitano added 2 commits February 12, 2025 10:39

Change formatting of ElfAArch64SectionFlags

25c34c0

Add tests for llvm-readobj and llvm-objcopy

2c47c28

smithp35 approved these changes Feb 12, 2025

View reviewed changes

Comment thread llvm/include/llvm/BinaryFormat/ELF.h

Comment thread llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp Outdated

Comment thread llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp Outdated

Address review feedback

835a800

jh7370 reviewed Feb 13, 2025

View reviewed changes

Comment thread llvm/test/tools/llvm-readobj/ELF/gnu-sections.test Outdated

Comment thread llvm/test/tools/llvm-readobj/ELF/section-arch-flags.test

Bugfix in llvm-readelf Key to Flags output

810e38d

jh7370 approved these changes Feb 13, 2025

View reviewed changes

Update arch-specific section flag test

bcb5275

jh7370 merged commit a190f15 into llvm:main Feb 14, 2025

Il-Capitano deleted the aarch64-execute-only-llvm branch February 18, 2025 15:19

shiltian mentioned this pull request Mar 10, 2025

[AMDGPU] Fix test failures when expensive checks are enabled #130644

Merged

Il-Capitano mentioned this pull request Mar 26, 2025

[AArch64] Bugfix when using execute-only and memtag sanitizer together #133084

Merged

oltolm mentioned this pull request Mar 9, 2026

The link to the ptrtoaddr PR is wrong in the release notes for LLVM 22.0.1. #185392

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