[LLD][ELF] Add `-z execute-only-report` that checks PURECODE section flags #128883

Il-Capitano · 2025-02-26T14:49:20Z

-z execute-only-report checks that all executable sections have either the SHF_AARCH64_PURECODE or SHF_ARM_PURECODE section flag set on AArch64 and ARM respectively.

llvmbot · 2025-02-26T14:49:58Z

@llvm/pr-subscribers-lld

@llvm/pr-subscribers-lld-elf

Author: Csanád Hajdú (Il-Capitano)

Changes

-z execute-only-report checks that all executable sections have either the SHF_AARCH64_PURECODE or SHF_ARM_PURECODE section flag set on AArch64 and ARM respectively.

Full diff: https://github.com/llvm/llvm-project/pull/128883.diff

6 Files Affected:

(modified) lld/ELF/Config.h (+1)
(modified) lld/ELF/Driver.cpp (+11-4)
(modified) lld/ELF/Writer.cpp (+34)
(added) lld/test/ELF/aarch64-execute-only-report.s (+40)
(added) lld/test/ELF/arm-execute-only-report.s (+36)
(added) lld/test/ELF/execute-only-report-error.s (+18)

diff --git a/lld/ELF/Config.h b/lld/ELF/Config.h
index f132b11b20c63..b5872b85efd3a 100644
--- a/lld/ELF/Config.h
+++ b/lld/ELF/Config.h
@@ -229,6 +229,7 @@ struct Config {
   StringRef zCetReport = "none";
   StringRef zPauthReport = "none";
   StringRef zGcsReport = "none";
+  StringRef zExecuteOnlyReport = "none";
   bool ltoBBAddrMap;
   llvm::StringRef ltoBasicBlockSections;
   std::pair<llvm::StringRef, llvm::StringRef> thinLTOObjectSuffixReplace;
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 70a293875f27b..8cf588ef27b09 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -406,6 +406,11 @@ static void checkOptions(Ctx &ctx) {
       ErrAlways(ctx) << "-z gcs only supported on AArch64";
   }
 
+  if (ctx.arg.emachine != EM_AARCH64 && ctx.arg.emachine != EM_ARM &&
+      ctx.arg.zExecuteOnlyReport != "none")
+    ErrAlways(ctx)
+        << "-z execute-only-report only supported on AArch64 and ARM";
+
   if (ctx.arg.emachine != EM_PPC64) {
     if (ctx.arg.tocOptimize)
       ErrAlways(ctx) << "--toc-optimize is only supported on PowerPC64 targets";
@@ -1620,10 +1625,12 @@ static void readConfigs(Ctx &ctx, opt::InputArgList &args) {
       ErrAlways(ctx) << errPrefix << pat.takeError() << ": " << kv.first;
   }
 
-  auto reports = {std::make_pair("bti-report", &ctx.arg.zBtiReport),
-                  std::make_pair("cet-report", &ctx.arg.zCetReport),
-                  std::make_pair("gcs-report", &ctx.arg.zGcsReport),
-                  std::make_pair("pauth-report", &ctx.arg.zPauthReport)};
+  auto reports = {
+      std::make_pair("bti-report", &ctx.arg.zBtiReport),
+      std::make_pair("cet-report", &ctx.arg.zCetReport),
+      std::make_pair("execute-only-report", &ctx.arg.zExecuteOnlyReport),
+      std::make_pair("gcs-report", &ctx.arg.zGcsReport),
+      std::make_pair("pauth-report", &ctx.arg.zPauthReport)};
   for (opt::Arg *arg : args.filtered(OPT_z)) {
     std::pair<StringRef, StringRef> option =
         StringRef(arg->getValue()).split('=');
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index a2c49343e5c8d..c747a5b5e1239 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -64,6 +64,7 @@ template <class ELFT> class Writer {
   void sortOrphanSections();
   void finalizeSections();
   void checkExecuteOnly();
+  void checkExecuteOnlyReport();
   void setReservedSymbolSections();
 
   SmallVector<std::unique_ptr<PhdrEntry>, 0> createPhdrs(Partition &part);
@@ -323,6 +324,7 @@ template <class ELFT> void Writer<ELFT>::run() {
   // finalizeSections does that.
   finalizeSections();
   checkExecuteOnly();
+  checkExecuteOnlyReport();
 
   // If --compressed-debug-sections is specified, compress .debug_* sections.
   // Do it right now because it changes the size of output sections.
@@ -2177,6 +2179,38 @@ template <class ELFT> void Writer<ELFT>::checkExecuteOnly() {
                             "data and code";
 }
 
+// Check which input sections of RX output sections don't have the
+// SHF_AARCH64_PURECODE or SHF_ARM_PURECODE flag set.
+template <class ELFT> void Writer<ELFT>::checkExecuteOnlyReport() {
+  if ((ctx.arg.emachine != EM_AARCH64 && ctx.arg.emachine != EM_ARM) ||
+      ctx.arg.zExecuteOnlyReport == "none")
+    return;
+
+  auto reportUnless = [&](bool cond) -> ELFSyncStream {
+    if (cond)
+      return {ctx, DiagLevel::None};
+    if (ctx.arg.zExecuteOnlyReport == "error")
+      return {ctx, DiagLevel::Err};
+    if (ctx.arg.zExecuteOnlyReport == "warning")
+      return {ctx, DiagLevel::Warn};
+    return {ctx, DiagLevel::None};
+  };
+
+  uint64_t purecodeFlag =
+      ctx.arg.emachine == EM_AARCH64 ? SHF_AARCH64_PURECODE : SHF_ARM_PURECODE;
+  StringRef purecodeFlagName = ctx.arg.emachine == EM_AARCH64
+                                   ? "SHF_AARCH64_PURECODE"
+                                   : "SHF_ARM_PURECODE";
+  SmallVector<InputSection *, 0> storage;
+  for (OutputSection *osec : ctx.outputSections)
+    if (osec->getPhdrFlags() == (PF_R | PF_X))
+      for (InputSection *sec : getInputSections(*osec, storage))
+        if (sec->file && sec->file->getName() != "<internal>")
+          reportUnless(sec->flags & purecodeFlag)
+              << "-z execute-only-report: " << sec << " does not have "
+              << purecodeFlagName << " flag set";
+}
+
 // The linker is expected to define SECNAME_start and SECNAME_end
 // symbols for a few sections. This function defines them.
 template <class ELFT> void Writer<ELFT>::addStartEndSymbols() {
diff --git a/lld/test/ELF/aarch64-execute-only-report.s b/lld/test/ELF/aarch64-execute-only-report.s
new file mode 100644
index 0000000000000..e56eed819d12b
--- /dev/null
+++ b/lld/test/ELF/aarch64-execute-only-report.s
@@ -0,0 +1,40 @@
+// REQUIRES: aarch64
+
+// RUN: llvm-mc --triple=aarch64 --filetype=obj -o %t.o %s
+// RUN: ld.lld --defsym absolute=0xf0000000 -z execute-only-report=none --fatal-warnings %t.o -o /dev/null
+// RUN: ld.lld --defsym absolute=0xf0000000 -z execute-only-report=warning %t.o -o /dev/null 2>&1 \
+// RUN:     | FileCheck --check-prefix=WARNING %s
+// RUN: ld.lld --defsym absolute=0xf0000000 --execute-only -z execute-only-report=warning %t.o -o /dev/null 2>&1 \
+// RUN:     | FileCheck --check-prefix=WARNING %s
+// RUN: not ld.lld --defsym absolute=0xf0000000 -z execute-only-report=error %t.o -o /dev/null 2>&1 \
+// RUN:     | FileCheck --check-prefix=ERROR %s
+// RUN: not ld.lld --defsym absolute=0xf0000000 --execute-only -z execute-only-report=error %t.o -o /dev/null 2>&1 \
+// RUN:     | FileCheck --check-prefix=ERROR %s
+
+// WARNING-NOT: warning: -z execute-only-report: {{.*}}.o:(.text) does not have SHF_AARCH64_PURECODE flag set
+// WARNING-NOT: warning: -z execute-only-report: {{.*}}.o:(.text.foo) does not have SHF_AARCH64_PURECODE flag set
+// WARNING: warning: -z execute-only-report: {{.*}}.o:(.text.bar) does not have SHF_AARCH64_PURECODE flag set
+// WARNING-NOT: warning: -z execute-only-report: <internal>:({{.*}}) does not have SHF_AARCH64_PURECODE flag set
+
+// ERROR-NOT: error: -z execute-only-report: {{.*}}.o:(.text) does not have SHF_AARCH64_PURECODE flag set
+// ERROR-NOT: error: -z execute-only-report: {{.*}}.o:(.text.foo) does not have SHF_AARCH64_PURECODE flag set
+// ERROR: error: -z execute-only-report: {{.*}}.o:(.text.bar) does not have SHF_AARCH64_PURECODE flag set
+// ERROR-NOT: error: -z execute-only-report: <internal>:({{.*}}) does not have SHF_AARCH64_PURECODE flag set
+
+.section .text,"axy",@progbits,unique,0
+.globl _start
+_start:
+  bl foo
+  bl bar
+  bl absolute
+  ret
+
+.section .text.foo,"axy",@progbits,unique,0
+.globl foo
+foo:
+  ret
+
+.section .text.bar,"ax",@progbits,unique,0
+.globl bar
+bar:
+  ret
diff --git a/lld/test/ELF/arm-execute-only-report.s b/lld/test/ELF/arm-execute-only-report.s
new file mode 100644
index 0000000000000..1676a8f654552
--- /dev/null
+++ b/lld/test/ELF/arm-execute-only-report.s
@@ -0,0 +1,36 @@
+// REQUIRES: arm
+
+// RUN: llvm-mc --triple=armv7 --filetype=obj -o %t.o %s
+// RUN: ld.lld --defsym absolute=0xf0000000 -z execute-only-report=none --fatal-warnings %t.o -o /dev/null
+// RUN: ld.lld --defsym absolute=0xf0000000 -z execute-only-report=warning %t.o -o /dev/null 2>&1 \
+// RUN:     | FileCheck --check-prefix=WARNING %s
+// RUN: not ld.lld --defsym absolute=0xf0000000 -z execute-only-report=error %t.o -o /dev/null 2>&1 \
+// RUN:     | FileCheck --check-prefix=ERROR %s
+
+// WARNING-NOT: warning: -z execute-only-report: {{.*}}.o:(.text) does not have SHF_ARM_PURECODE flag set
+// WARNING-NOT: warning: -z execute-only-report: {{.*}}.o:(.text.foo) does not have SHF_ARM_PURECODE flag set
+// WARNING: warning: -z execute-only-report: {{.*}}.o:(.text.bar) does not have SHF_ARM_PURECODE flag set
+// WARNING-NOT: warning: -z execute-only-report: <internal>:({{.*}}) does not have SHF_ARM_PURECODE flag set
+
+// ERROR-NOT: error: -z execute-only-report: {{.*}}.o:(.text) does not have SHF_ARM_PURECODE flag set
+// ERROR-NOT: error: -z execute-only-report: {{.*}}.o:(.text.foo) does not have SHF_ARM_PURECODE flag set
+// ERROR: error: -z execute-only-report: {{.*}}.o:(.text.bar) does not have SHF_ARM_PURECODE flag set
+// ERROR-NOT: error: -z execute-only-report: <internal>:({{.*}}) does not have SHF_ARM_PURECODE flag set
+
+.section .text,"axy",%progbits,unique,0
+.globl _start
+_start:
+  bl foo
+  bl bar
+  bl absolute
+  bx lr
+
+.section .text.foo,"axy",%progbits,unique,0
+.globl foo
+foo:
+  bx lr
+
+.section .text.bar,"ax",%progbits,unique,0
+.globl bar
+bar:
+  bx lr
diff --git a/lld/test/ELF/execute-only-report-error.s b/lld/test/ELF/execute-only-report-error.s
new file mode 100644
index 0000000000000..91afd4edfc0d2
--- /dev/null
+++ b/lld/test/ELF/execute-only-report-error.s
@@ -0,0 +1,18 @@
+// REQUIRES: x86
+
+// RUN: llvm-mc --triple=x86_64 --filetype=obj -o %t.o %s
+// RUN: not ld.lld -z execute-only-report=warning %t.o -o /dev/null 2>&1 \
+// RUN:     | FileCheck %s
+// RUN: not ld.lld -z execute-only-report=error %t.o -o /dev/null 2>&1 \
+// RUN:     | FileCheck %s
+
+// CHECK: error: -z execute-only-report only supported on AArch64 and ARM
+
+// RUN: not ld.lld -z execute-only-report=foo %t.o -o /dev/null 2>&1 \
+// RUN:     | FileCheck --check-prefix=INVALID %s
+
+// INVALID: error: -z execute-only-report= parameter foo is not recognized
+
+.globl _start
+_start:
+  ret

Il-Capitano · 2025-02-26T14:52:08Z

@MaskRay @smithp35 Can I ask you to review this, please?

MaskRay · 2025-02-26T16:50:16Z

lld/ELF/Writer.cpp

  // finalizeSections does that.
  finalizeSections();
  checkExecuteOnly();
+  checkExecuteOnlyReport();


move into checkExecuteOnly

I didn't do this yet, because I think that checkExecuteOnly and checkExecuteOnlyReport aside from the similar naming do different things and they should be separate.

lld/test/ELF/aarch64-execute-only-report.s

lld/test/ELF/execute-only-report-error.s

smithp35

Only a couple of suggestions over what MaskRay has already mentioned.

lld/ELF/Writer.cpp

MaskRay · 2025-03-01T07:42:20Z

lld/test/ELF/target-specific-options.s

I just noticed that the error message is not conventional. It should be
unknown -z execute-only-report= value: foo to match a few other options.

I am updating it. Sorry for making you rebase the PR.

No problem, let me know when it's done and I'll rebase.

Done in 7e8a06c

I rebased and updated the test.

`-z execute-only-report` checks that all executable sections have either the SHF_AARCH64_PURECODE or SHF_ARM_PURECODE section flag set on AArch64 and ARM respectively.

lld/ELF/Writer.cpp

llvmbot added lld lld:ELF labels Feb 26, 2025

MaskRay requested changes Feb 26, 2025

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smithp35 reviewed Feb 26, 2025

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MaskRay approved these changes Mar 1, 2025

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Il-Capitano added 4 commits March 1, 2025 19:20

[LLD][ELF] Add -z execute-only-report that checks PURECODE flags

69048e3

`-z execute-only-report` checks that all executable sections have either the SHF_AARCH64_PURECODE or SHF_ARM_PURECODE section flag set on AArch64 and ARM respectively.

Address review feedback in tests

aae4833

Address review feedback in Writer.cpp

144b93f

Update unknown argument error message

ddaf54d

Il-Capitano force-pushed the lld-z-execute-only-report branch from 38cf844 to ddaf54d Compare March 1, 2025 18:32

MaskRay approved these changes Mar 1, 2025

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lld/ELF/Writer.cpp Outdated Show resolved Hide resolved

Reduce indentation depth in checkExecuteOnlyReport

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MaskRay approved these changes Mar 1, 2025

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MaskRay merged commit 9b7b7d6 into llvm:main Mar 1, 2025
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Il-Capitano deleted the lld-z-execute-only-report branch March 1, 2025 22:14

[LLD][ELF] Add -z execute-only-report that checks PURECODE section flags #128883

[LLD][ELF] Add -z execute-only-report that checks PURECODE section flags #128883

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Il-Capitano commented Feb 26, 2025

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[LLD][ELF] Add `-z execute-only-report` that checks PURECODE section flags #128883

[LLD][ELF] Add `-z execute-only-report` that checks PURECODE section flags #128883

llvmbot commented Feb 26, 2025 •

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