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

`-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.

Author: Il-Capitano

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;

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('=');

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.
@@ -2176,6 +2178,41 @@ 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.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))
+      continue;
+    for (InputSection *sec : getInputSections(*osec, storage)) {
+      if (isa<SyntheticSection>(sec))
+        continue;
+      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() {

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

@@ -0,0 +1,44 @@
+// REQUIRES: aarch64
+
+// RUN: rm -rf %t && mkdir %t && cd %t
+// RUN: llvm-mc --triple=aarch64 --filetype=obj %s -o a.o
+
+// RUN: ld.lld --defsym absolute=0xf0000000 -z execute-only-report=none --fatal-warnings a.o
+
+// RUN: ld.lld --defsym absolute=0xf0000000 -z execute-only-report=warning a.o 2>&1 | \
+// RUN:     FileCheck --check-prefix=WARNING %s
+// RUN: ld.lld --defsym absolute=0xf0000000 --execute-only -z execute-only-report=warning a.o 2>&1 | \
+// RUN:     FileCheck --check-prefix=WARNING %s
+
+// WARNING-NOT: warning: -z execute-only-report: a.o:(.text) does not have SHF_AARCH64_PURECODE flag set
+// WARNING-NOT: warning: -z execute-only-report: a.o:(.text.foo) does not have SHF_AARCH64_PURECODE flag set
+// WARNING: warning: -z execute-only-report: a.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
+
+// RUN: not ld.lld --defsym absolute=0xf0000000 -z execute-only-report=error a.o 2>&1 | \
+// RUN:     FileCheck --check-prefix=ERROR %s
+// RUN: not ld.lld --defsym absolute=0xf0000000 --execute-only -z execute-only-report=error a.o 2>&1 | \
+// RUN:     FileCheck --check-prefix=ERROR %s
+
+// ERROR-NOT: error: -z execute-only-report: a.o:(.text) does not have SHF_AARCH64_PURECODE flag set
+// ERROR-NOT: error: -z execute-only-report: a.o:(.text.foo) does not have SHF_AARCH64_PURECODE flag set
+// ERROR: error: -z execute-only-report: a.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

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

@@ -0,0 +1,40 @@
+// REQUIRES: arm
+
+// RUN: rm -rf %t && mkdir %t && cd %t
+// RUN: llvm-mc --triple=armv7 --filetype=obj %s -o a.o
+
+// RUN: ld.lld --defsym absolute=0xf0000000 -z execute-only-report=none --fatal-warnings a.o
+
+// RUN: ld.lld --defsym absolute=0xf0000000 -z execute-only-report=warning a.o 2>&1 | \
+// RUN:     FileCheck --check-prefix=WARNING %s
+
+// WARNING-NOT: warning: -z execute-only-report: a.o:(.text) does not have SHF_ARM_PURECODE flag set
+// WARNING-NOT: warning: -z execute-only-report: a.o:(.text.foo) does not have SHF_ARM_PURECODE flag set
+// WARNING: warning: -z execute-only-report: a.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
+
+// RUN: not ld.lld --defsym absolute=0xf0000000 -z execute-only-report=error a.o 2>&1 | \
+// RUN:     FileCheck --check-prefix=ERROR %s
+
+// ERROR-NOT: error: -z execute-only-report: a.o:(.text) does not have SHF_ARM_PURECODE flag set
+// ERROR-NOT: error: -z execute-only-report: a.o:(.text.foo) does not have SHF_ARM_PURECODE flag set
+// ERROR: error: -z execute-only-report: a.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

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

@@ -13,5 +13,15 @@
 # RUN: not ld.lld %t --toc-optimize -o /dev/null 2>&1 | FileCheck %s --check-prefix=ERR-TOC
 # ERR-TOC: error: --toc-optimize is only supported on PowerPC64 targets
 
+# RUN: not ld.lld %t -z execute-only-report=warning -o /dev/null 2>&1 | \
+# RUN:     FileCheck %s --check-prefix=ERR-EXECUTE-ONLY
+# RUN: not ld.lld %t -z execute-only-report=error -o /dev/null 2>&1 | \
+# RUN:     FileCheck %s --check-prefix=ERR-EXECUTE-ONLY
+# ERR-EXECUTE-ONLY: error: -z execute-only-report only supported on AArch64 and ARM
+
+# RUN: not ld.lld %t -z execute-only-report=foo -o /dev/null 2>&1 | \
+# RUN:     FileCheck %s --check-prefix=ERR-EXECUTE-ONLY-INVALID
+# ERR-EXECUTE-ONLY-INVALID: error: unknown -z execute-only-report= value: foo
+
 .globl _start
 _start: