simplify pie/pic handling for android

[• rafael]

Summary

Android is quiet peculiar in that it default to PIC, not PIE. To enable PIE only optimizations on has to explicitly pass -fPIE. I just checked that behaviour with r9d sdk using gcc 4.8 -E -dM.

Currently that is implemented with some custom logic in the driver. The attached patch moves some of that to isPICDefault and isPIEDefault. The changes are

• Declare that android isPIEDefault and isPICDefault
• For running -cc1, give preference to isPICDefault over isPIEDefault, since that is the most restrictive.

The main behaviour is unchanged:

• clang -target arm-linux-android -S test.c -> -mrelocation-model pic -pic-level 1
• clang -target arm-linux-android -S test.c -fPIC -> -mrelocation-model pic -pic-level 2
• clang -target arm-linux-android -S test.c -fPIE -> -mrelocation-model pic -pic-level 2 -pie-level 2

The one change (which is reflected in the tests) is that enabling sanitizers doesn't force PIE. It is quiet surprising that currently enabling the sanitizers moves us from PIC to PIE.

[chandlerc]

Resigning as this patch has gotten quite stale. If someone is still interested, update or send a new patch.

[• rafael]

I can't even remember why I wrote this.

It was probably a drive by cleanup, so lets just delete it if it is stale.

lib/Driver/ToolChains.h

public:
 
   void
   AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                             llvm::opt::ArgStringList &CC1Args) const override;
   void
   AddClangCXXStdlibIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                                llvm::opt::ArgStringList &CC1Args) const override;
   bool isPIEDefault() const override;
+  bool isPICDefault() const override;
 
   std::string Linker;
   std::vector<std::string> ExtraOpts;
 
 protected:
   Tool *buildAssembler() const override;
   Tool *buildLinker() const override;
 

lib/Driver/ToolChains.cpp

for (unsigned i = 0; i < llvm::array_lengthof(LibStdCXXIncludePathCandidates);
     if (addLibStdCXXIncludePaths(LibStdCXXIncludePathCandidates[i],
                                  TripleStr + Multilib.includeSuffix(),
                                  DriverArgs, CC1Args))
       break;
   }
 }
 
 bool Linux::isPIEDefault() const {
+  if (getTriple().getEnvironment() == llvm::Triple::Android)
+    return true;
   return getSanitizerArgs().hasZeroBaseShadow();
 }
 
+bool Linux::isPICDefault() const {
+  return getTriple().getEnvironment() == llvm::Triple::Android;
+}
+
 /// DragonFly - DragonFly tool chain which can call as(1) and ld(1) directly.
 
 DragonFly::DragonFly(const Driver &D, const llvm::Triple& Triple, const ArgList &Args)
   : Generic_ELF(D, Triple, Args) {
 
   // Path mangling to find libexec
   getProgramPaths().push_back(getDriver().getInstalledDir());
   if (getDriver().getInstalledDir() != getDriver().Dir)

lib/Driver/Tools.cpp

if (isa<AnalyzeJobAction>(JA)) {
     CmdArgs.push_back("-w");
 
     // Add -Xanalyzer arguments when running as analyzer.
     Args.AddAllArgValues(CmdArgs, options::OPT_Xanalyzer);
   }
 
   CheckCodeGenerationOptions(D, Args);
 
-  bool PIE = getToolChain().isPIEDefault();
-  bool PIC = PIE || getToolChain().isPICDefault();
+  bool PIE = false;
+  bool PIC = false;
+  if (getToolChain().isPICDefault()) {
+    PIC = true;
+    PIE = false;
+  } else if (getToolChain().isPIEDefault()) {
+    PIC = PIE = true;
+  }
+
   bool IsPICLevelTwo = PIC;
 
   // Android-specific defaults for PIC/PIE
   if (getToolChain().getTriple().getEnvironment() == llvm::Triple::Android) {
     switch (getToolChain().getTriple().getArch()) {
     case llvm::Triple::arm:
     case llvm::Triple::armeb:
     case llvm::Triple::thumb:
     case llvm::Triple::thumbeb:
     case llvm::Triple::mips:
     case llvm::Triple::mipsel:
     case llvm::Triple::mips64:
     case llvm::Triple::mips64el:
-      PIC = true; // "-fpic"
-      break;
-
-    case llvm::Triple::x86:
-    case llvm::Triple::x86_64:
-      PIC = true; // "-fPIC"
-      IsPICLevelTwo = true;
+      IsPICLevelTwo = false;
       break;
 
     default:
       break;
     }
   }
 
   // For the PIC and PIE flag options, this logic is different from the
void gnutools::Link::ConstructJob(Compilation &C, const JobAction &JA,
                                   const ArgList &Args,
                                   const char *LinkingOutput) const {
   const toolchains::Linux& ToolChain =
     static_cast<const toolchains::Linux&>(getToolChain());
   const Driver &D = ToolChain.getDriver();
   const bool isAndroid =
     ToolChain.getTriple().getEnvironment() == llvm::Triple::Android;
   const bool IsPIE =
-    !Args.hasArg(options::OPT_shared) &&
-    !Args.hasArg(options::OPT_static) &&
-    (Args.hasArg(options::OPT_pie) || ToolChain.isPIEDefault() ||
-     // On Android every code is PIC so every executable is PIE
-     // Cannot use isPIEDefault here since otherwise
-     // PIE only logic will be enabled during compilation
-     isAndroid);
+      !Args.hasArg(options::OPT_shared) && !Args.hasArg(options::OPT_static) &&
+      (Args.hasArg(options::OPT_pie) || ToolChain.isPIEDefault());
 
   ArgStringList CmdArgs;
 
   // Silence warning for "clang -g foo.o -o foo"
   Args.ClaimAllArgs(options::OPT_g_Group);
   // and "clang -emit-llvm foo.o -o foo"
   Args.ClaimAllArgs(options::OPT_emit_llvm);
   // and for "clang -w foo.o -o foo". Other warning options are already

test/Driver/fsanitize.c

 // CHECK-TSAN-NO-PIE: "-mrelocation-model" "pic" "-pic-level" "2" "-pie-level" "2"
 // CHECK-TSAN-NO-PIE: "-pie"
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=memory %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-MSAN-NO-PIE
 // CHECK-MSAN-NO-PIE: "-mrelocation-model" "pic" "-pic-level" "2" "-pie-level" "2"
 // CHECK-MSAN-NO-PIE: "-pie"
 
 // RUN: %clang -target arm-linux-androideabi -fsanitize=address %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ANDROID-ASAN-NO-PIE
-// CHECK-ANDROID-ASAN-NO-PIE: "-mrelocation-model" "pic" "-pic-level" "2" "-pie-level" "2"
+// CHECK-ANDROID-ASAN-NO-PIE: "-mrelocation-model" "pic" "-pic-level" "1"
 // CHECK-ANDROID-ASAN-NO-PIE: "-pie"
 
 // RUN: %clang -target arm-linux-androideabi %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ANDROID-NO-ASAN
 // CHECK-ANDROID-NO-ASAN: "-mrelocation-model" "pic"
 
 // RUN: %clang -target x86_64-linux-gnu %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-RECOVER
 // RUN: %clang -target x86_64-linux-gnu %s -fsanitize-recover -### 2>&1 | FileCheck %s --check-prefix=CHECK-RECOVER
 // RUN: %clang -target x86_64-linux-gnu %s -fno-sanitize-recover -### 2>&1 | FileCheck %s --check-prefix=CHECK-NO-RECOVER