Revert "[libFuzzer] Link libFuzzer's own interceptors when other compiler runtimes are not linked."

This causes binaries linked with this runtime to crash on startup if
dlsym uses any of the intercepted functions. (For example, that happens
when using tcmalloc as the allocator: dlsym attempts to allocate memory
with malloc, and tcmalloc uses strncmp within its implementation.)

Also revert dependent commit "[libFuzzer] Disable implicit builtin knowledge about memcmp-like functions when -fsanitize=fuzzer-no-link is given."

This reverts commit f78d9fc and 12d1124.

Author: zygoloid

clang/include/clang/Driver/SanitizerArgs.h

@@ -74,7 +74,6 @@ class SanitizerArgs {
            !Sanitizers.has(SanitizerKind::Address) &&
            !Sanitizers.has(SanitizerKind::HWAddress);
   }
-  bool needsFuzzerInterceptors() const;
   bool needsUbsanRt() const;
   bool requiresMinimalRuntime() const { return MinimalRuntime; }
   bool needsDfsanRt() const { return Sanitizers.has(SanitizerKind::DataFlow); }

clang/lib/Driver/SanitizerArgs.cpp

@@ -240,10 +240,6 @@ static SanitizerMask parseSanitizeTrapArgs(const Driver &D,
   return TrappingKinds;
 }
 
-bool SanitizerArgs::needsFuzzerInterceptors() const {
-  return needsFuzzer() && !needsAsanRt() && !needsTsanRt() && !needsMsanRt();
-}
-
 bool SanitizerArgs::needsUbsanRt() const {
   // All of these include ubsan.
   if (needsAsanRt() || needsMsanRt() || needsHwasanRt() || needsTsanRt() ||
@@ -1088,22 +1084,6 @@ void SanitizerArgs::addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
       Sanitizers.has(SanitizerKind::Address))
     CmdArgs.push_back("-fno-assume-sane-operator-new");
 
-  // libFuzzer wants to intercept calls to certain library functions, so the
-  // following -fno-builtin-* flags force the compiler to emit interposable
-  // libcalls to these functions. Other sanitizers effectively do the same thing
-  // by marking all library call sites with NoBuiltin attribute in their LLVM
-  // pass. (see llvm::maybeMarkSanitizerLibraryCallNoBuiltin)
-  if (Sanitizers.has(SanitizerKind::FuzzerNoLink)) {
-    CmdArgs.push_back("-fno-builtin-memcmp");
-    CmdArgs.push_back("-fno-builtin-strncmp");
-    CmdArgs.push_back("-fno-builtin-strcmp");
-    CmdArgs.push_back("-fno-builtin-strncasecmp");
-    CmdArgs.push_back("-fno-builtin-strcasecmp");
-    CmdArgs.push_back("-fno-builtin-strstr");
-    CmdArgs.push_back("-fno-builtin-strcasestr");
-    CmdArgs.push_back("-fno-builtin-memmem");
-  }
-
   // Require -fvisibility= flag on non-Windows when compiling if vptr CFI is
   // enabled.
   if (Sanitizers.hasOneOf(CFIClasses) && !TC.getTriple().isOSWindows() &&

clang/lib/Driver/ToolChains/CommonArgs.cpp

@@ -784,9 +784,6 @@ bool tools::addSanitizerRuntimes(const ToolChain &TC, const ArgList &Args,
       !Args.hasArg(options::OPT_shared)) {
 
     addSanitizerRuntime(TC, Args, CmdArgs, "fuzzer", false, true);
-    if (SanArgs.needsFuzzerInterceptors())
-      addSanitizerRuntime(TC, Args, CmdArgs, "fuzzer_interceptors", false,
-                          true);
     if (!Args.hasArg(clang::driver::options::OPT_nostdlibxx))
       TC.AddCXXStdlibLibArgs(Args, CmdArgs);
   }

compiler-rt/lib/fuzzer/CMakeLists.txt

@@ -99,13 +99,6 @@ add_compiler_rt_object_libraries(RTfuzzer_main
   CFLAGS ${LIBFUZZER_CFLAGS}
   DEPS ${LIBFUZZER_DEPS})
 
-add_compiler_rt_object_libraries(RTfuzzer_interceptors
-  OS ${FUZZER_SUPPORTED_OS}
-  ARCHS ${FUZZER_SUPPORTED_ARCH}
-  SOURCES FuzzerInterceptors.cpp
-  CFLAGS ${LIBFUZZER_CFLAGS}
-  DEPS ${LIBFUZZER_DEPS})
-
 add_compiler_rt_runtime(clang_rt.fuzzer
   STATIC
   OS ${FUZZER_SUPPORTED_OS}
@@ -122,14 +115,6 @@ add_compiler_rt_runtime(clang_rt.fuzzer_no_main
   CFLAGS ${LIBFUZZER_CFLAGS}
   PARENT_TARGET fuzzer)
 
-add_compiler_rt_runtime(clang_rt.fuzzer_interceptors
-  STATIC
-  OS ${FUZZER_SUPPORTED_OS}
-  ARCHS ${FUZZER_SUPPORTED_ARCH}
-  OBJECT_LIBS RTfuzzer_interceptors
-  CFLAGS ${LIBFUZZER_CFLAGS}
-  PARENT_TARGET fuzzer)
-
 if(OS_NAME MATCHES "Linux|Fuchsia" AND
    COMPILER_RT_LIBCXX_PATH AND
    COMPILER_RT_LIBCXXABI_PATH)
@@ -163,10 +148,7 @@ if(OS_NAME MATCHES "Linux|Fuchsia" AND
     add_dependencies(RTfuzzer.${arch} libcxx_fuzzer_${arch}-build)
     target_compile_options(RTfuzzer_main.${arch} PRIVATE -isystem ${LIBCXX_${arch}_PREFIX}/include/c++/v1)
     add_dependencies(RTfuzzer_main.${arch} libcxx_fuzzer_${arch}-build)
-    target_compile_options(RTfuzzer_interceptors.${arch} PRIVATE -isystem ${LIBCXX_${arch}_PREFIX}/include/c++/v1)
-    add_dependencies(RTfuzzer_interceptors.${arch} libcxx_fuzzer_${arch}-build)
     partially_link_libcxx(fuzzer_no_main ${LIBCXX_${arch}_PREFIX} ${arch})
-    partially_link_libcxx(fuzzer_interceptors ${LIBCXX_${arch}_PREFIX} ${arch})
     partially_link_libcxx(fuzzer ${LIBCXX_${arch}_PREFIX} ${arch})
   endforeach()
 endif()

compiler-rt/lib/fuzzer/FuzzerInterceptors.cpp

@@ -1,8 +1,4 @@
 UNSUPPORTED: freebsd
 RUN: %cpp_compiler %S/MemcmpTest.cpp -o %t-MemcmpTest
 RUN: not %run %t-MemcmpTest               -seed=1 -runs=10000000   2>&1 | FileCheck %s
-
-RUN: %cpp_compiler -fno-sanitize=address %S/MemcmpTest.cpp -o %t-NoAsanMemcmpTest
-RUN: not %run %t-MemcmpTest               -seed=1 -runs=10000000   2>&1 | FileCheck %s
-
 CHECK: BINGO

compiler-rt/test/fuzzer/memcmp.test

@@ -1,8 +1,4 @@
 UNSUPPORTED: freebsd
 RUN: %cpp_compiler %S/Memcmp64BytesTest.cpp -o %t-Memcmp64BytesTest
 RUN: not %run %t-Memcmp64BytesTest        -seed=1 -runs=1000000   2>&1 | FileCheck %s
-
-RUN: %cpp_compiler -fno-sanitize=address %S/Memcmp64BytesTest.cpp -o %t-NoAsanMemcmp64BytesTest
-RUN: not %run %t-Memcmp64BytesTest        -seed=1 -runs=1000000   2>&1 | FileCheck %s
-
 CHECK: BINGO

compiler-rt/test/fuzzer/memcmp64.test

@@ -1,8 +1,5 @@
 UNSUPPORTED: freebsd
 RUN: %cpp_compiler %S/StrcmpTest.cpp -o %t-StrcmpTest
 RUN: not %run %t-StrcmpTest               -seed=1 -runs=2000000   2>&1 | FileCheck %s
-
-RUN: %cpp_compiler -fno-sanitize=address %S/StrcmpTest.cpp -o %t-NoAsanStrcmpTest
-RUN: not %run %t-StrcmpTest               -seed=1 -runs=2000000   2>&1 | FileCheck %s
-
 CHECK: BINGO
+

compiler-rt/test/fuzzer/strcmp.test

@@ -1,8 +1,5 @@
 UNSUPPORTED: freebsd
 RUN: %cpp_compiler %S/StrncmpTest.cpp -o %t-StrncmpTest
 RUN: not %run %t-StrncmpTest              -seed=2 -runs=10000000   2>&1 | FileCheck %s
-
-RUN: %cpp_compiler -fno-sanitize=address %S/StrncmpTest.cpp -o %t-NoAsanStrncmpTest
-RUN: not %run %t-StrncmpTest              -seed=2 -runs=10000000   2>&1 | FileCheck %s
-
 CHECK: BINGO
+

compiler-rt/test/fuzzer/strncmp.test

@@ -1,8 +1,5 @@
 UNSUPPORTED: freebsd
 RUN: %cpp_compiler %S/StrstrTest.cpp -o %t-StrstrTest
 RUN: not %run %t-StrstrTest               -seed=1 -runs=2000000   2>&1 | FileCheck %s
-
-RUN: %cpp_compiler -fno-sanitize=address %S/StrstrTest.cpp -o %t-NoAsanStrstrTest
-RUN: not %run %t-StrstrTest               -seed=1 -runs=2000000   2>&1 | FileCheck %s
-
 CHECK: BINGO
+