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

Summary: This patch disables implicit builtin knowledge about memcmp-like functions when compiling the program for fuzzing, i.e., when -fsanitize=fuzzer(-no-link) is given. This allows libFuzzer to always intercept memcmp-like functions as it effectively disables optimizing calls to such functions into different forms. This is done by adding a set of flags (-fno-builtin-memcmp and others) in the clang driver. Individual -fno-builtin-* flags previously used in several libFuzzer tests are now removed, as it is now done automatically in the clang driver.

The patch was once reverted in 8ef9e2b, as this patch was dependent on a reverted commit f78d9fc. This reverted commit was recommitted in 831ae45, so relanding this dependent patch too.

Reviewers: morehouse, hctim

Subscribers: cfe-commits, #sanitizers

Tags: #clang, #sanitizers

Differential Revision: https://reviews.llvm.org/D83987

Author: dokyungs

clang/lib/Driver/SanitizerArgs.cpp

@@ -1088,6 +1088,23 @@ 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-bcmp");
+    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() &&

compiler-rt/test/fuzzer/noasan-bcmp.test

@@ -0,0 +1,4 @@
+UNSUPPORTED: darwin, freebsd, windows
+RUN: %cpp_compiler -fno-sanitize=address -DMEMCMP=bcmp %S/MemcmpTest.cpp -o %t
+RUN: not %run %t -seed=1 -runs=10000000 2>&1 | FileCheck %s
+CHECK: BINGO

compiler-rt/test/fuzzer/noasan-memcmp.test

@@ -1,9 +1,9 @@
 UNSUPPORTED: darwin, freebsd, windows
 
-RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-memcmp %S/MemcmpTest.cpp -o %t-NoAsanMemcmpTest
+RUN: %cpp_compiler -fno-sanitize=address %S/MemcmpTest.cpp -o %t-NoAsanMemcmpTest
 RUN: not %run %t-NoAsanMemcmpTest -seed=1 -runs=10000000   2>&1 | FileCheck %s
 
-RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-calloc -fno-builtin-memcmp %S/CustomAllocator.cpp %S/MemcmpTest.cpp -o %t-NoAsanCustomAllocatorMemcmpTest
+RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-calloc %S/CustomAllocator.cpp %S/MemcmpTest.cpp -o %t-NoAsanCustomAllocatorMemcmpTest
 RUN: not %run %t-NoAsanCustomAllocatorMemcmpTest -seed=1 -runs=10000000   2>&1 | FileCheck %s
 
 CHECK: BINGO

compiler-rt/test/fuzzer/noasan-memcmp64.test

@@ -1,6 +1,6 @@
 UNSUPPORTED: darwin, freebsd, windows
 
-RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-memcmp %S/Memcmp64BytesTest.cpp -o %t-NoAsanMemcmp64BytesTest
+RUN: %cpp_compiler -fno-sanitize=address %S/Memcmp64BytesTest.cpp -o %t-NoAsanMemcmp64BytesTest
 RUN: not %run %t-NoAsanMemcmp64BytesTest -seed=1 -runs=1000000   2>&1 | FileCheck %s
 
 CHECK: BINGO

compiler-rt/test/fuzzer/noasan-strcmp.test

@@ -1,9 +1,9 @@
 UNSUPPORTED: darwin, freebsd, windows
 
-RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-strcmp %S/StrcmpTest.cpp -o %t-NoAsanStrcmpTest
+RUN: %cpp_compiler -fno-sanitize=address %S/StrcmpTest.cpp -o %t-NoAsanStrcmpTest
 RUN: not %run %t-NoAsanStrcmpTest -seed=1 -runs=2000000   2>&1 | FileCheck %s
 
-RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-calloc -fno-builtin-strcmp %S/CustomAllocator.cpp %S/StrcmpTest.cpp -o %t-NoAsanCustomAllocatorStrcmpTest
+RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-calloc %S/CustomAllocator.cpp %S/StrcmpTest.cpp -o %t-NoAsanCustomAllocatorStrcmpTest
 RUN: not %run %t-NoAsanCustomAllocatorStrcmpTest -seed=1 -runs=2000000   2>&1 | FileCheck %s
 
 CHECK: BINGO

compiler-rt/test/fuzzer/noasan-strncmp.test

@@ -1,9 +1,9 @@
 UNSUPPORTED: darwin, freebsd, windows
 
-RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-strncmp %S/StrncmpTest.cpp -o %t-NoAsanStrncmpTest
+RUN: %cpp_compiler -fno-sanitize=address %S/StrncmpTest.cpp -o %t-NoAsanStrncmpTest
 RUN: not %run %t-NoAsanStrncmpTest -seed=2 -runs=10000000   2>&1 | FileCheck %s
 
-RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-calloc -fno-builtin-strncmp %S/CustomAllocator.cpp %S/StrncmpTest.cpp -o %t-NoAsanCustomAllocatorStrncmpTest
+RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-calloc %S/CustomAllocator.cpp %S/StrncmpTest.cpp -o %t-NoAsanCustomAllocatorStrncmpTest
 RUN: not %run %t-NoAsanCustomAllocatorStrncmpTest -seed=2 -runs=10000000   2>&1 | FileCheck %s
 
 CHECK: BINGO

compiler-rt/test/fuzzer/noasan-strstr.test

@@ -1,9 +1,9 @@
 UNSUPPORTED: darwin, freebsd, windows
 
-RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-strstr %S/StrstrTest.cpp -o %t-NoAsanStrstrTest
+RUN: %cpp_compiler -fno-sanitize=address %S/StrstrTest.cpp -o %t-NoAsanStrstrTest
 RUN: not %run %t-NoAsanStrstrTest -seed=1 -runs=2000000   2>&1 | FileCheck %s
 
-RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-calloc -fno-builtin-strstr %S/CustomAllocator.cpp %S/StrstrTest.cpp -o %t-NoAsanCustomAllocatorStrstrTest
+RUN: %cpp_compiler -fno-sanitize=address -fno-builtin-calloc %S/CustomAllocator.cpp %S/StrstrTest.cpp -o %t-NoAsanCustomAllocatorStrstrTest
 RUN: not %run %t-NoAsanCustomAllocatorStrstrTest -seed=1 -runs=2000000   2>&1 | FileCheck %s
 
 CHECK: BINGO