[PATCH] D83987: [libFuzzer] Disable implicit builtin knowledge about memcmp-like functions when -fsanitize=fuzzer-no-link is given.

[Dokyung Song via Phabricator via cfe-commits]

dokyungs created this revision.
dokyungs added reviewers: morehouse, hctim.
Herald added projects: clang, Sanitizers.
Herald added subscribers: Sanitizers, cfe-commits.

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 inlibFuzzer tests are now removed, as it is now done automatically in the clang driver.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D83987

Files:
  clang/lib/Driver/SanitizerArgs.cpp
  compiler-rt/test/fuzzer/memcmp.test
  compiler-rt/test/fuzzer/memcmp64.test
  compiler-rt/test/fuzzer/strcmp.test
  compiler-rt/test/fuzzer/strncmp.test
  compiler-rt/test/fuzzer/strstr.test


Index: compiler-rt/test/fuzzer/strstr.test
===================================================================
--- compiler-rt/test/fuzzer/strstr.test
+++ compiler-rt/test/fuzzer/strstr.test
@@ -2,7 +2,7 @@
 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 -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-StrstrTest               -seed=1 -runs=2000000   2>&1 | FileCheck %s
 
 CHECK: BINGO
Index: compiler-rt/test/fuzzer/strncmp.test
===================================================================
--- compiler-rt/test/fuzzer/strncmp.test
+++ compiler-rt/test/fuzzer/strncmp.test
@@ -2,7 +2,7 @@
 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 -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-StrncmpTest              -seed=2 -runs=10000000   2>&1 | FileCheck %s
 
 CHECK: BINGO
Index: compiler-rt/test/fuzzer/strcmp.test
===================================================================
--- compiler-rt/test/fuzzer/strcmp.test
+++ compiler-rt/test/fuzzer/strcmp.test
@@ -2,7 +2,7 @@
 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 -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-StrcmpTest               -seed=1 -runs=2000000   2>&1 | FileCheck %s
 
 CHECK: BINGO
Index: compiler-rt/test/fuzzer/memcmp64.test
===================================================================
--- compiler-rt/test/fuzzer/memcmp64.test
+++ compiler-rt/test/fuzzer/memcmp64.test
@@ -2,7 +2,7 @@
 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 -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-Memcmp64BytesTest        -seed=1 -runs=1000000   2>&1 | FileCheck %s
 
 CHECK: BINGO
Index: compiler-rt/test/fuzzer/memcmp.test
===================================================================
--- compiler-rt/test/fuzzer/memcmp.test
+++ compiler-rt/test/fuzzer/memcmp.test
@@ -2,7 +2,7 @@
 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 -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-MemcmpTest               -seed=1 -runs=10000000   2>&1 | FileCheck %s
 
 CHECK: BINGO
Index: clang/lib/Driver/SanitizerArgs.cpp
===================================================================
--- clang/lib/Driver/SanitizerArgs.cpp
+++ clang/lib/Driver/SanitizerArgs.cpp
@@ -1088,6 +1088,17 @@
       Sanitizers.has(SanitizerKind::Address))
     CmdArgs.push_back("-fno-assume-sane-operator-new");
 
+  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() &&


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