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[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.

Reviewers: morehouse, hctim

Subscribers: cfe-commits, #sanitizers

Tags: #clang, #sanitizers

Differential Revision: https://reviews.llvm.org/D83987
This commit is contained in:
Dokyung Song 2020-07-16 21:24:06 +00:00
parent 2f99059aa0
commit 12d1124c49
6 changed files with 21 additions and 5 deletions
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16
clang/lib/Driver/SanitizerArgs.cpp
View File

@ -1088,6 +1088,22 @@ 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() &&

2
compiler-rt/test/fuzzer/memcmp.test
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@ -2,7 +2,7 @@ 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 -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

2
compiler-rt/test/fuzzer/memcmp64.test
View File

@ -2,7 +2,7 @@ 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 -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

2
compiler-rt/test/fuzzer/strcmp.test
View File

@ -2,7 +2,7 @@ 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 -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

2
compiler-rt/test/fuzzer/strncmp.test
View File

@ -2,7 +2,7 @@ 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 -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

2
compiler-rt/test/fuzzer/strstr.test
View File

@ -2,7 +2,7 @@ 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 -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