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[hwasan] An option to disable tag randomization. 

Summary:
Avoid flaky test failures by by using a monotonic number sequence of
heap tags.

Does not affect stack tags: the way we generate those guarantees
uniqueness for at least 30-something first allocas in any function,
as well as the UAR tag.

Reviewers: alekseyshl, kcc

Subscribers: llvm-commits, kubamracek

Differential Revision: https://reviews.llvm.org/D41882

llvm-svn: 322214
This commit is contained in:
Evgeniy Stepanov 2018-01-10 19:36:10 +00:00
parent 279cc1b5e2
commit 29e3f5b722
3 changed files with 15 additions and 7 deletions
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4
compiler-rt/lib/hwasan/hwasan_flags.inc
View File

@ -27,3 +27,7 @@ HWASAN_FLAG(bool, atexit, false, "")
// Test only flag to disable malloc/realloc/free memory tagging on startup.
// Tagging can be reenabled with __hwasan_enable_allocator_tagging().
HWASAN_FLAG(bool, disable_allocator_tagging, false, "")
// If false, use simple increment of a thread local counter to generate new
// tags.
HWASAN_FLAG(bool, random_tags, true, "")

16
compiler-rt/lib/hwasan/hwasan_thread.cc
View File

@ -29,7 +29,7 @@ HwasanThread *HwasanThread::Create(thread_callback_t start_routine,
thread->start_routine_ = start_routine;
thread->arg_ = arg;
thread->destructor_iterations_ = GetPthreadDestructorIterations();
thread->random_state_ = RandomSeed();
thread->random_state_ = flags()->random_tags ? RandomSeed() : 0;
return thread;
}
@ -97,11 +97,15 @@ static u32 xorshift(u32 state) {
tag_t HwasanThread::GenerateRandomTag() {
tag_t tag;
do {
if (!random_buffer_)
random_buffer_ = random_state_ = xorshift(random_state_);
CHECK(random_buffer_);
tag = random_buffer_ & 0xFF;
random_buffer_ >>= 8;
if (flags()->random_tags) {
if (!random_buffer_)
random_buffer_ = random_state_ = xorshift(random_state_);
CHECK(random_buffer_);
tag = random_buffer_ & 0xFF;
random_buffer_ >>= 8;
} else {
tag = random_state_ = (random_state_ + 1) & 0xFF;
}
} while (!tag);
return tag;
}

2
compiler-rt/test/hwasan/lit.cfg
View File

@ -18,7 +18,7 @@ def build_invocation(compile_flags):
config.substitutions.append( ("%clang_hwasan ", build_invocation(clang_hwasan_cflags)) )
config.substitutions.append( ("%clangxx_hwasan ", build_invocation(clang_hwasan_cxxflags)) )
default_hwasan_opts_str = ':'.join(['disable_allocator_tagging=1'] + config.default_sanitizer_opts)
default_hwasan_opts_str = ':'.join(['disable_allocator_tagging=1', 'random_tags=0'] + config.default_sanitizer_opts)
if default_hwasan_opts_str:
config.environment['HWASAN_OPTIONS'] = default_hwasan_opts_str
default_hwasan_opts_str += ':'