[compiler-rt] r210180 - [sancov] Handle fork.
Evgeniy Stepanov
eugeni.stepanov at gmail.com
Tue Dec 23 00:58:49 PST 2014
This is the main mode of execution on Android.
And in Chromium.
Better keep it.
On Tue, Dec 23, 2014 at 1:53 AM, Kostya Serebryany <kcc at google.com> wrote:
> I've stumbled upon this test while changing how the coverage logic works...
> Do we need coverage to work after fork but before exec at all?
> It actually doesn't fully work today either, but I want to break it even
> more...
>
> On Wed, Jun 4, 2014 at 5:13 AM, Evgeniy Stepanov <eugeni.stepanov at gmail.com>
> wrote:
>>
>> Author: eugenis
>> Date: Wed Jun 4 07:13:54 2014
>> New Revision: 210180
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=210180&view=rev
>> Log:
>> [sancov] Handle fork.
>>
>> Reset coverage data on fork().
>> For memory-mapped mode (coverage_direct=1) this helps avoid loss of data
>> (before this change two processes would write to the same file
>> simultaneously).
>> For normal mode, this reduces coverage dump size, because PCs from the
>> parent
>> process are no longer inherited by the child.
>>
>> Added:
>> compiler-rt/trunk/test/asan/TestCases/Linux/coverage-fork-direct.cc
>> (with props)
>> compiler-rt/trunk/test/asan/TestCases/Linux/coverage-fork.cc (with
>> props)
>> Modified:
>> compiler-rt/trunk/lib/asan/asan_interceptors.cc
>> compiler-rt/trunk/lib/asan/asan_interceptors.h
>> compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h
>> compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_libcdep.cc
>>
>> compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_mapping_libcdep.cc
>>
>> Modified: compiler-rt/trunk/lib/asan/asan_interceptors.cc
>> URL:
>> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/asan_interceptors.cc?rev=210180&r1=210179&r2=210180&view=diff
>>
>> ==============================================================================
>> --- compiler-rt/trunk/lib/asan/asan_interceptors.cc (original)
>> +++ compiler-rt/trunk/lib/asan/asan_interceptors.cc Wed Jun 4 07:13:54
>> 2014
>> @@ -697,6 +697,16 @@ INTERCEPTOR(int, __cxa_atexit, void (*fu
>> }
>> #endif // ASAN_INTERCEPT___CXA_ATEXIT
>>
>> +#if ASAN_INTERCEPT_FORK
>> +INTERCEPTOR(int, fork, void) {
>> + ENSURE_ASAN_INITED();
>> + if (common_flags()->coverage) CovBeforeFork();
>> + int pid = REAL(fork)();
>> + if (common_flags()->coverage) CovAfterFork(pid);
>> + return pid;
>> +}
>> +#endif // ASAN_INTERCEPT_FORK
>> +
>> #if SANITIZER_WINDOWS
>> INTERCEPTOR_WINAPI(DWORD, CreateThread,
>> void* security, uptr stack_size,
>> @@ -808,6 +818,10 @@ void InitializeAsanInterceptors() {
>> ASAN_INTERCEPT_FUNC(__cxa_atexit);
>> #endif
>>
>> +#if ASAN_INTERCEPT_FORK
>> + ASAN_INTERCEPT_FUNC(fork);
>> +#endif
>> +
>> // Some Windows-specific interceptors.
>> #if SANITIZER_WINDOWS
>> InitializeWindowsInterceptors();
>>
>> Modified: compiler-rt/trunk/lib/asan/asan_interceptors.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/asan_interceptors.h?rev=210180&r1=210179&r2=210180&view=diff
>>
>> ==============================================================================
>> --- compiler-rt/trunk/lib/asan/asan_interceptors.h (original)
>> +++ compiler-rt/trunk/lib/asan/asan_interceptors.h Wed Jun 4 07:13:54
>> 2014
>> @@ -27,6 +27,7 @@
>> # define ASAN_INTERCEPT_INDEX 1
>> # define ASAN_INTERCEPT_PTHREAD_CREATE 1
>> # define ASAN_INTERCEPT_MLOCKX 1
>> +# define ASAN_INTERCEPT_FORK 1
>> #else
>> # define ASAN_INTERCEPT_ATOLL_AND_STRTOLL 0
>> # define ASAN_INTERCEPT__LONGJMP 0
>> @@ -34,6 +35,7 @@
>> # define ASAN_INTERCEPT_INDEX 0
>> # define ASAN_INTERCEPT_PTHREAD_CREATE 0
>> # define ASAN_INTERCEPT_MLOCKX 0
>> +# define ASAN_INTERCEPT_FORK 0
>> #endif
>>
>> #if SANITIZER_FREEBSD || SANITIZER_LINUX
>>
>> Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h?rev=210180&r1=210179&r2=210180&view=diff
>>
>> ==============================================================================
>> --- compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h (original)
>> +++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h Wed Jun 4
>> 07:13:54 2014
>> @@ -193,6 +193,8 @@ void CovPrepareForSandboxing(__sanitizer
>> void SetSandboxingCallback(void (*f)());
>>
>> void CovUpdateMapping();
>> +void CovBeforeFork();
>> +void CovAfterFork(int child_pid);
>>
>> void InitTlsSize();
>> uptr GetTlsSize();
>>
>> Modified:
>> compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_libcdep.cc
>> URL:
>> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_libcdep.cc?rev=210180&r1=210179&r2=210180&view=diff
>>
>> ==============================================================================
>> --- compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_libcdep.cc
>> (original)
>> +++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_libcdep.cc
>> Wed Jun 4 07:13:54 2014
>> @@ -59,6 +59,8 @@ namespace __sanitizer {
>> class CoverageData {
>> public:
>> void Init();
>> + void BeforeFork();
>> + void AfterFork(int child_pid);
>> void Extend(uptr npcs);
>> void Add(uptr pc);
>>
>> @@ -86,6 +88,7 @@ class CoverageData {
>> StaticSpinMutex mu;
>>
>> void DirectOpen();
>> + void ReInit();
>> };
>>
>> static CoverageData coverage_data;
>> @@ -107,23 +110,47 @@ void CoverageData::DirectOpen() {
>> void CoverageData::Init() {
>> pc_array = reinterpret_cast<uptr *>(
>> MmapNoReserveOrDie(sizeof(uptr) * kPcArrayMaxSize, "CovInit"));
>> + pc_fd = kInvalidFd;
>> if (common_flags()->coverage_direct) {
>> atomic_store(&pc_array_size, 0, memory_order_relaxed);
>> atomic_store(&pc_array_index, 0, memory_order_relaxed);
>> } else {
>> - pc_fd = 0;
>> atomic_store(&pc_array_size, kPcArrayMaxSize, memory_order_relaxed);
>> atomic_store(&pc_array_index, 0, memory_order_relaxed);
>> }
>> }
>>
>> +void CoverageData::ReInit() {
>> + internal_munmap(pc_array, sizeof(uptr) * kPcArrayMaxSize);
>> + if (pc_fd != kInvalidFd) internal_close(pc_fd);
>> + if (common_flags()->coverage_direct) {
>> + // In memory-mapped mode we must extend the new file to the known
>> array
>> + // size.
>> + uptr size = atomic_load(&pc_array_size, memory_order_relaxed);
>> + Init();
>> + if (size) Extend(size);
>> + } else {
>> + Init();
>> + }
>> +}
>> +
>> +void CoverageData::BeforeFork() {
>> + mu.Lock();
>> +}
>> +
>> +void CoverageData::AfterFork(int child_pid) {
>> + // We are single-threaded so it's OK to release the lock early.
>> + mu.Unlock();
>> + if (child_pid == 0) ReInit();
>> +}
>> +
>> // Extend coverage PC array to fit additional npcs elements.
>> void CoverageData::Extend(uptr npcs) {
>> if (!common_flags()->coverage_direct) return;
>> SpinMutexLock l(&mu);
>>
>> - if (!pc_fd) DirectOpen();
>> - CHECK(pc_fd);
>> + if (pc_fd == kInvalidFd) DirectOpen();
>> + CHECK_NE(pc_fd, kInvalidFd);
>>
>> uptr size = atomic_load(&pc_array_size, memory_order_relaxed);
>> size += npcs * sizeof(uptr);
>> @@ -324,6 +351,15 @@ int MaybeOpenCovFile(const char *name) {
>> if (!common_flags()->coverage) return -1;
>> return CovOpenFile(true /* packed */, name);
>> }
>> +
>> +void CovBeforeFork() {
>> + coverage_data.BeforeFork();
>> +}
>> +
>> +void CovAfterFork(int child_pid) {
>> + coverage_data.AfterFork(child_pid);
>> +}
>> +
>> } // namespace __sanitizer
>>
>> extern "C" {
>>
>> Modified:
>> compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_mapping_libcdep.cc
>> URL:
>> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_mapping_libcdep.cc?rev=210180&r1=210179&r2=210180&view=diff
>>
>> ==============================================================================
>> ---
>> compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_mapping_libcdep.cc
>> (original)
>> +++
>> compiler-rt/trunk/lib/sanitizer_common/sanitizer_coverage_mapping_libcdep.cc
>> Wed Jun 4 07:13:54 2014
>> @@ -36,8 +36,27 @@
>> namespace __sanitizer {
>>
>> static const uptr kMaxNumberOfModules = 1 << 14;
>> +static const uptr kMaxTextSize = 64 * 1024;
>>
>> -static char *last_mapping;
>> +struct CachedMapping {
>> + public:
>> + bool TestAndUpdate(const char *new_mapping) {
>> + int new_pid = internal_getpid();
>> + if (last_mapping && last_pid == new_pid &&
>> + internal_strcmp(last_mapping, new_mapping) == 0)
>> + return false;
>> + if (!last_mapping) last_mapping = (char
>> *)InternalAlloc(kMaxTextSize);
>> + last_pid = new_pid;
>> + internal_strncpy(last_mapping, new_mapping, kMaxTextSize);
>> + return true;
>> + }
>> +
>> + private:
>> + char *last_mapping;
>> + int last_pid;
>> +};
>> +
>> +static CachedMapping cached_mapping;
>> static StaticSpinMutex mapping_mu;
>>
>> void CovUpdateMapping() {
>> @@ -45,7 +64,6 @@ void CovUpdateMapping() {
>>
>> SpinMutexLock l(&mapping_mu);
>>
>> - const uptr kMaxTextSize = 64 * 1024;
>> InternalScopedString text(kMaxTextSize);
>> InternalScopedBuffer<char> modules_data(kMaxNumberOfModules *
>> sizeof(LoadedModule));
>> @@ -66,9 +84,8 @@ void CovUpdateMapping() {
>> }
>>
>> // Do not write mapping if it is the same as the one we've wrote last
>> time.
>> - if (last_mapping && (internal_strcmp(last_mapping, text.data()) == 0))
>> return;
>> - if (!last_mapping) last_mapping = (char *)InternalAlloc(kMaxTextSize);
>> - internal_strncpy(last_mapping, text.data(), kMaxTextSize);
>> + if (!cached_mapping.TestAndUpdate(text.data()))
>> + return;
>>
>> int err;
>> InternalScopedString tmp_path(64 +
>>
>> Added: compiler-rt/trunk/test/asan/TestCases/Linux/coverage-fork-direct.cc
>> URL:
>> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/test/asan/TestCases/Linux/coverage-fork-direct.cc?rev=210180&view=auto
>>
>> ==============================================================================
>> --- compiler-rt/trunk/test/asan/TestCases/Linux/coverage-fork-direct.cc
>> (added)
>> +++ compiler-rt/trunk/test/asan/TestCases/Linux/coverage-fork-direct.cc
>> Wed Jun 4 07:13:54 2014
>> @@ -0,0 +1,38 @@
>> +// RUN: %clangxx_asan -mllvm -asan-coverage=1 %s -o %t
>> +// RUN: rm -rf %T/coverage-fork-direct
>> +// RUN: mkdir -p %T/coverage-fork-direct && cd %T/coverage-fork-direct
>> +// RUN: (ASAN_OPTIONS=coverage=1:coverage_direct=1:verbosity=1 %run %t; \
>> +// RUN: %sancov rawunpack *.sancov.raw; %sancov print *.sancov) 2>&1
>> +//
>> +// XFAIL: android
>> +
>> +#include <stdio.h>
>> +#include <string.h>
>> +#include <unistd.h>
>> +
>> +__attribute__((noinline))
>> +void foo() { printf("foo\n"); }
>> +
>> +__attribute__((noinline))
>> +void bar() { printf("bar\n"); }
>> +
>> +__attribute__((noinline))
>> +void baz() { printf("baz\n"); }
>> +
>> +int main(int argc, char **argv) {
>> + pid_t child_pid = fork();
>> + if (child_pid == 0) {
>> + fprintf(stderr, "Child PID: %d\n", getpid());
>> + baz();
>> + } else {
>> + fprintf(stderr, "Parent PID: %d\n", getpid());
>> + foo();
>> + bar();
>> + }
>> + return 0;
>> +}
>> +
>> +// CHECK-DAG: Child PID: [[ChildPID:[0-9]+]]
>> +// CHECK-DAG: Parent PID: [[ParentPID:[0-9]+]]
>> +// CHECK-DAG: read 3 PCs from {{.*}}.[[ParentPID]].sancov
>> +// CHECK-DAG: read 1 PCs from {{.*}}.[[ChildPID]].sancov
>>
>> Propchange:
>> compiler-rt/trunk/test/asan/TestCases/Linux/coverage-fork-direct.cc
>>
>> ------------------------------------------------------------------------------
>> svn:eol-style = LF
>>
>> Added: compiler-rt/trunk/test/asan/TestCases/Linux/coverage-fork.cc
>> URL:
>> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/test/asan/TestCases/Linux/coverage-fork.cc?rev=210180&view=auto
>>
>> ==============================================================================
>> --- compiler-rt/trunk/test/asan/TestCases/Linux/coverage-fork.cc (added)
>> +++ compiler-rt/trunk/test/asan/TestCases/Linux/coverage-fork.cc Wed Jun
>> 4 07:13:54 2014
>> @@ -0,0 +1,38 @@
>> +// RUN: %clangxx_asan -mllvm -asan-coverage=1 %s -o %t
>> +// RUN: export ASAN_OPTIONS=coverage=1:coverage_direct=0:verbosity=1
>> +// RUN: rm -rf %T/coverage-fork
>> +// RUN: mkdir -p %T/coverage-fork && cd %T/coverage-fork
>> +// RUN: %run %t 2>&1 | FileCheck %s
>> +//
>> +// XFAIL: android
>> +
>> +#include <stdio.h>
>> +#include <string.h>
>> +#include <unistd.h>
>> +
>> +__attribute__((noinline))
>> +void foo() { printf("foo\n"); }
>> +
>> +__attribute__((noinline))
>> +void bar() { printf("bar\n"); }
>> +
>> +__attribute__((noinline))
>> +void baz() { printf("baz\n"); }
>> +
>> +int main(int argc, char **argv) {
>> + pid_t child_pid = fork();
>> + if (child_pid == 0) {
>> + fprintf(stderr, "Child PID: %d\n", getpid());
>> + baz();
>> + } else {
>> + fprintf(stderr, "Parent PID: %d\n", getpid());
>> + foo();
>> + bar();
>> + }
>> + return 0;
>> +}
>> +
>> +// CHECK-DAG: Child PID: [[ChildPID:[0-9]+]]
>> +// CHECK-DAG: [[ChildPID]].sancov: 1 PCs written
>> +// CHECK-DAG: Parent PID: [[ParentPID:[0-9]+]]
>> +// CHECK-DAG: [[ParentPID]].sancov: 3 PCs written
>>
>> Propchange: compiler-rt/trunk/test/asan/TestCases/Linux/coverage-fork.cc
>>
>> ------------------------------------------------------------------------------
>> svn:eol-style = LF
>>
>>
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