1 files changed, 468 insertions, 0 deletions
diff --git a/gcc-4.9/libsanitizer/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc b/gcc-4.9/libsanitizer/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
new file mode 100644
index 000000000..6ee63ec31
--- /dev/null
+++ b/gcc-4.9/libsanitizer/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
@@ -0,0 +1,468 @@
+//===-- sanitizer_stoptheworld_linux_libcdep.cc ---------------------------===//
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// See sanitizer_stoptheworld.h for details.
+// This implementation was inspired by Markus Gutschke's linuxthreads.cc.
+//
+//===----------------------------------------------------------------------===//
+
+
+#include "sanitizer_platform.h"
+#if SANITIZER_LINUX && defined(__x86_64__)
+
+#include "sanitizer_stoptheworld.h"
+
+#include "sanitizer_platform_limits_posix.h"
+
+#include <errno.h>
+#include <sched.h> // for CLONE_* definitions
+#include <stddef.h>
+#include <sys/prctl.h> // for PR_* definitions
+#include <sys/ptrace.h> // for PTRACE_* definitions
+#include <sys/types.h> // for pid_t
+#if SANITIZER_ANDROID && defined(__arm__)
+# include <linux/user.h>  // for pt_regs
+#else
+# include <sys/user.h>  // for user_regs_struct
+#endif
+#include <sys/wait.h> // for signal-related stuff
+
+#ifdef sa_handler
+# undef sa_handler
+#endif
+
+#ifdef sa_sigaction
+# undef sa_sigaction
+#endif
+
+#include "sanitizer_common.h"
+#include "sanitizer_flags.h"
+#include "sanitizer_libc.h"
+#include "sanitizer_linux.h"
+#include "sanitizer_mutex.h"
+#include "sanitizer_placement_new.h"
+
+// This module works by spawning a Linux task which then attaches to every
+// thread in the caller process with ptrace. This suspends the threads, and
+// PTRACE_GETREGS can then be used to obtain their register state. The callback
+// supplied to StopTheWorld() is run in the tracer task while the threads are
+// suspended.
+// The tracer task must be placed in a different thread group for ptrace to
+// work, so it cannot be spawned as a pthread. Instead, we use the low-level
+// clone() interface (we want to share the address space with the caller
+// process, so we prefer clone() over fork()).
+//
+// We don't use any libc functions, relying instead on direct syscalls. There
+// are two reasons for this:
+// 1. calling a library function while threads are suspended could cause a
+// deadlock, if one of the treads happens to be holding a libc lock;
+// 2. it's generally not safe to call libc functions from the tracer task,
+// because clone() does not set up a thread-local storage for it. Any
+// thread-local variables used by libc will be shared between the tracer task
+// and the thread which spawned it.
+
+COMPILER_CHECK(sizeof(SuspendedThreadID) == sizeof(pid_t));
+
+namespace __sanitizer {
+// This class handles thread suspending/unsuspending in the tracer thread.
+class ThreadSuspender {
+ public:
+  explicit ThreadSuspender(pid_t pid)
+    : pid_(pid) {
+      CHECK_GE(pid, 0);
+    }
+  bool SuspendAllThreads();
+  void ResumeAllThreads();
+  void KillAllThreads();
+  SuspendedThreadsList &suspended_threads_list() {
+    return suspended_threads_list_;
+  }
+ private:
+  SuspendedThreadsList suspended_threads_list_;
+  pid_t pid_;
+  bool SuspendThread(SuspendedThreadID thread_id);
+};
+
+bool ThreadSuspender::SuspendThread(SuspendedThreadID thread_id) {
+  // Are we already attached to this thread?
+  // Currently this check takes linear time, however the number of threads is
+  // usually small.
+  if (suspended_threads_list_.Contains(thread_id))
+    return false;
+  int pterrno;
+  if (internal_iserror(internal_ptrace(PTRACE_ATTACH, thread_id, NULL, NULL),
+                       &pterrno)) {
+    // Either the thread is dead, or something prevented us from attaching.
+    // Log this event and move on.
+    if (common_flags()->verbosity)
+      Report("Could not attach to thread %d (errno %d).\n", thread_id, pterrno);
+    return false;
+  } else {
+    if (common_flags()->verbosity)
+      Report("Attached to thread %d.\n", thread_id);
+    // The thread is not guaranteed to stop before ptrace returns, so we must
+    // wait on it.
+    uptr waitpid_status;
+    HANDLE_EINTR(waitpid_status, internal_waitpid(thread_id, NULL, __WALL));
+    int wperrno;
+    if (internal_iserror(waitpid_status, &wperrno)) {
+      // Got a ECHILD error. I don't think this situation is possible, but it
+      // doesn't hurt to report it.
+      if (common_flags()->verbosity)
+        Report("Waiting on thread %d failed, detaching (errno %d).\n",
+            thread_id, wperrno);
+      internal_ptrace(PTRACE_DETACH, thread_id, NULL, NULL);
+      return false;
+    }
+    suspended_threads_list_.Append(thread_id);
+    return true;
+  }
+}
+
+void ThreadSuspender::ResumeAllThreads() {
+  for (uptr i = 0; i < suspended_threads_list_.thread_count(); i++) {
+    pid_t tid = suspended_threads_list_.GetThreadID(i);
+    int pterrno;
+    if (!internal_iserror(internal_ptrace(PTRACE_DETACH, tid, NULL, NULL),
+                          &pterrno)) {
+      if (common_flags()->verbosity)
+        Report("Detached from thread %d.\n", tid);
+    } else {
+      // Either the thread is dead, or we are already detached.
+      // The latter case is possible, for instance, if this function was called
+      // from a signal handler.
+      if (common_flags()->verbosity)
+        Report("Could not detach from thread %d (errno %d).\n", tid, pterrno);
+    }
+  }
+}
+
+void ThreadSuspender::KillAllThreads() {
+  for (uptr i = 0; i < suspended_threads_list_.thread_count(); i++)
+    internal_ptrace(PTRACE_KILL, suspended_threads_list_.GetThreadID(i),
+                    NULL, NULL);
+}
+
+bool ThreadSuspender::SuspendAllThreads() {
+  ThreadLister thread_lister(pid_);
+  bool added_threads;
+  do {
+    // Run through the directory entries once.
+    added_threads = false;
+    pid_t tid = thread_lister.GetNextTID();
+    while (tid >= 0) {
+      if (SuspendThread(tid))
+        added_threads = true;
+      tid = thread_lister.GetNextTID();
+    }
+    if (thread_lister.error()) {
+      // Detach threads and fail.
+      ResumeAllThreads();
+      return false;
+    }
+    thread_lister.Reset();
+  } while (added_threads);
+  return true;
+}
+
+// Pointer to the ThreadSuspender instance for use in signal handler.
+static ThreadSuspender *thread_suspender_instance = NULL;
+
+// Signals that should not be blocked (this is used in the parent thread as well
+// as the tracer thread).
+static const int kUnblockedSignals[] = { SIGABRT, SIGILL, SIGFPE, SIGSEGV,
+                                         SIGBUS, SIGXCPU, SIGXFSZ };
+
+// Structure for passing arguments into the tracer thread.
+struct TracerThreadArgument {
+  StopTheWorldCallback callback;
+  void *callback_argument;
+  // The tracer thread waits on this mutex while the parent finishes its
+  // preparations.
+  BlockingMutex mutex;
+  uptr parent_pid;
+};
+
+static DieCallbackType old_die_callback;
+
+// Signal handler to wake up suspended threads when the tracer thread dies.
+void TracerThreadSignalHandler(int signum, void *siginfo, void *) {
+  if (thread_suspender_instance != NULL) {
+    if (signum == SIGABRT)
+      thread_suspender_instance->KillAllThreads();
+    else
+      thread_suspender_instance->ResumeAllThreads();
+  }
+  internal__exit((signum == SIGABRT) ? 1 : 2);
+}
+
+static void TracerThreadDieCallback() {
+  // Generally a call to Die() in the tracer thread should be fatal to the
+  // parent process as well, because they share the address space.
+  // This really only works correctly if all the threads are suspended at this
+  // point. So we correctly handle calls to Die() from within the callback, but
+  // not those that happen before or after the callback. Hopefully there aren't
+  // a lot of opportunities for that to happen...
+  if (thread_suspender_instance)
+    thread_suspender_instance->KillAllThreads();
+  if (old_die_callback)
+    old_die_callback();
+}
+
+// Size of alternative stack for signal handlers in the tracer thread.
+static const int kHandlerStackSize = 4096;
+
+// This function will be run as a cloned task.
+static int TracerThread(void* argument) {
+  TracerThreadArgument *tracer_thread_argument =
+      (TracerThreadArgument *)argument;
+
+  internal_prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
+  // Check if parent is already dead.
+  if (internal_getppid() != tracer_thread_argument->parent_pid)
+    internal__exit(4);
+
+  // Wait for the parent thread to finish preparations.
+  tracer_thread_argument->mutex.Lock();
+  tracer_thread_argument->mutex.Unlock();
+
+  SetDieCallback(TracerThreadDieCallback);
+
+  ThreadSuspender thread_suspender(internal_getppid());
+  // Global pointer for the signal handler.
+  thread_suspender_instance = &thread_suspender;
+
+  // Alternate stack for signal handling.
+  InternalScopedBuffer<char> handler_stack_memory(kHandlerStackSize);
+  struct sigaltstack handler_stack;
+  internal_memset(&handler_stack, 0, sizeof(handler_stack));
+  handler_stack.ss_sp = handler_stack_memory.data();
+  handler_stack.ss_size = kHandlerStackSize;
+  internal_sigaltstack(&handler_stack, NULL);
+
+  // Install our handler for fatal signals. Other signals should be blocked by
+  // the mask we inherited from the caller thread.
+  for (uptr signal_index = 0; signal_index < ARRAY_SIZE(kUnblockedSignals);
+       signal_index++) {
+    __sanitizer_kernel_sigaction_t new_sigaction;
+    internal_memset(&new_sigaction, 0, sizeof(new_sigaction));
+    new_sigaction.sigaction = TracerThreadSignalHandler;
+    new_sigaction.sa_flags = SA_ONSTACK | SA_SIGINFO;
+    internal_sigfillset(&new_sigaction.sa_mask);
+    internal_sigaction(kUnblockedSignals[signal_index], &new_sigaction, NULL);
+  }
+
+  int exit_code = 0;
+  if (!thread_suspender.SuspendAllThreads()) {
+    if (common_flags()->verbosity)
+      Report("Failed suspending threads.\n");
+    exit_code = 3;
+  } else {
+    tracer_thread_argument->callback(thread_suspender.suspended_threads_list(),
+                                     tracer_thread_argument->callback_argument);
+    thread_suspender.ResumeAllThreads();
+    exit_code = 0;
+  }
+  thread_suspender_instance = NULL;
+  handler_stack.ss_flags = SS_DISABLE;
+  internal_sigaltstack(&handler_stack, NULL);
+  return exit_code;
+}
+
+class ScopedStackSpaceWithGuard {
+ public:
+  explicit ScopedStackSpaceWithGuard(uptr stack_size) {
+    stack_size_ = stack_size;
+    guard_size_ = GetPageSizeCached();
+    // FIXME: Omitting MAP_STACK here works in current kernels but might break
+    // in the future.
+    guard_start_ = (uptr)MmapOrDie(stack_size_ + guard_size_,
+                                   "ScopedStackWithGuard");
+    CHECK_EQ(guard_start_, (uptr)Mprotect((uptr)guard_start_, guard_size_));
+  }
+  ~ScopedStackSpaceWithGuard() {
+    UnmapOrDie((void *)guard_start_, stack_size_ + guard_size_);
+  }
+  void *Bottom() const {
+    return (void *)(guard_start_ + stack_size_ + guard_size_);
+  }
+
+ private:
+  uptr stack_size_;
+  uptr guard_size_;
+  uptr guard_start_;
+};
+
+// We have a limitation on the stack frame size, so some stuff had to be moved
+// into globals.
+static __sanitizer_kernel_sigset_t blocked_sigset;
+static __sanitizer_kernel_sigset_t old_sigset;
+static __sanitizer_kernel_sigaction_t old_sigactions
+    [ARRAY_SIZE(kUnblockedSignals)];
+
+class StopTheWorldScope {
+ public:
+  StopTheWorldScope() {
+    // Block all signals that can be blocked safely, and install
+    // default handlers for the remaining signals.
+    // We cannot allow user-defined handlers to run while the ThreadSuspender
+    // thread is active, because they could conceivably call some libc functions
+    // which modify errno (which is shared between the two threads).
+    internal_sigfillset(&blocked_sigset);
+    for (uptr signal_index = 0; signal_index < ARRAY_SIZE(kUnblockedSignals);
+         signal_index++) {
+      // Remove the signal from the set of blocked signals.
+      internal_sigdelset(&blocked_sigset, kUnblockedSignals[signal_index]);
+      // Install the default handler.
+      __sanitizer_kernel_sigaction_t new_sigaction;
+      internal_memset(&new_sigaction, 0, sizeof(new_sigaction));
+      new_sigaction.handler = SIG_DFL;
+      internal_sigfillset(&new_sigaction.sa_mask);
+      internal_sigaction(kUnblockedSignals[signal_index], &new_sigaction,
+                      &old_sigactions[signal_index]);
+    }
+    int sigprocmask_status =
+        internal_sigprocmask(SIG_BLOCK, &blocked_sigset, &old_sigset);
+    CHECK_EQ(sigprocmask_status, 0); // sigprocmask should never fail
+    // Make this process dumpable. Processes that are not dumpable cannot be
+    // attached to.
+    process_was_dumpable_ = internal_prctl(PR_GET_DUMPABLE, 0, 0, 0, 0);
+    if (!process_was_dumpable_)
+      internal_prctl(PR_SET_DUMPABLE, 1, 0, 0, 0);
+    old_die_callback = GetDieCallback();
+  }
+
+  ~StopTheWorldScope() {
+    SetDieCallback(old_die_callback);
+    // Restore the dumpable flag.
+    if (!process_was_dumpable_)
+      internal_prctl(PR_SET_DUMPABLE, 0, 0, 0, 0);
+    // Restore the signal handlers.
+    for (uptr signal_index = 0; signal_index < ARRAY_SIZE(kUnblockedSignals);
+         signal_index++) {
+      internal_sigaction(kUnblockedSignals[signal_index],
+                &old_sigactions[signal_index], NULL);
+    }
+    internal_sigprocmask(SIG_SETMASK, &old_sigset, &old_sigset);
+  }
+
+ private:
+  int process_was_dumpable_;
+};
+
+// When sanitizer output is being redirected to file (i.e. by using log_path),
+// the tracer should write to the parent's log instead of trying to open a new
+// file. Alert the logging code to the fact that we have a tracer.
+struct ScopedSetTracerPID {
+  explicit ScopedSetTracerPID(uptr tracer_pid) {
+    stoptheworld_tracer_pid = tracer_pid;
+    stoptheworld_tracer_ppid = internal_getpid();
+  }
+  ~ScopedSetTracerPID() {
+    stoptheworld_tracer_pid = 0;
+    stoptheworld_tracer_ppid = 0;
+  }
+};
+
+void StopTheWorld(StopTheWorldCallback callback, void *argument) {
+  StopTheWorldScope in_stoptheworld;
+  // Prepare the arguments for TracerThread.
+  struct TracerThreadArgument tracer_thread_argument;
+  tracer_thread_argument.callback = callback;
+  tracer_thread_argument.callback_argument = argument;
+  tracer_thread_argument.parent_pid = internal_getpid();
+  const uptr kTracerStackSize = 2 * 1024 * 1024;
+  ScopedStackSpaceWithGuard tracer_stack(kTracerStackSize);
+  // Block the execution of TracerThread until after we have set ptrace
+  // permissions.
+  tracer_thread_argument.mutex.Lock();
+  uptr tracer_pid = internal_clone(
+      TracerThread, tracer_stack.Bottom(),
+      CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_UNTRACED,
+      &tracer_thread_argument, 0 /* parent_tidptr */, 0 /* newtls */, 0
+      /* child_tidptr */);
+  int local_errno = 0;
+  if (internal_iserror(tracer_pid, &local_errno)) {
+    if (common_flags()->verbosity)
+      Report("Failed spawning a tracer thread (errno %d).\n", local_errno);
+    tracer_thread_argument.mutex.Unlock();
+  } else {
+    ScopedSetTracerPID scoped_set_tracer_pid(tracer_pid);
+    // On some systems we have to explicitly declare that we want to be traced
+    // by the tracer thread.
+#ifdef PR_SET_PTRACER
+    internal_prctl(PR_SET_PTRACER, tracer_pid, 0, 0, 0);
+#endif
+    // Allow the tracer thread to start.
+    tracer_thread_argument.mutex.Unlock();
+    // Since errno is shared between this thread and the tracer thread, we
+    // must avoid using errno while the tracer thread is running.
+    // At this point, any signal will either be blocked or kill us, so waitpid
+    // should never return (and set errno) while the tracer thread is alive.
+    uptr waitpid_status = internal_waitpid(tracer_pid, NULL, __WALL);
+    if (internal_iserror(waitpid_status, &local_errno)) {
+      if (common_flags()->verbosity)
+        Report("Waiting on the tracer thread failed (errno %d).\n",
+            local_errno);
+    }
+  }
+}
+
+// Platform-specific methods from SuspendedThreadsList.
+#if SANITIZER_ANDROID && defined(__arm__)
+typedef pt_regs regs_struct;
+#define REG_SP ARM_sp
+
+#elif SANITIZER_LINUX && defined(__arm__)
+typedef user_regs regs_struct;
+#define REG_SP uregs[13]
+
+#elif defined(__i386__) || defined(__x86_64__)
+typedef user_regs_struct regs_struct;
+#if defined(__i386__)
+#define REG_SP esp
+#else
+#define REG_SP rsp
+#endif
+
+#elif defined(__powerpc__) || defined(__powerpc64__)
+typedef pt_regs regs_struct;
+#define REG_SP gpr[PT_R1]
+
+#elif defined(__mips__)
+typedef struct user regs_struct;
+#define REG_SP regs[EF_REG29]
+
+#else
+#error "Unsupported architecture"
+#endif // SANITIZER_ANDROID && defined(__arm__)
+
+int SuspendedThreadsList::GetRegistersAndSP(uptr index,
+                                            uptr *buffer,
+                                            uptr *sp) const {
+  pid_t tid = GetThreadID(index);
+  regs_struct regs;
+  int pterrno;
+  if (internal_iserror(internal_ptrace(PTRACE_GETREGS, tid, NULL, &regs),
+                       &pterrno)) {
+    if (common_flags()->verbosity)
+      Report("Could not get registers from thread %d (errno %d).\n",
+           tid, pterrno);
+    return -1;
+  }
+
+  *sp = regs.REG_SP;
+  internal_memcpy(buffer, &regs, sizeof(regs));
+  return 0;
+}
+
+uptr SuspendedThreadsList::RegisterCount() {
+  return sizeof(regs_struct) / sizeof(uptr);
+}
+}  // namespace __sanitizer
+
+#endif  // SANITIZER_LINUX && defined(__x86_64__)