libsanitizer/sanitizer_common/sanitizer_stoptheworld_netbsd_libcdep.cpp

   1 //===-- sanitizer_stoptheworld_netbsd_libcdep.cpp -------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // See sanitizer_stoptheworld.h for details.
  10 // This implementation was inspired by Markus Gutschke's linuxthreads.cc.
  11 //
  12 // This is a NetBSD variation of Linux stoptheworld implementation
  13 // See sanitizer_stoptheworld_linux_libcdep.cpp for code comments.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "sanitizer_platform.h"
  18
  19 #if SANITIZER_NETBSD
  20
  21 #include "sanitizer_stoptheworld.h"
  22
  23 #include "sanitizer_atomic.h"
  24 #include "sanitizer_platform_limits_posix.h"
  25
  26 #include <sys/types.h>
  27
  28 #include <sys/ptrace.h>
  29 #include <sys/uio.h>
  30 #include <sys/wait.h>
  31
  32 #include <machine/reg.h>
  33
  34 #include <elf.h>
  35 #include <errno.h>
  36 #include <sched.h>
  37 #include <signal.h>
  38 #include <stddef.h>
  39
  40 #define internal_sigaction_norestorer internal_sigaction
  41
  42 #include "sanitizer_common.h"
  43 #include "sanitizer_flags.h"
  44 #include "sanitizer_libc.h"
  45 #include "sanitizer_linux.h"
  46 #include "sanitizer_mutex.h"
  47 #include "sanitizer_placement_new.h"
  48
  49 namespace __sanitizer {
  50
  51 class SuspendedThreadsListNetBSD : public SuspendedThreadsList {
  52  public:
  53   SuspendedThreadsListNetBSD() { thread_ids_.reserve(1024); }
  54
  55   tid_t GetThreadID(uptr index) const;
  56   uptr ThreadCount() const;
  57   bool ContainsTid(tid_t thread_id) const;
  58   void Append(tid_t tid);
  59
  60   PtraceRegistersStatus GetRegistersAndSP(uptr index, uptr *buffer,
  61                                           uptr *sp) const;
  62   uptr RegisterCount() const;
  63
  64  private:
  65   InternalMmapVector<tid_t> thread_ids_;
  66 };
  67
  68 struct TracerThreadArgument {
  69   StopTheWorldCallback callback;
  70   void *callback_argument;
  71   BlockingMutex mutex;
  72   atomic_uintptr_t done;
  73   uptr parent_pid;
  74 };
  75
  76 class ThreadSuspender {
  77  public:
  78   explicit ThreadSuspender(pid_t pid, TracerThreadArgument *arg)
  79       : arg(arg), pid_(pid) {
  80     CHECK_GE(pid, 0);
  81   }
  82   bool SuspendAllThreads();
  83   void ResumeAllThreads();
  84   void KillAllThreads();
  85   SuspendedThreadsListNetBSD &suspended_threads_list() {
  86     return suspended_threads_list_;
  87   }
  88   TracerThreadArgument *arg;
  89
  90  private:
  91   SuspendedThreadsListNetBSD suspended_threads_list_;
  92   pid_t pid_;
  93 };
  94
  95 void ThreadSuspender::ResumeAllThreads() {
  96   int pterrno;
  97   if (!internal_iserror(internal_ptrace(PT_DETACH, pid_, (void *)(uptr)1, 0),
  98                         &pterrno)) {
  99     VReport(2, "Detached from process %d.\n", pid_);
 100   } else {
 101     VReport(1, "Could not detach from process %d (errno %d).\n", pid_, pterrno);
 102   }
 103 }
 104
 105 void ThreadSuspender::KillAllThreads() {
 106   internal_ptrace(PT_KILL, pid_, nullptr, 0);
 107 }
 108
 109 bool ThreadSuspender::SuspendAllThreads() {
 110   int pterrno;
 111   if (internal_iserror(internal_ptrace(PT_ATTACH, pid_, nullptr, 0),
 112                        &pterrno)) {
 113     Printf("Could not attach to process %d (errno %d).\n", pid_, pterrno);
 114     return false;
 115   }
 116
 117   int status;
 118   uptr waitpid_status;
 119   HANDLE_EINTR(waitpid_status, internal_waitpid(pid_, &status, 0));
 120
 121   VReport(2, "Attached to process %d.\n", pid_);
 122
 123   struct ptrace_lwpinfo pl;
 124   int val;
 125   pl.pl_lwpid = 0;
 126   while ((val = ptrace(PT_LWPINFO, pid_, (void *)&pl, sizeof(pl))) != -1 &&
 127          pl.pl_lwpid != 0) {
 128     suspended_threads_list_.Append(pl.pl_lwpid);
 129     VReport(2, "Appended thread %d in process %d.\n", pl.pl_lwpid, pid_);
 130   }
 131   return true;
 132 }
 133
 134 // Pointer to the ThreadSuspender instance for use in signal handler.
 135 static ThreadSuspender *thread_suspender_instance = nullptr;
 136
 137 // Synchronous signals that should not be blocked.
 138 static const int kSyncSignals[] = {SIGABRT, SIGILL,  SIGFPE, SIGSEGV,
 139                                    SIGBUS,  SIGXCPU, SIGXFSZ};
 140
 141 static void TracerThreadDieCallback() {
 142   ThreadSuspender *inst = thread_suspender_instance;
 143   if (inst && stoptheworld_tracer_pid == internal_getpid()) {
 144     inst->KillAllThreads();
 145     thread_suspender_instance = nullptr;
 146   }
 147 }
 148
 149 // Signal handler to wake up suspended threads when the tracer thread dies.
 150 static void TracerThreadSignalHandler(int signum, __sanitizer_siginfo *siginfo,
 151                                       void *uctx) {
 152   SignalContext ctx(siginfo, uctx);
 153   Printf("Tracer caught signal %d: addr=0x%zx pc=0x%zx sp=0x%zx\n", signum,
 154          ctx.addr, ctx.pc, ctx.sp);
 155   ThreadSuspender *inst = thread_suspender_instance;
 156   if (inst) {
 157     if (signum == SIGABRT)
 158       inst->KillAllThreads();
 159     else
 160       inst->ResumeAllThreads();
 161     RAW_CHECK(RemoveDieCallback(TracerThreadDieCallback));
 162     thread_suspender_instance = nullptr;
 163     atomic_store(&inst->arg->done, 1, memory_order_relaxed);
 164   }
 165   internal__exit((signum == SIGABRT) ? 1 : 2);
 166 }
 167
 168 // Size of alternative stack for signal handlers in the tracer thread.
 169 static const int kHandlerStackSize = 8192;
 170
 171 // This function will be run as a cloned task.
 172 static int TracerThread(void *argument) {
 173   TracerThreadArgument *tracer_thread_argument =
 174       (TracerThreadArgument *)argument;
 175
 176   // Check if parent is already dead.
 177   if (internal_getppid() != tracer_thread_argument->parent_pid)
 178     internal__exit(4);
 179
 180   // Wait for the parent thread to finish preparations.
 181   tracer_thread_argument->mutex.Lock();
 182   tracer_thread_argument->mutex.Unlock();
 183
 184   RAW_CHECK(AddDieCallback(TracerThreadDieCallback));
 185
 186   ThreadSuspender thread_suspender(internal_getppid(), tracer_thread_argument);
 187   // Global pointer for the signal handler.
 188   thread_suspender_instance = &thread_suspender;
 189
 190   // Alternate stack for signal handling.
 191   InternalMmapVector<char> handler_stack_memory(kHandlerStackSize);
 192   stack_t handler_stack;
 193   internal_memset(&handler_stack, 0, sizeof(handler_stack));
 194   handler_stack.ss_sp = handler_stack_memory.data();
 195   handler_stack.ss_size = kHandlerStackSize;
 196   internal_sigaltstack(&handler_stack, nullptr);
 197
 198   // Install our handler for synchronous signals. Other signals should be
 199   // blocked by the mask we inherited from the parent thread.
 200   for (uptr i = 0; i < ARRAY_SIZE(kSyncSignals); i++) {
 201     __sanitizer_sigaction act;
 202     internal_memset(&act, 0, sizeof(act));
 203     act.sigaction = TracerThreadSignalHandler;
 204     act.sa_flags = SA_ONSTACK | SA_SIGINFO;
 205     internal_sigaction_norestorer(kSyncSignals[i], &act, 0);
 206   }
 207
 208   int exit_code = 0;
 209   if (!thread_suspender.SuspendAllThreads()) {
 210     VReport(1, "Failed suspending threads.\n");
 211     exit_code = 3;
 212   } else {
 213     tracer_thread_argument->callback(thread_suspender.suspended_threads_list(),
 214                                      tracer_thread_argument->callback_argument);
 215     thread_suspender.ResumeAllThreads();
 216     exit_code = 0;
 217   }
 218   RAW_CHECK(RemoveDieCallback(TracerThreadDieCallback));
 219   thread_suspender_instance = nullptr;
 220   atomic_store(&tracer_thread_argument->done, 1, memory_order_relaxed);
 221   return exit_code;
 222 }
 223
 224 class ScopedStackSpaceWithGuard {
 225  public:
 226   explicit ScopedStackSpaceWithGuard(uptr stack_size) {
 227     stack_size_ = stack_size;
 228     guard_size_ = GetPageSizeCached();
 229     // FIXME: Omitting MAP_STACK here works in current kernels but might break
 230     // in the future.
 231     guard_start_ =
 232         (uptr)MmapOrDie(stack_size_ + guard_size_, "ScopedStackWithGuard");
 233     CHECK(MprotectNoAccess((uptr)guard_start_, guard_size_));
 234   }
 235   ~ScopedStackSpaceWithGuard() {
 236     UnmapOrDie((void *)guard_start_, stack_size_ + guard_size_);
 237   }
 238   void *Bottom() const {
 239     return (void *)(guard_start_ + stack_size_ + guard_size_);
 240   }
 241
 242  private:
 243   uptr stack_size_;
 244   uptr guard_size_;
 245   uptr guard_start_;
 246 };
 247
 248 static __sanitizer_sigset_t blocked_sigset;
 249 static __sanitizer_sigset_t old_sigset;
 250
 251 struct ScopedSetTracerPID {
 252   explicit ScopedSetTracerPID(uptr tracer_pid) {
 253     stoptheworld_tracer_pid = tracer_pid;
 254     stoptheworld_tracer_ppid = internal_getpid();
 255   }
 256   ~ScopedSetTracerPID() {
 257     stoptheworld_tracer_pid = 0;
 258     stoptheworld_tracer_ppid = 0;
 259   }
 260 };
 261
 262 void StopTheWorld(StopTheWorldCallback callback, void *argument) {
 263   // Prepare the arguments for TracerThread.
 264   struct TracerThreadArgument tracer_thread_argument;
 265   tracer_thread_argument.callback = callback;
 266   tracer_thread_argument.callback_argument = argument;
 267   tracer_thread_argument.parent_pid = internal_getpid();
 268   atomic_store(&tracer_thread_argument.done, 0, memory_order_relaxed);
 269   const uptr kTracerStackSize = 2 * 1024 * 1024;
 270   ScopedStackSpaceWithGuard tracer_stack(kTracerStackSize);
 271
 272   tracer_thread_argument.mutex.Lock();
 273
 274   internal_sigfillset(&blocked_sigset);
 275   for (uptr i = 0; i < ARRAY_SIZE(kSyncSignals); i++)
 276     internal_sigdelset(&blocked_sigset, kSyncSignals[i]);
 277   int rv = internal_sigprocmask(SIG_BLOCK, &blocked_sigset, &old_sigset);
 278   CHECK_EQ(rv, 0);
 279   uptr tracer_pid = internal_clone(TracerThread, tracer_stack.Bottom(),
 280                                    CLONE_VM | CLONE_FS | CLONE_FILES,
 281                                    &tracer_thread_argument);
 282   internal_sigprocmask(SIG_SETMASK, &old_sigset, 0);
 283   int local_errno = 0;
 284   if (internal_iserror(tracer_pid, &local_errno)) {
 285     VReport(1, "Failed spawning a tracer thread (errno %d).\n", local_errno);
 286     tracer_thread_argument.mutex.Unlock();
 287   } else {
 288     ScopedSetTracerPID scoped_set_tracer_pid(tracer_pid);
 289
 290     tracer_thread_argument.mutex.Unlock();
 291
 292     while (atomic_load(&tracer_thread_argument.done, memory_order_relaxed) == 0)
 293       sched_yield();
 294
 295     for (;;) {
 296       uptr waitpid_status = internal_waitpid(tracer_pid, nullptr, __WALL);
 297       if (!internal_iserror(waitpid_status, &local_errno))
 298         break;
 299       if (local_errno == EINTR)
 300         continue;
 301       VReport(1, "Waiting on the tracer thread failed (errno %d).\n",
 302               local_errno);
 303       break;
 304     }
 305   }
 306 }
 307
 308 tid_t SuspendedThreadsListNetBSD::GetThreadID(uptr index) const {
 309   CHECK_LT(index, thread_ids_.size());
 310   return thread_ids_[index];
 311 }
 312
 313 uptr SuspendedThreadsListNetBSD::ThreadCount() const {
 314   return thread_ids_.size();
 315 }
 316
 317 bool SuspendedThreadsListNetBSD::ContainsTid(tid_t thread_id) const {
 318   for (uptr i = 0; i < thread_ids_.size(); i++) {
 319     if (thread_ids_[i] == thread_id)
 320       return true;
 321   }
 322   return false;
 323 }
 324
 325 void SuspendedThreadsListNetBSD::Append(tid_t tid) {
 326   thread_ids_.push_back(tid);
 327 }
 328
 329 PtraceRegistersStatus SuspendedThreadsListNetBSD::GetRegistersAndSP(
 330     uptr index, uptr *buffer, uptr *sp) const {
 331   lwpid_t tid = GetThreadID(index);
 332   pid_t ppid = internal_getppid();
 333   struct reg regs;
 334   int pterrno;
 335   bool isErr =
 336       internal_iserror(internal_ptrace(PT_GETREGS, ppid, &regs, tid), &pterrno);
 337   if (isErr) {
 338     VReport(1,
 339             "Could not get registers from process %d thread %d (errno %d).\n",
 340             ppid, tid, pterrno);
 341     return pterrno == ESRCH ? REGISTERS_UNAVAILABLE_FATAL
 342                             : REGISTERS_UNAVAILABLE;
 343   }
 344
 345   *sp = PTRACE_REG_SP(&regs);
 346   internal_memcpy(buffer, &regs, sizeof(regs));
 347
 348   return REGISTERS_AVAILABLE;
 349 }
 350
 351 uptr SuspendedThreadsListNetBSD::RegisterCount() const {
 352   return sizeof(struct reg) / sizeof(uptr);
 353 }
 354 }  // namespace __sanitizer
 355
 356 #endif