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diff --git a/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cpp b/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cpp
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+//===-- sanitizer_stoptheworld_linux_libcdep.cpp --------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// 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__) || defined(__mips__) || \
+ defined(__aarch64__) || defined(__powerpc64__) || \
+ defined(__s390__) || defined(__i386__) || \
+ defined(__arm__))
+
+#include "sanitizer_stoptheworld.h"
+
+#include "sanitizer_platform_limits_posix.h"
+#include "sanitizer_atomic.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
+#include <sys/uio.h> // for iovec
+#include <elf.h> // for NT_PRSTATUS
+#if defined(__aarch64__) && !SANITIZER_ANDROID
+// GLIBC 2.20+ sys/user does not include asm/ptrace.h
+# include <asm/ptrace.h>
+#endif
+#include <sys/user.h> // for user_regs_struct
+#if SANITIZER_ANDROID && SANITIZER_MIPS
+# include <asm/reg.h> // for mips SP register in sys/user.h
+#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"
+
+// Sufficiently old kernel headers don't provide this value, but we can still
+// call prctl with it. If the runtime kernel is new enough, the prctl call will
+// have the desired effect; if the kernel is too old, the call will error and we
+// can ignore said error.
+#ifndef PR_SET_PTRACER
+#define PR_SET_PTRACER 0x59616d61
+#endif
+
+// 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.
+
+namespace __sanitizer {
+
+class SuspendedThreadsListLinux : public SuspendedThreadsList {
+ public:
+ SuspendedThreadsListLinux() { thread_ids_.reserve(1024); }
+
+ tid_t GetThreadID(uptr index) const;
+ uptr ThreadCount() const;
+ bool ContainsTid(tid_t thread_id) const;
+ void Append(tid_t tid);
+
+ PtraceRegistersStatus GetRegistersAndSP(uptr index, uptr *buffer,
+ uptr *sp) const;
+ uptr RegisterCount() const;
+
+ private:
+ InternalMmapVector<tid_t> thread_ids_;
+};
+
+// 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;
+ // Tracer thread signals its completion by setting done.
+ atomic_uintptr_t done;
+ uptr parent_pid;
+};
+
+// This class handles thread suspending/unsuspending in the tracer thread.
+class ThreadSuspender {
+ public:
+ explicit ThreadSuspender(pid_t pid, TracerThreadArgument *arg)
+ : arg(arg)
+ , pid_(pid) {
+ CHECK_GE(pid, 0);
+ }
+ bool SuspendAllThreads();
+ void ResumeAllThreads();
+ void KillAllThreads();
+ SuspendedThreadsListLinux &suspended_threads_list() {
+ return suspended_threads_list_;
+ }
+ TracerThreadArgument *arg;
+ private:
+ SuspendedThreadsListLinux suspended_threads_list_;
+ pid_t pid_;
+ bool SuspendThread(tid_t thread_id);
+};
+
+bool ThreadSuspender::SuspendThread(tid_t tid) {
+ // 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_.ContainsTid(tid)) return false;
+ int pterrno;
+ if (internal_iserror(internal_ptrace(PTRACE_ATTACH, tid, nullptr, nullptr),
+ &pterrno)) {
+ // Either the thread is dead, or something prevented us from attaching.
+ // Log this event and move on.
+ VReport(1, "Could not attach to thread %zu (errno %d).\n", (uptr)tid,
+ pterrno);
+ return false;
+ } else {
+ VReport(2, "Attached to thread %zu.\n", (uptr)tid);
+ // The thread is not guaranteed to stop before ptrace returns, so we must
+ // wait on it. Note: if the thread receives a signal concurrently,
+ // we can get notification about the signal before notification about stop.
+ // In such case we need to forward the signal to the thread, otherwise
+ // the signal will be missed (as we do PTRACE_DETACH with arg=0) and
+ // any logic relying on signals will break. After forwarding we need to
+ // continue to wait for stopping, because the thread is not stopped yet.
+ // We do ignore delivery of SIGSTOP, because we want to make stop-the-world
+ // as invisible as possible.
+ for (;;) {
+ int status;
+ uptr waitpid_status;
+ HANDLE_EINTR(waitpid_status, internal_waitpid(tid, &status, __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.
+ VReport(1, "Waiting on thread %zu failed, detaching (errno %d).\n",
+ (uptr)tid, wperrno);
+ internal_ptrace(PTRACE_DETACH, tid, nullptr, nullptr);
+ return false;
+ }
+ if (WIFSTOPPED(status) && WSTOPSIG(status) != SIGSTOP) {
+ internal_ptrace(PTRACE_CONT, tid, nullptr,
+ (void*)(uptr)WSTOPSIG(status));
+ continue;
+ }
+ break;
+ }
+ suspended_threads_list_.Append(tid);
+ return true;
+ }
+}
+
+void ThreadSuspender::ResumeAllThreads() {
+ for (uptr i = 0; i < suspended_threads_list_.ThreadCount(); i++) {
+ pid_t tid = suspended_threads_list_.GetThreadID(i);
+ int pterrno;
+ if (!internal_iserror(internal_ptrace(PTRACE_DETACH, tid, nullptr, nullptr),
+ &pterrno)) {
+ VReport(2, "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.
+ VReport(1, "Could not detach from thread %d (errno %d).\n", tid, pterrno);
+ }
+ }
+}
+
+void ThreadSuspender::KillAllThreads() {
+ for (uptr i = 0; i < suspended_threads_list_.ThreadCount(); i++)
+ internal_ptrace(PTRACE_KILL, suspended_threads_list_.GetThreadID(i),
+ nullptr, nullptr);
+}
+
+bool ThreadSuspender::SuspendAllThreads() {
+ ThreadLister thread_lister(pid_);
+ bool retry = true;
+ InternalMmapVector<tid_t> threads;
+ threads.reserve(128);
+ for (int i = 0; i < 30 && retry; ++i) {
+ retry = false;
+ switch (thread_lister.ListThreads(&threads)) {
+ case ThreadLister::Error:
+ ResumeAllThreads();
+ return false;
+ case ThreadLister::Incomplete:
+ retry = true;
+ break;
+ case ThreadLister::Ok:
+ break;
+ }
+ for (tid_t tid : threads) {
+ if (SuspendThread(tid))
+ retry = true;
+ }
+ }
+ return suspended_threads_list_.ThreadCount();
+}
+
+// Pointer to the ThreadSuspender instance for use in signal handler.
+static ThreadSuspender *thread_suspender_instance = nullptr;
+
+// Synchronous signals that should not be blocked.
+static const int kSyncSignals[] = { SIGABRT, SIGILL, SIGFPE, SIGSEGV, SIGBUS,
+ SIGXCPU, SIGXFSZ };
+
+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...
+ ThreadSuspender *inst = thread_suspender_instance;
+ if (inst && stoptheworld_tracer_pid == internal_getpid()) {
+ inst->KillAllThreads();
+ thread_suspender_instance = nullptr;
+ }
+}
+
+// Signal handler to wake up suspended threads when the tracer thread dies.
+static void TracerThreadSignalHandler(int signum, __sanitizer_siginfo *siginfo,
+ void *uctx) {
+ SignalContext ctx(siginfo, uctx);
+ Printf("Tracer caught signal %d: addr=0x%zx pc=0x%zx sp=0x%zx\n", signum,
+ ctx.addr, ctx.pc, ctx.sp);
+ ThreadSuspender *inst = thread_suspender_instance;
+ if (inst) {
+ if (signum == SIGABRT)
+ inst->KillAllThreads();
+ else
+ inst->ResumeAllThreads();
+ RAW_CHECK(RemoveDieCallback(TracerThreadDieCallback));
+ thread_suspender_instance = nullptr;
+ atomic_store(&inst->arg->done, 1, memory_order_relaxed);
+ }
+ internal__exit((signum == SIGABRT) ? 1 : 2);
+}
+
+// Size of alternative stack for signal handlers in the tracer thread.
+static const int kHandlerStackSize = 8192;
+
+// 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();
+
+ RAW_CHECK(AddDieCallback(TracerThreadDieCallback));
+
+ ThreadSuspender thread_suspender(internal_getppid(), tracer_thread_argument);
+ // Global pointer for the signal handler.
+ thread_suspender_instance = &thread_suspender;
+
+ // Alternate stack for signal handling.
+ InternalMmapVector<char> handler_stack_memory(kHandlerStackSize);
+ stack_t 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, nullptr);
+
+ // Install our handler for synchronous signals. Other signals should be
+ // blocked by the mask we inherited from the parent thread.
+ for (uptr i = 0; i < ARRAY_SIZE(kSyncSignals); i++) {
+ __sanitizer_sigaction act;
+ internal_memset(&act, 0, sizeof(act));
+ act.sigaction = TracerThreadSignalHandler;
+ act.sa_flags = SA_ONSTACK | SA_SIGINFO;
+ internal_sigaction_norestorer(kSyncSignals[i], &act, 0);
+ }
+
+ int exit_code = 0;
+ if (!thread_suspender.SuspendAllThreads()) {
+ VReport(1, "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;
+ }
+ RAW_CHECK(RemoveDieCallback(TracerThreadDieCallback));
+ thread_suspender_instance = nullptr;
+ atomic_store(&tracer_thread_argument->done, 1, memory_order_relaxed);
+ 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(MprotectNoAccess((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_sigset_t blocked_sigset;
+static __sanitizer_sigset_t old_sigset;
+
+class StopTheWorldScope {
+ public:
+ StopTheWorldScope() {
+ // 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);
+ }
+
+ ~StopTheWorldScope() {
+ // Restore the dumpable flag.
+ if (!process_was_dumpable_)
+ internal_prctl(PR_SET_DUMPABLE, 0, 0, 0, 0);
+ }
+
+ 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();
+ atomic_store(&tracer_thread_argument.done, 0, memory_order_relaxed);
+ 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();
+ // Signal handling story.
+ // We don't want async signals to be delivered to the tracer thread,
+ // so we block all async signals before creating the thread. An async signal
+ // handler can temporary modify errno, which is shared with this thread.
+ // We ought to use pthread_sigmask here, because sigprocmask has undefined
+ // behavior in multithreaded programs. However, on linux sigprocmask is
+ // equivalent to pthread_sigmask with the exception that pthread_sigmask
+ // does not allow to block some signals used internally in pthread
+ // implementation. We are fine with blocking them here, we are really not
+ // going to pthread_cancel the thread.
+ // The tracer thread should not raise any synchronous signals. But in case it
+ // does, we setup a special handler for sync signals that properly kills the
+ // parent as well. Note: we don't pass CLONE_SIGHAND to clone, so handlers
+ // in the tracer thread won't interfere with user program. Double note: if a
+ // user does something along the lines of 'kill -11 pid', that can kill the
+ // process even if user setup own handler for SEGV.
+ // Thing to watch out for: this code should not change behavior of user code
+ // in any observable way. In particular it should not override user signal
+ // handlers.
+ internal_sigfillset(&blocked_sigset);
+ for (uptr i = 0; i < ARRAY_SIZE(kSyncSignals); i++)
+ internal_sigdelset(&blocked_sigset, kSyncSignals[i]);
+ int rv = internal_sigprocmask(SIG_BLOCK, &blocked_sigset, &old_sigset);
+ CHECK_EQ(rv, 0);
+ uptr tracer_pid = internal_clone(
+ TracerThread, tracer_stack.Bottom(),
+ CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_UNTRACED,
+ &tracer_thread_argument, nullptr /* parent_tidptr */,
+ nullptr /* newtls */, nullptr /* child_tidptr */);
+ internal_sigprocmask(SIG_SETMASK, &old_sigset, 0);
+ int local_errno = 0;
+ if (internal_iserror(tracer_pid, &local_errno)) {
+ VReport(1, "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.
+ internal_prctl(PR_SET_PTRACER, tracer_pid, 0, 0, 0);
+ // Allow the tracer thread to start.
+ tracer_thread_argument.mutex.Unlock();
+ // NOTE: errno is shared between this thread and the tracer thread.
+ // internal_waitpid() may call syscall() which can access/spoil errno,
+ // so we can't call it now. Instead we for the tracer thread to finish using
+ // the spin loop below. Man page for sched_yield() says "In the Linux
+ // implementation, sched_yield() always succeeds", so let's hope it does not
+ // spoil errno. Note that this spin loop runs only for brief periods before
+ // the tracer thread has suspended us and when it starts unblocking threads.
+ while (atomic_load(&tracer_thread_argument.done, memory_order_relaxed) == 0)
+ sched_yield();
+ // Now the tracer thread is about to exit and does not touch errno,
+ // wait for it.
+ for (;;) {
+ uptr waitpid_status = internal_waitpid(tracer_pid, nullptr, __WALL);
+ if (!internal_iserror(waitpid_status, &local_errno))
+ break;
+ if (local_errno == EINTR)
+ continue;
+ VReport(1, "Waiting on the tracer thread failed (errno %d).\n",
+ local_errno);
+ break;
+ }
+ }
+}
+
+// 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;
+# if SANITIZER_ANDROID
+# define REG_SP regs[EF_R29]
+# else
+# define REG_SP regs[EF_REG29]
+# endif
+
+#elif defined(__aarch64__)
+typedef struct user_pt_regs regs_struct;
+#define REG_SP sp
+#define ARCH_IOVEC_FOR_GETREGSET
+
+#elif defined(__s390__)
+typedef _user_regs_struct regs_struct;
+#define REG_SP gprs[15]
+#define ARCH_IOVEC_FOR_GETREGSET
+
+#else
+#error "Unsupported architecture"
+#endif // SANITIZER_ANDROID && defined(__arm__)
+
+tid_t SuspendedThreadsListLinux::GetThreadID(uptr index) const {
+ CHECK_LT(index, thread_ids_.size());
+ return thread_ids_[index];
+}
+
+uptr SuspendedThreadsListLinux::ThreadCount() const {
+ return thread_ids_.size();
+}
+
+bool SuspendedThreadsListLinux::ContainsTid(tid_t thread_id) const {
+ for (uptr i = 0; i < thread_ids_.size(); i++) {
+ if (thread_ids_[i] == thread_id) return true;
+ }
+ return false;
+}
+
+void SuspendedThreadsListLinux::Append(tid_t tid) {
+ thread_ids_.push_back(tid);
+}
+
+PtraceRegistersStatus SuspendedThreadsListLinux::GetRegistersAndSP(
+ uptr index, uptr *buffer, uptr *sp) const {
+ pid_t tid = GetThreadID(index);
+ regs_struct regs;
+ int pterrno;
+#ifdef ARCH_IOVEC_FOR_GETREGSET
+ struct iovec regset_io;
+ regset_io.iov_base = &regs;
+ regset_io.iov_len = sizeof(regs_struct);
+ bool isErr = internal_iserror(internal_ptrace(PTRACE_GETREGSET, tid,
+ (void*)NT_PRSTATUS, (void*)&regset_io),
+ &pterrno);
+#else
+ bool isErr = internal_iserror(internal_ptrace(PTRACE_GETREGS, tid, nullptr,
+ &regs), &pterrno);
+#endif
+ if (isErr) {
+ VReport(1, "Could not get registers from thread %d (errno %d).\n", tid,
+ pterrno);
+ // ESRCH means that the given thread is not suspended or already dead.
+ // Therefore it's unsafe to inspect its data (e.g. walk through stack) and
+ // we should notify caller about this.
+ return pterrno == ESRCH ? REGISTERS_UNAVAILABLE_FATAL
+ : REGISTERS_UNAVAILABLE;
+ }
+
+ *sp = regs.REG_SP;
+ internal_memcpy(buffer, &regs, sizeof(regs));
+ return REGISTERS_AVAILABLE;
+}
+
+uptr SuspendedThreadsListLinux::RegisterCount() const {
+ return sizeof(regs_struct) / sizeof(uptr);
+}
+} // namespace __sanitizer
+
+#endif // SANITIZER_LINUX && (defined(__x86_64__) || defined(__mips__)
+ // || defined(__aarch64__) || defined(__powerpc64__)
+ // || defined(__s390__) || defined(__i386__) || defined(__arm__)