FEX-Emu--FEX/Source/Tools/LinuxEmulation/LinuxSyscalls/Syscalls/Thread.cpp

// SPDX-License-Identifier: MIT
/*
$info$
tags: LinuxSyscalls|syscalls-shared
$end_info$
*/

#include "FEXCore/IR/IR.h"
#include "LinuxSyscalls/SignalDelegator.h"
#include "LinuxSyscalls/Syscalls.h"
#include "LinuxSyscalls/Syscalls/Thread.h"
#include "LinuxSyscalls/x64/Syscalls.h"
#include "LinuxSyscalls/x64/Thread.h"
#include "LinuxSyscalls/x32/Syscalls.h"
#include "LinuxSyscalls/x32/Thread.h"

#include <FEXCore/Core/Context.h>
#include <FEXCore/Core/CodeLoader.h>
#include <FEXCore/Core/X86Enums.h>
#include <FEXCore/Debug/InternalThreadState.h>
#include <FEXCore/IR/IR.h>

#include <FEXHeaderUtils/Syscalls.h>

#include <grp.h>
#include <limits.h>
#include <linux/futex.h>
#include <stdint.h>
#include <sched.h>
#include <sys/personality.h>
#include <sys/poll.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <unistd.h>
#include <sys/fsuid.h>

ARG_TO_STR(idtype_t, "%u")

namespace FEX::HLE {

  struct ExecutionThreadHandler {
    FEXCore::Context::Context *CTX;
    FEXCore::Core::InternalThreadState *Thread;
  };

  static void *ThreadHandler(void* Data) {
    ExecutionThreadHandler *Handler = reinterpret_cast<ExecutionThreadHandler*>(Data);
    auto CTX = Handler->CTX;
    auto Thread = Handler->Thread;
    FEXCore::Allocator::free(Handler);
    FEX::HLE::_SyscallHandler->GetSignalDelegator()->RegisterTLSState(Thread);
    CTX->ExecutionThread(Thread);
    FEX::HLE::_SyscallHandler->GetSignalDelegator()->UninstallTLSState(Thread);
    FEX::HLE::_SyscallHandler->TM.DestroyThread(Thread);
    return nullptr;
  }

  FEXCore::Core::InternalThreadState *CreateNewThread(FEXCore::Context:: Context *CTX, FEXCore::Core::CpuStateFrame *Frame, FEX::HLE::clone3_args *args) {
    uint64_t flags = args->args.flags;
    FEXCore::Core::CPUState NewThreadState{};
    // Clone copies the parent thread's state
    memcpy(&NewThreadState, Frame, sizeof(FEXCore::Core::CPUState));

    NewThreadState.gregs[FEXCore::X86State::REG_RAX] = 0;
    if (args->Type == TYPE_CLONE3) {
      // stack pointer points to the lowest address to the stack
      // set RSP to stack + size
      NewThreadState.gregs[FEXCore::X86State::REG_RSP] = args->args.stack + args->args.stack_size;
    }
    else {
      NewThreadState.gregs[FEXCore::X86State::REG_RSP] = args->args.stack;
    }

    auto NewThread = FEX::HLE::_SyscallHandler->TM.CreateThread(0, 0, &NewThreadState, args->args.parent_tid);

    if (FEX::HLE::_SyscallHandler->Is64BitMode()) {
      if (flags & CLONE_SETTLS) {
        x64::SetThreadArea(NewThread->CurrentFrame, reinterpret_cast<void*>(args->args.tls));
      }
      // Set us to start just after the syscall instruction
      x64::AdjustRipForNewThread(NewThread->CurrentFrame);
    }
    else {
      if (flags & CLONE_SETTLS) {
        x32::SetThreadArea(NewThread->CurrentFrame, reinterpret_cast<void*>(args->args.tls));
      }
      x32::AdjustRipForNewThread(NewThread->CurrentFrame);
    }

    // We need to do some post-thread creation setup.
    NewThread->StartPaused = true;

    // Initialize a new thread for execution.
    ExecutionThreadHandler *Arg = reinterpret_cast<ExecutionThreadHandler*>(FEXCore::Allocator::malloc(sizeof(ExecutionThreadHandler)));
    Arg->CTX = CTX;
    Arg->Thread = NewThread;
    NewThread->ExecutionThread = FEXCore::Threads::Thread::Create(ThreadHandler, Arg);

    // Wait for the thread to have started.
    NewThread->ThreadWaiting.Wait();

    if (FEX::HLE::_SyscallHandler->NeedXIDCheck()) {
      // The first time an application creates a thread, GLIBC installs their SETXID signal handler.
      // FEX needs to capture all signals and defer them to the guest.
      // Once FEX creates its first guest thread, overwrite the GLIBC SETXID handler *again* to ensure
      // FEX maintains control of the signal handler on this signal.
      FEX::HLE::_SyscallHandler->GetSignalDelegator()->CheckXIDHandler();
      FEX::HLE::_SyscallHandler->DisableXIDCheck();
    }

    // Return the new threads TID
    uint64_t Result = NewThread->ThreadManager.GetTID();

    // Sets the child TID to pointer in ParentTID
    if (flags & CLONE_PARENT_SETTID) {
      *reinterpret_cast<pid_t*>(args->args.parent_tid) = Result;
    }

    // Sets the child TID to the pointer in ChildTID
    if (flags & CLONE_CHILD_SETTID) {
      NewThread->ThreadManager.set_child_tid = reinterpret_cast<int32_t*>(args->args.child_tid);
      *reinterpret_cast<pid_t*>(args->args.child_tid) = Result;
    }

    // When the thread exits, clear the child thread ID at ChildTID
    // Additionally wakeup a futex at that address
    // Address /may/ be changed with SET_TID_ADDRESS syscall
    if (flags & CLONE_CHILD_CLEARTID) {
      NewThread->ThreadManager.clear_child_tid = reinterpret_cast<int32_t*>(args->args.child_tid);
    }

    // clone3 flag
    if (flags & CLONE_PIDFD) {
      // Use pidfd_open to emulate this flag
      const int pidfd = ::syscall(SYSCALL_DEF(pidfd_open), Result, 0);
      if (Result == ~0ULL) {
        LogMan::Msg::EFmt("Couldn't get pidfd of TID {}\n", Result);
      }
      else {
        *reinterpret_cast<int*>(args->args.pidfd) = pidfd;
      }
    }

    FEX::HLE::_SyscallHandler->TM.TrackThread(NewThread);

    return NewThread;
  }

  uint64_t HandleNewClone(FEXCore::Core::InternalThreadState *Thread, FEXCore::Context::Context *CTX, FEXCore::Core::CpuStateFrame *Frame, FEX::HLE::clone3_args *CloneArgs) {
    auto GuestArgs = &CloneArgs->args;
    uint64_t flags = GuestArgs->flags;
    auto NewThread = Thread;
    bool CreatedNewThreadObject{};

    if (flags & CLONE_THREAD) {
      FEXCore::Core::CPUState NewThreadState{};
      // Clone copies the parent thread's state
      memcpy(&NewThreadState, Frame, sizeof(FEXCore::Core::CPUState));

      NewThreadState.gregs[FEXCore::X86State::REG_RAX] = 0;
      if (GuestArgs->stack == 0) {
        // Copies in the original thread's stack
      }
      else {
        NewThreadState.gregs[FEXCore::X86State::REG_RSP] = GuestArgs->stack;
      }

      // Overwrite thread
      NewThread = FEX::HLE::_SyscallHandler->TM.CreateThread(0, 0, &NewThreadState, GuestArgs->parent_tid);

      // CLONE_PARENT_SETTID, CLONE_CHILD_SETTID, CLONE_CHILD_CLEARTID, CLONE_PIDFD will be handled by kernel
      // Call execution thread directly since we already are on the new thread
      NewThread->StartRunning.NotifyAll(); // Clear the start running flag
      CreatedNewThreadObject = true;
    }
    else{
      // If we don't have CLONE_THREAD then we are effectively a fork
      // Clear all the other threads that are being tracked
      // Frame->Thread is /ONLY/ safe to access when CLONE_THREAD flag is not set
      // Unlock the mutexes on both sides of the fork
      FEX::HLE::_SyscallHandler->UnlockAfterFork(Frame->Thread, true);

      ::syscall(SYS_rt_sigprocmask, SIG_SETMASK, &CloneArgs->SignalMask, nullptr, sizeof(CloneArgs->SignalMask));

      Thread->CurrentFrame->State.gregs[FEXCore::X86State::REG_RAX] = 0;
      if (GuestArgs->stack == 0) {
        // Copies in the original thread's stack
      }
      else {
        Thread->CurrentFrame->State.gregs[FEXCore::X86State::REG_RSP] = GuestArgs->stack;
      }
    }

    if (CloneArgs->Type == TYPE_CLONE3) {
      // If we are coming from a clone3 handler then we need to adjust RSP.
      Thread->CurrentFrame->State.gregs[FEXCore::X86State::REG_RSP] += CloneArgs->args.stack_size;
    }

    if (FEX::HLE::_SyscallHandler->Is64BitMode()) {
      if (flags & CLONE_SETTLS) {
        x64::SetThreadArea(NewThread->CurrentFrame, reinterpret_cast<void*>(GuestArgs->tls));
      }
      // Set us to start just after the syscall instruction
      x64::AdjustRipForNewThread(NewThread->CurrentFrame);
    }
    else {
      if (flags & CLONE_SETTLS) {
        x32::SetThreadArea(NewThread->CurrentFrame, reinterpret_cast<void*>(GuestArgs->tls));
      }
      x32::AdjustRipForNewThread(NewThread->CurrentFrame);
    }

    // Depending on clone settings, our TID and PID could have changed
    Thread->ThreadManager.TID = FHU::Syscalls::gettid();
    Thread->ThreadManager.PID = ::getpid();
    FEX::HLE::_SyscallHandler->FM.UpdatePID(Thread->ThreadManager.PID);

    if (CreatedNewThreadObject) {
      FEX::HLE::_SyscallHandler->TM.TrackThread(Thread);
    }

    FEX::HLE::_SyscallHandler->GetSignalDelegator()->RegisterTLSState(Thread);

    // Start exuting the thread directly
    // Our host clone starts in a new stack space, so it can't return back to the JIT space
    CTX->ExecutionThread(Thread);

    FEX::HLE::_SyscallHandler->GetSignalDelegator()->UninstallTLSState(Thread);

    // The rest of the context remains as is and the thread will continue executing
    return Thread->StatusCode;
  }

  uint64_t ForkGuest(FEXCore::Core::InternalThreadState *Thread, FEXCore::Core::CpuStateFrame *Frame, uint32_t flags, void *stack, size_t StackSize, pid_t *parent_tid, pid_t *child_tid, void *tls) {
    // Just before we fork, we lock all syscall mutexes so that both processes will end up with a locked mutex

    uint64_t Mask{~0ULL};
    ::syscall(SYS_rt_sigprocmask, SIG_SETMASK, &Mask, &Mask, sizeof(Mask));

    FEX::HLE::_SyscallHandler->LockBeforeFork(Frame->Thread);

    const bool IsVFork = flags & CLONE_VFORK;
    pid_t Result{};
    int VForkFDs[2];
    if (IsVFork) {
      // Use pipes as a mechanism for knowing when the child process is exiting.
      // FEX can't use `waitpid` for this since the child process may want to use it.
      // If we use `waitpid` then the kernel won't return the same data if asked again.
      pipe2(VForkFDs, O_CLOEXEC);

      // XXX: We don't currently support a real `vfork` as it causes problems.
      // Currently behaves like a fork (with wait after the fact), which isn't correct. Need to find where the problem is
      Result = fork();

      if (Result == 0) {
        // Close the read end of the pipe.
        // Keep the write end open so the parent can poll it.
        close(VForkFDs[0]);
      }
      else {
        // Close the write end of the pipe.
        close(VForkFDs[1]);
      }
    }
    else {
      Result = fork();
    }
    const bool IsChild = Result == 0;

    if (IsChild) {
      // Unlock the mutexes on both sides of the fork
      FEX::HLE::_SyscallHandler->UnlockAfterFork(Frame->Thread, IsChild);

      ::syscall(SYS_rt_sigprocmask, SIG_SETMASK, &Mask, nullptr, sizeof(Mask));

      // Child
      // update the internal TID
      Thread->ThreadManager.TID = FHU::Syscalls::gettid();
      Thread->ThreadManager.PID = ::getpid();
      FEX::HLE::_SyscallHandler->FM.UpdatePID(Thread->ThreadManager.PID);
      Thread->ThreadManager.clear_child_tid = nullptr;

      // only a  single thread running so no need to remove anything from the thread array

      // Handle child setup now
      if (stack != nullptr) {
        // use specified stack
        Frame->State.gregs[FEXCore::X86State::REG_RSP] = reinterpret_cast<uint64_t>(stack) + StackSize;
      } else {
        // In the case of fork and nullptr stack then the child uses the same stack space as the parent
        // Same virtual address, different addressspace
      }

      if (FEX::HLE::_SyscallHandler->Is64BitMode()) {
        if (flags & CLONE_SETTLS) {
          x64::SetThreadArea(Frame, tls);
        }
      }
      else {
        // 32bit TLS doesn't just set the fs register
        if (flags & CLONE_SETTLS) {
          x32::SetThreadArea(Frame, tls);
        }
      }

      // Sets the child TID to the pointer in ChildTID
      if (flags & CLONE_CHILD_SETTID) {
        Thread->ThreadManager.set_child_tid = child_tid;
        *child_tid = Thread->ThreadManager.TID;
      }

      // When the thread exits, clear the child thread ID at ChildTID
      // Additionally wakeup a futex at that address
      // Address /may/ be changed with SET_TID_ADDRESS syscall
      if (flags & CLONE_CHILD_CLEARTID) {
        Thread->ThreadManager.clear_child_tid = child_tid;
      }

      // the rest of the context remains as is, this thread will keep executing
      return 0;
    } else {
      if (Result != -1) {
        if (flags & CLONE_PARENT_SETTID) {
          *parent_tid = Result;
        }
      }

      // Unlock the mutexes on both sides of the fork
      FEX::HLE::_SyscallHandler->UnlockAfterFork(Frame->Thread, IsChild);

      ::syscall(SYS_rt_sigprocmask, SIG_SETMASK, &Mask, nullptr, sizeof(Mask));

      // VFork needs the parent to wait for the child to exit.
      if (IsVFork) {
        // Wait for the read end of the pipe to close.
        pollfd PollFD{};
        PollFD.fd = VForkFDs[0];
        PollFD.events = POLLIN | POLLOUT | POLLRDHUP | POLLERR | POLLHUP | POLLNVAL;

        // Mask all signals until the child process returns.
        sigset_t SignalMask{};
        sigfillset(&SignalMask);
        while (ppoll(&PollFD, 1, nullptr, &SignalMask) == -1 && errno == EINTR);

        // Close the read end now.
        close(VForkFDs[0]);
      }

      // Parent
      SYSCALL_ERRNO();
    }
  }

  void RegisterThread(FEX::HLE::SyscallHandler *Handler) {
    using namespace FEXCore::IR;

    REGISTER_SYSCALL_IMPL(rt_sigreturn, [](FEXCore::Core::CpuStateFrame *Frame) -> uint64_t {
      FEX::HLE::_SyscallHandler->GetSignalDelegator()->HandleSignalHandlerReturn(true);
      FEX_UNREACHABLE;
    });

    REGISTER_SYSCALL_IMPL_FLAGS(fork, SyscallFlags::DEFAULT, [](FEXCore::Core::CpuStateFrame *Frame) -> uint64_t {
      return ForkGuest(Frame->Thread, Frame, 0, 0, 0, 0, 0, 0);
    });

    REGISTER_SYSCALL_IMPL_FLAGS(vfork, SyscallFlags::DEFAULT, [](FEXCore::Core::CpuStateFrame *Frame) -> uint64_t {
      return ForkGuest(Frame->Thread, Frame, CLONE_VFORK, 0, 0, 0, 0, 0);
    });

    REGISTER_SYSCALL_IMPL_FLAGS(getpgrp, SyscallFlags::OPTIMIZETHROUGH | SyscallFlags::NOSYNCSTATEONENTRY,
      [](FEXCore::Core::CpuStateFrame *Frame) -> uint64_t {
      uint64_t Result = ::getpgrp();
      SYSCALL_ERRNO();
    });

    REGISTER_SYSCALL_IMPL_FLAGS(clone3, SyscallFlags::DEFAULT, ([](FEXCore::Core::CpuStateFrame *Frame, FEX::HLE::kernel_clone3_args *cl_args, size_t size) -> uint64_t {
      FEX::HLE::clone3_args args{};
      args.Type = TypeOfClone::TYPE_CLONE3;
      memcpy(&args.args, cl_args, std::min(sizeof(FEX::HLE::kernel_clone3_args), size));
      return CloneHandler(Frame, &args);
    }));

    REGISTER_SYSCALL_IMPL_FLAGS(exit, SyscallFlags::OPTIMIZETHROUGH | SyscallFlags::NOSYNCSTATEONENTRY | SyscallFlags::NORETURN,
      [](FEXCore::Core::CpuStateFrame *Frame, int status) -> uint64_t {
      auto Thread = Frame->Thread;

      // TLS/DTV teardown is something FEX can't control. Disable glibc checking when we leave a pthread.
      // Since this thread is hard stopping, we can't track the TLS/DTV teardown in FEX's thread handling.
      FEXCore::Allocator::YesIKnowImNotSupposedToUseTheGlibcAllocator::HardDisable();

      if (Thread->ThreadManager.clear_child_tid) {
        std::atomic<uint32_t> *Addr = reinterpret_cast<std::atomic<uint32_t>*>(Thread->ThreadManager.clear_child_tid);
        Addr->store(0);
        syscall(SYSCALL_DEF(futex),
          Thread->ThreadManager.clear_child_tid,
          FUTEX_WAKE,
          ~0ULL,
          0,
          0,
          0);
      }

      Thread->StatusCode = status;
      FEX::HLE::_SyscallHandler->TM.StopThread(Thread);

      return 0;
    });

    REGISTER_SYSCALL_IMPL_FLAGS(prctl, SyscallFlags::OPTIMIZETHROUGH | SyscallFlags::NOSYNCSTATEONENTRY,
      [](FEXCore::Core::CpuStateFrame *Frame, int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5) -> uint64_t {
      uint64_t Result{};
#ifndef PR_GET_AUXV
#define PR_GET_AUXV 0x41555856
#endif
      switch (option) {
      case PR_SET_SECCOMP:
      case PR_GET_SECCOMP:
        // FEX doesn't support seccomp
        return -EINVAL;
        break;
      case PR_GET_AUXV: {
        if (arg4 || arg5) {
          return -EINVAL;
        }

        void* addr = reinterpret_cast<void*>(arg2);
        size_t UserSize = reinterpret_cast<size_t>(arg3);

        uint64_t auxvBase=0;
        uint64_t auxvSize=0;
        FEX::HLE::_SyscallHandler->GetCodeLoader()->GetAuxv(auxvBase, auxvSize);
        size_t MinSize = std::min(auxvSize, UserSize);

        memcpy(addr, reinterpret_cast<void*>(auxvBase), MinSize);

        // Returns the size of auxv without truncation.
        return auxvSize;
      }
      default:
        Result = ::prctl(option, arg2, arg3, arg4, arg5);
      break;
      }
      SYSCALL_ERRNO();
    });

    REGISTER_SYSCALL_IMPL_FLAGS(arch_prctl, SyscallFlags::DEFAULT,
      [](FEXCore::Core::CpuStateFrame *Frame, int code, unsigned long addr) -> uint64_t {
      constexpr uint64_t TASK_MAX = (1ULL << 48); // 48-bits until we can query the host side VA sanely. AArch64 doesn't expose this in cpuinfo
      uint64_t Result{};
      switch (code) {
        case 0x1001: // ARCH_SET_GS
          if (addr >= TASK_MAX) {
            // Ignore a non-canonical address
            return -EPERM;
          }
          Frame->State.gs_cached = addr;
          Result = 0;
        break;
        case 0x1002: // ARCH_SET_FS
          if (addr >= TASK_MAX) {
            // Ignore a non-canonical address
            return -EPERM;
          }
          Frame->State.fs_cached = addr;
          Result = 0;
        break;
        case 0x1003: // ARCH_GET_FS
          *reinterpret_cast<uint64_t*>(addr) = Frame->State.fs_cached;
          Result = 0;
        break;
        case 0x1004: // ARCH_GET_GS
          *reinterpret_cast<uint64_t*>(addr) = Frame->State.gs_cached;
          Result = 0;
        break;
        case 0x3001: // ARCH_CET_STATUS
          Result = -EINVAL; // We don't support CET, return EINVAL
        break;
        case 0x1011: // ARCH_GET_CPUID
          return 1;
        break;
        case 0x1012: // ARCH_SET_CPUID
          return -ENODEV; // Claim we don't support faulting on CPUID
        break;
        default:
          LogMan::Msg::EFmt("Unknown prctl: 0x{:x}", code);
          Result = -EINVAL;
        break;
      }
      SYSCALL_ERRNO();
    });

    REGISTER_SYSCALL_IMPL_FLAGS(set_tid_address, SyscallFlags::OPTIMIZETHROUGH | SyscallFlags::NOSYNCSTATEONENTRY,
      [](FEXCore::Core::CpuStateFrame *Frame, int *tidptr) -> uint64_t {
      auto Thread = Frame->Thread;
      Thread->ThreadManager.clear_child_tid = tidptr;
      return Thread->ThreadManager.GetTID();
    });

    REGISTER_SYSCALL_IMPL_FLAGS(exit_group, SyscallFlags::OPTIMIZETHROUGH | SyscallFlags::NOSYNCSTATEONENTRY | SyscallFlags::NORETURN,
      [](FEXCore::Core::CpuStateFrame *Frame, int status) -> uint64_t {

      // Save telemetry if we're exiting.
      FEX::HLE::_SyscallHandler->GetSignalDelegator()->SaveTelemetry();

      syscall(SYSCALL_DEF(exit_group), status);
      // This will never be reached
      std::terminate();
    });
  }
}