rpcsx/rpcsx-os/thread.cpp

#include "thread.hpp"
#include "align.hpp"
#include "orbis/sys/sysentry.hpp"
#include "orbis/thread/Process.hpp"
#include "orbis/thread/Thread.hpp"
#include "orbis/utils/Logs.hpp"
#include <asm/prctl.h>
#include <csignal>
#include <immintrin.h>
#include <link.h>
#include <linux/prctl.h>
#include <sys/prctl.h>
#include <ucontext.h>
#include <unistd.h>
#include <xbyak/xbyak.h>

static std::size_t getSigStackSize() {
  static auto sigStackSize = std::max<std::size_t>(
      SIGSTKSZ, ::utils::alignUp(64 * 1024 * 1024, sysconf(_SC_PAGE_SIZE)));
  return sigStackSize;
}

static auto setContext = [] {
  struct SetContext : Xbyak::CodeGenerator {
    SetContext() {
      mov(rbp, rdi);
      mov(rax, qword[rbp + REG_RAX * sizeof(unsigned long long)]);
      mov(rdi, qword[rbp + REG_RDI * sizeof(unsigned long long)]);
      mov(rdx, qword[rbp + REG_RDX * sizeof(unsigned long long)]);
      mov(rcx, qword[rbp + REG_RCX * sizeof(unsigned long long)]);
      mov(rbx, qword[rbp + REG_RBX * sizeof(unsigned long long)]);
      mov(rsi, qword[rbp + REG_RSI * sizeof(unsigned long long)]);
      mov(rsp, qword[rbp + REG_RSP * sizeof(unsigned long long)]);

      mov(rbp, qword[rbp + REG_RIP * sizeof(unsigned long long)]);
      call(rbp);
    }
  } static setContextStorage;

  return setContextStorage.getCode<void (*)(const mcontext_t &)>();
}();

static void copy(orbis::MContext &dst, const mcontext_t &src) {
  // dst.onstack = src.gregs[REG_ONSTACK];
  dst.rdi = src.gregs[REG_RDI];
  dst.rsi = src.gregs[REG_RSI];
  dst.rdx = src.gregs[REG_RDX];
  dst.rcx = src.gregs[REG_RCX];
  dst.r8 = src.gregs[REG_R8];
  dst.r9 = src.gregs[REG_R9];
  dst.rax = src.gregs[REG_RAX];
  dst.rbx = src.gregs[REG_RBX];
  dst.rbp = src.gregs[REG_RBP];
  dst.r10 = src.gregs[REG_R10];
  dst.r11 = src.gregs[REG_R11];
  dst.r12 = src.gregs[REG_R12];
  dst.r13 = src.gregs[REG_R13];
  dst.r14 = src.gregs[REG_R14];
  dst.r15 = src.gregs[REG_R15];
  dst.trapno = src.gregs[REG_TRAPNO];
  dst.fs = src.gregs[REG_CSGSFS] & 0xffff;
  dst.gs = (src.gregs[REG_CSGSFS] >> 16) & 0xffff;
  // dst.addr = src.gregs[REG_ADDR];
  // dst.flags = src.gregs[REG_FLAGS];
  // dst.es = src.gregs[REG_ES];
  // dst.ds = src.gregs[REG_DS];
  dst.err = src.gregs[REG_ERR];
  dst.rip = src.gregs[REG_RIP];
  dst.cs = (src.gregs[REG_CSGSFS] >> 32) & 0xffff;
  dst.rflags = src.gregs[REG_EFL];
  dst.rsp = src.gregs[REG_RSP];
  // dst.ss = src.gregs[REG_SS];
  dst.len = sizeof(orbis::MContext);
  // dst.fpformat = src.gregs[REG_FPFORMAT];
  // dst.ownedfp = src.gregs[REG_OWNEDFP];
  // dst.lbrfrom = src.gregs[REG_LBRFROM];
  // dst.lbrto = src.gregs[REG_LBRTO];
  // dst.aux1 = src.gregs[REG_AUX1];
  // dst.aux2 = src.gregs[REG_AUX2];
  // dst.fpstate = src.gregs[REG_FPSTATE];
  // dst.fsbase = src.gregs[REG_FSBASE];
  // dst.gsbase = src.gregs[REG_GSBASE];
  // dst.xfpustate = src.gregs[REG_XFPUSTATE];
  // dst.xfpustate_len = src.gregs[REG_XFPUSTATE_LEN];
}

static void copy(orbis::Thread *thread, orbis::UContext &dst,
                 const ucontext_t &src) {
  dst = {};
  dst.stack.sp = thread->stackStart;
  dst.stack.size = (char *)thread->stackEnd - (char *)thread->stackStart;
  dst.stack.align = 0x10000;
  dst.sigmask = thread->sigMask;
  copy(dst.mcontext, src.uc_mcontext);
}

static __attribute__((no_stack_protector)) void
handleSigSys(int sig, siginfo_t *info, void *ucontext) {
  if (auto hostFs = _readgsbase_u64()) {
    _writefsbase_u64(hostFs);
  }

  // rx::printStackTrace(reinterpret_cast<ucontext_t *>(ucontext),
  // rx::thread::g_current, 1);
  auto thread = orbis::g_currentThread;
  auto prevContext = std::exchange(thread->context, ucontext);
  {
    std::lock_guard lock(thread->mtx);
    copy(thread, thread->sigReturns.emplace_back(),
         *reinterpret_cast<ucontext_t *>(ucontext));
  }
  if ((std::uint64_t)&thread < 0x100'0000'0000) {
    ORBIS_LOG_ERROR("unexpected sigsys signal stack", thread->tid, sig,
                    (std::uint64_t)&thread);
    std::abort();
  }

  auto altStack = malloc(getSigStackSize());
  rx::thread::setupSignalStack(altStack);

  sigset_t set;
  sigemptyset(&set);
  sigaddset(&set, SIGUSR1);
  sigaddset(&set, SIGSYS);
  pthread_sigmask(SIG_UNBLOCK, &set, NULL);

  orbis::syscall_entry(thread);

  pthread_sigmask(SIG_BLOCK, &set, NULL);

  std::free(altStack);
  if (thread == orbis::g_currentThread) {
    std::lock_guard lock(thread->mtx);
    thread->sigReturns.pop_back();
  }
  thread = orbis::g_currentThread;
  thread->context = prevContext;
  _writefsbase_u64(thread->fsBase);
}

__attribute__((no_stack_protector)) static void
handleSigUser(int sig, siginfo_t *info, void *ucontext) {
  if (auto hostFs = _readgsbase_u64()) {
    _writefsbase_u64(hostFs);
  }

  auto context = reinterpret_cast<ucontext_t *>(ucontext);
  bool inGuestCode = context->uc_mcontext.gregs[REG_RIP] < 0x100'0000'0000;
  auto thread = orbis::g_currentThread;

  if ((std::uint64_t)&context < 0x100'0000'0000) {
    ORBIS_LOG_ERROR("unexpected sigusr signal stack", thread->tid, sig,
                    inGuestCode, (std::uint64_t)&context);
    std::abort();
  }

  int guestSignal = -3;
  {
    std::lock_guard lock(thread->mtx);
    if (thread->signalQueue.empty()) {
      ORBIS_LOG_ERROR("unexpected user signal", thread->tid, sig, inGuestCode);
      return;
    }

    guestSignal = thread->signalQueue.front();
    thread->signalQueue.pop_front();

    copy(thread, thread->sigReturns.emplace_back(), *context);
  }

  if (guestSignal == -1) {
    auto altStack = malloc(getSigStackSize());
    rx::thread::setupSignalStack(altStack);

    sigset_t set;
    sigemptyset(&set);
    sigaddset(&set, SIGUSR1);
    sigaddset(&set, SIGSYS);
    pthread_sigmask(SIG_UNBLOCK, &set, NULL);

    thread->suspended++;
    // ORBIS_LOG_ERROR("suspending thread", thread->tid);
    while (thread->suspended > 0) {
      ::sleep(1);
    }

    pthread_sigmask(SIG_BLOCK, &set, NULL);
    free(altStack);

    // ORBIS_LOG_ERROR("thread wake", thread->tid);
  }

  if (guestSignal == -2) {
    // ORBIS_LOG_ERROR("thread resume signal", thread->tid);

    std::lock_guard lock(thread->mtx);
    thread->sigReturns.pop_back();
    --thread->suspended;
  }

  if (inGuestCode) {
    _writefsbase_u64(thread->fsBase);
  }
}

void rx::thread::initialize() {
  struct sigaction act {};
  act.sa_sigaction = handleSigSys;
  act.sa_flags = SA_SIGINFO | SA_ONSTACK;

  sigaddset(&act.sa_mask, SIGSYS);
  sigaddset(&act.sa_mask, SIGUSR1);

  if (sigaction(SIGSYS, &act, NULL)) {
    perror("Error sigaction:");
    exit(-1);
  }

  act.sa_sigaction = handleSigUser;

  if (sigaction(SIGUSR1, &act, NULL)) {
    perror("Error sigaction:");
    exit(-1);
  }
}

void rx::thread::deinitialize() {}

void *rx::thread::setupSignalStack(void *address) {
  stack_t ss{}, oss{};

  if (address == NULL) {
    std::fprintf(stderr, "attempt to set null signal stack, %p - %zx\n",
                 address, getSigStackSize());
    std::exit(EXIT_FAILURE);
  }

  ss.ss_sp = address;
  ss.ss_size = getSigStackSize();
  ss.ss_flags = 1 << 31;

  if (sigaltstack(&ss, &oss) == -1) {
    perror("sigaltstack");
    std::exit(EXIT_FAILURE);
  }

  return oss.ss_sp;
}

void *rx::thread::setupSignalStack() {
  auto data = malloc(getSigStackSize());
  if (data == nullptr) {
    std::fprintf(stderr, "malloc produces null, %zx\n", getSigStackSize());
    std::exit(EXIT_FAILURE);
  }
  return setupSignalStack(data);
}

void rx::thread::setupThisThread() {
  sigset_t unblockSigs{};
  sigset_t oldSigmask{};
  sigaddset(&unblockSigs, SIGSYS);
  sigaddset(&unblockSigs, SIGUSR1);
  if (pthread_sigmask(SIG_UNBLOCK, &unblockSigs, &oldSigmask)) {
    perror("pthread_sigmask failed\n");
    std::exit(-1);
  }

  if (prctl(PR_SET_SYSCALL_USER_DISPATCH, PR_SYS_DISPATCH_ON,
            (void *)0x100'0000'0000, ~0ull - 0x100'0000'0000, nullptr)) {
    perror("prctl failed\n");
    std::exit(-1);
  }
}

void rx::thread::invoke(orbis::Thread *thread) {
  orbis::g_currentThread = thread;

  std::uint64_t hostFs = _readfsbase_u64();
  _writegsbase_u64(hostFs);

  _writefsbase_u64(thread->fsBase);
  auto context = reinterpret_cast<ucontext_t *>(thread->context);

  setContext(context->uc_mcontext);
  _writefsbase_u64(hostFs);
}