rpcsx/rpcsx-os/thread.cpp

#include "thread.hpp"
#include "orbis/sys/sysentry.hpp"
#include <asm/prctl.h>
#include <csignal>
#include <immintrin.h>
#include <link.h>
#include <linux/prctl.h>
#include <string>
#include <sys/prctl.h>
#include <sys/ucontext.h>
#include <ucontext.h>
#include <unistd.h>

thread_local orbis::Thread *rx::thread::g_current = nullptr;

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

  auto prevContext = std::exchange(rx::thread::g_current->context, ucontext);
  orbis::syscall_entry(rx::thread::g_current);
  rx::thread::g_current->context = prevContext;
  _writefsbase_u64(rx::thread::g_current->fsBase);
}

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

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

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

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

  sigset_t unblockSigs{};
  sigset_t oldSigmask{};
  sigaddset(&unblockSigs, SIGSYS);
  if (pthread_sigmask(SIG_UNBLOCK, &unblockSigs, &oldSigmask)) {
    perror("pthread_sigmask failed\n");
    exit(-1);
  }

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

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

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

  asm volatile("movq %1, %%rsp\n"
               "callq *%0\n"
               :
               : "rm"(context->uc_mcontext.gregs[REG_RIP]),
                 "rm"(context->uc_mcontext.gregs[REG_RSP]),
                 "D"(context->uc_mcontext.gregs[REG_RDI]),
                 "S"(context->uc_mcontext.gregs[REG_RSI]),
                 "d"(context->uc_mcontext.gregs[REG_RDX]),
                 "c"(context->uc_mcontext.gregs[REG_RCX]),
                 "b"(context->uc_mcontext.gregs[REG_RBX])
               : "memory");
  _writefsbase_u64(hostFs);
}