FEX-Emu--FEX/Source/Tests/VDSO_Emulation.cpp

#include "VDSO_Emulation.h"
#include "FEXCore/IR/IR.h"

#include <FEXCore/Config/Config.h>
#include <FEXCore/Utils/MathUtils.h>
#include <FEXCore/Utils/LogManager.h>

#include <dlfcn.h>
#include <fcntl.h>
#include <filesystem>
#include <sys/mman.h>
#include <sys/time.h>
#include <unistd.h>

namespace FEX::VDSO {
  using TimeType = decltype(::time)*;
  using GetTimeOfDayType = decltype(::gettimeofday)*;
  using ClockGetTimeType = decltype(::clock_gettime)*;
  using ClockGetResType = decltype(::clock_getres)*;
  using GetCPUType = decltype(::getcpu)*;

  TimeType TimePtr = ::time;
  GetTimeOfDayType GetTimeOfDayPtr = ::gettimeofday;
  ClockGetTimeType ClockGetTimePtr = ::clock_gettime;
  ClockGetResType ClockGetResPtr = ::clock_getres;
  GetCPUType GetCPUPtr = ::getcpu;

  static void time(void* ArgsRV) {
    struct ArgsRV_t {
      time_t *a_0;
      uint64_t rv;
    } *args = reinterpret_cast<ArgsRV_t*>(ArgsRV);

    args->rv = TimePtr(args->a_0);
  }

  static void gettimeofday(void* ArgsRV) {
    struct ArgsRV_t {
      struct timeval *tv;
      struct timezone *tz;
      uint64_t rv;
    } *args = reinterpret_cast<ArgsRV_t*>(ArgsRV);

    args->rv = GetTimeOfDayPtr(args->tv, args->tz);
  }

  static void clock_gettime(void* ArgsRV) {
    struct ArgsRV_t {
      clockid_t clk_id;
      struct timespec *tp;
      uint64_t rv;
    } *args = reinterpret_cast<ArgsRV_t*>(ArgsRV);

    args->rv = ClockGetTimePtr(args->clk_id, args->tp);
  }

  static void clock_getres(void* ArgsRV) {
    struct ArgsRV_t {
      clockid_t clk_id;
      struct timespec *tp;
      uint64_t rv;
    } *args = reinterpret_cast<ArgsRV_t*>(ArgsRV);

    args->rv = ClockGetResPtr(args->clk_id, args->tp);
  }

  static void getcpu(void* ArgsRV) {
    struct ArgsRV_t {
      uint32_t *cpu;
      uint32_t *node;
      uint64_t rv;
    } *args = reinterpret_cast<ArgsRV_t*>(ArgsRV);

    args->rv = GetCPUPtr(args->cpu, args->node);
  }

  void LoadHostVDSO() {
    void *vdso = dlopen("linux-vdso.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
    if (!vdso) {
      vdso = dlopen("linux-gate.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
    }

    if (!vdso) {
      // We couldn't load VDSO, fallback to C implementations. Which will still be faster than emulated libc versions.
      LogMan::Msg::IFmt("linux-vdso implementation falling back to libc. Consider enabling VDSO in your kernel.");
      return;
    }

    auto SymbolPtr = dlsym(vdso, "__vdso_time");
    if (SymbolPtr) {
      TimePtr = reinterpret_cast<TimeType>(SymbolPtr);
    }

    SymbolPtr = dlsym(vdso, "__vdso_gettimeofday");
    if (SymbolPtr) {
      GetTimeOfDayPtr = reinterpret_cast<GetTimeOfDayType>(SymbolPtr);
    }

    SymbolPtr = dlsym(vdso, "__vdso_clock_gettime");
    if (SymbolPtr) {
      ClockGetTimePtr = reinterpret_cast<ClockGetTimeType>(SymbolPtr);
    }

    SymbolPtr = dlsym(vdso, "__vdso_clock_getres");
    if (SymbolPtr) {
      ClockGetResPtr = reinterpret_cast<ClockGetResType>(SymbolPtr);
    }

    SymbolPtr = dlsym(vdso, "__vdso_getcpu");
    if (SymbolPtr) {
      GetCPUPtr = reinterpret_cast<GetCPUType>(SymbolPtr);
    }
    dlclose(vdso);
  }

  static std::vector<FEXCore::IR::ThunkDefinition> VDSODefinitions = {
    {
        // sha256(libVDSO:time)
        { 0x37, 0x63, 0x46, 0xb0, 0x79, 0x06, 0x5f, 0x9d, 0x00, 0xb6, 0x8d, 0xfd, 0x9e, 0x4a, 0x62, 0xcd, 0x1e, 0x6c, 0xcc, 0x22, 0xcd, 0xb2, 0xc0, 0x17, 0x7d, 0x42, 0x6a, 0x40, 0xd1, 0xeb, 0xfa, 0xe0 },
        &FEX::VDSO::time
    },
    {
        // sha256(libVDSO:gettimeofday)
        { 0x77, 0x2a, 0xde, 0x1c, 0x13, 0x2d, 0xe9, 0x48, 0xaf, 0xe0, 0xba, 0xcc, 0x6a, 0x89, 0xff, 0xca, 0x4a, 0xdc, 0xd5, 0x63, 0x2c, 0xc5, 0x62, 0x8b, 0x5d, 0xde, 0x0b, 0x15, 0x35, 0xc6, 0xc7, 0x14 },
        &FEX::VDSO::gettimeofday
    },
    {
        // sha256(libVDSO:clock_gettime)
        { 0x3c, 0x96, 0x9b, 0x2d, 0xc3, 0xad, 0x2b, 0x3b, 0x9c, 0x4e, 0x4d, 0xca, 0x1c, 0xe8, 0x18, 0x4a, 0x12, 0x8a, 0xe4, 0xc1, 0x56, 0x92, 0x73, 0xce, 0x65, 0x85, 0x5f, 0x65, 0x7e, 0x94, 0x26, 0xbe },
        &FEX::VDSO::clock_gettime
    },
    {
        // sha256(libVDSO:clock_getres)
        { 0xe4, 0xa1, 0xf6, 0x23, 0x35, 0xae, 0xb7, 0xb6, 0xb0, 0x37, 0xc5, 0xc3, 0xa3, 0xfd, 0xbf, 0xa2, 0xa1, 0xc8, 0x95, 0x78, 0xe5, 0x76, 0x86, 0xdb, 0x3e, 0x6c, 0x54, 0xd5, 0x02, 0x60, 0xd8, 0x6d },
        &FEX::VDSO::clock_getres
    },
    {
        // sha256(libVDSO:getcpu)
        { 0x39, 0x83, 0x39, 0x36, 0x0f, 0x68, 0xd6, 0xfc, 0xc2, 0x3a, 0x97, 0x11, 0x85, 0x09, 0xc7, 0x25, 0xbb, 0x50, 0x49, 0x55, 0x6b, 0x0c, 0x9f, 0x50, 0x37, 0xf5, 0x9d, 0xb0, 0x38, 0x58, 0x57, 0x12 },
        &FEX::VDSO::getcpu
    },
  };

  void* LoadVDSOThunks(MapperFn Mapper) {
    void* VDSOBase{};
    FEX_CONFIG_OPT(ThunkGuestLibs, THUNKGUESTLIBS);

    // Load VDSO if we can
    auto ThunkGuestPath = std::filesystem::path(ThunkGuestLibs()) / "libVDSO-guest.so";
    int VDSOFD = ::open(ThunkGuestPath.string().c_str(), O_RDONLY);

    if (VDSOFD != -1) {
      // Get file size
      size_t VDSOSize = lseek(VDSOFD, 0, SEEK_END);

      if (VDSOSize >= 4) {
        // Reset to beginning
        lseek(VDSOFD, 0, SEEK_SET);
        VDSOSize = FEXCore::AlignUp(VDSOSize, 4096);

        // Map the VDSO file to memory
        VDSOBase = Mapper(nullptr, VDSOSize, PROT_READ, MAP_PRIVATE, VDSOFD, 0);

        // Since we found our VDSO thunk library, find our host VDSO function implementations.
        LoadHostVDSO();

      }
      close(VDSOFD);
    }

    return VDSOBase;
  }

  std::vector<FEXCore::IR::ThunkDefinition> const& GetVDSOThunkDefinitions() {
    return VDSODefinitions;
  }
}