////////////////////////////////////////////////////////////////////////////////
//
// The University of Illinois/NCSA
// Open Source License (NCSA)
//
// Copyright (c) 2014-2020, Advanced Micro Devices, Inc. All rights reserved.
//
// Developed by:
//
//                 AMD Research and AMD HSA Software Development
//
//                 Advanced Micro Devices, Inc.
//
//                 www.amd.com
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal with the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
//  - Redistributions of source code must retain the above copyright notice,
//    this list of conditions and the following disclaimers.
//  - Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimers in
//    the documentation and/or other materials provided with the distribution.
//  - Neither the names of Advanced Micro Devices, Inc,
//    nor the names of its contributors may be used to endorse or promote
//    products derived from this Software without specific prior written
//    permission.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
// OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS WITH THE SOFTWARE.
//
////////////////////////////////////////////////////////////////////////////////

#ifndef HSA_RUNTIME_CORE_LOADER_EXECUTABLE_HPP_
#define HSA_RUNTIME_CORE_LOADER_EXECUTABLE_HPP_

#include <array>
#include <cassert>
#include <cstdint>
#include <iostream>
#include <libelf.h>
#if defined(__linux__)
#include <link.h>
#endif
#include <list>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>
#include <cstring>
#include "inc/hsa.h"
#include "inc/hsa_ext_image.h"
#include "core/inc/amd_hsa_loader.hpp"
#include "core/inc/amd_hsa_code.hpp"
#include "inc/amd_hsa_kernel_code.h"
#include "amd_hsa_locks.hpp"

#if defined(_WIN32) || defined(_WIN64)
// r_version history:
// 1: Initial debug protocol
// 2: New trap handler ABI. The reason for halting a wave is recorded in ttmp11[8:7].
// 3: New trap handler ABI. A wave halted at S_ENDPGM rewinds its PC by 8 bytes, and sets
// ttmp11[9]=1. 4: New trap handler ABI. Save the trap id in ttmp11[16:9] 5: New trap handler ABI.
// Save the PC in ttmp11[22:7] ttmp6[31:0], and park the wave if stopped 6: New trap handler ABI.
// ttmp6[25:0] contains dispatch index modulo queue size 7: New trap handler ABI. Send interrupts as
// a bitmask, coalescing concurrent exceptions. 8: New trap handler ABI. for gfx942: Initialize
// ttmp[4:5] if ttmp11[31] == 0. 9: New trap handler ABI. For gfx11: Save PC in ttmp11[22:7]
// ttmp6[31:0], and park the wave if stopped. 10: New trap handler ABI. Set status.skip_export when
// halting the wave.
//                           For gfx942, set ttmp6[31] = 0 if ttmp11[31] == 0.
#if _WIN64
#define __WORDSIZE 64
#else
#define __WORDSIZE 32
#endif

#define __ELF_NATIVE_CLASS __WORDSIZE

/* We use this macro to refer to ELF types independent of the native wordsize.
   `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'.  */
#define _ElfW_1(e, w, t) e##w##t
#define _ElfW(e, w, t) _ElfW_1(e, w, _##t)
#define ElfW(type) _ElfW(Elf, __ELF_NATIVE_CLASS, type)

/* Structure describing a loaded shared object.  The `l_next' and `l_prev'
   members form a chain of all the shared objects loaded at startup.

   These data structures exist in space used by the run-time dynamic linker;
   modifying them may have disastrous results.  */

struct link_map {
  /* These first few members are part of the protocol with the debugger.
     This is the same format used in SVR4.  */

  ElfW(Addr) l_addr;                /* Difference between the address in the ELF
                                       file and the addresses in memory.  */
  char* l_name;                     /* Absolute file name object was found in.  */
  ElfW(Dyn) * l_ld;                 /* Dynamic section of the shared object.  */
  struct link_map *l_next, *l_prev; /* Chain of loaded objects.  */
};

struct r_debug {
  /* Version number for this protocol.  It should be greater than 0.  */
  int r_version;

  struct link_map* r_map; /* Head of the chain of loaded objects.  */

  /* This is the address of a function internal to the run-time linker,
     that will always be called when the linker begins to map in a
     library or unmap it, and again when the mapping change is complete.
     The debugger can set a breakpoint at this address if it wants to
     notice shared object mapping changes.  */
  ElfW(Addr) r_brk;
  enum RT {
    /* This state value describes the mapping change taking place when
       the `r_brk' address is called.  */
    RT_CONSISTENT, /* Mapping change is complete.  */
    RT_ADD,        /* Beginning to add a new object.  */
    RT_DELETE      /* Beginning to remove an object mapping.  */
  } r_state;

  ElfW(Addr) r_ldbase; /* Base address the linker is loaded at.  */
};
#endif

namespace rocr {
namespace amd {
namespace hsa {
namespace loader {

class MemoryAddress;
class SymbolImpl;
class KernelSymbol;
class VariableSymbol;
class ExecutableImpl;

//===----------------------------------------------------------------------===//
// SymbolImpl.                                                                //
//===----------------------------------------------------------------------===//

typedef uint32_t symbol_attribute32_t;

class SymbolImpl: public Symbol {
public:
  virtual ~SymbolImpl() {}

  bool IsKernel() const {
    return HSA_SYMBOL_KIND_KERNEL == kind;
  }
  bool IsVariable() const {
    return HSA_SYMBOL_KIND_VARIABLE == kind;
  }

  bool is_loaded;
  hsa_symbol_kind_t kind;
  std::string module_name;
  std::string symbol_name;
  hsa_symbol_linkage_t linkage;
  bool is_definition;
  uint64_t address;
  hsa_agent_t agent;

  hsa_agent_t GetAgent() override {
    return agent;
  }

protected:
  SymbolImpl(const bool &_is_loaded,
             const hsa_symbol_kind_t &_kind,
             const std::string &_module_name,
             const std::string &_symbol_name,
             const hsa_symbol_linkage_t &_linkage,
             const bool &_is_definition,
             const uint64_t &_address = 0)
    : is_loaded(_is_loaded)
    , kind(_kind)
    , module_name(_module_name)
    , symbol_name(_symbol_name)
    , linkage(_linkage)
    , is_definition(_is_definition)
    , address(_address) {}

  virtual bool GetInfo(hsa_symbol_info32_t symbol_info, void* value) override;

 private:
  SymbolImpl(const SymbolImpl &s);
  SymbolImpl& operator=(const SymbolImpl &s);
};

//===----------------------------------------------------------------------===//
// KernelSymbol.                                                              //
//===----------------------------------------------------------------------===//

class KernelSymbol final: public SymbolImpl {
public:
  KernelSymbol(const bool &_is_loaded,
               const std::string &_module_name,
               const std::string &_symbol_name,
               const hsa_symbol_linkage_t &_linkage,
               const bool &_is_definition,
               const uint32_t &_kernarg_segment_size,
               const uint32_t &_kernarg_segment_alignment,
               const uint32_t &_group_segment_size,
               const uint32_t &_private_segment_size,
               const bool &_is_dynamic_callstack,
               const uint32_t &_size,
               const uint32_t &_alignment,
               const uint32_t &_wavefront_size,
               const uint64_t &_address = 0)
    : SymbolImpl(_is_loaded,
                 HSA_SYMBOL_KIND_KERNEL,
                 _module_name,
                 _symbol_name,
                 _linkage,
                 _is_definition,
                 _address)
    , full_name(_module_name.empty() ? _symbol_name : _module_name + "::" + _symbol_name)
    , kernarg_segment_size(_kernarg_segment_size)
    , kernarg_segment_alignment(_kernarg_segment_alignment)
    , group_segment_size(_group_segment_size)
    , private_segment_size(_private_segment_size)
    , is_dynamic_callstack(_is_dynamic_callstack)
    , size(_size)
    , alignment(_alignment)
    , wavefront_size(_wavefront_size)
    , debug_info{} {}

  ~KernelSymbol() {}

  bool GetInfo(hsa_symbol_info32_t symbol_info, void *value);

  std::string full_name;
  uint32_t kernarg_segment_size;
  uint32_t kernarg_segment_alignment;
  uint32_t group_segment_size;
  uint32_t private_segment_size;
  bool is_dynamic_callstack;
  uint32_t size;
  uint32_t alignment;
  uint32_t wavefront_size;
  amd_runtime_loader_debug_info_t debug_info;

private:
  KernelSymbol(const KernelSymbol &ks);
  KernelSymbol& operator=(const KernelSymbol &ks);
};

//===----------------------------------------------------------------------===//
// VariableSymbol.                                                            //
//===----------------------------------------------------------------------===//

class VariableSymbol final: public SymbolImpl {
public:
  VariableSymbol(const bool &_is_loaded,
                 const std::string &_module_name,
                 const std::string &_symbol_name,
                 const hsa_symbol_linkage_t &_linkage,
                 const bool &_is_definition,
                 const hsa_variable_allocation_t &_allocation,
                 const hsa_variable_segment_t &_segment,
                 const uint32_t &_size,
                 const uint32_t &_alignment,
                 const bool &_is_constant,
                 const bool &_is_external = false,
                 const uint64_t &_address = 0)
    : SymbolImpl(_is_loaded,
                 HSA_SYMBOL_KIND_VARIABLE,
                 _module_name,
                 _symbol_name,
                 _linkage,
                 _is_definition,
                 _address)
    , allocation(_allocation)
    , segment(_segment)
    , size(_size)
    , alignment(_alignment)
    , is_constant(_is_constant)
    , is_external(_is_external) {}

  ~VariableSymbol() {}

  bool GetInfo(hsa_symbol_info32_t symbol_info, void *value);

  hsa_variable_allocation_t allocation;
  hsa_variable_segment_t segment;
  uint32_t size;
  uint32_t alignment;
  bool is_constant;
  bool is_external;

private:
  VariableSymbol(const VariableSymbol &vs);
  VariableSymbol& operator=(const VariableSymbol &vs);
};

//===----------------------------------------------------------------------===//
// Logger.                                                                    //
//===----------------------------------------------------------------------===//

class Logger final {
public:
  Logger(std::ostream &Stream = std::cerr) : OutStream(Stream) {}

  template <typename T>
  Logger &operator<<(const T &Data) {
    if (!IsLoggingEnabled())
      return *this;
    OutStream << Data;
    return *this;
  }

private:
  Logger(const Logger &L);
  Logger& operator=(const Logger &L);

  bool IsLoggingEnabled() const {
    const char *enable_logging = getenv("LOADER_ENABLE_LOGGING");
    if (!enable_logging)
      return false;
    if (std::string(enable_logging) == "0")
      return false;
    return true;
  }

  std::ostream &OutStream;
};

//===----------------------------------------------------------------------===//
// Executable.                                                                //
//===----------------------------------------------------------------------===//

class ExecutableImpl;
class LoadedCodeObjectImpl;
class Segment;

class ExecutableObject {
protected:
  ExecutableImpl *owner;
  hsa_agent_t agent;

public:
  ExecutableObject(ExecutableImpl *owner_, hsa_agent_t agent_)
    : owner(owner_), agent(agent_) { }

  ExecutableImpl* Owner() const { return owner; }
  hsa_agent_t Agent() const { return agent; }
  virtual void Print(std::ostream& out) = 0;
  virtual void Destroy() = 0;

  virtual ~ExecutableObject() { }
};

class LoadedCodeObjectImpl : public LoadedCodeObject, public ExecutableObject {
friend class AmdHsaCodeLoader;
private:
  LoadedCodeObjectImpl(const LoadedCodeObjectImpl&);
  LoadedCodeObjectImpl& operator=(const LoadedCodeObjectImpl&);

  const void *elf_data;
  const size_t elf_size;
  std::vector<Segment*> loaded_segments;

public:
  LoadedCodeObjectImpl(ExecutableImpl *owner_, hsa_agent_t agent_, const void *elf_data_, size_t elf_size_)
    : ExecutableObject(owner_, agent_), elf_data(elf_data_), elf_size(elf_size_) {
      memset(&r_debug_info, 0, sizeof(r_debug_info));
    }

  const void* ElfData() const { return elf_data; }
  size_t ElfSize() const { return elf_size; }
  std::vector<Segment*>& LoadedSegments() { return loaded_segments; }

  bool GetInfo(amd_loaded_code_object_info_t attribute, void *value) override;

  hsa_status_t IterateLoadedSegments(
    hsa_status_t (*callback)(
      amd_loaded_segment_t loaded_segment,
      void *data),
    void *data) override;

  void Print(std::ostream& out) override;

  void Destroy() override {}

  hsa_agent_t getAgent() const override;
  hsa_executable_t getExecutable() const override;
  uint64_t getElfData() const override;
  uint64_t getElfSize() const override;
  uint64_t getStorageOffset() const override;
  uint64_t getLoadBase() const override;
  uint64_t getLoadSize() const override;
  int64_t getDelta() const override;
  std::string getUri() const override;

  link_map r_debug_info;
};

class Segment : public LoadedSegment, public ExecutableObject {
private:
  amdgpu_hsa_elf_segment_t segment;
  void *ptr;
  size_t size;
  uint64_t vaddr;
  bool frozen;
  size_t storage_offset;

public:
  Segment(ExecutableImpl *owner_, hsa_agent_t agent_, amdgpu_hsa_elf_segment_t segment_, void* ptr_, size_t size_, uint64_t vaddr_, size_t storage_offset_)
    : ExecutableObject(owner_, agent_), segment(segment_),
      ptr(ptr_), size(size_), vaddr(vaddr_), frozen(false), storage_offset(storage_offset_) { }

  amdgpu_hsa_elf_segment_t ElfSegment() const { return segment; }
  void* Ptr() const { return ptr; }
  size_t Size() const { return size; }
  uint64_t VAddr() const { return vaddr; }
  size_t StorageOffset() const { return storage_offset;  }

  bool GetInfo(amd_loaded_segment_info_t attribute, void *value) override;

  uint64_t Offset(uint64_t addr); // Offset within segment. Used together with ptr with loader context functions.

  void* Address(uint64_t addr); // Address in segment. Used for relocations and valid on agent.

  bool Freeze();

  bool IsAddressInSegment(uint64_t addr);
  void Copy(uint64_t addr, const void* src, size_t size);
  void Print(std::ostream& out) override;
  void Destroy() override;
};

class Sampler : public ExecutableObject {
private:
  hsa_ext_sampler_t samp;

public:
  Sampler(ExecutableImpl *owner, hsa_agent_t agent, hsa_ext_sampler_t samp_)
    : ExecutableObject(owner, agent), samp(samp_) { }
  void Print(std::ostream& out) override;
  void Destroy() override;
};

class Image : public ExecutableObject {
private:
  hsa_ext_image_t img;

public:
  Image(ExecutableImpl *owner, hsa_agent_t agent, hsa_ext_image_t img_)
    : ExecutableObject(owner, agent), img(img_) { }
  void Print(std::ostream& out) override;
  void Destroy() override;
};

typedef std::string ProgramSymbol;
typedef std::unordered_map<ProgramSymbol, SymbolImpl*> ProgramSymbolMap;

typedef std::pair<std::string, hsa_agent_t> AgentSymbol;
struct ASC {
  bool operator()(const AgentSymbol &las, const AgentSymbol &ras) const {
    return las.first == ras.first && las.second.handle == ras.second.handle;
  }
};
struct ASH {
  size_t operator()(const AgentSymbol &as) const {
    size_t h = std::hash<std::string>()(as.first);
    size_t i = std::hash<uint64_t>()(as.second.handle);
    return h ^ (i << 1);
  }
};
typedef std::unordered_map<AgentSymbol, SymbolImpl*, ASH, ASC> AgentSymbolMap;

class ExecutableImpl final: public Executable {
friend class AmdHsaCodeLoader;
public:
  const hsa_profile_t& profile() const {
    return profile_;
  }
  const hsa_executable_state_t& state() const {
    return state_;
  }

  ExecutableImpl(
      const hsa_profile_t &_profile,
      Context *context,
      size_t id,
      hsa_default_float_rounding_mode_t default_float_rounding_mode);

  ExecutableImpl(
      const hsa_profile_t &_profile,
      std::unique_ptr<Context> unique_context,
      size_t id,
      hsa_default_float_rounding_mode_t default_float_rounding_mode);

  ~ExecutableImpl();

  hsa_status_t GetInfo(hsa_executable_info_t executable_info, void *value) override;

  hsa_status_t DefineProgramExternalVariable(
    const char *name, void *address) override;

  hsa_status_t DefineAgentExternalVariable(
    const char *name,
    hsa_agent_t agent,
    hsa_variable_segment_t segment,
    void *address) override;

  hsa_status_t LoadCodeObject(
    hsa_agent_t agent,
    hsa_code_object_t code_object,
    const char *options,
    const std::string &uri,
    hsa_loaded_code_object_t *loaded_code_object) override;

  hsa_status_t LoadCodeObject(
    hsa_agent_t agent,
    hsa_code_object_t code_object,
    size_t code_object_size,
    const char *options,
    const std::string &uri,
    hsa_loaded_code_object_t *loaded_code_object) override;

  hsa_status_t Freeze(const char *options) override;

  hsa_status_t Validate(uint32_t *result) override {
    amd::hsa::common::ReaderLockGuard<amd::hsa::common::ReaderWriterLock> reader_lock(rw_lock_);
    assert(result);
    *result = 0;
    return HSA_STATUS_SUCCESS;
  }

  /// @note needed for hsa v1.0.
  /// @todo remove during loader refactoring.
  bool IsProgramSymbol(const char *symbol_name) override;

  Symbol* GetSymbol(
    const char *symbol_name,
    const hsa_agent_t *agent) override;

  hsa_status_t IterateSymbols(
    iterate_symbols_f callback, void *data) override;

  /// @since hsa v1.1.
  hsa_status_t IterateAgentSymbols(
      hsa_agent_t agent,
      hsa_status_t (*callback)(hsa_executable_t exec,
                               hsa_agent_t agent,
                               hsa_executable_symbol_t symbol,
                               void *data),
      void *data) override;

  /// @since hsa v1.1.
  hsa_status_t IterateProgramSymbols(
      hsa_status_t (*callback)(hsa_executable_t exec,
                               hsa_executable_symbol_t symbol,
                               void *data),
      void *data) override;

  hsa_status_t IterateLoadedCodeObjects(
    hsa_status_t (*callback)(
      hsa_executable_t executable,
      hsa_loaded_code_object_t loaded_code_object,
      void *data),
    void *data) override;

  size_t GetNumSegmentDescriptors() override;

  size_t QuerySegmentDescriptors(
    hsa_ven_amd_loader_segment_descriptor_t *segment_descriptors,
    size_t total_num_segment_descriptors,
    size_t first_empty_segment_descriptor) override;

  uint64_t FindHostAddress(uint64_t device_address) override;

  void EnableReadOnlyMode();
  void DisableReadOnlyMode();

  void Print(std::ostream& out) override;
  bool PrintToFile(const std::string& filename) override;

  Context* context() { return context_; }
  size_t id() { return id_; }

private:
  ExecutableImpl(const ExecutableImpl &e);
  ExecutableImpl& operator=(const ExecutableImpl &e);

  std::unique_ptr<amd::hsa::code::AmdHsaCode> code;

  Symbol* GetSymbolInternal(
    const char *symbol_name,
    const hsa_agent_t *agent);

  hsa_status_t LoadSegments(hsa_agent_t agent, const code::AmdHsaCode *c,
                            uint32_t majorVersion);
  hsa_status_t LoadSegmentsV1(hsa_agent_t agent, const code::AmdHsaCode *c);
  hsa_status_t LoadSegmentsV2(hsa_agent_t agent, const code::AmdHsaCode *c);
  hsa_status_t LoadSegmentV1(hsa_agent_t agent, const code::Segment *s);
  hsa_status_t LoadSegmentV2(const code::Segment *data_segment,
                             loader::Segment *load_segment);

  hsa_status_t LoadSymbol(hsa_agent_t agent, amd::hsa::code::Symbol* sym, uint32_t majorVersion);
  hsa_status_t LoadDefinitionSymbol(hsa_agent_t agent, amd::hsa::code::Symbol* sym, uint32_t majorVersion);
  hsa_status_t LoadDeclarationSymbol(hsa_agent_t agent, amd::hsa::code::Symbol* sym, uint32_t majorVersion);

  hsa_status_t ApplyRelocations(hsa_agent_t agent, amd::hsa::code::AmdHsaCode *c);
  hsa_status_t ApplyStaticRelocationSection(hsa_agent_t agent, amd::hsa::code::RelocationSection* sec);
  hsa_status_t ApplyStaticRelocation(hsa_agent_t agent, amd::hsa::code::Relocation *rel);
  hsa_status_t ApplyDynamicRelocationSection(hsa_agent_t agent, amd::hsa::code::RelocationSection* sec);
  hsa_status_t ApplyDynamicRelocation(hsa_agent_t agent, amd::hsa::code::Relocation *rel);

  Segment* VirtualAddressSegment(uint64_t vaddr);
  uint64_t SymbolAddress(hsa_agent_t agent, amd::hsa::code::Symbol* sym);
  uint64_t SymbolAddress(hsa_agent_t agent, amd::elf::Symbol* sym);
  Segment* SymbolSegment(hsa_agent_t agent, amd::hsa::code::Symbol* sym);
  Segment* SectionSegment(hsa_agent_t agent, amd::hsa::code::Section* sec);

  amd::hsa::common::ReaderWriterLock rw_lock_;
  hsa_profile_t profile_;
  Context *context_;
  std::unique_ptr<Context> unique_context_;
  Logger logger_;
  const size_t id_;
  hsa_default_float_rounding_mode_t default_float_rounding_mode_;
  hsa_executable_state_t state_;

  ProgramSymbolMap program_symbols_;
  AgentSymbolMap agent_symbols_;
  std::vector<ExecutableObject*> objects;
  Segment *program_allocation_segment;
  std::vector<LoadedCodeObjectImpl*> loaded_code_objects;
};

class AmdHsaCodeLoader : public Loader {
private:
  Context* context;
  std::vector<Executable*> executables;
  amd::hsa::common::ReaderWriterLock rw_lock_;

public:
  AmdHsaCodeLoader(Context* context_)
    : context(context_) { assert(context); }

  Context* GetContext() const override { return context; }

  Executable* CreateExecutable(
      hsa_profile_t profile,
      const char *options,
      hsa_default_float_rounding_mode_t default_float_rounding_mode = HSA_DEFAULT_FLOAT_ROUNDING_MODE_DEFAULT) override;

  Executable* CreateExecutable(
      std::unique_ptr<Context> isolated_context,
      hsa_profile_t profile,
      const char *options,
      hsa_default_float_rounding_mode_t default_float_rounding_mode = HSA_DEFAULT_FLOAT_ROUNDING_MODE_DEFAULT) override;

  hsa_status_t FreezeExecutable(Executable *executable, const char *options) override;
  void DestroyExecutable(Executable *executable) override;

  hsa_status_t IterateExecutables(
    hsa_status_t (*callback)(
      hsa_executable_t executable,
      void *data),
    void *data) override;

  hsa_status_t QuerySegmentDescriptors(
    hsa_ven_amd_loader_segment_descriptor_t *segment_descriptors,
    size_t *num_segment_descriptors) override;
  #undef FindExecutable
  hsa_executable_t FindExecutable(uint64_t device_address) override;

  uint64_t FindHostAddress(uint64_t device_address) override;

  void PrintHelp(std::ostream& out) override;

  void EnableReadOnlyMode();
  void DisableReadOnlyMode();
};

} // namespace loader
} // namespace hsa
} // namespace amd
} // namespace rocr

#endif // HSA_RUNTIME_CORE_LOADER_EXECUTABLE_HPP_
