// Copyright 2016 The Fuchsia Authors
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT

#ifndef ZIRCON_KERNEL_OBJECT_INCLUDE_OBJECT_PROCESS_DISPATCHER_H_
#define ZIRCON_KERNEL_OBJECT_INCLUDE_OBJECT_PROCESS_DISPATCHER_H_

#include <zircon/syscalls/object.h>
#include <zircon/types.h>

#include <fbl/array.h>
#include <fbl/canary.h>
#include <fbl/intrusive_double_list.h>
#include <fbl/name.h>
#include <fbl/ref_counted.h>
#include <fbl/ref_ptr.h>
#include <kernel/brwlock.h>
#include <kernel/event.h>
#include <kernel/mutex.h>
#include <kernel/task_runtime_stats.h>
#include <kernel/thread.h>
#include <ktl/array.h>
#include <ktl/forward.h>
#include <ktl/span.h>
#include <object/dispatcher.h>
#include <object/exceptionate.h>
#include <object/futex_context.h>
#include <object/handle.h>
#include <object/handle_table.h>
#include <object/job_policy.h>
#include <object/shareable_process_state.h>
#include <object/thread_dispatcher.h>
#include <vm/vm_aspace.h>

class JobDispatcher;
class VmoInfoWriter;

namespace internal {
// Tag for a ProcessDispatcher's parent JobDispatcher's raw job list.
struct ProcessDispatcherRawJobListTag {};
// Tag for a ProcessDispatcher's parent JobDispatcher's job list.
struct ProcessDispatcherJobListTag {};
}  // namespace internal

class ProcessDispatcher final
    : public SoloDispatcher<ProcessDispatcher, ZX_DEFAULT_PROCESS_RIGHTS>,
      public fbl::ContainableBaseClasses<
          fbl::TaggedDoublyLinkedListable<ProcessDispatcher*,
                                          internal::ProcessDispatcherRawJobListTag>,
          fbl::TaggedSinglyLinkedListable<fbl::RefPtr<ProcessDispatcher>,
                                          internal::ProcessDispatcherJobListTag>> {
 public:
  using RawJobListTag = internal::ProcessDispatcherRawJobListTag;
  using JobListTag = internal::ProcessDispatcherJobListTag;

  static zx_status_t Create(fbl::RefPtr<JobDispatcher> job, ktl::string_view name, uint32_t flags,
                            KernelHandle<ProcessDispatcher>* handle, zx_rights_t* rights,
                            KernelHandle<VmAddressRegionDispatcher>* root_vmar_handle,
                            zx_rights_t* root_vmar_rights);

  static ProcessDispatcher* GetCurrent() {
    ThreadDispatcher* current = ThreadDispatcher::GetCurrent();
    DEBUG_ASSERT(current);
    return current->process();
  }

  static void ExitCurrent(int64_t retcode) __NO_RETURN {
    ThreadDispatcher* current = ThreadDispatcher::GetCurrent();
    DEBUG_ASSERT(current);
    current->process()->Exit(retcode);
  }

  // Dispatcher implementation
  zx_obj_type_t get_type() const final { return ZX_OBJ_TYPE_PROCESS; }
  void on_zero_handles() final;
  zx_koid_t get_related_koid() const final;

  ~ProcessDispatcher() final;

  // state of the process
  enum class State {
    INITIAL,  // initial state, no thread present in process
    RUNNING,  // first thread has started and is running
    DYING,    // process has delivered kill signal to all threads
    DEAD,     // all threads have entered DEAD state and potentially dropped refs on process
  };

  // Performs initialization on a newly constructed ProcessDispatcher
  // If this fails, then the object is invalid and should be deleted
  zx_status_t Initialize();

  // Accessors.
  HandleTable& handle_table() { return shared_state_->handle_table(); }
  const HandleTable& handle_table() const { return shared_state_->handle_table(); }
  FutexContext& futex_context() { return shared_state_->futex_context(); }
  State state() const;
  fbl::RefPtr<VmAspace> aspace() { return aspace_; }
  fbl::RefPtr<JobDispatcher> job();

  void get_name(char (&out_name)[ZX_MAX_NAME_LEN]) const final;
  zx_status_t set_name(const char* name, size_t len) final;

  void Kill(int64_t retcode);

  // Suspends the process.
  //
  // Suspending a process causes all child threads to suspend as well as any new children
  // that are added until the process is resumed. Suspend() is cumulative, so the process
  // will only resume once Resume() has been called an equal number of times.
  //
  // Returns ZX_OK on success, or ZX_ERR_BAD_STATE iff the process is dying or dead.
  zx_status_t Suspend();
  void Resume();

  // Syscall helpers
  void GetInfo(zx_info_process_t* info) const;
  zx_status_t GetStats(zx_info_task_stats_t* stats) const;

  // Accumulate the runtime of all threads that previously ran or are currently running under this
  // process.
  zx_status_t AccumulateRuntimeTo(zx_info_task_runtime_t* info) const;

  // NOTE: Code outside of the syscall layer should not typically know about
  // user_ptrs; do not use this pattern as an example.
  zx_status_t GetAspaceMaps(VmAspace* current_aspace, user_out_ptr<zx_info_maps_t> maps, size_t max,
                            size_t* actual, size_t* available) const;
  zx_status_t GetVmos(VmAspace* current_aspace, VmoInfoWriter& vmos, size_t max, size_t* actual,
                      size_t* available);
  zx_status_t GetThreads(fbl::Array<zx_koid_t>* threads) const;
  zx_status_t SetCriticalToJob(fbl::RefPtr<JobDispatcher> critical_to_job, bool retcode_nonzero);

  Exceptionate* exceptionate(Exceptionate::Type type);

  // The following two methods can be slow and inaccurate and should only be
  // called from diagnostics code.
  uint32_t ThreadCount() const;
  size_t PageCount() const;

  // Look up a process given its koid.
  // Returns nullptr if not found.
  static fbl::RefPtr<ProcessDispatcher> LookupProcessById(zx_koid_t koid);

  // Look up a thread in this process given its koid.
  // Returns nullptr if not found.
  fbl::RefPtr<ThreadDispatcher> LookupThreadById(zx_koid_t koid);

  uintptr_t get_debug_addr() const;
  zx_status_t set_debug_addr(uintptr_t addr);

  uintptr_t get_dyn_break_on_load() const;
  zx_status_t set_dyn_break_on_load(uintptr_t break_on_load);

  // Checks |condition| and enforces the parent job's policy.
  //
  // Depending on the parent job's policy, this method may signal an exception
  // on the calling thread or signal that the current process should be
  // killed.
  //
  // Must be called by syscalls before performing an action represented by an
  // ZX_POL_xxxxx condition. If the return value is ZX_OK the action can
  // proceed; otherwise, the process is not allowed to perform the action,
  // and the status value should be returned to the usermode caller.
  //
  // E.g., in sys_channel_create:
  //
  //     auto up = ProcessDispatcher::GetCurrent();
  //     zx_status_t res = up->EnforceBasicPolicy(ZX_POL_NEW_CHANNEL);
  //     if (res != ZX_OK) {
  //         // Channel creation denied by the calling process's
  //         // parent job's policy.
  //         return res;
  //     }
  //     // Ok to create a channel.
  __WARN_UNUSED_RESULT
  zx_status_t EnforceBasicPolicy(uint32_t condition);

  // Returns this job's timer slack policy.
  TimerSlack GetTimerSlackPolicy() const;

  // return a cached copy of the vdso code address or compute a new one
  uintptr_t vdso_code_address() {
    if (unlikely(vdso_code_address_ == 0)) {
      return cache_vdso_code_address();
    }
    return vdso_code_address_;
  }

  // Retrieve the aggregated runtime of exited threads under this process.
  TaskRuntimeStats GetAggregatedRuntime() const TA_EXCL(get_lock());

 private:
  // Exit the current Process. It is an error to call this on anything other than the current
  // process. Please use ExitCurrent() instead of calling this directly.
  void Exit(int64_t retcode) __NO_RETURN;

  // compute the vdso code address and store in vdso_code_address_
  uintptr_t cache_vdso_code_address();

  // The diagnostic code is allow to know about the internals of this code.
  friend void DumpProcessList();
  friend void KillProcess(zx_koid_t id);
  friend void DumpProcessMemoryUsage(const char* prefix, size_t min_pages);

  ProcessDispatcher(fbl::RefPtr<ShareableProcessState> shared_state, fbl::RefPtr<JobDispatcher> job,
                    ktl::string_view name, uint32_t flags);

  ProcessDispatcher(const ProcessDispatcher&) = delete;
  ProcessDispatcher& operator=(const ProcessDispatcher&) = delete;

  void OnProcessStartForJobDebugger(ThreadDispatcher* t, const arch_exception_context_t* context);

  // Thread lifecycle support.
  friend class ThreadDispatcher;
  // Takes the given ThreadDispatcher and transitions it from the INITIALIZED state to a runnable
  // state (RUNNING or SUSPENDED depending on whether this process is suspended) by calling
  // ThreadDispatcher::MakeRunnable. The thread is then added to the thread_list_ for this process
  // and we transition to running if this is the initial_thread.
  zx_status_t AddInitializedThread(ThreadDispatcher* t, bool initial_thread,
                                   const ThreadDispatcher::EntryState& entry);
  void RemoveThread(ThreadDispatcher* t);

  void SetStateLocked(State) TA_REQ(get_lock());
  void FinishDeadTransition();

  // Kill all threads
  void KillAllThreadsLocked() TA_REQ(get_lock());

  const fbl::RefPtr<ShareableProcessState> shared_state_;

  // the enclosing job
  const fbl::RefPtr<JobDispatcher> job_;

  // Job that this process is critical to.
  //
  // We require that the job is the parent of this process, or an ancestor.
  fbl::RefPtr<JobDispatcher> critical_to_job_ TA_GUARDED(get_lock());
  bool retcode_nonzero_ TA_GUARDED(get_lock()) = false;

  // Policy set by the Job during Create().
  //
  // It is critical that this field is immutable as it will be accessed without synchronization.
  const JobPolicy policy_;

  // list of threads in this process
  fbl::DoublyLinkedList<ThreadDispatcher*> thread_list_ TA_GUARDED(get_lock());

  // our address space
  fbl::RefPtr<VmAspace> aspace_;

  // our state
  State state_ TA_GUARDED(get_lock()) = State::INITIAL;

  // Suspend count; incremented on Suspend(), decremented on Resume().
  int suspend_count_ TA_GUARDED(get_lock()) = 0;

  // True if FinishDeadTransition has been called.
  // This is used as a sanity check only.
  bool completely_dead_ = false;

  // process return code
  int64_t retcode_ = 0;

  Exceptionate exceptionate_;
  Exceptionate debug_exceptionate_;

  // This is the value of _dl_debug_addr from ld.so.
  // See third_party/ulib/musl/ldso/dynlink.c.
  uintptr_t debug_addr_ TA_GUARDED(get_lock()) = 0;

  // Whether the dynamic loader should issue a debug trap when loading a shared library,
  // either initially or when running (e.g. dlopen).
  //
  // See docs/reference/syscalls/object_get_property.md
  // See third_party/ulib/musl/ldso/dynlink.c.
  uintptr_t dyn_break_on_load_ TA_GUARDED(get_lock()) = 0;

  // This is a cache of aspace()->vdso_code_address().
  uintptr_t vdso_code_address_ = 0;

  // The time at which the process was started.
  zx_time_t start_time_ = 0;

  // The user-friendly process name. For debug purposes only. That
  // is, there is no mechanism to mint a handle to a process via this name.
  fbl::Name<ZX_MAX_NAME_LEN> name_;

  // Aggregated runtime stats from exited threads.
  TaskRuntimeStats aggregated_runtime_stats_ TA_GUARDED(get_lock());
};

const char* StateToString(ProcessDispatcher::State state);

#endif  // ZIRCON_KERNEL_OBJECT_INCLUDE_OBJECT_PROCESS_DISPATCHER_H_