text: #include "ProcFS.h"
  #include "Console.h"
  #include "KSyms.h"
  #include "Process.h"
  #include "Scheduler.h"
  #include "StdLib.h"
  #include <AK/JsonArray.h>
  #include <AK/JsonObject.h>
  #include <AK/JsonValue.h>
  #include <AK/StringBuilder.h>
  #include <Kernel/Arch/i386/CPU.h>
  #include <Kernel/FileSystem/Custody.h>
  #include <Kernel/FileSystem/FileDescription.h>
  #include <Kernel/FileSystem/VirtualFileSystem.h>
  #include <Kernel/KParams.h>
  #include <Kernel/Net/NetworkAdapter.h>
  #include <Kernel/PCI.h>
  #include <Kernel/VM/MemoryManager.h>
  #include <Kernel/kmalloc.h>
  #include <LibC/errno_numbers.h>
  
  enum ProcParentDirectory {
      PDI_AbstractRoot = 0,
      PDI_Root,
      PDI_Root_sys,
      PDI_PID,
      PDI_PID_fd,
  };
  
  enum ProcFileType {
      FI_Invalid = 0,
  
      FI_Root = 1, // directory
  
      __FI_Root_Start,
      FI_Root_mm,
      FI_Root_mounts,
      FI_Root_df,
      FI_Root_kmalloc,
      FI_Root_all,
      FI_Root_memstat,
      FI_Root_cpuinfo,
      FI_Root_inodes,
      FI_Root_dmesg,
      FI_Root_pci,
      FI_Root_uptime,
      FI_Root_cmdline,
      FI_Root_netadapters,
      FI_Root_self, // symlink
      FI_Root_sys,  // directory
      __FI_Root_End,
  
      FI_PID,
  
      __FI_PID_Start,
      FI_PID_vm,
      FI_PID_vmo,
      FI_PID_stack,
      FI_PID_regs,
      FI_PID_fds,
      FI_PID_exe, // symlink
      FI_PID_cwd, // symlink
      FI_PID_fd,  // directory
      __FI_PID_End,
  
      FI_MaxStaticFileIndex,
  };
  
  static inline pid_t to_pid(const InodeIdentifier& identifier)
  {
  #ifdef PROCFS_DEBUG
      dbgprintf("to_pid, index=%08x -> %u\n", identifier.index(), identifier.index() >> 16);
  #endif
      return identifier.index() >> 16u;
  }
  
  static inline ProcParentDirectory to_proc_parent_directory(const InodeIdentifier& identifier)
  {
      return (ProcParentDirectory)((identifier.index() >> 12) & 0xf);
  }
  
  static inline int to_fd(const InodeIdentifier& identifier)
  {
      ASSERT(to_proc_parent_directory(identifier) == PDI_PID_fd);
      return (identifier.index() & 0xff) - FI_MaxStaticFileIndex;
  }
  
  static inline int to_sys_index(const InodeIdentifier& identifier)
  {
      ASSERT(to_proc_parent_directory(identifier) == PDI_Root_sys);
      return identifier.index() & 0xff;
  }
  
  static inline InodeIdentifier to_identifier(unsigned fsid, ProcParentDirectory parent, pid_t pid, ProcFileType proc_file_type)
  {
      return { fsid, ((unsigned)parent << 12u) | ((unsigned)pid << 16u) | (unsigned)proc_file_type };
  }
  
  static inline InodeIdentifier to_identifier_with_fd(unsigned fsid, pid_t pid, int fd)
  {
      return { fsid, (PDI_PID_fd << 12u) | ((unsigned)pid << 16u) | (FI_MaxStaticFileIndex + fd) };
  }
  
  static inline InodeIdentifier sys_var_to_identifier(unsigned fsid, unsigned index)
  {
      ASSERT(index < 256);
      return { fsid, (PDI_Root_sys << 12u) | index };
  }
  
  static inline InodeIdentifier to_parent_id(const InodeIdentifier& identifier)
  {
      switch (to_proc_parent_directory(identifier)) {
      case PDI_AbstractRoot:
      case PDI_Root:
          return { identifier.fsid(), FI_Root };
      case PDI_Root_sys:
          return { identifier.fsid(), FI_Root_sys };
      case PDI_PID:
          return to_identifier(identifier.fsid(), PDI_Root, to_pid(identifier), FI_PID);
      case PDI_PID_fd:
          return to_identifier(identifier.fsid(), PDI_PID, to_pid(identifier), FI_PID_fd);
      }
      ASSERT_NOT_REACHED();
  }
  
  #if 0
  static inline u8 to_unused_metadata(const InodeIdentifier& identifier)
  {
      return (identifier.index() >> 8) & 0xf;
  }
  #endif
  
  static inline ProcFileType to_proc_file_type(const InodeIdentifier& identifier)
  {
      return (ProcFileType)(identifier.index() & 0xff);
  }
  
  static inline bool is_process_related_file(const InodeIdentifier& identifier)
  {
      if (to_proc_file_type(identifier) == FI_PID)
          return true;
      auto proc_parent_directory = to_proc_parent_directory(identifier);
      switch (proc_parent_directory) {
      case PDI_PID:
      case PDI_PID_fd:
          return true;
      default:
          return false;
      }
  }
  
  static inline bool is_directory(const InodeIdentifier& identifier)
  {
      auto proc_file_type = to_proc_file_type(identifier);
      switch (proc_file_type) {
      case FI_Root:
      case FI_Root_sys:
      case FI_PID:
      case FI_PID_fd:
          return true;
      default:
          return false;
      }
  }
  
  static inline bool is_persistent_inode(const InodeIdentifier& identifier)
  {
      return to_proc_parent_directory(identifier) == PDI_Root_sys;
  }
  
  static ProcFS* s_the;
  
  ProcFS& ProcFS::the()
  {
      ASSERT(s_the);
      return *s_the;
  }
  
  NonnullRefPtr<ProcFS> ProcFS::create()
  {
      return adopt(*new ProcFS);
  }
  
  ProcFS::~ProcFS()
  {
  }
  
  ByteBuffer procfs$pid_fds(InodeIdentifier identifier)
  {
      auto handle = ProcessInspectionHandle::from_pid(to_pid(identifier));
      if (!handle)
          return {};
      auto& process = handle->process();
      if (process.number_of_open_file_descriptors() == 0)
          return {};
      JsonArray array;
      for (int i = 0; i < process.max_open_file_descriptors(); ++i) {
          auto* description = process.file_description(i);
          if (!description)
              continue;
          JsonObject description_object;
          description_object.set("fd", i);
          description_object.set("absolute_path", description->absolute_path());
          array.append(move(description_object));
      }
      return array.serialized().to_byte_buffer();
  }
  
  ByteBuffer procfs$pid_fd_entry(InodeIdentifier identifier)
  {
      auto handle = ProcessInspectionHandle::from_pid(to_pid(identifier));
      if (!handle)
          return {};
      auto& process = handle->process();
      int fd = to_fd(identifier);
      auto* description = process.file_description(fd);
      if (!description)
          return {};
      return description->absolute_path().to_byte_buffer();
  }
  
  ByteBuffer procfs$pid_vm(InodeIdentifier identifier)
  {
      auto handle = ProcessInspectionHandle::from_pid(to_pid(identifier));
      if (!handle)
          return {};
      auto& process = handle->process();
      JsonArray array;
      for (auto& region : process.regions()) {
          JsonObject region_object;
          region_object.set("readable", region.is_readable());
          region_object.set("writable", region.is_writable());
          region_object.set("address", region.vaddr().get());
          region_object.set("size", region.size());
          region_object.set("amount_resident", region.amount_resident());
          region_object.set("name", region.name());
          array.append(move(region_object));
      }
      return array.serialized().to_byte_buffer();
  }
  
  ByteBuffer procfs$pci(InodeIdentifier)
  {
      StringBuilder builder;
      PCI::enumerate_all([&builder](PCI::Address address, PCI::ID id) {
          builder.appendf("%b:%b.%b %w:%w\n", address.bus(), address.slot(), address.function(), id.vendor_id, id.device_id);
      });
      return builder.to_byte_buffer();
  }
  
  ByteBuffer procfs$uptime(InodeIdentifier)
  {
      StringBuilder builder;
      builder.appendf("%u\n", (u32)(g_uptime / 1000));
      return builder.to_byte_buffer();
  }
  
  ByteBuffer procfs$cmdline(InodeIdentifier)
  {
      StringBuilder builder;
      builder.appendf("%s\n", KParams::the().cmdline().characters());
      return builder.to_byte_buffer();
  }
  
  ByteBuffer procfs$netadapters(InodeIdentifier)
  {
      StringBuilder builder;
      NetworkAdapter::for_each([&builder](auto& adapter) {
          builder.appendf("%s,%s,%s,%s\n",
              adapter.name().characters(),
              adapter.class_name(),
              adapter.mac_address().to_string().characters(),
              adapter.ipv4_address().to_string().characters());
      });
      return builder.to_byte_buffer();
  }
  
  ByteBuffer procfs$pid_vmo(InodeIdentifier identifier)
  {
      auto handle = ProcessInspectionHandle::from_pid(to_pid(identifier));
      if (!handle)
          return {};
      auto& process = handle->process();
      StringBuilder builder;
      builder.appendf("BEGIN       END         SIZE        NAME\n");
      for (auto& region : process.regions()) {
          builder.appendf("%x -- %x    %x    %s\n",
              region.vaddr().get(),
              region.vaddr().offset(region.size() - 1).get(),
              region.size(),
              region.name().characters());
          builder.appendf("VMO: %s \"%s\" @ %x(%u)\n",
              region.vmo().is_anonymous() ? "anonymous" : "file-backed",
              region.vmo().name().characters(),
              &region.vmo(),
              region.vmo().ref_count());
          for (int i = 0; i < region.vmo().page_count(); ++i) {
              auto& physical_page = region.vmo().physical_pages()[i];
              builder.appendf("P%x%s(%u) ",
                  physical_page ? physical_page->paddr().get() : 0,
                  region.should_cow(i) ? "!" : "",
                  physical_page ? physical_page->ref_count() : 0);
          }
          builder.appendf("\n");
      }
      return builder.to_byte_buffer();
  }
  
  ByteBuffer procfs$pid_stack(InodeIdentifier identifier)
  {
      auto handle = ProcessInspectionHandle::from_pid(to_pid(identifier));
      if (!handle)
          return {};
      auto& process = handle->process();
      return process.backtrace(*handle).to_byte_buffer();
  }
  
  ByteBuffer procfs$pid_regs(InodeIdentifier identifier)
  {
      auto handle = ProcessInspectionHandle::from_pid(to_pid(identifier));
      if (!handle)
          return {};
      auto& process = handle->process();
      StringBuilder builder;
      process.for_each_thread([&](Thread& thread) {
          builder.appendf("Thread %d:\n", thread.tid());
          auto& tss = thread.tss();
          builder.appendf("eax: %x\n", tss.eax);
          builder.appendf("ebx: %x\n", tss.ebx);
          builder.appendf("ecx: %x\n", tss.ecx);
          builder.appendf("edx: %x\n", tss.edx);
          builder.appendf("esi: %x\n", tss.esi);
          builder.appendf("edi: %x\n", tss.edi);
          builder.appendf("ebp: %x\n", tss.ebp);
          builder.appendf("cr3: %x\n", tss.cr3);
          builder.appendf("flg: %x\n", tss.eflags);
          builder.appendf("sp:  %w:%x\n", tss.ss, tss.esp);
          builder.appendf("pc:  %w:%x\n", tss.cs, tss.eip);
          return IterationDecision::Continue;
      });
      return builder.to_byte_buffer();
  }
  
  ByteBuffer procfs$pid_exe(InodeIdentifier identifier)
  {
      auto handle = ProcessInspectionHandle::from_pid(to_pid(identifier));
      if (!handle)
          return {};
      auto& process = handle->process();
      auto* custody = process.executable();
      ASSERT(custody);
      return custody->absolute_path().to_byte_buffer();
  }
  
  ByteBuffer procfs$pid_cwd(InodeIdentifier identifier)
  {
      auto handle = ProcessInspectionHandle::from_pid(to_pid(identifier));
      if (!handle)
          return {};
      return handle->process().current_directory().absolute_path().to_byte_buffer();
  }
  
  ByteBuffer procfs$self(InodeIdentifier)
  {
      char buffer[16];
      ksprintf(buffer, "%u", current->pid());
      return ByteBuffer::copy((const u8*)buffer, strlen(buffer));
  }
  
  ByteBuffer procfs$mm(InodeIdentifier)
  {
      // FIXME: Implement
      InterruptDisabler disabler;
      StringBuilder builder;
      for (auto* vmo : MM.m_vmos) {
          builder.appendf("VMO: %p %s(%u): p:%4u %s\n",
              vmo,
              vmo->is_anonymous() ? "anon" : "file",
              vmo->ref_count(),
              vmo->page_count(),
              vmo->name().characters());
      }
      builder.appendf("VMO count: %u\n", MM.m_vmos.size());
      builder.appendf("Free physical pages: %u\n", MM.user_physical_pages() - MM.user_physical_pages_used());
      builder.appendf("Free supervisor physical pages: %u\n", MM.super_physical_pages() - MM.super_physical_pages_used());
      return builder.to_byte_buffer();
  }
  
  ByteBuffer procfs$dmesg(InodeIdentifier)
  {
      InterruptDisabler disabler;
      StringBuilder builder;
      for (char ch : Console::the().logbuffer())
          builder.append(ch);
      return builder.to_byte_buffer();
  }
  
  ByteBuffer procfs$mounts(InodeIdentifier)
  {
      // FIXME: This is obviously racy against the VFS mounts changing.
      StringBuilder builder;
      VFS::the().for_each_mount([&builder](auto& mount) {
          auto& fs = mount.guest_fs();
          builder.appendf("%s @ ", fs.class_name());
          if (!mount.host().is_valid())
              builder.appendf("/");
          else {
              builder.appendf("%u:%u", mount.host().fsid(), mount.host().index());
              builder.append(' ');
              builder.append(mount.absolute_path());
          }
          builder.append('\n');
      });
      return builder.to_byte_buffer();
  }
  
  ByteBuffer procfs$df(InodeIdentifier)
  {
      // FIXME: This is obviously racy against the VFS mounts changing.
      JsonArray json;
      VFS::the().for_each_mount([&json](auto& mount) {
          auto& fs = mount.guest_fs();
          JsonObject fs_object;
          fs_object.set("class_name", fs.class_name());
          fs_object.set("total_block_count", fs.total_block_count());
          fs_object.set("free_block_count", fs.free_block_count());
          fs_object.set("total_inode_count", fs.total_inode_count());
          fs_object.set("free_inode_count", fs.free_inode_count());
          fs_object.set("mount_point", mount.absolute_path());
          json.append(fs_object);
      });
      return json.serialized().to_byte_buffer();
  }
  
  ByteBuffer procfs$cpuinfo(InodeIdentifier)
  {
      StringBuilder builder;
      {
          CPUID cpuid(0);
          builder.appendf("cpuid:     ");
          auto emit_u32 = [&](u32 value) {
              builder.appendf("%c%c%c%c",
                  value & 0xff,
                  (value >> 8) & 0xff,
                  (value >> 16) & 0xff,
                  (value >> 24) & 0xff);
          };
          emit_u32(cpuid.ebx());
          emit_u32(cpuid.edx());
          emit_u32(cpuid.ecx());
          builder.appendf("\n");
      }
      {
          CPUID cpuid(1);
          u32 stepping = cpuid.eax() & 0xf;
          u32 model = (cpuid.eax() >> 4) & 0xf;
          u32 family = (cpuid.eax() >> 8) & 0xf;
          u32 type = (cpuid.eax() >> 12) & 0x3;
          u32 extended_model = (cpuid.eax() >> 16) & 0xf;
          u32 extended_family = (cpuid.eax() >> 20) & 0xff;
          u32 display_model;
          u32 display_family;
          if (family == 15) {
              display_family = family + extended_family;
              display_model = model + (extended_model << 4);
          } else if (family == 6) {
              display_family = family;
              display_model = model + (extended_model << 4);
          } else {
              display_family = family;
              display_model = model;
          }
          builder.appendf("family:    %u\n", display_family);
          builder.appendf("model:     %u\n", display_model);
          builder.appendf("stepping:  %u\n", stepping);
          builder.appendf("type:      %u\n", type);
      }
      {
          // FIXME: Check first that this is supported by calling CPUID with eax=0x80000000
          //        and verifying that the returned eax>=0x80000004.
          alignas(u32) char buffer[48];
          u32* bufptr = reinterpret_cast<u32*>(buffer);
          auto copy_brand_string_part_to_buffer = [&](u32 i) {
              CPUID cpuid(0x80000002 + i);
              *bufptr++ = cpuid.eax();
              *bufptr++ = cpuid.ebx();
              *bufptr++ = cpuid.ecx();
              *bufptr++ = cpuid.edx();
          };
          copy_brand_string_part_to_buffer(0);
          copy_brand_string_part_to_buffer(1);
          copy_brand_string_part_to_buffer(2);
          builder.appendf("brandstr:  \"%s\"\n", buffer);
      }
      return builder.to_byte_buffer();
  }
  
  ByteBuffer procfs$kmalloc(InodeIdentifier)
  {
      StringBuilder builder;
      builder.appendf(
          "eternal:      %u\n"
          "allocated:    %u\n"
          "free:         %u\n",
          kmalloc_sum_eternal,
          sum_alloc,
          sum_free);
      return builder.to_byte_buffer();
  }
  
  ByteBuffer procfs$memstat(InodeIdentifier)
  {
      InterruptDisabler disabler;
      JsonObject json;
      json.set("kmalloc_allocated", sum_alloc);
      json.set("kmalloc_available", sum_free);
      json.set("kmalloc_eternal_allocated", kmalloc_sum_eternal);
      json.set("user_physical_allocated", MM.user_physical_pages_used());
      json.set("user_physical_available", MM.user_physical_pages());
      json.set("super_physical_allocated", MM.super_physical_pages_used());
      json.set("super_physical_available", MM.super_physical_pages());
      json.set("kmalloc_call_count", g_kmalloc_call_count);
      json.set("kfree_call_count", g_kfree_call_count);
      return json.serialized().to_byte_buffer();
  }
  
  ByteBuffer procfs$all(InodeIdentifier)
  {
      InterruptDisabler disabler;
      auto processes = Process::all_processes();
      JsonArray array;
  
      // Keep this in sync with CProcessStatistics.
      auto build_process = [&](const Process& process) {
          JsonObject process_object;
          process_object.set("pid", process.pid());
          process_object.set("times_scheduled", process.main_thread().times_scheduled());
          process_object.set("pgid", process.tty() ? process.tty()->pgid() : 0);
          process_object.set("pgp", process.pgid());
          process_object.set("sid", process.sid());
          process_object.set("uid", process.uid());
          process_object.set("gid", process.gid());
          process_object.set("state", process.main_thread().state_string());
          process_object.set("ppid", process.ppid());
          process_object.set("nfds", process.number_of_open_file_descriptors());
          process_object.set("name", process.name());
          process_object.set("tty", process.tty() ? process.tty()->tty_name() : "notty");
          process_object.set("amount_virtual", process.amount_virtual());
          process_object.set("amount_resident", process.amount_resident());
          process_object.set("amount_shared", process.amount_shared());
          process_object.set("ticks", process.main_thread().ticks());
          process_object.set("priority", to_string(process.priority()));
          process_object.set("syscall_count", process.syscall_count());
          process_object.set("icon_id", process.icon_id());
          array.append(process_object);
      };
      build_process(*Scheduler::colonel());
      for (auto* process : processes)
          build_process(*process);
      return array.serialized().to_byte_buffer();
  }
  
  ByteBuffer procfs$inodes(InodeIdentifier)
  {
      extern HashTable<Inode*>& all_inodes();
      StringBuilder builder;
      for (auto it : all_inodes()) {
          RefPtr<Inode> inode = *it;
          builder.appendf("Inode{K%x} %02u:%08u (%u)\n", inode.ptr(), inode->fsid(), inode->index(), inode->ref_count());
      }
      return builder.to_byte_buffer();
  }
  
  struct SysVariableData final : public ProcFSInodeCustomData {
      virtual ~SysVariableData() override {}
  
      enum Type {
          Invalid,
          Boolean,
          String,
      };
      Type type { Invalid };
      Function<void()> notify_callback;
      void* address;
  };
  
  static ByteBuffer read_sys_bool(InodeIdentifier inode_id)
  {
      auto inode_ptr = ProcFS::the().get_inode(inode_id);
      if (!inode_ptr)
          return {};
      auto& inode = static_cast<ProcFSInode&>(*inode_ptr);
      ASSERT(inode.custom_data());
      auto buffer = ByteBuffer::create_uninitialized(2);
      auto& custom_data = *static_cast<const SysVariableData*>(inode.custom_data());
      ASSERT(custom_data.type == SysVariableData::Boolean);
      ASSERT(custom_data.address);
      auto* lockable_bool = reinterpret_cast<Lockable<bool>*>(custom_data.address);
      {
          LOCKER(lockable_bool->lock());
          buffer[0] = lockable_bool->resource() ? '1' : '0';
      }
      buffer[1] = '\n';
      return buffer;
  }
  
  static ssize_t write_sys_bool(InodeIdentifier inode_id, const ByteBuffer& data)
  {
      auto inode_ptr = ProcFS::the().get_inode(inode_id);
      if (!inode_ptr)
          return {};
      auto& inode = static_cast<ProcFSInode&>(*inode_ptr);
      ASSERT(inode.custom_data());
      if (data.is_empty() || !(data[0] == '0' || data[0] == '1'))
          return data.size();
  
      auto& custom_data = *static_cast<const SysVariableData*>(inode.custom_data());
      auto* lockable_bool = reinterpret_cast<Lockable<bool>*>(custom_data.address);
      {
          LOCKER(lockable_bool->lock());
          lockable_bool->resource() = data[0] == '1';
      }
      if (custom_data.notify_callback)
          custom_data.notify_callback();
      return data.size();
  }
  
  static ByteBuffer read_sys_string(InodeIdentifier inode_id)
  {
      auto inode_ptr = ProcFS::the().get_inode(inode_id);
      if (!inode_ptr)
          return {};
      auto& inode = static_cast<ProcFSInode&>(*inode_ptr);
      ASSERT(inode.custom_data());
      auto buffer = ByteBuffer::create_uninitialized(2);
      auto& custom_data = *static_cast<const SysVariableData*>(inode.custom_data());
      ASSERT(custom_data.type == SysVariableData::String);
      ASSERT(custom_data.address);
      auto* lockable_string = reinterpret_cast<Lockable<String>*>(custom_data.address);
      LOCKER(lockable_string->lock());
      return lockable_string->resource().to_byte_buffer();
  }
  
  static ssize_t write_sys_string(InodeIdentifier inode_id, const ByteBuffer& data)
  {
      auto inode_ptr = ProcFS::the().get_inode(inode_id);
      if (!inode_ptr)
          return {};
      auto& inode = static_cast<ProcFSInode&>(*inode_ptr);
      ASSERT(inode.custom_data());
      auto& custom_data = *static_cast<const SysVariableData*>(inode.custom_data());
      ASSERT(custom_data.address);
      {
          auto* lockable_string = reinterpret_cast<Lockable<String>*>(custom_data.address);
          LOCKER(lockable_string->lock());
          lockable_string->resource() = String((const char*)data.pointer(), data.size());
      }
      if (custom_data.notify_callback)
          custom_data.notify_callback();
      return data.size();
  }
  
  void ProcFS::add_sys_bool(String&& name, Lockable<bool>& var, Function<void()>&& notify_callback)
  {
      InterruptDisabler disabler;
  
      int index = m_sys_entries.size();
      auto inode = adopt(*new ProcFSInode(*this, sys_var_to_identifier(fsid(), index).index()));
      auto data = make<SysVariableData>();
      data->type = SysVariableData::Boolean;
      data->notify_callback = move(notify_callback);
      data->address = &var;
      inode->set_custom_data(move(data));
      m_sys_entries.empend(strdup(name.characters()), 0, read_sys_bool, write_sys_bool, move(inode));
  }
  
  void ProcFS::add_sys_string(String&& name, Lockable<String>& var, Function<void()>&& notify_callback)
  {
      InterruptDisabler disabler;
  
      int index = m_sys_entries.size();
      auto inode = adopt(*new ProcFSInode(*this, sys_var_to_identifier(fsid(), index).index()));
      auto data = make<SysVariableData>();
      data->type = SysVariableData::String;
      data->notify_callback = move(notify_callback);
      data->address = &var;
      inode->set_custom_data(move(data));
      m_sys_entries.empend(strdup(name.characters()), 0, read_sys_string, write_sys_string, move(inode));
  }
  
  bool ProcFS::initialize()
  {
      return true;
  }
  
  const char* ProcFS::class_name() const
  {
      return "ProcFS";
  }
  
  RefPtr<Inode> ProcFS::create_inode(InodeIdentifier, const String&, mode_t, off_t, dev_t, int&)
  {
      kprintf("FIXME: Implement ProcFS::create_inode()?\n");
      return {};
  }
  
  RefPtr<Inode> ProcFS::create_directory(InodeIdentifier, const String&, mode_t, int& error)
  {
      error = -EROFS;
      return nullptr;
  }
  
  InodeIdentifier ProcFS::root_inode() const
  {
      return { fsid(), FI_Root };
  }
  
  RefPtr<Inode> ProcFS::get_inode(InodeIdentifier inode_id) const
  {
  #ifdef PROCFS_DEBUG
      dbgprintf("ProcFS::get_inode(%u)\n", inode_id.index());
  #endif
      if (inode_id == root_inode())
          return m_root_inode;
  
      if (to_proc_parent_directory(inode_id) == ProcParentDirectory::PDI_Root_sys) {
          auto sys_index = to_sys_index(inode_id);
          if (sys_index < m_sys_entries.size())
              return m_sys_entries[sys_index].inode;
      }
  
      LOCKER(m_inodes_lock);
      auto it = m_inodes.find(inode_id.index());
      if (it == m_inodes.end()) {
          auto inode = adopt(*new ProcFSInode(const_cast<ProcFS&>(*this), inode_id.index()));
          m_inodes.set(inode_id.index(), inode.ptr());
          return inode;
      }
      return (*it).value;
  }
  
  ProcFSInode::ProcFSInode(ProcFS& fs, unsigned index)
      : Inode(fs, index)
  {
  }
  
  ProcFSInode::~ProcFSInode()
  {
      LOCKER(fs().m_inodes_lock);
      fs().m_inodes.remove(index());
  }
  
  InodeMetadata ProcFSInode::metadata() const
  {
  #ifdef PROCFS_DEBUG
      dbgprintf("ProcFSInode::metadata(%u)\n", index());
  #endif
      InodeMetadata metadata;
      metadata.inode = identifier();
      metadata.ctime = mepoch;
      metadata.atime = mepoch;
      metadata.mtime = mepoch;
      auto proc_parent_directory = to_proc_parent_directory(identifier());
      auto pid = to_pid(identifier());
      auto proc_file_type = to_proc_file_type(identifier());
  
  #ifdef PROCFS_DEBUG
      dbgprintf("  -> pid: %d, fi: %u, pdi: %u\n", pid, proc_file_type, proc_parent_directory);
  #endif
  
      if (is_process_related_file(identifier())) {
          auto handle = ProcessInspectionHandle::from_pid(pid);
          metadata.uid = handle->process().sys$getuid();
          metadata.gid = handle->process().sys$getgid();
      }
  
      if (proc_parent_directory == PDI_PID_fd) {
          metadata.mode = 00120777;
          return metadata;
      }
  
      if (proc_parent_directory == PDI_Root_sys) {
          metadata.mode = 00100644;
          return metadata;
      }
  
      switch (proc_file_type) {
      case FI_Root_self:
      case FI_PID_cwd:
      case FI_PID_exe:
          metadata.mode = 0120777;
          break;
      case FI_Root:
      case FI_Root_sys:
      case FI_PID:
      case FI_PID_fd:
          metadata.mode = 040777;
          break;
      default:
          metadata.mode = 0100644;
          break;
      }
  #ifdef PROCFS_DEBUG
      dbgprintf("Returning mode %o\n", metadata.mode);
  #endif
      return metadata;
  }
  
  ssize_t ProcFSInode::read_bytes(off_t offset, ssize_t count, u8* buffer, FileDescription* description) const
  {
  #ifdef PROCFS_DEBUG
      dbgprintf("ProcFS: read_bytes %u\n", index());
  #endif
      ASSERT(offset >= 0);
      ASSERT(buffer);
  
      auto* directory_entry = fs().get_directory_entry(identifier());
  
      Function<ByteBuffer(InodeIdentifier)> callback_tmp;
      Function<ByteBuffer(InodeIdentifier)>* read_callback { nullptr };
      if (directory_entry) {
          read_callback = &directory_entry->read_callback;
      } else {
          if (to_proc_parent_directory(identifier()) == PDI_PID_fd) {
              callback_tmp = procfs$pid_fd_entry;
              read_callback = &callback_tmp;
          }
      }
  
      ASSERT(read_callback);
  
      ByteBuffer generated_data;
      if (!description) {
          generated_data = (*read_callback)(identifier());
      } else {
          if (!description->generator_cache())
              description->generator_cache() = (*read_callback)(identifier());
          generated_data = description->generator_cache();
      }
  
      auto& data = generated_data;
      ssize_t nread = min(static_cast<off_t>(data.size() - offset), static_cast<off_t>(count));
      memcpy(buffer, data.pointer() + offset, nread);
      if (nread == 0 && description && description->generator_cache())
          description->generator_cache().clear();
      return nread;
  }
  
  InodeIdentifier ProcFS::ProcFSDirectoryEntry::identifier(unsigned fsid) const
  {
      return to_identifier(fsid, PDI_Root, 0, (ProcFileType)proc_file_type);
  }
  
  bool ProcFSInode::traverse_as_directory(Function<bool(const FS::DirectoryEntry&)> callback) const
  {
  #ifdef PROCFS_DEBUG
      dbgprintf("ProcFS: traverse_as_directory %u\n", index());
  #endif
  
      if (!::is_directory(identifier()))
          return false;
  
      auto pid = to_pid(identifier());
      auto proc_file_type = to_proc_file_type(identifier());
      auto parent_id = to_parent_id(identifier());
  
      callback({ ".", 1, identifier(), 2 });
      callback({ "..", 2, parent_id, 2 });
  
      switch (proc_file_type) {
      case FI_Root:
          for (auto& entry : fs().m_entries) {
              // FIXME: strlen() here is sad.
              if (!entry.name)
                  continue;
              if (entry.proc_file_type > __FI_Root_Start && entry.proc_file_type < __FI_Root_End)
                  callback({ entry.name, (int)strlen(entry.name), to_identifier(fsid(), PDI_Root, 0, (ProcFileType)entry.proc_file_type), 0 });
          }
          for (auto pid_child : Process::all_pids()) {
              char name[16];
              int name_length = ksprintf(name, "%u", pid_child);
              callback({ name, name_length, to_identifier(fsid(), PDI_Root, pid_child, FI_PID), 0 });
          }
          break;
  
      case FI_Root_sys:
          for (int i = 0; i < fs().m_sys_entries.size(); ++i) {
              auto& entry = fs().m_sys_entries[i];
              callback({ entry.name, (int)strlen(entry.name), sys_var_to_identifier(fsid(), i), 0 });
          }
          break;
  
      case FI_PID: {
          auto handle = ProcessInspectionHandle::from_pid(pid);
          if (!handle)
              return false;
          auto& process = handle->process();
          for (auto& entry : fs().m_entries) {
              if (entry.proc_file_type > __FI_PID_Start && entry.proc_file_type < __FI_PID_End) {
                  if (entry.proc_file_type == FI_PID_exe && !process.executable())
                      continue;
                  // FIXME: strlen() here is sad.
                  callback({ entry.name, (int)strlen(entry.name), to_identifier(fsid(), PDI_PID, pid, (ProcFileType)entry.proc_file_type), 0 });
              }
          }
      } break;
  
      case FI_PID_fd: {
          auto handle = ProcessInspectionHandle::from_pid(pid);
          if (!handle)
              return false;
          auto& process = handle->process();
          for (int i = 0; i < process.max_open_file_descriptors(); ++i) {
              auto* description = process.file_description(i);
              if (!description)
                  continue;
              char name[16];
              int name_length = ksprintf(name, "%u", i);
              callback({ name, name_length, to_identifier_with_fd(fsid(), pid, i), 0 });
          }
      } break;
      default:
          return true;
      }
  
      return true;
  }
  
  InodeIdentifier ProcFSInode::lookup(StringView name)
  {
      ASSERT(is_directory());
      if (name == ".")
          return identifier();
      if (name == "..")
          return to_parent_id(identifier());
  
      auto proc_file_type = to_proc_file_type(identifier());
  
      if (proc_file_type == FI_Root) {
          for (auto& entry : fs().m_entries) {
              if (entry.name == nullptr)
                  continue;
              if (entry.proc_file_type > __FI_Root_Start && entry.proc_file_type < __FI_Root_End) {
                  if (name == entry.name) {
                      return to_identifier(fsid(), PDI_Root, 0, (ProcFileType)entry.proc_file_type);
                  }
              }
          }
          bool ok;
          unsigned name_as_number = name.to_uint(ok);
          if (ok) {
              bool process_exists = false;
              {
                  InterruptDisabler disabler;
                  process_exists = Process::from_pid(name_as_number);
              }
              if (process_exists)
                  return to_identifier(fsid(), PDI_Root, name_as_number, FI_PID);
          }
          return {};
      }
  
      if (proc_file_type == FI_Root_sys) {
          for (int i = 0; i < fs().m_sys_entries.size(); ++i) {
              auto& entry = fs().m_sys_entries[i];
              if (name == entry.name)
                  return sys_var_to_identifier(fsid(), i);
          }
          return {};
      }
  
      if (proc_file_type == FI_PID) {
          auto handle = ProcessInspectionHandle::from_pid(to_pid(identifier()));
          if (!handle)
              return {};
          auto& process = handle->process();
          for (auto& entry : fs().m_entries) {
              if (entry.proc_file_type > __FI_PID_Start && entry.proc_file_type < __FI_PID_End) {
                  if (entry.proc_file_type == FI_PID_exe && !process.executable())
                      continue;
                  if (entry.name == nullptr)
                      continue;
                  if (name == entry.name) {
                      return to_identifier(fsid(), PDI_PID, to_pid(identifier()), (ProcFileType)entry.proc_file_type);
                  }
              }
          }
          return {};
      }
  
      if (proc_file_type == FI_PID_fd) {
          bool ok;
          unsigned name_as_number = name.to_uint(ok);
          if (ok) {
              bool fd_exists = false;
              {
                  InterruptDisabler disabler;
                  if (auto* process = Process::from_pid(to_pid(identifier())))
                      fd_exists = process->file_description(name_as_number);
              }
              if (fd_exists)
                  return to_identifier_with_fd(fsid(), to_pid(identifier()), name_as_number);
          }
      }
      return {};
  }
  
  void ProcFSInode::flush_metadata()
  {
  }
  
  ssize_t ProcFSInode::write_bytes(off_t offset, ssize_t size, const u8* buffer, FileDescription*)
  {
      auto* directory_entry = fs().get_directory_entry(identifier());
      if (!directory_entry || !directory_entry->write_callback)
          return -EPERM;
      ASSERT(is_persistent_inode(identifier()));
      // FIXME: Being able to write into ProcFS at a non-zero offset seems like something we should maybe support..
      ASSERT(offset == 0);
      bool success = directory_entry->write_callback(identifier(), ByteBuffer::wrap(buffer, size));
      ASSERT(success);
      return 0;
  }
  
  KResult ProcFSInode::add_child(InodeIdentifier child_id, const StringView& name, mode_t)
  {
      (void)child_id;
      (void)name;
      return KResult(-EPERM);
  }
  
  KResult ProcFSInode::remove_child(const StringView& name)
  {
      (void)name;
      return KResult(-EPERM);
  }
  
  ProcFSInodeCustomData::~ProcFSInodeCustomData()
  {
  }
  
  size_t ProcFSInode::directory_entry_count() const
  {
      ASSERT(is_directory());
      size_t count = 0;
      traverse_as_directory([&count](const FS::DirectoryEntry&) {
          ++count;
          return true;
      });
      return count;
  }
  
  KResult ProcFSInode::chmod(mode_t)
  {
      return KResult(-EPERM);
  }
  
  ProcFS::ProcFS()
  {
      s_the = this;
      m_root_inode = adopt(*new ProcFSInode(*this, 1));
      m_entries.resize(FI_MaxStaticFileIndex);
      m_entries[FI_Root_mm] = { "mm", FI_Root_mm, procfs$mm };
      m_entries[FI_Root_mounts] = { "mounts", FI_Root_mounts, procfs$mounts };
      m_entries[FI_Root_df] = { "df", FI_Root_df, procfs$df };
      m_entries[FI_Root_kmalloc] = { "kmalloc", FI_Root_kmalloc, procfs$kmalloc };
      m_entries[FI_Root_all] = { "all", FI_Root_all, procfs$all };
      m_entries[FI_Root_memstat] = { "memstat", FI_Root_memstat, procfs$memstat };
      m_entries[FI_Root_cpuinfo] = { "cpuinfo", FI_Root_cpuinfo, procfs$cpuinfo };
      m_entries[FI_Root_inodes] = { "inodes", FI_Root_inodes, procfs$inodes };
      m_entries[FI_Root_dmesg] = { "dmesg", FI_Root_dmesg, procfs$dmesg };
      m_entries[FI_Root_self] = { "self", FI_Root_self, procfs$self };
      m_entries[FI_Root_pci] = { "pci", FI_Root_pci, procfs$pci };
      m_entries[FI_Root_uptime] = { "uptime", FI_Root_uptime, procfs$uptime };
      m_entries[FI_Root_cmdline] = { "cmdline", FI_Root_cmdline, procfs$cmdline };
      m_entries[FI_Root_netadapters] = { "netadapters", FI_Root_netadapters, procfs$netadapters };
      m_entries[FI_Root_sys] = { "sys", FI_Root_sys };
  
      m_entries[FI_PID_vm] = { "vm", FI_PID_vm, procfs$pid_vm };
      m_entries[FI_PID_vmo] = { "vmo", FI_PID_vmo, procfs$pid_vmo };
      m_entries[FI_PID_stack] = { "stack", FI_PID_stack, procfs$pid_stack };
      m_entries[FI_PID_regs] = { "regs", FI_PID_regs, procfs$pid_regs };
      m_entries[FI_PID_fds] = { "fds", FI_PID_fds, procfs$pid_fds };
      m_entries[FI_PID_exe] = { "exe", FI_PID_exe, procfs$pid_exe };
      m_entries[FI_PID_cwd] = { "cwd", FI_PID_cwd, procfs$pid_cwd };
      m_entries[FI_PID_fd] = { "fd", FI_PID_fd };
  
      m_kmalloc_stack_helper.resource() = g_dump_kmalloc_stacks;
      add_sys_bool("kmalloc_stacks", m_kmalloc_stack_helper, [this] {
          g_dump_kmalloc_stacks = m_kmalloc_stack_helper.resource();
      });
  }
  
  ProcFS::ProcFSDirectoryEntry* ProcFS::get_directory_entry(InodeIdentifier identifier) const
  {
      if (to_proc_parent_directory(identifier) == PDI_Root_sys) {
          auto sys_index = to_sys_index(identifier);
          if (sys_index < m_sys_entries.size())
              return const_cast<ProcFSDirectoryEntry*>(&m_sys_entries[sys_index]);
          return nullptr;
      }
      auto proc_file_type = to_proc_file_type(identifier);
      if (proc_file_type != FI_Invalid && proc_file_type < FI_MaxStaticFileIndex)
          return const_cast<ProcFSDirectoryEntry*>(&m_entries[proc_file_type]);
      return nullptr;
  }
  
  KResult ProcFSInode::chown(uid_t, gid_t)
  {
      return KResult(-EPERM);
  }
  