Kernel: More work towards POSIX SHM, also add ftruncate().

Kernel/FileSystem/FileDescriptor.cpp

@@ -11,6 +11,7 @@
 #include <Kernel/Process.h>
 #include <Kernel/Devices/BlockDevice.h>
 #include <Kernel/VM/MemoryManager.h>
+#include <Kernel/SharedMemory.h>
 
 Retained<FileDescriptor> FileDescriptor::create(RetainPtr<Inode>&& inode)
 {
@@ -357,6 +358,11 @@ const char* to_string(SocketRole role)
  }
 }
 
+bool FileDescriptor::is_file() const
+{
+ return !is_tty() && !is_fifo() && !is_device() && !is_socket() && !is_shared_memory();
+}
+
 KResultOr<String> FileDescriptor::absolute_path()
 {
  Stopwatch sw("absolute_path");
@@ -439,3 +445,12 @@ const CharacterDevice* FileDescriptor::character_device() const
 {
  return is_character_device() ? static_cast<const CharacterDevice*>(device()) : nullptr;
 }
+
+KResult FileDescriptor::truncate(off_t length)
+{
+ if (is_file()) {
+ return m_inode->truncate(length);
+ }
+ ASSERT(is_shared_memory());
+ return shared_memory()->truncate(length);
+}

Kernel/FileSystem/FileDescriptor.h

@@ -15,6 +15,7 @@ class MasterPTY;
 class Process;
 class Region;
 class CharacterDevice;
+class SharedMemory;
 
 class FileDescriptor : public Retainable<FileDescriptor> {
 public:
@@ -85,13 +86,20 @@ class FileDescriptor : public Retainable<FileDescriptor> {
  bool is_fifo() const { return m_fifo; }
  FIFO::Direction fifo_direction() { return m_fifo_direction; }
 
+ bool is_file() const;
+ bool is_shared_memory() const { return m_shared_memory; }
+ SharedMemory* shared_memory() { return m_shared_memory.ptr(); }
+ const SharedMemory* shared_memory() const { return m_shared_memory.ptr(); }
+
  ByteBuffer& generator_cache() { return m_generator_cache; }
 
  void set_original_inode(Badge<VFS>, Retained<Inode>&& inode) { m_inode = move(inode); }
 
  SocketRole socket_role() const { return m_socket_role; }
  void set_socket_role(SocketRole);
 
+ KResult truncate(off_t);
+
 private:
  friend class VFS;
  FileDescriptor(RetainPtr<Socket>&&, SocketRole);
@@ -115,6 +123,8 @@ class FileDescriptor : public Retainable<FileDescriptor> {
  RetainPtr<FIFO> m_fifo;
  FIFO::Direction m_fifo_direction { FIFO::Neither };
 
+ RetainPtr<SharedMemory> m_shared_memory;
+
  bool m_closed { false };
 };
 

Kernel/Makefile

@@ -31,6 +31,7 @@ KERNEL_OBJS = \
  ELF/ELFImage.o \
  ELF/ELFLoader.o \
  KSyms.o \
+ SharedMemory.o \
  FileSystem/DevPtsFS.o \
  Devices/BXVGADevice.o \
  PCI.o \

Kernel/Process.cpp

@@ -2468,3 +2468,14 @@ int Process::sys$shm_unlink(const char* name)
  return -EFAULT;
  return -ENOTIMPL;
 }
+
+int Process::sys$ftruncate(int fd, off_t length)
+{
+ auto* descriptor = file_descriptor(fd);
+ if (!descriptor)
+ return -EBADF;
+ // FIXME: Check that fd is writable, otherwise EINVAL.
+ if (!descriptor->is_file() && !descriptor->is_shared_memory())
+ return -EINVAL;
+ return descriptor->truncate(length);
+}

Kernel/Process.h

@@ -101,6 +101,7 @@ class Process : public InlineLinkedListNode<Process>, public Weakable<Process> {
  int sys$donate(int tid);
  int sys$shm_open(const char* name, int flags, mode_t);
  int sys$shm_unlink(const char* name);
+ int sys$ftruncate(int fd, off_t);
  pid_t sys$setsid();
  pid_t sys$getsid(pid_t);
  int sys$setpgid(pid_t pid, pid_t pgid);

Kernel/SharedMemory.cpp

@@ -0,0 +1,27 @@
+#include <Kernel/SharedMemory.h>
+#include <Kernel/VM/VMObject.h>
+
+SharedMemory::SharedMemory()
+{
+}
+
+SharedMemory::~SharedMemory()
+{
+}
+
+KResult SharedMemory::truncate(int length)
+{
+ if (!length) {
+ m_vmo = nullptr;
+ return KSuccess;
+ }
+
+ if (!m_vmo) {
+ m_vmo = VMObject::create_anonymous(length);
+ return KSuccess;
+ }
+
+ // FIXME: Support truncation.
+ ASSERT_NOT_REACHED();
+ return KResult(-ENOTIMPL);
+}

Kernel/SharedMemory.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <AK/Retainable.h>
+#include <AK/RetainPtr.h>
+#include <Kernel/KResult.h>
+
+class VMObject;
+
+class SharedMemory : public Retainable<SharedMemory> {
+public:
+ static Retained<SharedMemory> create();
+ ~SharedMemory();
+
+ KResult truncate(int);
+
+private:
+ SharedMemory();
+
+ int m_uid { 0 };
+ int m_gid { 0 };
+ RetainPtr<VMObject> m_vmo;
+};

Kernel/Syscall.cpp

@@ -247,6 +247,8 @@ static dword handle(RegisterDump& regs, dword function, dword arg1, dword arg2,
  return current->process().sys$shm_open((const char*)arg1, (int)arg2, (mode_t)arg3);
  case Syscall::SC_shm_close:
  return current->process().sys$shm_unlink((const char*)arg1);
+ case Syscall::SC_ftruncate:
+ return current->process().sys$ftruncate((int)arg1, (off_t)arg2);
  default:
  kprintf("<%u> int0x82: Unknown function %u requested {%x, %x, %x}\n", current->process().pid(), function, arg1, arg2, arg3);
  break;

Kernel/Syscall.h

@@ -98,6 +98,7 @@
  __ENUMERATE_SYSCALL(rename) \
  __ENUMERATE_SYSCALL(shm_open) \
  __ENUMERATE_SYSCALL(shm_close) \
+ __ENUMERATE_SYSCALL(ftruncate) \
 
 
 namespace Syscall {

LibC/unistd.cpp

@@ -442,7 +442,8 @@ int create_thread(int(*entry)(void*), void* argument)
 
 int ftruncate(int fd, off_t length)
 {
- ASSERT_NOT_REACHED();
+ int rc = syscall(SC_ftruncate, fd, length);
+ __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
 int gettid()