Kernel: Yet more work on bringing up POSIX SHM.

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/60a819c14ac

AK/Retained.h

@@ -35,7 +35,7 @@ class CONSUMABLE(unconsumed) Retained {
 public:
     enum AdoptTag { Adopt };
 
-    RETURN_TYPESTATE(unconsumed) Retained(const T& object) : m_ptr(&object) { m_ptr->retain(); }
+    RETURN_TYPESTATE(unconsumed) Retained(const T& object) : m_ptr(const_cast<T*>(&object)) { m_ptr->retain(); }
     RETURN_TYPESTATE(unconsumed) Retained(T& object) : m_ptr(&object) { m_ptr->retain(); }
     template<typename U> RETURN_TYPESTATE(unconsumed) Retained(U& object) : m_ptr(&static_cast<T&>(object)) { m_ptr->retain(); }
     RETURN_TYPESTATE(unconsumed) Retained(AdoptTag, T& object) : m_ptr(&object) { }

Kernel/FileSystem/FileDescriptor.cpp

@@ -23,6 +23,11 @@ Retained<FileDescriptor> FileDescriptor::create(RetainPtr<Device>&& device)
     return adopt(*new FileDescriptor(move(device)));
 }
 
+Retained<FileDescriptor> FileDescriptor::create(RetainPtr<SharedMemory>&& shared_memory)
+{
+    return adopt(*new FileDescriptor(move(shared_memory)));
+}
+
 Retained<FileDescriptor> FileDescriptor::create(RetainPtr<Socket>&& socket, SocketRole role)
 {
     return adopt(*new FileDescriptor(move(socket), role));
@@ -48,6 +53,11 @@ FileDescriptor::FileDescriptor(RetainPtr<Device>&& device)
 {
 }
 
+FileDescriptor::FileDescriptor(RetainPtr<SharedMemory>&& shared_memory)
+    : m_shared_memory(move(shared_memory))
+{
+}
+
 FileDescriptor::FileDescriptor(RetainPtr<Socket>&& socket, SocketRole role)
     : m_socket(move(socket))
 {
@@ -397,6 +407,8 @@ bool FileDescriptor::supports_mmap() const
 {
     if (m_inode)
         return true;
+    if (m_shared_memory)
+        return true;
     if (m_device)
         return m_device->is_block_device();
     return false;
@@ -409,6 +421,12 @@ Region* FileDescriptor::mmap(Process& process, LinearAddress laddr, size_t offse
     if (is_block_device())
         return static_cast<BlockDevice&>(*m_device).mmap(process, laddr, offset, size);
 
+    if (is_shared_memory()) {
+        if (!shared_memory()->vmo())
+            return nullptr;
+        return process.allocate_region_with_vmo(laddr, size, *shared_memory()->vmo(), offset, shared_memory()->name(), true, true);
+    }
+
     ASSERT(m_inode);
     // FIXME: If PROT_EXEC, check that the underlying file system isn't mounted noexec.
     String region_name;

Kernel/FileSystem/FileDescriptor.h

@@ -9,13 +9,13 @@
 #include <AK/Retainable.h>
 #include <AK/Badge.h>
 #include <Kernel/Net/Socket.h>
+#include <Kernel/SharedMemory.h>
 
 class TTY;
 class MasterPTY;
 class Process;
 class Region;
 class CharacterDevice;
-class SharedMemory;
 
 class FileDescriptor : public Retainable<FileDescriptor> {
 public:
@@ -23,6 +23,7 @@ public:
     static Retained<FileDescriptor> create(RetainPtr<Socket>&&, SocketRole = SocketRole::None);
     static Retained<FileDescriptor> create(RetainPtr<Inode>&&);
     static Retained<FileDescriptor> create(RetainPtr<Device>&&);
+    static Retained<FileDescriptor> create(RetainPtr<SharedMemory>&&);
     static Retained<FileDescriptor> create_pipe_writer(FIFO&);
     static Retained<FileDescriptor> create_pipe_reader(FIFO&);
     ~FileDescriptor();
@@ -105,6 +106,7 @@ private:
     FileDescriptor(RetainPtr<Socket>&&, SocketRole);
     explicit FileDescriptor(RetainPtr<Inode>&&);
     explicit FileDescriptor(RetainPtr<Device>&&);
+    explicit FileDescriptor(RetainPtr<SharedMemory>&&);
     FileDescriptor(FIFO&, FIFO::Direction);
 
     RetainPtr<Inode> m_inode;

Kernel/KResult.h

@@ -58,6 +58,14 @@ public:
     T& value() { ASSERT(!m_is_error); return *reinterpret_cast<T*>(&m_storage); }
     const T& value() const { ASSERT(!m_is_error); return *reinterpret_cast<T*>(&m_storage); }
 
+    T release_value()
+    {
+        ASSERT(!m_is_error);
+        T released_value = *reinterpret_cast<T*>(&m_storage);
+        value().~T();
+        return released_value;
+    }
+
 private:
     char m_storage[sizeof(T)] __attribute__((aligned(sizeof(T))));
     KResult m_error;

Kernel/Process.cpp

@@ -22,6 +22,7 @@
 #include <Kernel/TTY/MasterPTY.h>
 #include <Kernel/ELF/exec_elf.h>
 #include <AK/StringBuilder.h>
+#include <Kernel/SharedMemory.h>
 
 //#define DEBUG_IO
 //#define TASK_DEBUG
@@ -2459,14 +2460,22 @@ int Process::sys$shm_open(const char* name, int flags, mode_t mode)
 {
     if (!validate_read_str(name))
         return -EFAULT;
-    return -ENOTIMPL;
+    int fd = alloc_fd();
+    if (fd < 0)
+        return fd;
+    auto shm_or_error = SharedMemory::open(String(name), flags, mode);
+    if (shm_or_error.is_error())
+        return shm_or_error.error();
+    auto descriptor = FileDescriptor::create(shm_or_error.value().ptr());
+    m_fds[fd].set(move(descriptor), FD_CLOEXEC);
+    return fd;
 }
 
 int Process::sys$shm_unlink(const char* name)
 {
     if (!validate_read_str(name))
         return -EFAULT;
-    return -ENOTIMPL;
+    return SharedMemory::unlink(String(name));
 }
 
 int Process::sys$ftruncate(int fd, off_t length)

Kernel/SharedMemory.cpp

@@ -1,7 +1,48 @@
 #include <Kernel/SharedMemory.h>
 #include <Kernel/VM/VMObject.h>
+#include <Kernel/Lock.h>
+#include <Kernel/Process.h>
+#include <AK/HashMap.h>
 
-SharedMemory::SharedMemory()
+Lockable<HashMap<String, RetainPtr<SharedMemory>>>& shared_memories()
+{
+    static Lockable<HashMap<String, RetainPtr<SharedMemory>>>* map;
+    if (!map)
+        map = new Lockable<HashMap<String, RetainPtr<SharedMemory>>>;
+    return *map;
+}
+
+KResultOr<Retained<SharedMemory>> SharedMemory::open(const String& name, int flags, mode_t mode)
+{
+    LOCKER(shared_memories().lock());
+    auto it = shared_memories().resource().find(name);
+    if (it != shared_memories().resource().end()) {
+        auto shared_memory = it->value;
+        // FIXME: Improved access checking.
+        if (shared_memory->uid() != current->process().uid())
+            return KResult(-EACCES);
+        return *shared_memory;
+    }
+    auto shared_memory = adopt(*new SharedMemory(name, current->process().uid(), current->process().gid(), mode));
+    shared_memories().resource().set(name, shared_memory.ptr());
+    return shared_memory;
+}
+
+KResult SharedMemory::unlink(const String& name)
+{
+    LOCKER(shared_memories().lock());
+    auto it = shared_memories().resource().find(name);
+    if (it == shared_memories().resource().end())
+        return KResult(-ENOENT);
+    shared_memories().resource().remove(it);
+    return KSuccess;
+}
+
+SharedMemory::SharedMemory(const String& name, uid_t uid, gid_t gid, mode_t mode)
+    : m_name(name)
+    , m_uid(uid)
+    , m_gid(gid)
+    , m_mode(mode)
 {
 }
 

Kernel/SharedMemory.h

@@ -2,21 +2,31 @@
 
 #include <AK/Retainable.h>
 #include <AK/RetainPtr.h>
+#include <AK/AKString.h>
 #include <Kernel/KResult.h>
+#include <Kernel/UnixTypes.h>
 
 class VMObject;
 
 class SharedMemory : public Retainable<SharedMemory> {
 public:
-    static Retained<SharedMemory> create();
+    static KResultOr<Retained<SharedMemory>> open(const String& name, int flags, mode_t);
+    static KResult unlink(const String& name);
     ~SharedMemory();
 
+    String name() const { return m_name; }
     KResult truncate(int);
+    VMObject* vmo() { return m_vmo.ptr(); }
+    const VMObject* vmo() const { return m_vmo.ptr(); }
+    uid_t uid() const { return m_uid; }
+    gid_t gid() const { return m_gid; }
 
 private:
-    SharedMemory();
+    SharedMemory(const String& name, uid_t, gid_t, mode_t);
 
-    int m_uid { 0 };
-    int m_gid { 0 };
+    String m_name;
+    uid_t m_uid { 0 };
+    gid_t m_gid { 0 };
+    mode_t m_mode { 0 };
     RetainPtr<VMObject> m_vmo;
 };