kernel: Add /dev/tty

kernel/CMakeLists.txt

@@ -76,6 +76,7 @@ set(SOURCES
     src/fs/devices/PTYMultiplexer.cpp
     src/fs/devices/MasterPTY.cpp
     src/fs/devices/SlavePTY.cpp
+    src/fs/devices/TTYLink.cpp
     src/fs/InitRD.cpp
     src/binfmt/ELF.cpp
     src/binfmt/BinaryFormat.cpp

kernel/src/fs/devices/DeviceRegistry.cpp

@@ -8,6 +8,7 @@
 #include "fs/devices/MouseDevice.h"
 #include "fs/devices/NullDevice.h"
 #include "fs/devices/PTYMultiplexer.h"
+#include "fs/devices/TTYLink.h"
 #include "fs/devices/UARTDevice.h"
 #include "fs/devices/ZeroDevice.h"
 #include "fs/tmpfs/FileSystem.h"
@@ -99,6 +100,12 @@ namespace DeviceRegistry
 
         TRY(fs->root_inode()->add_entry(multiplexer, "ptmx"));
 
+        auto ttylink = TRY(make_shared<TTYLink>());
+        ttylink->set_fs(*fs);
+        ttylink->set_inode_number(TRY(fs->allocate_inode_number()));
+
+        TRY(fs->root_inode()->add_entry(ttylink, "tty"));
+
         return fs;
     }
 }

kernel/src/fs/devices/MasterPTY.cpp

@@ -29,7 +29,7 @@ Result<SharedPtr<VFS::Inode>> MasterPTY::create_pair(int index)
     master->m_window.ws_row = 25;
 
     slave->m_master = master.ptr();
-    slave->m_metadata.devid = luna_dev_makedev(DeviceRegistry::Terminal, index + 1);
+    slave->m_metadata.devid = luna_dev_makedev(DeviceRegistry::Terminal, index + 2);
     slave->m_metadata.uid = Scheduler::current()->auth.euid;
     slave->m_metadata.gid = Scheduler::current()->auth.egid;
     slave->m_metadata.mode = 0620;

kernel/src/fs/devices/TTYLink.cpp

@@ -0,0 +1,15 @@
+#include "fs/devices/TTYLink.h"
+#include "thread/Scheduler.h"
+
+TTYLink::TTYLink()
+{
+    m_metadata.devid = luna_dev_makedev(DeviceRegistry::Terminal, 1);
+    m_metadata.mode = 0666;
+}
+
+Result<SharedPtr<VFS::Inode>> TTYLink::open()
+{
+    if (!Scheduler::current()->controlling_terminal) return err(ENXIO);
+
+    return Scheduler::current()->controlling_terminal;
+}

kernel/src/fs/devices/TTYLink.h

@@ -0,0 +1,75 @@
+#pragma once
+#include "fs/VFS.h"
+#include "fs/devices/DeviceRegistry.h"
+#include "fs/devices/MasterPTY.h"
+#include <luna/Bitset.h>
+
+/* /dev/tty implementation. */
+class TTYLink : public VFS::DeviceInode
+{
+  public:
+    TTYLink();
+
+    VFS::InodeType type() const override
+    {
+        return VFS::InodeType::CharacterDevice;
+    }
+
+    void set_fs(VFS::FileSystem& fs)
+    {
+        m_fs = &fs;
+    }
+
+    void set_inode_number(usize inum)
+    {
+        m_metadata.inum = inum;
+    }
+
+    Result<u64> query_shared_memory(off_t, usize) override
+    {
+        unreachable();
+    }
+
+    Result<SharedPtr<VFS::Inode>> open() override;
+
+    VFS::FileSystem* fs() const override
+    {
+        return m_fs;
+    }
+
+    Result<usize> read(u8*, usize, usize) const override
+    {
+        unreachable();
+    }
+
+    Result<usize> write(const u8*, usize, usize) override
+    {
+        unreachable();
+    }
+
+    Result<void> truncate(usize) override
+    {
+        // POSIX says truncate is for regular files, but doesn't tell us what error to return for non-regular files.
+        return err(EINVAL);
+    }
+
+    bool will_block_if_read() const override
+    {
+        unreachable();
+    }
+
+    void did_link() override
+    {
+        m_metadata.nlinks++;
+    }
+
+    void did_unlink() override
+    {
+        m_metadata.nlinks--;
+    }
+
+    virtual ~TTYLink() = default;
+
+  private:
+    VFS::FileSystem* m_fs;
+};

kernel/src/thread/Thread.h

@@ -110,6 +110,8 @@ struct Thread : public LinkedListNode<Thread>
     Bitset<sigset_t> pending_signals { 0 };
     bool interrupted { false };
 
+    SharedPtr<VFS::Inode> controlling_terminal;
+
     bool unrestricted_task { false };
 
     FPData fp_data;