From 4527d9852aa8c0627320c730bf3f9b8efa6f8ee8 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sun, 6 Sep 2020 18:48:24 +0200
Subject: [PATCH] Kernel: Track time-of-last-write in SlavePTY and report it as
 mtime

---
 Kernel/FileSystem/DevPtsFS.cpp | 13 ++++++++++---
 Kernel/FileSystem/DevPtsFS.h   |  3 ++-
 Kernel/TTY/SlavePTY.cpp        |  1 +
 Kernel/TTY/SlavePTY.h          |  5 ++++-
 4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/Kernel/FileSystem/DevPtsFS.cpp b/Kernel/FileSystem/DevPtsFS.cpp
index 7ee4d28aa0e..01b78c44c00 100644
--- a/Kernel/FileSystem/DevPtsFS.cpp
+++ b/Kernel/FileSystem/DevPtsFS.cpp
@@ -50,7 +50,7 @@ static AK::Singleton<HashTable<unsigned>> s_ptys;
 
 bool DevPtsFS::initialize()
 {
-    m_root_inode = adopt(*new DevPtsFSInode(*this, 1));
+    m_root_inode = adopt(*new DevPtsFSInode(*this, 1, nullptr));
     m_root_inode->m_metadata.inode = { fsid(), 1 };
     m_root_inode->m_metadata.mode = 0040555;
     m_root_inode->m_metadata.uid = 0;
@@ -86,7 +86,7 @@ RefPtr<Inode> DevPtsFS::get_inode(InodeIdentifier inode_id) const
     auto* device = Device::get_device(201, pty_index);
     ASSERT(device);
 
-    auto inode = adopt(*new DevPtsFSInode(const_cast<DevPtsFS&>(*this), inode_id.index()));
+    auto inode = adopt(*new DevPtsFSInode(const_cast<DevPtsFS&>(*this), inode_id.index(), static_cast<SlavePTY*>(device)));
     inode->m_metadata.inode = inode_id;
     inode->m_metadata.size = 0;
     inode->m_metadata.uid = device->uid();
@@ -109,9 +109,11 @@ void DevPtsFS::unregister_slave_pty(SlavePTY& slave_pty)
     s_ptys->remove(slave_pty.index());
 }
 
-DevPtsFSInode::DevPtsFSInode(DevPtsFS& fs, unsigned index)
+DevPtsFSInode::DevPtsFSInode(DevPtsFS& fs, unsigned index, SlavePTY* pty)
     : Inode(fs, index)
 {
+    if (pty)
+        m_pty = pty->make_weak_ptr();
 }
 
 DevPtsFSInode::~DevPtsFSInode()
@@ -130,6 +132,11 @@ ssize_t DevPtsFSInode::write_bytes(off_t, ssize_t, const u8*, FileDescription*)
 
 InodeMetadata DevPtsFSInode::metadata() const
 {
+    if (m_pty) {
+        auto metadata = m_metadata;
+        metadata.mtime = m_pty->time_of_last_write();
+        return metadata;
+    }
     return m_metadata;
 }
 
diff --git a/Kernel/FileSystem/DevPtsFS.h b/Kernel/FileSystem/DevPtsFS.h
index 1942a1f6670..3c302180fe5 100644
--- a/Kernel/FileSystem/DevPtsFS.h
+++ b/Kernel/FileSystem/DevPtsFS.h
@@ -64,7 +64,7 @@ public:
     virtual ~DevPtsFSInode() override;
 
 private:
-    DevPtsFSInode(DevPtsFS&, unsigned index);
+    DevPtsFSInode(DevPtsFS&, unsigned index, SlavePTY*);
 
     // ^Inode
     virtual ssize_t read_bytes(off_t, ssize_t, u8* buffer, FileDescription*) const override;
@@ -80,6 +80,7 @@ private:
     virtual KResult chmod(mode_t) override;
     virtual KResult chown(uid_t, gid_t) override;
 
+    WeakPtr<SlavePTY> m_pty;
     InodeMetadata m_metadata;
 };
 
diff --git a/Kernel/TTY/SlavePTY.cpp b/Kernel/TTY/SlavePTY.cpp
index dd18963596a..6a5106df381 100644
--- a/Kernel/TTY/SlavePTY.cpp
+++ b/Kernel/TTY/SlavePTY.cpp
@@ -74,6 +74,7 @@ void SlavePTY::on_master_write(const u8* buffer, ssize_t size)
 
 ssize_t SlavePTY::on_tty_write(const u8* data, ssize_t size)
 {
+    m_time_of_last_write = kgettimeofday().tv_sec;
     return m_master->on_slave_write(data, size);
 }
 
diff --git a/Kernel/TTY/SlavePTY.h b/Kernel/TTY/SlavePTY.h
index 700f63e028f..ff86f0c04d4 100644
--- a/Kernel/TTY/SlavePTY.h
+++ b/Kernel/TTY/SlavePTY.h
@@ -40,6 +40,8 @@ public:
     void on_master_write(const u8*, ssize_t);
     unsigned index() const { return m_index; }
 
+    time_t time_of_last_write() const { return m_time_of_last_write; }
+
 private:
     // ^TTY
     virtual String tty_name() const override;
@@ -57,7 +59,8 @@ private:
     SlavePTY(MasterPTY&, unsigned index);
 
     RefPtr<MasterPTY> m_master;
-    unsigned m_index;
+    time_t m_time_of_last_write { 0 };
+    unsigned m_index { 0 };
     char m_tty_name[32];
 };