Kernel: Make File::stat() & friends return Error<struct stat>

Instead of making the caller provide a stat buffer, let's just return
one as a value.

Kernel/FileSystem/FIFO.cpp

@@ -137,11 +137,11 @@ ErrorOr<NonnullOwnPtr<KString>> FIFO::pseudo_path(const OpenFileDescription&) co
     return KString::formatted("fifo:{}", m_fifo_id);
 }
 
-ErrorOr<void> FIFO::stat(::stat& st) const
+ErrorOr<struct stat> FIFO::stat() const
 {
-    memset(&st, 0, sizeof(st));
+    struct stat st = {};
     st.st_mode = S_IFIFO;
-    return {};
+    return st;
 }
 
 }

Kernel/FileSystem/FIFO.h

@@ -42,7 +42,7 @@ private:
     // ^File
     virtual ErrorOr<size_t> write(OpenFileDescription&, u64, const UserOrKernelBuffer&, size_t) override;
     virtual ErrorOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override;
-    virtual ErrorOr<void> stat(::stat&) const override;
+    virtual ErrorOr<struct stat> stat() const override;
     virtual bool can_read(const OpenFileDescription&, size_t) const override;
     virtual bool can_write(const OpenFileDescription&, size_t) const override;
     virtual ErrorOr<NonnullOwnPtr<KString>> pseudo_path(const OpenFileDescription&) const override;

Kernel/FileSystem/File.h

@@ -91,7 +91,7 @@ public:
     virtual ErrorOr<size_t> write(OpenFileDescription&, u64, const UserOrKernelBuffer&, size_t) = 0;
     virtual ErrorOr<void> ioctl(OpenFileDescription&, unsigned request, Userspace<void*> arg);
     virtual ErrorOr<Memory::Region*> mmap(Process&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared);
-    virtual ErrorOr<void> stat(::stat&) const { return EBADF; }
+    virtual ErrorOr<struct stat> stat() const { return EBADF; }
 
     // Although this might be better described "name" or "description", these terms already have other meanings.
     virtual ErrorOr<NonnullOwnPtr<KString>> pseudo_path(const OpenFileDescription&) const = 0;

Kernel/FileSystem/InodeFile.h

@@ -34,7 +34,7 @@ public:
     virtual ErrorOr<size_t> write(OpenFileDescription&, u64, const UserOrKernelBuffer&, size_t) override;
     virtual ErrorOr<void> ioctl(OpenFileDescription&, unsigned request, Userspace<void*> arg) override;
     virtual ErrorOr<Memory::Region*> mmap(Process&, OpenFileDescription&, Memory::VirtualRange const&, u64 offset, int prot, bool shared) override;
-    virtual ErrorOr<void> stat(::stat& buffer) const override { return inode().metadata().stat(buffer); }
+    virtual ErrorOr<struct stat> stat() const override { return inode().metadata().stat(); }
 
     virtual ErrorOr<NonnullOwnPtr<KString>> pseudo_path(const OpenFileDescription&) const override;
 

Kernel/FileSystem/InodeMetadata.h

@@ -86,10 +86,11 @@ struct InodeMetadata {
     bool is_setuid() const { return Kernel::is_setuid(mode); }
     bool is_setgid() const { return Kernel::is_setgid(mode); }
 
-    ErrorOr<void> stat(stat& buffer) const
+    ErrorOr<struct stat> stat() const
     {
         if (!is_valid())
             return EIO;
+        struct stat buffer = {};
         buffer.st_rdev = encoded_device(major_device, minor_device);
         buffer.st_ino = inode.index().value();
         buffer.st_mode = mode;
@@ -106,7 +107,7 @@ struct InodeMetadata {
         buffer.st_mtim.tv_nsec = 0;
         buffer.st_ctim.tv_sec = ctime;
         buffer.st_ctim.tv_nsec = 0;
-        return {};
+        return buffer;
     }
 
     InodeIdentifier inode;

Kernel/FileSystem/OpenFileDescription.cpp

@@ -97,13 +97,13 @@ Thread::FileBlocker::BlockFlags OpenFileDescription::should_unblock(Thread::File
     return unblock_flags;
 }
 
-ErrorOr<void> OpenFileDescription::stat(::stat& buffer)
+ErrorOr<struct stat> OpenFileDescription::stat()
 {
     MutexLocker locker(m_lock);
     // FIXME: This is due to the Device class not overriding File::stat().
     if (m_inode)
-        return m_inode->metadata().stat(buffer);
+        return m_inode->metadata().stat();
-    return m_file->stat(buffer);
+    return m_file->stat();
 }
 
 ErrorOr<off_t> OpenFileDescription::seek(off_t offset, int whence)

Kernel/FileSystem/OpenFileDescription.h

@@ -49,7 +49,7 @@ public:
     ErrorOr<off_t> seek(off_t, int whence);
     ErrorOr<size_t> read(UserOrKernelBuffer&, size_t);
     ErrorOr<size_t> write(const UserOrKernelBuffer& data, size_t);
-    ErrorOr<void> stat(::stat&);
+    ErrorOr<struct stat> stat();
 
     // NOTE: These ignore the current offset of this file description.
     ErrorOr<size_t> read(UserOrKernelBuffer&, u64 offset, size_t);

Kernel/Net/Socket.cpp

@@ -263,11 +263,11 @@ ErrorOr<void> Socket::shutdown(int how)
     return {};
 }
 
-ErrorOr<void> Socket::stat(::stat& st) const
+ErrorOr<struct stat> Socket::stat() const
 {
-    memset(&st, 0, sizeof(st));
+    struct stat st = {};
     st.st_mode = S_IFSOCK;
-    return {};
+    return st;
 }
 
 void Socket::set_connected(bool connected)

Kernel/Net/Socket.h

@@ -104,7 +104,7 @@ public:
     // ^File
     virtual ErrorOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override final;
     virtual ErrorOr<size_t> write(OpenFileDescription&, u64, const UserOrKernelBuffer&, size_t) override final;
-    virtual ErrorOr<void> stat(::stat&) const override;
+    virtual ErrorOr<struct stat> stat() const override;
     virtual ErrorOr<NonnullOwnPtr<KString>> pseudo_path(const OpenFileDescription&) const override = 0;
 
     bool has_receive_timeout() const { return m_receive_timeout != Time::zero(); }

Kernel/Syscalls/stat.cpp

@@ -16,8 +16,7 @@ ErrorOr<FlatPtr> Process::sys$fstat(int fd, Userspace<stat*> user_statbuf)
     VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this)
     REQUIRE_PROMISE(stdio);
     auto description = TRY(fds().open_file_description(fd));
-    stat buffer = {};
+    auto buffer = TRY(description->stat());
-    TRY(description->stat(buffer));
     TRY(copy_to_user(user_statbuf, &buffer));
     return 0;
 }
@@ -42,8 +41,7 @@ ErrorOr<FlatPtr> Process::sys$stat(Userspace<const Syscall::SC_stat_params*> use
         base = base_description->custody();
     }
     auto metadata = TRY(VirtualFileSystem::the().lookup_metadata(path->view(), *base, params.follow_symlinks ? 0 : O_NOFOLLOW_NOERROR));
-    stat statbuf = {};
+    auto statbuf = TRY(metadata.stat());
-    TRY(metadata.stat(statbuf));
     TRY(copy_to_user(params.statbuf, &statbuf));
     return 0;
 }