Kernel+Userland: Remove chroot functionality

We are not using this for anything and it's just been sitting there
gathering dust for well over a year, so let's stop carrying all this
complexity around for no good reason.

Kernel/API/Syscall.h

@@ -55,7 +55,6 @@ enum class NeedsBigProcessLock {
     S(chdir, NeedsBigProcessLock::Yes)                      \
     S(chmod, NeedsBigProcessLock::Yes)                      \
     S(chown, NeedsBigProcessLock::Yes)                      \
-    S(chroot, NeedsBigProcessLock::Yes)                     \
     S(clock_gettime, NeedsBigProcessLock::No)               \
     S(clock_nanosleep, NeedsBigProcessLock::No)             \
     S(clock_settime, NeedsBigProcessLock::Yes)              \

Kernel/CMakeLists.txt

@@ -195,7 +195,6 @@ set(KERNEL_SOURCES
     Syscalls/chdir.cpp
     Syscalls/chmod.cpp
     Syscalls/chown.cpp
-    Syscalls/chroot.cpp
     Syscalls/clock.cpp
     Syscalls/debug.cpp
     Syscalls/disown.cpp

Kernel/FileSystem/ProcFS.cpp

@@ -360,12 +360,6 @@ KResultOr<NonnullRefPtr<Inode>> ProcFSProcessDirectoryInode::lookup(StringView n
             return maybe_inode.error();
         return maybe_inode.release_value();
     }
-    if (name == "root") {
-        auto maybe_inode = ProcFSProcessPropertyInode::try_create_for_pid_property(procfs(), SegmentedProcFSIndex::MainProcessProperty::RootLink, associated_pid());
-        if (maybe_inode.is_error())
-            return maybe_inode.error();
-        return maybe_inode.release_value();
-    }
 
     return ENOENT;
 }
@@ -515,8 +509,6 @@ static mode_t determine_procfs_process_inode_mode(SegmentedProcFSIndex::ProcessS
         return S_IFLNK | 0777;
     if (main_property == SegmentedProcFSIndex::MainProcessProperty::CurrentWorkDirectoryLink)
         return S_IFLNK | 0777;
-    if (main_property == SegmentedProcFSIndex::MainProcessProperty::RootLink)
-        return S_IFLNK | 0777;
     return S_IFREG | 0400;
 }
 
@@ -625,8 +617,6 @@ KResult ProcFSProcessPropertyInode::try_to_acquire_data(Process& process, KBuffe
         return process.procfs_get_perf_events(builder);
     case SegmentedProcFSIndex::MainProcessProperty::VirtualMemoryStats:
         return process.procfs_get_virtual_memory_stats(builder);
-    case SegmentedProcFSIndex::MainProcessProperty::RootLink:
-        return process.procfs_get_root_link(builder);
     default:
         VERIFY_NOT_REACHED();
     }

Kernel/FileSystem/VirtualFileSystem.cpp

@@ -934,9 +934,8 @@ KResultOr<NonnullRefPtr<Custody>> VirtualFileSystem::resolve_path_without_veil(S
 
     GenericLexer path_lexer(path);
     auto current_process = Process::current();
-    auto& current_root = current_process->root_directory();
 
-    NonnullRefPtr<Custody> custody = path[0] == '/' ? current_root : base;
+    NonnullRefPtr<Custody> custody = path[0] == '/' ? root_custody() : base;
     bool extra_iteration = path[path.length() - 1] == '/';
 
     while (!path_lexer.is_eof() || extra_iteration) {

Kernel/Process.cpp

@@ -609,8 +609,6 @@ void Process::finalize()
     m_tty = nullptr;
     m_executable = nullptr;
     m_cwd = nullptr;
-    m_root_directory = nullptr;
-    m_root_directory_relative_to_global_root = nullptr;
     m_arguments.clear();
     m_environment.clear();
 
@@ -775,25 +773,6 @@ void Process::FileDescriptionAndFlags::set(NonnullRefPtr<FileDescription>&& desc
     m_flags = flags;
 }
 
-Custody& Process::root_directory()
-{
-    if (!m_root_directory)
-        m_root_directory = VirtualFileSystem::the().root_custody();
-    return *m_root_directory;
-}
-
-Custody& Process::root_directory_relative_to_global_root()
-{
-    if (!m_root_directory_relative_to_global_root)
-        m_root_directory_relative_to_global_root = root_directory();
-    return *m_root_directory_relative_to_global_root;
-}
-
-void Process::set_root_directory(const Custody& root)
-{
-    m_root_directory = root;
-}
-
 void Process::set_tty(TTY* tty)
 {
     m_tty = tty;

Kernel/Process.h

@@ -57,7 +57,6 @@ Time kgettimeofday();
     __ENUMERATE_PLEDGE_PROMISE(fattr)     \
     __ENUMERATE_PLEDGE_PROMISE(tty)       \
     __ENUMERATE_PLEDGE_PROMISE(chown)     \
-    __ENUMERATE_PLEDGE_PROMISE(chroot)    \
     __ENUMERATE_PLEDGE_PROMISE(thread)    \
     __ENUMERATE_PLEDGE_PROMISE(video)     \
     __ENUMERATE_PLEDGE_PROMISE(accept)    \
@@ -392,7 +391,6 @@ public:
     KResultOr<FlatPtr> sys$profiling_disable(pid_t);
     KResultOr<FlatPtr> sys$profiling_free_buffer(pid_t);
     KResultOr<FlatPtr> sys$futex(Userspace<const Syscall::SC_futex_params*>);
-    KResultOr<FlatPtr> sys$chroot(Userspace<const char*> path, size_t path_length, int mount_flags);
     KResultOr<FlatPtr> sys$pledge(Userspace<const Syscall::SC_pledge_params*>);
     KResultOr<FlatPtr> sys$unveil(Userspace<const Syscall::SC_unveil_params*>);
     KResultOr<FlatPtr> sys$perf_event(int type, FlatPtr arg1, FlatPtr arg2);
@@ -454,10 +452,6 @@ public:
     Mutex& big_lock() { return m_big_lock; }
     Mutex& ptrace_lock() { return m_ptrace_lock; }
 
-    Custody& root_directory();
-    Custody& root_directory_relative_to_global_root();
-    void set_root_directory(const Custody&);
-
     bool has_promises() const { return m_protected_values.has_promises; }
     bool has_promised(Pledge pledge) const { return m_protected_values.promises & (1u << (u32)pledge); }
 
@@ -559,7 +553,6 @@ public:
     KResult procfs_get_pledge_stats(KBufferBuilder& builder) const;
     KResult procfs_get_virtual_memory_stats(KBufferBuilder& builder) const;
     KResult procfs_get_binary_link(KBufferBuilder& builder) const;
-    KResult procfs_get_root_link(KBufferBuilder& builder) const;
     KResult procfs_get_current_work_directory_link(KBufferBuilder& builder) const;
     mode_t binary_link_required_mode() const;
     KResultOr<size_t> procfs_get_thread_stack(ThreadID thread_id, KBufferBuilder& builder) const;
@@ -760,8 +753,6 @@ private:
 
     RefPtr<Custody> m_executable;
     RefPtr<Custody> m_cwd;
-    RefPtr<Custody> m_root_directory;
-    RefPtr<Custody> m_root_directory_relative_to_global_root;
 
     Vector<String> m_arguments;
     Vector<String> m_environment;

Kernel/ProcessExposed.h

@@ -31,7 +31,6 @@ enum class MainProcessProperty {
     CurrentWorkDirectoryLink = 5,
     PerformanceEvents = 6,
     VirtualMemoryStats = 7,
-    RootLink = 8,
 };
 
 enum class ProcessSubDirectory {

Kernel/ProcessProcFSTraits.cpp

@@ -65,7 +65,6 @@ KResult Process::ProcessProcFSTraits::traverse_as_directory(unsigned fsid, Funct
     callback({ "cwd", { fsid, SegmentedProcFSIndex::build_segmented_index_for_main_property_in_pid_directory(process->pid(), SegmentedProcFSIndex::MainProcessProperty::CurrentWorkDirectoryLink) }, 0 });
     callback({ "perf_events", { fsid, SegmentedProcFSIndex::build_segmented_index_for_main_property_in_pid_directory(process->pid(), SegmentedProcFSIndex::MainProcessProperty::PerformanceEvents) }, 0 });
     callback({ "vm", { fsid, SegmentedProcFSIndex::build_segmented_index_for_main_property_in_pid_directory(process->pid(), SegmentedProcFSIndex::MainProcessProperty::VirtualMemoryStats) }, 0 });
-    callback({ "root", { fsid, SegmentedProcFSIndex::build_segmented_index_for_main_property_in_pid_directory(process->pid(), SegmentedProcFSIndex::MainProcessProperty::RootLink) }, 0 });
     return KSuccess;
 }
 

Kernel/ProcessSpecificExposed.cpp

@@ -218,12 +218,6 @@ KResult Process::procfs_get_fds_stats(KBufferBuilder& builder) const
     return KSuccess;
 }
 
-KResult Process::procfs_get_root_link(KBufferBuilder& builder) const
-{
-    builder.append_bytes(const_cast<Process&>(*this).root_directory_relative_to_global_root().absolute_path().to_byte_buffer());
-    return KSuccess;
-}
-
 KResult Process::procfs_get_virtual_memory_stats(KBufferBuilder& builder) const
 {
     JsonArraySerializer array { builder };

Kernel/Syscalls/chroot.cpp

@@ -1,38 +0,0 @@
-/*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
- *
- * SPDX-License-Identifier: BSD-2-Clause
- */
-
-#include <AK/StringView.h>
-#include <Kernel/FileSystem/Custody.h>
-#include <Kernel/FileSystem/VirtualFileSystem.h>
-#include <Kernel/Process.h>
-
-namespace Kernel {
-
-KResultOr<FlatPtr> Process::sys$chroot(Userspace<const char*> user_path, size_t path_length, int mount_flags)
-{
-    VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
-    if (!is_superuser())
-        return EPERM;
-    REQUIRE_PROMISE(chroot);
-    auto path = get_syscall_path_argument(user_path, path_length);
-    if (path.is_error())
-        return path.error();
-    auto directory_or_error = VirtualFileSystem::the().open_directory(path.value()->view(), current_directory());
-    if (directory_or_error.is_error())
-        return directory_or_error.error();
-    auto directory = directory_or_error.value();
-    m_root_directory_relative_to_global_root = directory;
-    int chroot_mount_flags = mount_flags == -1 ? directory->mount_flags() : mount_flags;
-
-    auto custody_or_error = Custody::try_create(nullptr, "", directory->inode(), chroot_mount_flags);
-    if (custody_or_error.is_error())
-        return custody_or_error.error();
-
-    set_root_directory(custody_or_error.release_value());
-    return 0;
-}
-
-}

Kernel/Syscalls/fork.cpp

@@ -21,8 +21,6 @@ KResultOr<FlatPtr> Process::sys$fork(RegisterState& regs)
     auto child = Process::create(child_first_thread, m_name, uid(), gid(), pid(), m_is_kernel_process, m_cwd, m_executable, m_tty, this);
     if (!child || !child_first_thread)
         return ENOMEM;
-    child->m_root_directory = m_root_directory;
-    child->m_root_directory_relative_to_global_root = m_root_directory_relative_to_global_root;
     child->m_veil_state = m_veil_state;
     child->m_unveiled_paths = m_unveiled_paths.deep_copy();
 

Kernel/Syscalls/unveil.cpp

@@ -92,7 +92,7 @@ KResultOr<FlatPtr> Process::sys$unveil(Userspace<const Syscall::SC_unveil_params
     // If this case is encountered, the parent node of the path is returned and the custody of that inode is used instead.
     RefPtr<Custody> parent_custody; // Parent inode in case of ENOENT
     OwnPtr<KString> new_unveiled_path;
-    auto custody_or_error = VirtualFileSystem::the().resolve_path_without_veil(path.view(), root_directory(), &parent_custody);
+    auto custody_or_error = VirtualFileSystem::the().resolve_path_without_veil(path.view(), VirtualFileSystem::the().root_custody(), &parent_custody);
     if (!custody_or_error.is_error()) {
         new_unveiled_path = custody_or_error.value()->try_create_absolute_path();
         if (!new_unveiled_path)

Kernel/init.cpp

@@ -325,8 +325,6 @@ void init_stage2(void*)
         PANIC("VirtualFileSystem::mount_root failed");
     }
 
-    Process::current()->set_root_directory(VirtualFileSystem::the().root_custody());
-
     // Switch out of early boot mode.
     g_in_early_boot = false;