Kernel: Factor address space management out of the Process class

This patch adds Space, a class representing a process's address space.

- Each Process has a Space.
- The Space owns the PageDirectory and all Regions in the Process.

This allows us to reorganize sys$execve() so that it constructs and
populates a new Space fully before committing to it.

Previously, we would construct the new address space while still
running in the old one, and encountering an error meant we had to do
tedious and error-prone rollback.

Those problems are now gone, replaced by what's hopefully a set of much
smaller problems and missing cleanups. :^)

1 files changed, 8 insertions, 58 deletions

diff --git a/Kernel/Process.h b/Kernel/Process.h
index 9fdd863efd..427dbb660d 100644
--- a/Kernel/Process.h
+++ b/Kernel/Process.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -48,6 +48,7 @@
 #include <Kernel/UnveilNode.h>
 #include <Kernel/VM/AllocationStrategy.h>
 #include <Kernel/VM/RangeAllocator.h>
+#include <Kernel/VM/Space.h>
 #include <LibC/signal_numbers.h>
 #include <LibELF/exec_elf.h>
 
@@ -99,6 +100,8 @@ enum class VeilState {
 
 typedef HashMap<FlatPtr, RefPtr<FutexQueue>> FutexQueues;
 
+struct LoadResult;
+
 class Process
     : public RefCounted<Process>
     , public InlineLinkedListNode<Process>
@@ -164,9 +167,6 @@ public:
     bool is_kernel_process() const { return m_is_kernel_process; }
     bool is_user_process() const { return !m_is_kernel_process; }
 
-    PageDirectory& page_directory() { return *m_page_directory; }
-    const PageDirectory& page_directory() const { return *m_page_directory; }
-
     static RefPtr<Process> from_pid(ProcessID);
     static SessionID get_sid_from_pgid(ProcessGroupID pgid);
 
@@ -188,8 +188,6 @@ public:
     bool is_dumpable() const { return m_dumpable; }
     void set_dumpable(bool dumpable) { m_dumpable = dumpable; }
 
-    ThreadID exec_tid() const { return m_exec_tid; }
-
     mode_t umask() const { return m_umask; }
 
     bool in_group(gid_t) const;
@@ -209,8 +207,6 @@ public:
     void die();
     void finalize();
 
-    ALWAYS_INLINE SpinLock<u32>& get_lock() const { return m_lock; }
-
     ThreadTracer* tracer() { return m_tracer.ptr(); }
     bool is_traced() const { return !!m_tracer; }
     void start_tracing_from(ProcessID tracer);
@@ -373,14 +369,6 @@ public:
     const TTY* tty() const { return m_tty; }
     void set_tty(TTY*);
 
-    size_t region_count() const { return m_regions.size(); }
-    const NonnullOwnPtrVector<Region>& regions() const
-    {
-        ASSERT(m_lock.is_locked());
-        return m_regions;
-    }
-    void dump_regions();
-
     u32 m_ticks_in_user { 0 };
     u32 m_ticks_in_kernel { 0 };
 
@@ -410,25 +398,12 @@ public:
 
     int exec(String path, Vector<String> arguments, Vector<String> environment, int recusion_depth = 0);
 
-    struct LoadResult {
-        FlatPtr load_base { 0 };
-        FlatPtr entry_eip { 0 };
-        size_t size { 0 };
-        FlatPtr program_headers { 0 };
-        size_t num_program_headers { 0 };
-        WeakPtr<Region> tls_region;
-        size_t tls_size { 0 };
-        size_t tls_alignment { 0 };
-        WeakPtr<Region> stack_region;
-    };
-
     enum class ShouldAllocateTls {
         No = 0,
         Yes,
     };
 
     KResultOr<LoadResult> load(NonnullRefPtr<FileDescription> main_program_description, RefPtr<FileDescription> interpreter_description, const Elf32_Ehdr& main_program_header);
-    KResultOr<LoadResult> load_elf_object(FileDescription& object_description, FlatPtr load_offset, ShouldAllocateTls);
     KResultOr<FlatPtr> get_interpreter_load_offset(const Elf32_Ehdr& main_program_header, FileDescription& main_program_description, FileDescription& interpreter_description);
 
     bool is_superuser() const
@@ -436,13 +411,6 @@ public:
         return m_euid == 0;
     }
 
-    KResultOr<Region*> allocate_region_with_vmobject(const Range&, NonnullRefPtr<VMObject>, size_t offset_in_vmobject, const String& name, int prot, bool shared);
-    KResultOr<Region*> allocate_region(const Range&, const String& name, int prot = PROT_READ | PROT_WRITE, AllocationStrategy strategy = AllocationStrategy::Reserve);
-    bool deallocate_region(Region& region);
-
-    Region& allocate_split_region(const Region& source_region, const Range&, size_t offset_in_vmobject);
-    Vector<Region*, 2> split_region_around_range(const Region& source_region, const Range&);
-
     void terminate_due_to_signal(u8 signal);
     KResult send_signal(u8 signal, Process* sender);
 
@@ -503,7 +471,8 @@ public:
 
     PerformanceEventBuffer* perf_events() { return m_perf_event_buffer; }
 
-    bool enforces_syscall_regions() const { return m_enforces_syscall_regions; }
+    Space& space() { return *m_space; }
+    const Space& space() const { return *m_space; }
 
 private:
     friend class MemoryManager;
@@ -518,10 +487,6 @@ private:
     Process(RefPtr<Thread>& first_thread, const String& name, uid_t, gid_t, ProcessID ppid, bool is_kernel_process, RefPtr<Custody> cwd = nullptr, RefPtr<Custody> executable = nullptr, TTY* = nullptr, Process* fork_parent = nullptr);
     static ProcessID allocate_pid();
 
-    Optional<Range> allocate_range(VirtualAddress, size_t, size_t alignment = PAGE_SIZE);
-
-    Region& add_region(NonnullOwnPtr<Region>);
-
     void kill_threads_except_self();
     void kill_all_threads();
     bool dump_core();
@@ -552,13 +517,13 @@ private:
 
     void clear_futex_queues_on_exec();
 
-    RefPtr<PageDirectory> m_page_directory;
-
     Process* m_prev { nullptr };
     Process* m_next { nullptr };
 
     String m_name;
 
+    OwnPtr<Space> m_space;
+
     ProcessID m_pid { 0 };
     SessionID m_sid { 0 };
     RefPtr<ProcessGroup> m_pg;
@@ -570,8 +535,6 @@ private:
     uid_t m_suid { 0 };
     gid_t m_sgid { 0 };
 
-    ThreadID m_exec_tid { 0 };
-
     OwnPtr<ThreadTracer> m_tracer;
 
     static const int m_max_open_file_descriptors { FD_SETSIZE };
@@ -617,16 +580,6 @@ private:
 
     RefPtr<TTY> m_tty;
 
-    Region* find_region_from_range(const Range&);
-    Region* find_region_containing(const Range&);
-
-    NonnullOwnPtrVector<Region> m_regions;
-    struct RegionLookupCache {
-        Optional<Range> range;
-        WeakPtr<Region> region;
-    };
-    RegionLookupCache m_region_lookup_cache;
-
     ProcessID m_ppid { 0 };
     mode_t m_umask { 022 };
 
@@ -639,12 +592,9 @@ private:
     size_t m_master_tls_alignment { 0 };
 
     Lock m_big_lock { "Process" };
-    mutable SpinLock<u32> m_lock;
 
     RefPtr<Timer> m_alarm_timer;
 
-    bool m_enforces_syscall_regions { false };
-
     bool m_has_promises { false };
     u32 m_promises { 0 };
     bool m_has_execpromises { false };