diff --git a/Kernel/Arch/x86/Processor.h b/Kernel/Arch/x86/Processor.h
index 200c5831ab5..5488556d4a7 100644
--- a/Kernel/Arch/x86/Processor.h
+++ b/Kernel/Arch/x86/Processor.h
@@ -289,7 +289,7 @@ public:
     ALWAYS_INLINE static Thread* idle_thread()
     {
         // See comment in Processor::current_thread
-        return (Thread*)read_fs_u32(__builtin_offsetof(Processor, m_idle_thread));
+        return (Thread*)read_fs_ptr(__builtin_offsetof(Processor, m_idle_thread));
     }
 
     ALWAYS_INLINE u32 get_id() const
diff --git a/Kernel/Arch/x86/common/CPU.cpp b/Kernel/Arch/x86/common/CPU.cpp
new file mode 100644
index 00000000000..fcfd4be5fd4
--- /dev/null
+++ b/Kernel/Arch/x86/common/CPU.cpp
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Assertions.h>
+#include <AK/Types.h>
+#include <Kernel/Arch/x86/CPU.h>
+#include <Kernel/Arch/x86/Processor.h>
+#include <Kernel/Arch/x86/TrapFrame.h>
+#include <Kernel/KSyms.h>
+#include <Kernel/Process.h>
+
+void __assertion_failed(const char* msg, const char* file, unsigned line, const char* func)
+{
+    asm volatile("cli");
+    critical_dmesgln("ASSERTION FAILED: {}", msg);
+    critical_dmesgln("{}:{} in {}", file, line, func);
+
+    abort();
+}
+
+[[noreturn]] void abort()
+{
+    // Switch back to the current process's page tables if there are any.
+    // Otherwise stack walking will be a disaster.
+    auto process = Process::current();
+    if (process)
+        MM.enter_process_paging_scope(*process);
+
+    Kernel::dump_backtrace();
+    Processor::halt();
+
+    abort();
+}
+
+[[noreturn]] void _abort()
+{
+    asm volatile("ud2");
+    __builtin_unreachable();
+}
diff --git a/Kernel/Arch/x86/common/Processor.cpp b/Kernel/Arch/x86/common/Processor.cpp
index 96281902d79..00efca9e9fa 100644
--- a/Kernel/Arch/x86/common/Processor.cpp
+++ b/Kernel/Arch/x86/common/Processor.cpp
@@ -485,7 +485,13 @@ Vector<FlatPtr> Processor::capture_stack_trace(Thread& thread, size_t max_frames
             // to be ebp.
             ProcessPagingScope paging_scope(thread.process());
             auto& tss = thread.tss();
-            u32* stack_top = reinterpret_cast<u32*>(tss.esp);
+            u32* stack_top;
+#if ARCH(I386)
+            stack_top = reinterpret_cast<u32*>(tss.esp);
+#else
+            (void)tss;
+            TODO();
+#endif
             if (is_user_range(VirtualAddress(stack_top), sizeof(FlatPtr))) {
                 if (!copy_from_user(&frame_ptr, &((FlatPtr*)stack_top)[0]))
                     frame_ptr = 0;
@@ -494,7 +500,11 @@ Vector<FlatPtr> Processor::capture_stack_trace(Thread& thread, size_t max_frames
                 if (!safe_memcpy(&frame_ptr, &((FlatPtr*)stack_top)[0], sizeof(FlatPtr), fault_at))
                     frame_ptr = 0;
             }
+#if ARCH(I386)
             eip = tss.eip;
+#else
+            TODO();
+#endif
             // TODO: We need to leave the scheduler lock here, but we also
             //       need to prevent the target thread from being run while
             //       we walk the stack
diff --git a/Kernel/Arch/x86/i386/ProcessorInfo.cpp b/Kernel/Arch/x86/common/ProcessorInfo.cpp
similarity index 100%
rename from Kernel/Arch/x86/i386/ProcessorInfo.cpp
rename to Kernel/Arch/x86/common/ProcessorInfo.cpp
diff --git a/Kernel/Arch/x86/i386/CPU.cpp b/Kernel/Arch/x86/i386/CPU.cpp
index 2b464c37ac3..99296b7deea 100644
--- a/Kernel/Arch/x86/i386/CPU.cpp
+++ b/Kernel/Arch/x86/i386/CPU.cpp
@@ -101,32 +101,3 @@ extern "C" u32 do_init_context(Thread* thread, u32 flags)
 }
 
 }
-
-void __assertion_failed(const char* msg, const char* file, unsigned line, const char* func)
-{
-    asm volatile("cli");
-    critical_dmesgln("ASSERTION FAILED: {}", msg);
-    critical_dmesgln("{}:{} in {}", file, line, func);
-
-    abort();
-}
-
-[[noreturn]] void abort()
-{
-    // Switch back to the current process's page tables if there are any.
-    // Otherwise stack walking will be a disaster.
-    auto process = Process::current();
-    if (process)
-        MM.enter_process_paging_scope(*process);
-
-    Kernel::dump_backtrace();
-    Processor::halt();
-
-    abort();
-}
-
-[[noreturn]] void _abort()
-{
-    asm volatile("ud2");
-    __builtin_unreachable();
-}
diff --git a/Kernel/Arch/x86/i386/InterruptEntry.cpp b/Kernel/Arch/x86/i386/InterruptEntry.cpp
index 6a52802b7c7..0df2fd65331 100644
--- a/Kernel/Arch/x86/i386/InterruptEntry.cpp
+++ b/Kernel/Arch/x86/i386/InterruptEntry.cpp
@@ -6,6 +6,7 @@
 
 #include <Kernel/Arch/x86/DescriptorTable.h>
 #include <Kernel/Arch/x86/TrapFrame.h>
+
 // clang-format off
 asm(
     ".globl interrupt_common_asm_entry\n"
diff --git a/Kernel/Arch/x86/i386/Processor.cpp b/Kernel/Arch/x86/i386/Processor.cpp
index dd08a0813ad..1432a94b02f 100644
--- a/Kernel/Arch/x86/i386/Processor.cpp
+++ b/Kernel/Arch/x86/i386/Processor.cpp
@@ -37,7 +37,6 @@ asm(
 );
 // clang-format on
 
-#if ARCH(I386)
 // clang-format off
 asm(
 ".global do_assume_context \n"
@@ -59,7 +58,6 @@ asm(
 "    jmp enter_thread_context \n"
 );
 // clang-format on
-#endif
 
 String Processor::platform_string() const
 {
diff --git a/Kernel/Arch/x86/x86_64/Boot/boot.S b/Kernel/Arch/x86/x86_64/Boot/boot.S
index 8e1d9d27ba9..3a6f624dba9 100644
--- a/Kernel/Arch/x86/x86_64/Boot/boot.S
+++ b/Kernel/Arch/x86/x86_64/Boot/boot.S
@@ -317,7 +317,8 @@ apic_ap_start32:
     movl $0x80000001, %eax
     cpuid
     testl $0x100000, %edx
-    je (1f - apic_ap_start + 0x8000)
+    // TODO: Uncomment this
+    //je (1f - apic_ap_start + 0x8000)
     /* turn on IA32_EFER.NXE */
     movl $0xc0000080, %ecx
     rdmsr
diff --git a/Kernel/Arch/x86/x86_64/CPU.cpp b/Kernel/Arch/x86/x86_64/CPU.cpp
new file mode 100644
index 00000000000..8d9c0954d3b
--- /dev/null
+++ b/Kernel/Arch/x86/x86_64/CPU.cpp
@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Assertions.h>
+#include <AK/Types.h>
+
+#include <Kernel/Arch/x86/CPU.h>
+#include <Kernel/Arch/x86/Processor.h>
+#include <Kernel/Arch/x86/TrapFrame.h>
+#include <Kernel/KSyms.h>
+#include <Kernel/Process.h>
+#include <Kernel/Thread.h>
+
+namespace Kernel {
+
+// The compiler can't see the calls to these functions inside assembly.
+// Declare them, to avoid dead code warnings.
+extern "C" void enter_thread_context(Thread* from_thread, Thread* to_thread) __attribute__((used));
+extern "C" void context_first_init(Thread* from_thread, Thread* to_thread, TrapFrame* trap) __attribute__((used));
+extern "C" u32 do_init_context(Thread* thread, u32 flags) __attribute__((used));
+
+extern "C" void enter_thread_context(Thread* from_thread, Thread* to_thread)
+{
+    (void)from_thread;
+    (void)to_thread;
+    TODO();
+}
+
+extern "C" void context_first_init([[maybe_unused]] Thread* from_thread, [[maybe_unused]] Thread* to_thread, [[maybe_unused]] TrapFrame* trap)
+{
+    TODO();
+}
+
+extern "C" u32 do_init_context(Thread* thread, u32 flags)
+{
+    (void)thread;
+    (void)flags;
+    TODO();
+}
+}
diff --git a/Kernel/Arch/x86/x86_64/InterruptEntry.cpp b/Kernel/Arch/x86/x86_64/InterruptEntry.cpp
new file mode 100644
index 00000000000..991583929f1
--- /dev/null
+++ b/Kernel/Arch/x86/x86_64/InterruptEntry.cpp
@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021, Gunnar Beutner <gbeutner@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/Arch/x86/DescriptorTable.h>
+#include <Kernel/Arch/x86/TrapFrame.h>
+
+// clang-format off
+asm(
+".globl interrupt_common_asm_entry\n"
+"interrupt_common_asm_entry: \n"
+"    int3 \n" // FIXME
+".globl common_trap_exit \n"
+"common_trap_exit: \n"
+// another thread may have handled this trap at this point, so don't
+// make assumptions about the stack other than there's a TrapFrame
+// and a pointer to it.
+"    call exit_trap \n"
+"    int3 \n" // FIXME
+);
+// clang-format on
diff --git a/Kernel/Arch/x86/x86_64/Processor.cpp b/Kernel/Arch/x86/x86_64/Processor.cpp
index 7db6c9ad4ce..01c41a0481d 100644
--- a/Kernel/Arch/x86/x86_64/Processor.cpp
+++ b/Kernel/Arch/x86/x86_64/Processor.cpp
@@ -88,6 +88,7 @@ u32 Processor::init_context(Thread& thread, bool leave_crit)
     // TODO: handle NT?
     VERIFY((cpu_flags() & 0x24000) == 0); // Assume !(NT | VM)
 
+#if 0
     auto& tss = thread.tss();
     bool return_to_user = (tss.cs & 3) != 0;
 
@@ -116,7 +117,6 @@ u32 Processor::init_context(Thread& thread, bool leave_crit)
     // However, the first step is to always start in kernel mode with thread_context_first_enter
     RegisterState& iretframe = *reinterpret_cast<RegisterState*>(stack_top);
     // FIXME: copy state to be recovered through TSS
-    TODO();
 
     // make space for a trap frame
     stack_top -= sizeof(TrapFrame);
@@ -161,6 +161,9 @@ u32 Processor::init_context(Thread& thread, bool leave_crit)
     tss.gs = GDT_SELECTOR_DATA0;
     tss.ss = GDT_SELECTOR_DATA0;
     tss.fs = GDT_SELECTOR_PROC;
+#else
+    TODO();
+#endif
     return stack_top;
 }
 
@@ -202,11 +205,15 @@ UNMAP_AFTER_INIT void Processor::initialize_context_switching(Thread& initial_th
 
     auto& tss = initial_thread.tss();
     m_tss = tss;
+#if 0
     m_tss.esp0 = tss.esp0;
     m_tss.ss0 = GDT_SELECTOR_DATA0;
     // user mode needs to be able to switch to kernel mode:
     m_tss.cs = m_tss.ds = m_tss.es = m_tss.gs = m_tss.ss = GDT_SELECTOR_CODE0 | 3;
     m_tss.fs = GDT_SELECTOR_PROC | 3;
+#else
+    TODO();
+#endif
 
     m_scheduler_initialized = true;
 
diff --git a/Kernel/Arch/x86/x86_64/SafeMem.cpp b/Kernel/Arch/x86/x86_64/SafeMem.cpp
new file mode 100644
index 00000000000..bbc622e771a
--- /dev/null
+++ b/Kernel/Arch/x86/x86_64/SafeMem.cpp
@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2021, Gunnar Beutner <gbeutner@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/Arch/x86/SafeMem.h>
+
+#define CODE_SECTION(section_name) __attribute__((section(section_name)))
+
+namespace Kernel {
+
+CODE_SECTION(".text.safemem")
+NEVER_INLINE bool safe_memcpy(void* dest_ptr, const void* src_ptr, size_t n, void*& fault_at)
+{
+    (void)dest_ptr;
+    (void)src_ptr;
+    (void)n;
+    (void)fault_at;
+    TODO();
+}
+
+CODE_SECTION(".text.safemem")
+NEVER_INLINE ssize_t safe_strnlen(const char* str, size_t max_n, void*& fault_at)
+{
+    (void)str;
+    (void)max_n;
+    (void)fault_at;
+    TODO();
+}
+
+CODE_SECTION(".text.safemem")
+NEVER_INLINE bool safe_memset(void* dest_ptr, int c, size_t n, void*& fault_at)
+{
+    (void)dest_ptr;
+    (void)c;
+    (void)n;
+    (void)fault_at;
+    TODO();
+}
+
+CODE_SECTION(".text.safemem.atomic")
+NEVER_INLINE Optional<u32> safe_atomic_fetch_add_relaxed(volatile u32* var, u32 val)
+{
+    (void)var;
+    (void)val;
+    TODO();
+}
+
+CODE_SECTION(".text.safemem.atomic")
+NEVER_INLINE Optional<u32> safe_atomic_exchange_relaxed(volatile u32* var, u32 val)
+{
+    (void)var;
+    (void)val;
+    TODO();
+}
+
+CODE_SECTION(".text.safemem.atomic")
+NEVER_INLINE Optional<u32> safe_atomic_load_relaxed(volatile u32* var)
+{
+    (void)var;
+    TODO();
+}
+
+CODE_SECTION(".text.safemem.atomic")
+NEVER_INLINE bool safe_atomic_store_relaxed(volatile u32* var, u32 val)
+{
+    (void)var;
+    (void)val;
+    TODO();
+}
+
+CODE_SECTION(".text.safemem.atomic")
+NEVER_INLINE Optional<bool> safe_atomic_compare_exchange_relaxed(volatile u32* var, u32& expected, u32 val)
+{
+    (void)var;
+    (void)expected;
+    (void)val;
+    TODO();
+}
+
+bool handle_safe_access_fault(RegisterState& regs, u32 fault_address)
+{
+    (void)regs;
+    (void)fault_address;
+    TODO();
+}
+
+}
diff --git a/Kernel/CMakeLists.txt b/Kernel/CMakeLists.txt
index 47c2021927b..b3bfdf8de0c 100644
--- a/Kernel/CMakeLists.txt
+++ b/Kernel/CMakeLists.txt
@@ -275,15 +275,16 @@ set(KERNEL_SOURCES
     ${CMAKE_CURRENT_SOURCE_DIR}/Arch/x86/${KERNEL_ARCH}/CPU.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/Arch/x86/${KERNEL_ARCH}/InterruptEntry.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/Arch/x86/${KERNEL_ARCH}/Processor.cpp
-    ${CMAKE_CURRENT_SOURCE_DIR}/Arch/x86/${KERNEL_ARCH}/ProcessorInfo.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/Arch/x86/${KERNEL_ARCH}/SafeMem.cpp
 )
 
 set(KERNEL_SOURCES
     ${KERNEL_SOURCES}
     ${CMAKE_CURRENT_SOURCE_DIR}/Arch/x86/common/ASM_wrapper.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/Arch/x86/common/CPU.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/Arch/x86/common/Interrupts.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/Arch/x86/common/Processor.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/Arch/x86/common/ProcessorInfo.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/Arch/x86/common/TrapFrame.cpp
 )
 
@@ -395,7 +396,7 @@ if (ENABLE_KERNEL_LTO)
     check_ipo_supported()
     set_property(TARGET Kernel PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
 endif()
-target_link_libraries(Kernel kernel_heap gcc stdc++)
+target_link_libraries(Kernel kernel_heap gcc supc++)
 add_dependencies(Kernel kernel_heap)
 install(TARGETS Kernel RUNTIME DESTINATION boot)
 
diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
index f5e4aad9731..e42c045757e 100644
--- a/Kernel/Process.cpp
+++ b/Kernel/Process.cpp
@@ -20,6 +20,7 @@
 #include <Kernel/KBufferBuilder.h>
 #include <Kernel/KSyms.h>
 #include <Kernel/Module.h>
+#include <Kernel/Panic.h>
 #include <Kernel/PerformanceEventBuffer.h>
 #include <Kernel/PerformanceManager.h>
 #include <Kernel/Process.h>
@@ -179,8 +180,14 @@ RefPtr<Process> Process::create_kernel_process(RefPtr<Thread>& first_thread, Str
     auto process = Process::create(first_thread, move(name), (uid_t)0, (gid_t)0, ProcessID(0), true);
     if (!first_thread || !process)
         return {};
+#if ARCH(I386)
     first_thread->tss().eip = (FlatPtr)entry;
     first_thread->tss().esp = FlatPtr(entry_data); // entry function argument is expected to be in tss.esp
+#else
+    (void)entry;
+    (void)entry_data;
+    PANIC("Process::create_kernel_process() not implemented");
+#endif
 
     if (process->pid() != 0) {
         process->ref();
@@ -640,9 +647,15 @@ RefPtr<Thread> Process::create_kernel_thread(void (*entry)(void*), void* entry_d
     if (!joinable)
         thread->detach();
 
+#if ARCH(I386)
     auto& tss = thread->tss();
     tss.eip = (FlatPtr)entry;
     tss.esp = FlatPtr(entry_data); // entry function argument is expected to be in tss.esp
+#else
+    (void)entry;
+    (void)entry_data;
+    PANIC("Process::create_kernel_thread() not implemented");
+#endif
 
     ScopedSpinLock lock(g_scheduler_lock);
     thread->set_state(Thread::State::Runnable);
diff --git a/Kernel/Scheduler.cpp b/Kernel/Scheduler.cpp
index a3b25aad4bd..5ce64493814 100644
--- a/Kernel/Scheduler.cpp
+++ b/Kernel/Scheduler.cpp
@@ -228,10 +228,14 @@ bool Scheduler::pick_next()
 
     auto& thread_to_schedule = pull_next_runnable_thread();
     if constexpr (SCHEDULER_DEBUG) {
+#if ARCH(I386)
         dbgln("Scheduler[{}]: Switch to {} @ {:04x}:{:08x}",
             Processor::id(),
             thread_to_schedule,
             thread_to_schedule.tss().cs, thread_to_schedule.tss().eip);
+#else
+        PANIC("Scheduler::pick_next() not implemented");
+#endif
     }
 
     // We need to leave our first critical section before switching context,
@@ -571,14 +575,22 @@ void dump_thread_list()
     dbgln("Scheduler thread list for processor {}:", Processor::id());
 
     auto get_cs = [](Thread& thread) -> u16 {
+#if ARCH(I386)
         if (!thread.current_trap())
             return thread.tss().cs;
+#else
+        PANIC("get_cs() not implemented");
+#endif
         return thread.get_register_dump_from_stack().cs;
     };
 
     auto get_eip = [](Thread& thread) -> u32 {
+#if ARCH(I386)
         if (!thread.current_trap())
             return thread.tss().eip;
+#else
+        PANIC("get_eip() not implemented");
+#endif
         return thread.get_register_dump_from_stack().eip;
     };
 
diff --git a/Kernel/Syscalls/execve.cpp b/Kernel/Syscalls/execve.cpp
index 20ae7dcf420..2485b95d4a6 100644
--- a/Kernel/Syscalls/execve.cpp
+++ b/Kernel/Syscalls/execve.cpp
@@ -11,6 +11,7 @@
 #include <Kernel/Debug.h>
 #include <Kernel/FileSystem/Custody.h>
 #include <Kernel/FileSystem/FileDescription.h>
+#include <Kernel/Panic.h>
 #include <Kernel/PerformanceManager.h>
 #include <Kernel/Process.h>
 #include <Kernel/Random.h>
@@ -635,6 +636,7 @@ KResult Process::do_exec(NonnullRefPtr<FileDescription> main_program_description
     }
     new_main_thread->reset_fpu_state();
 
+#if ARCH(I386)
     auto& tss = new_main_thread->m_tss;
     tss.cs = GDT_SELECTOR_CODE3 | 3;
     tss.ds = GDT_SELECTOR_DATA3 | 3;
@@ -646,6 +648,10 @@ KResult Process::do_exec(NonnullRefPtr<FileDescription> main_program_description
     tss.esp = new_userspace_esp;
     tss.cr3 = space().page_directory().cr3();
     tss.ss2 = pid().value();
+#else
+    (void)new_userspace_esp;
+    PANIC("Process::do_exec() not implemented");
+#endif
 
     {
         TemporaryChange profiling_disabler(m_profiling, was_profiling);
diff --git a/Kernel/Syscalls/fork.cpp b/Kernel/Syscalls/fork.cpp
index 1f7d7086421..2161506da63 100644
--- a/Kernel/Syscalls/fork.cpp
+++ b/Kernel/Syscalls/fork.cpp
@@ -7,6 +7,7 @@
 #include <Kernel/Debug.h>
 #include <Kernel/FileSystem/Custody.h>
 #include <Kernel/FileSystem/FileDescription.h>
+#include <Kernel/Panic.h>
 #include <Kernel/PerformanceManager.h>
 #include <Kernel/Process.h>
 #include <Kernel/VM/Region.h>
@@ -43,6 +44,7 @@ KResultOr<pid_t> Process::sys$fork(RegisterState& regs)
     dbgln_if(FORK_DEBUG, "fork: child={}", child);
     child->space().set_enforces_syscall_regions(space().enforces_syscall_regions());
 
+#if ARCH(I386)
     auto& child_tss = child_first_thread->m_tss;
     child_tss.eax = 0; // fork() returns 0 in the child :^)
     child_tss.ebx = regs.ebx;
@@ -62,6 +64,10 @@ KResultOr<pid_t> Process::sys$fork(RegisterState& regs)
     child_tss.ss = regs.userspace_ss;
 
     dbgln_if(FORK_DEBUG, "fork: child will begin executing at {:04x}:{:08x} with stack {:04x}:{:08x}, kstack {:04x}:{:08x}", child_tss.cs, child_tss.eip, child_tss.ss, child_tss.esp, child_tss.ss0, child_tss.esp0);
+#else
+    (void)regs;
+    PANIC("Process::sys$fork() not implemented.");
+#endif
 
     {
         ScopedSpinLock lock(space().get_lock());
diff --git a/Kernel/Syscalls/thread.cpp b/Kernel/Syscalls/thread.cpp
index 6ecdd3c46b3..ee934a0b2e5 100644
--- a/Kernel/Syscalls/thread.cpp
+++ b/Kernel/Syscalls/thread.cpp
@@ -8,6 +8,7 @@
 #include <AK/String.h>
 #include <AK/StringBuilder.h>
 #include <AK/StringView.h>
+#include <Kernel/Panic.h>
 #include <Kernel/PerformanceManager.h>
 #include <Kernel/Process.h>
 #include <Kernel/VM/MemoryManager.h>
@@ -60,11 +61,16 @@ KResultOr<int> Process::sys$create_thread(void* (*entry)(void*), Userspace<const
     if (!is_thread_joinable)
         thread->detach();
 
+#if ARCH(I386)
     auto& tss = thread->tss();
     tss.eip = (FlatPtr)entry;
     tss.eflags = 0x0202;
     tss.cr3 = space().page_directory().cr3();
     tss.esp = user_esp.value();
+#else
+    (void)entry;
+    PANIC("Process::sys$create_thread() not implemented");
+#endif
 
     auto tsr_result = thread->make_thread_specific_region({});
     if (tsr_result.is_error())
diff --git a/Kernel/Thread.cpp b/Kernel/Thread.cpp
index 9e8f8510040..90f047c45ff 100644
--- a/Kernel/Thread.cpp
+++ b/Kernel/Thread.cpp
@@ -86,6 +86,7 @@ Thread::Thread(NonnullRefPtr<Process> process, NonnullOwnPtr<Region> kernel_stac
     reset_fpu_state();
     m_tss.iomapbase = sizeof(TSS32);
 
+#if ARCH(I386)
     // Only IF is set when a process boots.
     m_tss.eflags = 0x0202;
 
@@ -106,10 +107,14 @@ Thread::Thread(NonnullRefPtr<Process> process, NonnullOwnPtr<Region> kernel_stac
     }
 
     m_tss.cr3 = m_process->space().page_directory().cr3();
+#else
+    PANIC("Thread::Thread() not implemented");
+#endif
 
     m_kernel_stack_base = m_kernel_stack_region->vaddr().get();
     m_kernel_stack_top = m_kernel_stack_region->vaddr().offset(default_kernel_stack_size).get() & 0xfffffff8u;
 
+#if ARCH(I386)
     if (m_process->is_kernel_process()) {
         m_tss.esp = m_tss.esp0 = m_kernel_stack_top;
     } else {
@@ -118,6 +123,9 @@ Thread::Thread(NonnullRefPtr<Process> process, NonnullOwnPtr<Region> kernel_stac
         m_tss.ss0 = GDT_SELECTOR_DATA0;
         m_tss.esp0 = m_kernel_stack_top;
     }
+#else
+    PANIC("Thread::Thread() not implemented");
+#endif
 
     // We need to add another reference if we could successfully create
     // all the resources needed for this thread. The reason for this is that
@@ -801,12 +809,12 @@ DispatchSignalResult Thread::dispatch_signal(u8 signal)
         FlatPtr old_esp = *stack;
         FlatPtr ret_eip = state.eip;
         FlatPtr ret_eflags = state.eflags;
+
+        dbgln_if(SIGNAL_DEBUG, "Setting up user stack to return to EIP {:p}, ESP {:p}", ret_eip, old_esp);
 #elif ARCH(X86_64)
         FlatPtr* stack = &state.userspace_esp;
 #endif
 
-        dbgln_if(SIGNAL_DEBUG, "Setting up user stack to return to EIP {:p}, ESP {:p}", ret_eip, old_esp);
-
 #if ARCH(I386)
         // Align the stack to 16 bytes.
         // Note that we push 56 bytes (4 * 14) on to the stack,
@@ -826,8 +834,9 @@ DispatchSignalResult Thread::dispatch_signal(u8 signal)
         push_value_on_user_stack(stack, state.esi);
         push_value_on_user_stack(stack, state.edi);
 
-#elif ARCH(X86_64)
+#else
         // FIXME
+        PANIC("Thread:dispatch_signal() not implemented");
 #endif
 
         // PUSH old_signal_mask
@@ -848,7 +857,12 @@ DispatchSignalResult Thread::dispatch_signal(u8 signal)
     setup_stack(regs);
     regs.eip = process.signal_trampoline().get();
 
+#if ARCH(I386)
     dbgln_if(SIGNAL_DEBUG, "Thread in state '{}' has been primed with signal handler {:04x}:{:08x} to deliver {}", state_string(), m_tss.cs, m_tss.eip, signal);
+#else
+    PANIC("Thread:dispatch_signal() not implemented");
+#endif
+
     return DispatchSignalResult::Continue;
 }
 
diff --git a/Kernel/VM/MemoryManager.cpp b/Kernel/VM/MemoryManager.cpp
index cccfca3fc1f..34eea25c01b 100644
--- a/Kernel/VM/MemoryManager.cpp
+++ b/Kernel/VM/MemoryManager.cpp
@@ -11,6 +11,7 @@
 #include <Kernel/FileSystem/Inode.h>
 #include <Kernel/Heap/kmalloc.h>
 #include <Kernel/Multiboot.h>
+#include <Kernel/Panic.h>
 #include <Kernel/Process.h>
 #include <Kernel/Sections.h>
 #include <Kernel/StdLib.h>
@@ -732,8 +733,13 @@ void MemoryManager::enter_space(Space& space)
     VERIFY(current_thread != nullptr);
     ScopedSpinLock lock(s_mm_lock);
 
+#if ARCH(I386)
     current_thread->tss().cr3 = space.page_directory().cr3();
     write_cr3(space.page_directory().cr3());
+#else
+    (void)space;
+    PANIC("MemoryManager::enter_space not implemented");
+#endif
 }
 
 void MemoryManager::flush_tlb_local(VirtualAddress vaddr, size_t page_count)
diff --git a/Kernel/VM/ProcessPagingScope.cpp b/Kernel/VM/ProcessPagingScope.cpp
index 05ab320574b..db3bee8026d 100644
--- a/Kernel/VM/ProcessPagingScope.cpp
+++ b/Kernel/VM/ProcessPagingScope.cpp
@@ -5,6 +5,7 @@
  */
 
 #include <Kernel/Arch/x86/InterruptDisabler.h>
+#include <Kernel/Panic.h>
 #include <Kernel/VM/MemoryManager.h>
 #include <Kernel/VM/ProcessPagingScope.h>
 
@@ -20,7 +21,11 @@ ProcessPagingScope::ProcessPagingScope(Process& process)
 ProcessPagingScope::~ProcessPagingScope()
 {
     InterruptDisabler disabler;
+#if ARCH(I386)
     Thread::current()->tss().cr3 = m_previous_cr3;
+#else
+    PANIC("ProcessPagingScope::~ProcessPagingScope() not implemented");
+#endif
     write_cr3(m_previous_cr3);
 }