Kernel: Move end_of_kernel_image after the .ksyms section

Without this we won't be able to detect whether .ksyms overlaps the end
of the page table we set up for the kernel image.

Kernel/Arch/x86/common/Interrupts.cpp

@@ -29,6 +29,8 @@ extern FlatPtr start_of_unmap_after_init;
 extern FlatPtr end_of_unmap_after_init;
 extern FlatPtr start_of_ro_after_init;
 extern FlatPtr end_of_ro_after_init;
+extern FlatPtr start_of_kernel_ksyms;
+extern FlatPtr end_of_kernel_ksyms;
 
 namespace Kernel {
 
@@ -335,6 +337,11 @@ void page_fault_handler(TrapFrame* trap)
         PANIC("Attempt to access UNMAP_AFTER_INIT section");
     }
 
+    if (fault_address >= (FlatPtr)&start_of_kernel_ksyms && fault_address < (FlatPtr)&end_of_kernel_ksyms) {
+        dump(regs);
+        PANIC("Attempt to access KSYMS section");
+    }
+
     PageFault fault { regs.exception_code, VirtualAddress { fault_address } };
     auto response = MM.handle_page_fault(fault);
 

Kernel/VM/MemoryManager.cpp

@@ -31,6 +31,8 @@ extern FlatPtr start_of_ro_after_init;
 extern FlatPtr end_of_ro_after_init;
 extern FlatPtr start_of_unmap_after_init;
 extern FlatPtr end_of_unmap_after_init;
+extern FlatPtr start_of_kernel_ksyms;
+extern FlatPtr end_of_kernel_ksyms;
 
 extern multiboot_module_entry_t multiboot_copy_boot_modules_array[16];
 extern size_t multiboot_copy_boot_modules_count;
@@ -114,7 +116,7 @@ UNMAP_AFTER_INIT void MemoryManager::protect_readonly_after_init_memory()
     }
 }
 
-void MemoryManager::unmap_memory_after_init()
+void MemoryManager::unmap_text_after_init()
 {
     ScopedSpinLock mm_lock(s_mm_lock);
     ScopedSpinLock page_lock(kernel_page_directory().get_lock());
@@ -130,7 +132,24 @@ void MemoryManager::unmap_memory_after_init()
     }
 
     dmesgln("Unmapped {} KiB of kernel text after init! :^)", (end - start) / KiB);
-    //Processor::halt();
+}
+
+void MemoryManager::unmap_ksyms_after_init()
+{
+    ScopedSpinLock mm_lock(s_mm_lock);
+    ScopedSpinLock page_lock(kernel_page_directory().get_lock());
+
+    auto start = page_round_down((FlatPtr)&start_of_kernel_ksyms);
+    auto end = page_round_up((FlatPtr)&end_of_kernel_ksyms);
+
+    // Unmap the entire .ksyms section
+    for (auto i = start; i < end; i += PAGE_SIZE) {
+        auto& pte = *ensure_pte(kernel_page_directory(), VirtualAddress(i));
+        pte.clear();
+        flush_tlb(&kernel_page_directory(), VirtualAddress(i));
+    }
+
+    dmesgln("Unmapped {} KiB of kernel symbols after init! :^)", (end - start) / KiB);
 }
 
 UNMAP_AFTER_INIT void MemoryManager::register_reserved_ranges()

Kernel/VM/MemoryManager.h

@@ -126,7 +126,8 @@ public:
     void set_page_writable_direct(VirtualAddress, bool);
 
     void protect_readonly_after_init_memory();
-    void unmap_memory_after_init();
+    void unmap_text_after_init();
+    void unmap_ksyms_after_init();
 
     static void enter_process_paging_scope(Process&);
     static void enter_space(Space&);

Kernel/init.cpp

@@ -273,7 +273,10 @@ void init_stage2(void*)
     MM.protect_readonly_after_init_memory();
 
     // NOTE: Everything marked UNMAP_AFTER_INIT becomes inaccessible after this point.
-    MM.unmap_memory_after_init();
+    MM.unmap_text_after_init();
+
+    // NOTE: Everything in the .ksyms section becomes inaccessible after this point.
+    MM.unmap_ksyms_after_init();
 
     int error;
 

Kernel/linker.ld

@@ -93,10 +93,13 @@ SECTIONS
         *(.heap)
     } :bss
 
-    end_of_kernel_image = .;
 
     .ksyms ALIGN(4K) : AT (ADDR(.ksyms) - KERNEL_VIRTUAL_BASE)
     {
+        start_of_kernel_ksyms = .;
         *(.kernel_symbols)
+        end_of_kernel_ksyms = .;
     } :ksyms
+
+    end_of_kernel_image = .;
 }