Revert "Kernel/x86: Bake the Prekernel and the Kernel into one image"

Some hardware/software configurations crash KVM as soon as we try to
start Serenity. The exact cause is currently unknown, so just fully
revert it for now.

This reverts commit 897c4e5145474d55b247a4a3b5e6bf5420279e2f.

4 files changed, 17 insertions, 46 deletions

diff --git a/Kernel/Prekernel/CMakeLists.txt b/Kernel/Prekernel/CMakeLists.txt
index a007bb9376..f554ce4820 100644
--- a/Kernel/Prekernel/CMakeLists.txt
+++ b/Kernel/Prekernel/CMakeLists.txt
@@ -8,21 +8,14 @@ set(SOURCES
     )
 
 if ("${SERENITY_ARCH}" STREQUAL "x86_64")
-    set(PREKERNEL_TARGET kernel_x86-64)
+    set(PREKERNEL_TARGET Prekernel64)
 elseif("${SERENITY_ARCH}" STREQUAL "aarch64")
     message(SEND_ERROR "Prekernel is not needed on aarch64 and should not be compiled!")
 endif()
 
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -static")
 
-add_library(KernelObject OBJECT IMPORTED)
-
-set_property(TARGET KernelObject PROPERTY 
-    IMPORTED_OBJECTS ${CMAKE_CURRENT_BINARY_DIR}/../Kernel.o
-)
-
-add_executable(${PREKERNEL_TARGET} ${SOURCES} $<TARGET_OBJECTS:KernelObject>)
-add_dependencies(${PREKERNEL_TARGET} Kernel)
+add_executable(${PREKERNEL_TARGET} ${SOURCES})
 target_compile_options(${PREKERNEL_TARGET} PRIVATE -no-pie -fno-pic -fno-threadsafe-statics)
 
 target_link_options(${PREKERNEL_TARGET} PRIVATE LINKER:-T ${CMAKE_CURRENT_SOURCE_DIR}/linker.ld -nostdlib LINKER:--no-pie)
@@ -34,20 +27,13 @@ elseif(CMAKE_CXX_COMPILER_ID MATCHES "Clang$")
     target_link_libraries(${PREKERNEL_TARGET} PRIVATE clang_rt.builtins)
 endif()
 
-if ("${SERENITY_ARCH}" STREQUAL "x86_64")
-    set(ELF_OBJCOPY_TARGET "elf32-i386")
-elseif("${SERENITY_ARCH}" STREQUAL "aarch64")
-    message(SEND_ERROR "Prekernel is not needed on aarch64 and should not be compiled!")
-endif()
-
-
 add_custom_command(
     TARGET ${PREKERNEL_TARGET} POST_BUILD
-    COMMAND ${CMAKE_OBJCOPY} -O ${ELF_OBJCOPY_TARGET} ${CMAKE_CURRENT_BINARY_DIR}/${PREKERNEL_TARGET} ${CMAKE_CURRENT_BINARY_DIR}/../Kernel
+    COMMAND ${CMAKE_OBJCOPY} -O elf32-i386 ${CMAKE_CURRENT_BINARY_DIR}/${PREKERNEL_TARGET} ${CMAKE_CURRENT_BINARY_DIR}/Prekernel
     BYPRODUCTS ${CMAKE_CURRENT_BINARY_DIR}/Prekernel
 )
 
-install(FILES "${CMAKE_CURRENT_BINARY_DIR}/../Kernel" DESTINATION boot)
+install(FILES "${CMAKE_CURRENT_BINARY_DIR}/Prekernel" DESTINATION boot)
 
 # Remove options which the Prekernel environment doesn't support.
 get_target_property(PREKERNEL_TARGET_OPTIONS ${PREKERNEL_TARGET} COMPILE_OPTIONS)
diff --git a/Kernel/Prekernel/Prekernel.h b/Kernel/Prekernel/Prekernel.h
index 65e876ad83..7c0176fc12 100644
--- a/Kernel/Prekernel/Prekernel.h
+++ b/Kernel/Prekernel/Prekernel.h
@@ -41,11 +41,8 @@ struct [[gnu::packed]] BootInfo {
     u32 multiboot_flags;
     u64 multiboot_memory_map;
     u32 multiboot_memory_map_count;
-    u64 multiboot_modules_physical_ptr;
+    u64 multiboot_modules;
     u32 multiboot_modules_count;
-    u32 multiboot_module_ramdisk_physical_start;
-    u32 multiboot_module_ramdisk_physical_end;
-    u32 multiboot_module_ramdisk_physical_string_addr;
     u64 multiboot_framebuffer_addr;
     u32 multiboot_framebuffer_pitch;
     u32 multiboot_framebuffer_width;
diff --git a/Kernel/Prekernel/init.cpp b/Kernel/Prekernel/init.cpp
index 53ff0c94fb..b892b75647 100644
--- a/Kernel/Prekernel/init.cpp
+++ b/Kernel/Prekernel/init.cpp
@@ -27,9 +27,6 @@ extern "C" [[noreturn]] void __stack_chk_fail();
 extern "C" u8 start_of_prekernel_image[];
 extern "C" u8 end_of_prekernel_image[];
 
-extern "C" u8 _binary_Kernel_standalone_start[];
-extern "C" u8 end_of_prekernel_image_after_kernel_image[];
-
 extern "C" u8 gdt64ptr[];
 extern "C" u16 code64_sel;
 extern "C" u64 boot_pml4t[512];
@@ -79,7 +76,12 @@ u64 generate_secure_seed();
 
 extern "C" [[noreturn]] void init()
 {
-    u8* kernel_image = _binary_Kernel_standalone_start;
+    if (multiboot_info_ptr->mods_count < 1)
+        halt();
+
+    multiboot_module_entry_t* kernel_module = (multiboot_module_entry_t*)(FlatPtr)multiboot_info_ptr->mods_addr;
+
+    u8* kernel_image = (u8*)(FlatPtr)kernel_module->start;
     // copy the ELF header and program headers because we might end up overwriting them
     ElfW(Ehdr) kernel_elf_header = *(ElfW(Ehdr)*)kernel_image;
     ElfW(Phdr) kernel_program_headers[16];
@@ -87,8 +89,8 @@ extern "C" [[noreturn]] void init()
         halt();
     __builtin_memcpy(kernel_program_headers, kernel_image + kernel_elf_header.e_phoff, sizeof(ElfW(Phdr)) * kernel_elf_header.e_phnum);
 
-    FlatPtr kernel_physical_base = (FlatPtr)kernel_image;
-    FlatPtr default_kernel_load_base = KERNEL_MAPPING_BASE + kernel_physical_base;
+    FlatPtr kernel_physical_base = 0x200000;
+    FlatPtr default_kernel_load_base = KERNEL_MAPPING_BASE + 0x200000;
 
     FlatPtr kernel_load_base = default_kernel_load_base;
 
@@ -166,6 +168,9 @@ extern "C" [[noreturn]] void init()
         __builtin_memset((u8*)kernel_load_base + kernel_program_header.p_vaddr + kernel_program_header.p_filesz, 0, kernel_program_header.p_memsz - kernel_program_header.p_filesz);
     }
 
+    multiboot_info_ptr->mods_count--;
+    multiboot_info_ptr->mods_addr += sizeof(multiboot_module_entry_t);
+
     auto adjust_by_mapping_base = [kernel_mapping_base](auto ptr) {
         return (decltype(ptr))((FlatPtr)ptr + kernel_mapping_base);
     };
@@ -189,16 +194,8 @@ extern "C" [[noreturn]] void init()
     info.multiboot_flags = multiboot_info_ptr->flags;
     info.multiboot_memory_map = adjust_by_mapping_base((FlatPtr)multiboot_info_ptr->mmap_addr);
     info.multiboot_memory_map_count = multiboot_info_ptr->mmap_length / sizeof(multiboot_memory_map_t);
-    info.multiboot_modules_physical_ptr = (FlatPtr)multiboot_info_ptr->mods_addr;
+    info.multiboot_modules = adjust_by_mapping_base((FlatPtr)multiboot_info_ptr->mods_addr);
     info.multiboot_modules_count = multiboot_info_ptr->mods_count;
-
-    if (info.multiboot_modules_count > 0) {
-        auto* entry = reinterpret_cast<multiboot_module_entry*>(multiboot_info_ptr->mods_addr);
-        info.multiboot_module_ramdisk_physical_start = entry->start;
-        info.multiboot_module_ramdisk_physical_end = entry->end;
-        info.multiboot_module_ramdisk_physical_string_addr = entry->string_addr;
-    }
-
     if ((multiboot_info_ptr->flags & MULTIBOOT_INFO_FRAMEBUFFER_INFO) != 0) {
         info.multiboot_framebuffer_addr = multiboot_info_ptr->framebuffer_addr;
         info.multiboot_framebuffer_pitch = multiboot_info_ptr->framebuffer_pitch;
diff --git a/Kernel/Prekernel/linker.ld b/Kernel/Prekernel/linker.ld
index 32cf31436e..1204520540 100644
--- a/Kernel/Prekernel/linker.ld
+++ b/Kernel/Prekernel/linker.ld
@@ -44,13 +44,4 @@ SECTIONS
     } :bss
 
     end_of_prekernel_image = .;
-
-    .Kernel_image ALIGN(4K) : AT (ADDR(.Kernel_image))
-    {
-        _binary_Kernel_standalone_start = .;
-        KEEP(*(.Kernel_image))
-    }
-
-    end_of_prekernel_image_after_kernel_image = .;
-
 }