mirror of
https://github.com/RGBCube/serenity
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Kernel: Support loading the kernel at almost arbitrary virtual addresses
This enables further work on implementing KASLR by adding relocation support to the pre-kernel and updating the kernel to be less dependent on specific virtual memory layouts.
This commit is contained in:
Gunnar Beutner
Andreas Kling
parent
e3d2ca6bd2
commit
57417a3d6e
20 changed files with 123 additions and 87 deletions
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@ -12,6 +12,7 @@
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#include <Kernel/Prekernel/Prekernel.h>
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#include <Kernel/VirtualAddress.h>
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#include <LibC/elf.h>
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#include <LibELF/Relocation.h>
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// Defined in the linker script
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extern size_t __stack_chk_guard;
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@ -28,7 +29,8 @@ extern "C" u64 boot_pdpt[512];
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extern "C" u64 boot_pd0[512];
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extern "C" u64 boot_pd0_pts[512 * (MAX_KERNEL_SIZE >> 21 & 0x1ff)];
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extern "C" u64 boot_pd_kernel[512];
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extern "C" u64 boot_pd_kernel_pts[512 * (MAX_KERNEL_SIZE >> 21 & 0x1ff)];
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extern "C" u64 boot_pd_kernel_pt0[512];
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extern "C" u64 boot_pd_kernel_image_pts[512 * (MAX_KERNEL_SIZE >> 21 & 0x1ff)];
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extern "C" u64 boot_pd_kernel_pt1023[512];
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extern "C" char const kernel_cmdline[4096];
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@ -38,10 +40,20 @@ extern "C" {
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multiboot_info_t* multiboot_info_ptr;
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}
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[[noreturn]] static void halt()
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{
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asm volatile("hlt");
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__builtin_unreachable();
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}
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void __stack_chk_fail()
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{
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asm("ud2");
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__builtin_unreachable();
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halt();
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}
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void __assertion_failed(char const*, char const*, unsigned int, char const*)
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{
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halt();
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}
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namespace Kernel {
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@ -50,11 +62,6 @@ namespace Kernel {
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// We declare them here to ensure their signatures don't accidentally change.
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extern "C" [[noreturn]] void init();
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static void halt()
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{
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asm volatile("hlt");
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}
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// SerenityOS Pre-Kernel Environment C++ entry point :^)
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//
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// This is where C++ execution begins, after boot.S transfers control here.
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@ -75,50 +82,63 @@ extern "C" [[noreturn]] void init()
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halt();
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__builtin_memcpy(kernel_program_headers, kernel_image + kernel_elf_header.e_phoff, sizeof(ElfW(Phdr)) * kernel_elf_header.e_phnum);
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FlatPtr kernel_load_base = 0;
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FlatPtr kernel_physical_base = 0x200000;
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#if ARCH(I386)
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FlatPtr kernel_load_base = 0xc0200000;
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#else
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FlatPtr kernel_load_base = 0x2000200000;
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#endif
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FlatPtr kernel_load_end = 0;
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for (size_t i = 0; i < kernel_elf_header.e_phnum; i++) {
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auto& kernel_program_header = kernel_program_headers[i];
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if (kernel_program_header.p_type != PT_LOAD)
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continue;
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auto start = kernel_program_header.p_vaddr;
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auto start = kernel_load_base + kernel_program_header.p_vaddr;
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auto end = start + kernel_program_header.p_memsz;
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if (start < (FlatPtr)end_of_prekernel_image)
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halt();
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if (kernel_program_header.p_paddr < (FlatPtr)end_of_prekernel_image)
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if (kernel_physical_base + kernel_program_header.p_paddr < (FlatPtr)end_of_prekernel_image)
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halt();
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if (kernel_load_base == 0 || start < kernel_load_base)
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kernel_load_base = start;
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if (end > kernel_load_end)
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kernel_load_end = end;
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}
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// align to 1GB
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kernel_load_base &= ~(FlatPtr)0x3fffffff;
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FlatPtr kernel_mapping_base = kernel_load_base & ~(FlatPtr)0x3fffffff;
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VERIFY(kernel_load_base % 0x1000 == 0);
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VERIFY(kernel_load_base >= kernel_mapping_base + 0x200000);
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#if ARCH(I386)
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int pdpt_flags = 0x1;
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#else
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int pdpt_flags = 0x3;
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#endif
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boot_pdpt[(kernel_load_base >> 30) & 0x1ffu] = (FlatPtr)boot_pd_kernel | pdpt_flags;
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boot_pdpt[(kernel_mapping_base >> 30) & 0x1ffu] = (FlatPtr)boot_pd_kernel | pdpt_flags;
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for (size_t i = 0; i <= (kernel_load_end - kernel_load_base) >> 21; i++)
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boot_pd_kernel[i] = (FlatPtr)&boot_pd_kernel_pts[i * 512] | 0x3;
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boot_pd_kernel[0] = (FlatPtr)boot_pd_kernel_pt0 | 0x3;
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__builtin_memset(boot_pd_kernel_pts, 0, sizeof(boot_pd_kernel_pts));
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for (FlatPtr vaddr = kernel_load_base; vaddr <= kernel_load_end; vaddr += PAGE_SIZE * 512)
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boot_pd_kernel[(vaddr - kernel_mapping_base) >> 21] = (FlatPtr)(&boot_pd_kernel_image_pts[(vaddr - kernel_load_base) >> 12]) | 0x3;
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__builtin_memset(boot_pd_kernel_pt0, 0, sizeof(boot_pd_kernel_pt0));
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VERIFY((size_t)end_of_prekernel_image < array_size(boot_pd_kernel_pt0) * PAGE_SIZE);
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/* pseudo-identity map 0M - end_of_prekernel_image */
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for (size_t i = 0; i < (FlatPtr)end_of_prekernel_image / PAGE_SIZE; i++)
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boot_pd_kernel_pts[i] = i * PAGE_SIZE | 0x3;
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boot_pd_kernel_pt0[i] = i * PAGE_SIZE | 0x3;
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__builtin_memset(boot_pd_kernel_image_pts, 0, sizeof(boot_pd_kernel_image_pts));
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for (size_t i = 0; i < kernel_elf_header.e_phnum; i++) {
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auto& kernel_program_header = kernel_program_headers[i];
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if (kernel_program_header.p_type != PT_LOAD)
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continue;
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for (FlatPtr offset = 0; offset < kernel_program_header.p_memsz; offset += PAGE_SIZE) {
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auto pte_index = (kernel_program_header.p_vaddr + offset - kernel_load_base) >> 12;
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boot_pd_kernel_pts[pte_index] = (kernel_program_header.p_paddr + offset) | 0x3;
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auto pte_index = ((kernel_load_base & 0x1fffff) + kernel_program_header.p_vaddr + offset) >> 12;
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boot_pd_kernel_image_pts[pte_index] = (kernel_physical_base + kernel_program_header.p_paddr + offset) | 0x3;
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}
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}
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@ -130,28 +150,29 @@ extern "C" [[noreturn]] void init()
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auto& kernel_program_header = kernel_program_headers[i];
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if (kernel_program_header.p_type != PT_LOAD)
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continue;
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__builtin_memmove((u8*)kernel_program_header.p_vaddr, kernel_image + kernel_program_header.p_offset, kernel_program_header.p_filesz);
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__builtin_memmove((u8*)kernel_load_base + kernel_program_header.p_vaddr, kernel_image + kernel_program_header.p_offset, kernel_program_header.p_filesz);
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}
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for (ssize_t i = kernel_elf_header.e_phnum - 1; i >= 0; i--) {
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auto& kernel_program_header = kernel_program_headers[i];
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if (kernel_program_header.p_type != PT_LOAD)
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continue;
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__builtin_memset((u8*)kernel_program_header.p_vaddr + kernel_program_header.p_filesz, 0, kernel_program_header.p_memsz - kernel_program_header.p_filesz);
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__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);
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}
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multiboot_info_ptr->mods_count--;
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multiboot_info_ptr->mods_addr += sizeof(multiboot_module_entry_t);
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auto adjust_by_load_base = [kernel_load_base](auto ptr) {
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return (decltype(ptr))((FlatPtr)ptr + kernel_load_base);
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auto adjust_by_mapping_base = [kernel_mapping_base](auto ptr) {
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return (decltype(ptr))((FlatPtr)ptr + kernel_mapping_base);
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};
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BootInfo info;
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info.start_of_prekernel_image = (PhysicalPtr)start_of_prekernel_image;
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info.end_of_prekernel_image = (PhysicalPtr)end_of_prekernel_image;
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info.physical_to_virtual_offset = kernel_load_base;
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info.kernel_base = kernel_load_base;
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info.physical_to_virtual_offset = kernel_load_base - kernel_physical_base;
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info.kernel_mapping_base = kernel_mapping_base;
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info.kernel_load_base = kernel_load_base;
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#if ARCH(X86_64)
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info.gdt64ptr = (PhysicalPtr)gdt64ptr;
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info.code64_sel = code64_sel;
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@ -160,12 +181,12 @@ extern "C" [[noreturn]] void init()
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info.boot_pdpt = (PhysicalPtr)boot_pdpt;
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info.boot_pd0 = (PhysicalPtr)boot_pd0;
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info.boot_pd_kernel = (PhysicalPtr)boot_pd_kernel;
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info.boot_pd_kernel_pt1023 = (FlatPtr)adjust_by_load_base(boot_pd_kernel_pt1023);
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info.kernel_cmdline = (FlatPtr)adjust_by_load_base(kernel_cmdline);
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info.boot_pd_kernel_pt1023 = (FlatPtr)adjust_by_mapping_base(boot_pd_kernel_pt1023);
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info.kernel_cmdline = (FlatPtr)adjust_by_mapping_base(kernel_cmdline);
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info.multiboot_flags = multiboot_info_ptr->flags;
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info.multiboot_memory_map = adjust_by_load_base((FlatPtr)multiboot_info_ptr->mmap_addr);
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info.multiboot_memory_map = adjust_by_mapping_base((FlatPtr)multiboot_info_ptr->mmap_addr);
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info.multiboot_memory_map_count = multiboot_info_ptr->mmap_length / sizeof(multiboot_memory_map_t);
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info.multiboot_modules = adjust_by_load_base((FlatPtr)multiboot_info_ptr->mods_addr);
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info.multiboot_modules = adjust_by_mapping_base((FlatPtr)multiboot_info_ptr->mods_addr);
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info.multiboot_modules_count = multiboot_info_ptr->mods_count;
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info.multiboot_framebuffer_addr = multiboot_info_ptr->framebuffer_addr;
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info.multiboot_framebuffer_pitch = multiboot_info_ptr->framebuffer_pitch;
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@ -178,9 +199,11 @@ extern "C" [[noreturn]] void init()
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#if ARCH(I386)
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"add %0, %%esp"
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#else
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"add %0, %%rsp"
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"movabs %0, %%rax\n"
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"add %%rax, %%rsp"
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#endif
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::"g"(kernel_load_base));
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::"g"(kernel_mapping_base)
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: "ax");
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// unmap the 0-1MB region
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for (size_t i = 0; i < 256; i++)
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@ -192,8 +215,10 @@ extern "C" [[noreturn]] void init()
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reload_cr3();
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void (*entry)(BootInfo const&) = (void (*)(BootInfo const&))kernel_elf_header.e_entry;
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entry(*adjust_by_load_base(&info));
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ELF::perform_relative_relocations(kernel_load_base);
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void (*entry)(BootInfo const&) = (void (*)(BootInfo const&))(kernel_load_base + kernel_elf_header.e_entry);
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entry(*adjust_by_mapping_base(&info));
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__builtin_unreachable();
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}
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