diff options
Diffstat (limited to 'arch/x86_64/src/boot')
| -rw-r--r-- | arch/x86_64/src/boot/boot.s | 80 |
1 files changed, 39 insertions, 41 deletions
diff --git a/arch/x86_64/src/boot/boot.s b/arch/x86_64/src/boot/boot.s index 7b4e193..8d27ea1 100644 --- a/arch/x86_64/src/boot/boot.s +++ b/arch/x86_64/src/boot/boot.s @@ -7,38 +7,38 @@ * Uninitialized data for the bootstrapping process. */ .section .boot_bss, "aw", @nobits + +/** + * Reserve some space for the Multiboot 2 information pointer. + */ +.global multiboot_information_pointer +multiboot_information_pointer: .skip 4 + +/** + * Align page maps to 4 KiB or the assembler code, will cause crashes when attempting to enable paging. + */ .align 4096 /** - * Reserve space for the page maps we are going to used during startup. + * Reserve space for the page maps we are going to use during startup. * * Note: We are going to use large pages to make the initial mapping code * simpler. * * We need: * - A single PML 4 (since we will only use 4-level paging) - * - 2 PML 3s (since we need to map high (-2GiB) and low (1+MiB) memory) - * - 2 PML 2s (since we need to map high (-2GiB) and low (1+MiB) memory) + * - 1 PML 3 + * - 1 PML 2 */ .global page_map_level_4 page_map_level_4: .skip 512 * 8 -.global page_map_level_3_low -page_map_level_3_low: .skip 512 * 8 -.global page_map_level_3_high -page_map_level_3_high: .skip 512 * 8 - -.global page_map_level_2_low -page_map_level_2_low: .skip 512 * 8 -.global page_map_level_2_high -page_map_level_2_high: .skip 512 * 8 +.global page_map_level_3 +page_map_level_3: .skip 512 * 8 -/** - * Reserve some space for the Multiboot 2 information pointer. - */ -.global multiboot_information_pointer -multiboot_information_pointer: .skip 4 +.global page_map_level_2 +page_map_level_2: .skip 512 * 8 /** * Stack space for the bootstrapping process. @@ -86,6 +86,7 @@ global_descriptor_table_pointer: * We are going to print some messages in case we panic during boot, so we are * going to store them here as well */ +.global message_prefix_panic message_prefix_panic: .string "TeachOS Panic: " message_not_loaded_by_multiboot2: @@ -113,6 +114,12 @@ vga_buffer_pointer: .long 0xb8000 .align 16 .code32 +.global halt +halt: +1: + hlt + jmp 1b + /** * Print a given panic message and then halt the machine. * @@ -133,7 +140,7 @@ _panic: call _print add $8, %esp - hlt + call halt /** * Print a message via the VGA buffer. @@ -193,7 +200,7 @@ _start: lgdt (global_descriptor_table_pointer) jmp $global_descriptor_table_code,$_transition_to_long_mode - hlt + call halt /** * Assert that the CPU supports going into long mode. @@ -306,31 +313,23 @@ enable_sse: * * We map all physical memory we were loaded in plus one additional page. The * mapping is done in terms of huge pages (2 MiB per page) to save on required - * page map entries. Note that we also map memory both in the low and high - * virtual address ranges, giving us two ways of accessing it. We need to do - * this, because the bootstrapping code lives in low memory, while the rest of - * the kernel will reside on the high end. + * page map entries. */ prepare_page_maps: - /* Add an entry to the PML4, pointing to the low PML3 */ - mov $page_map_level_3_low, %eax - or $0x3, %eax - mov %eax, (page_map_level_4 + ((0x0000000000100000 >> 39) & 0x1ff) * 8) - - /* Add an entry to the PML4, pointing to the high PML3 */ - mov $page_map_level_3_high, %eax - or $0x3, %eax - mov %eax, (page_map_level_4 + ((0xffffffff80100000 >> 39) & 0x1ff) * 8) + /* Map the P4 table recursively */ + mov $page_map_level_4, %eax + or $0b11, %eax /* Write present + writable flags into eax register */ + mov %eax, (page_map_level_4 + 511 * 8) - /* Add an entry to the low PML3, pointing to the low PML2 */ - mov $page_map_level_2_low, %eax + /* Add an entry to the PML4, pointing to the PML3 */ + mov $page_map_level_3, %eax or $0x3, %eax - mov %eax, (page_map_level_3_low + ((0x0000000000100000 >> 30) & 0x1ff) * 8) + mov %eax, (page_map_level_4 + ((0x0000000000100000 >> 39) & 0x1ff) * 8) - /* Add an entry to the high PML3, pointing to the high PML2 */ - mov $page_map_level_2_high, %eax + /* Add an entry to the PML3, pointing to the PML2 */ + mov $page_map_level_2, %eax or $0x3, %eax - mov %eax, (page_map_level_3_high + ((0xffffffff80100000 >> 30) & 0x1ff) * 8) + mov %eax, (page_map_level_3 + ((0x0000000000100000 >> 30) & 0x1ff) * 8) xor %ecx, %ecx @@ -342,8 +341,7 @@ prepare_page_maps: mov $(1 << 21), %eax mul %ecx or $((1 << 0) | (1 << 1) | (1 << 7)), %eax - mov %eax, page_map_level_2_low(,%ecx,8) - mov %eax, page_map_level_2_high(,%ecx,8) + mov %eax, page_map_level_2(,%ecx,8) inc %ecx cmp %esi, %ecx @@ -367,4 +365,4 @@ _transition_to_long_mode: call _init call kernel_main - hlt + call halt |