diff options
| -rw-r--r-- | .vscode/settings.json | 4 | ||||
| -rw-r--r-- | arch/x86_64/src/boot/boot.s | 512 |
2 files changed, 269 insertions, 247 deletions
diff --git a/.vscode/settings.json b/.vscode/settings.json index e8e872e..0d62c95 100644 --- a/.vscode/settings.json +++ b/.vscode/settings.json @@ -14,5 +14,9 @@ "[cpp]": { "editor.formatOnSave": true, "editor.tabSize": 2, + }, + + "[gas]": { + "editor.rulers": [80] } }
\ No newline at end of file diff --git a/arch/x86_64/src/boot/boot.s b/arch/x86_64/src/boot/boot.s index f3d9585..7a46795 100644 --- a/arch/x86_64/src/boot/boot.s +++ b/arch/x86_64/src/boot/boot.s @@ -1,50 +1,22 @@ -.extern _end_physical -.extern _init -.extern kernel_main - - /** - * Uninitialized data for the bootstrapping process. + * @brief Uninitialized data for the bootstrapping process. */ .section .boot_bss, "aw", @nobits /** - * Reserve some space for the Multiboot 2 information pointer. + * @brief Storage for the multiboot2 information pointer. */ .global multiboot_information_pointer multiboot_information_pointer: .skip 8 -/** - * 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 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) - * - 1 PML 3 - * - 1 PML 2 - */ - -.global page_map_level_4 page_map_level_4: .skip 512 * 8 - -.global page_map_level_3 page_map_level_3: .skip 512 * 8 - -.global page_map_level_2 page_map_level_2: .skip 512 * 8 /** - * Stack space for the bootstrapping process. - * - * Note: We are going to reserve 1 MiB for now. If/when the kernel requires - * more space to run, it will have to relocate the stack. + * @brief Storage for the bootstrap stack. */ .section .boot_stack, "aw", @nobits .align 16 @@ -53,210 +25,240 @@ stack_bottom: .skip 1 << 20 stack_top: /** - * Constants for the bootstrapping process. + * @brief Constants for the bootstrapping process. */ .section .boot_rodata, "a", @progbits /** - * A valid Global Descriptor Table is still required in long mode. - * - * Bit 41: "A" in the access byte => mark the segment as accessed. - * Bit 41: "RW" in the access byte => mark the segment as readable (code) or writable (data). - * Bit 43: "E" in the access byte => mark the segment as executable. - * Bit 44: "S" in the access byte => mark the segment as code or data. - * Bit 47: "P" in the access byte => mark the segment as being present. - * Bit 53: "L" in the flags byte => mark the segment as being for long mode + * @brief A basic GDT for long mode. */ - global_descriptor_table: +.set GDT_ACCESSED, 40 +.set GDT_READ_WRITE, 41 +.set GDT_EXECUTABLE, 43 +.set GDT_DESCRIPTOR_TYPE, 44 +.set GDT_PRESENT, 47 +.set GDT_LONG_MODE, 53 global_descriptor_table_null = . - global_descriptor_table .quad 0 global_descriptor_table_code = . - global_descriptor_table -.quad (1<<40) | (1<<41) | (1<<43) | (1<<44) | (1<<47) | (1<<53) +.quad (1 << GDT_ACCESSED) | (1 << GDT_READ_WRITE) | (1 << GDT_EXECUTABLE) | (1 << GDT_DESCRIPTOR_TYPE) | (1 << GDT_PRESENT) | (1 << GDT_LONG_MODE) global_descriptor_table_data = . - global_descriptor_table -.quad (1<<40) | (1<<41) | (1<<44) | (1<<47) +.quad (1 << GDT_ACCESSED) | (1 << GDT_READ_WRITE) | (1 << GDT_DESCRIPTOR_TYPE) | (1 << GDT_PRESENT) global_descriptor_table_end: -/** - * 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: -.string "The operating system was not loaded by a Multiboot 2 loader." -message_cpuid_instruction_no_supported: -.string "The 'cpuid' instruction is not supported on this platform." -mesage_long_mode_not_supported: -.string "Long mode is not supported by this platform." +message_prefix_panic: .string "Panic: " +message_not_loaded_by_multiboot2: .string "The operating system was not loaded by a Multiboot 2 loader." +message_cpuid_instruction_no_supported: .string "The 'cpuid' instruction is not supported on this platform." +message_long_mode_not_supported: .string "Long mode is not supported by this platform." +message_return_from_kernel_main: .string "Execution returned from kernel main." /** - * Mutable data for the bootstrapping process. + * @brief Initialized data for the bootstrapping process. */ .section .boot_data, "aw", @progbits /** - * We need a pointer to our current position in the VGA text buffer. + * @brief A pointer to the current position within the VGA text buffer. */ .global vga_buffer_pointer vga_buffer_pointer: .quad 0xb8000 /** - * Code for the bootstrapping process. + * @brief Code for the bootstrapping process. */ .section .boot_text, "ax", @progbits .align 16 .code32 -.global halt -halt: -1: - hlt - jmp 1b +.macro pie_base + push %esi + call 0f + 0: + pop %esi +.endm + +.macro function_start + push %ebp + mov %esp, %ebp +.endm + +.macro function_end + leave + ret +.endm + +.macro pie_function_start + function_start + pie_base +.endm + +.macro pie_function_end + pop %esi + function_end +.endm /** - * Print a given panic message and then halt the machine. + * @brief Prepare the environment and start the kernel. * - * Parameters: - * - [stack - 0] message: the message to print + * This function performs all necessary checks to ensure the system was loaded + * by the expected loader and supports all features required to run the kernel. + * If successful, it prepares the system by setting up memory virtualization + * and then start the kernel proper. + * + * @param %eax The Multiboot 2 magic marker. + * @param %ebx The Multiboot 2 information pointer. + * @return void This function does not return. */ -_panic: - push %ebp +.global _start +_start: + call 0f +0: + pop %esi + + lea (stack_top - 0b)(%esi), %ecx + + mov %ecx, %esp mov %esp, %ebp - call .Lpanic_get_ip -.Lpanic_get_ip: - pop %eax - lea (message_prefix_panic - .Lpanic_get_ip)(%eax), %eax + call _assert_loaded_by_multiboot2_loader + call _save_multiboot_information_pointer - push %eax - push $0x4f - call _print - add $8, %esp + call _assert_cpuid_instruction_is_supported + call _assert_cpu_supports_long_mode - push 8(%ebp) - push 0x4f - call _print - add $8, %esp + call _prepare_page_maps + call _enable_paging + call _enable_sse + call _reload_gdt + + lea (_transition_to_long_mode - 0b)(%esi), %eax + pushl $global_descriptor_table_code + pushl %eax + lret + +/** + * @brief Halt the system. + * + * This function will instruct the CPU to halt. It will try to keep the CPU + * halted, even if interrupts occur. + * + * @return This function never returns. + */ +.global halt +_halt: + function_start - call halt +1: + hlt + jmp 1b + + function_end /** - * Print a message via the VGA buffer. + * @brief Print a message via the VGA text buffer. * - * Parameters: - * - [stack - 4] message: the message to print - * - [stack - 0] color: the color of the message + * @param ebp+12 The message to print. + * @param ebp+8 The color to print the message in. */ _print: - push %ebp - mov %esp, %ebp + pie_function_start - push %ebx - push %esi push %edi + push %ebx - call .Lprint_get_ip -.Lprint_get_ip: - pop %edi - lea (vga_buffer_pointer - .Lprint_get_ip)(%edi), %edi - - mov 8(%ebp), %eax - mov 12(%ebp), %ebx + mov 8(%ebp), %al + mov 12(%ebp), %edx mov $0, %ecx - mov (%edi), %esi - -.Lprint_loop: - mov (%ebx, %ecx), %dl - test %dl, %dl - je .Lupdate_vga_buffer_address - mov %dl, (%esi, %ecx, 2) - mov %al, 1(%esi, %ecx, 2) + lea (vga_buffer_pointer - 0b)(%esi), %edi + mov (%edi), %edi + +1: + mov (%edx, %ecx), %bl + test %bl, %bl + je 2f + mov %bl, (%edi, %ecx, 2) + mov %al, 1(%edi, %ecx, 2) inc %ecx - jmp .Lprint_loop + jmp 1b -.Lupdate_vga_buffer_address: +2: shl $1, %ecx - add %ecx, %esi - mov %esi, (%edi) + add %ecx, %edi + lea (vga_buffer_pointer - 0b)(%esi), %ecx + mov %edi, (%ecx) -.Lprint_end: - pop %edi - pop %esi pop %ebx - mov %ebp, %esp - pop %ebp - ret + pop %edi + + pie_function_end /** - * This is our entry point after being loaded by the bootloader. + * @brief Print a given panic message and then halt the machine as if by calling ::halt() * - * Having this in assembly makes it easier for us to keep things together. + * @param ebp+4 A message to print. + * @return This function does not return. */ -.global _start -_start: - call .Lstart_get_ip -.Lstart_get_ip: - pop %esi - lea (stack_top - .Lstart_get_ip)(%esi), %ecx - - mov %ecx, %esp - mov %esp, %ebp +_panic: + pie_function_start - call assert_loaded_by_multiboot2_loader - call assert_cpuid_instruction_is_supported - call assert_cpu_supports_long_mode - call prepare_page_maps - call enable_paging - call enable_sse + lea (message_prefix_panic - 0b)(%esi), %eax - sub $10, %esp - lea (global_descriptor_table - .Lstart_get_ip)(%esi), %eax - movw $(global_descriptor_table_end - global_descriptor_table -1), (%esp) - mov %eax, 2(%esp) - movl $0, 6(%esp) + push %eax + push $0x4f + call _print - lgdt (%esp) - add $10, %esp + mov 16(%ebp), %eax + mov %eax, 8(%ebp) + call _print + add $8, %esp - lea (_transition_to_long_mode - .Lstart_get_ip)(%esi), %eax - pushl $global_descriptor_table_code - pushl %eax - lret + call _halt - call halt + pie_function_end /** - * Assert that the CPU supports going into long mode. + * Assert that we were loaded by a Multiboot 2 compliant bootloader. + * + * This assertion will panic the system if the magic signature was not found. + * If we were loaded my an appropriate bootloader, this function also saves + * the provided MBI pointer to `multiboot_information_pointer`. */ -assert_cpu_supports_long_mode: - mov $0x80000000, %eax - cpuid - cmp $0x80000001, %eax - jb .Llong_mode_assertion_failed +_assert_loaded_by_multiboot2_loader: + pie_function_start - mov $0x80000001, %eax - cpuid - test $(1 << 29), %edx - jz .Llong_mode_assertion_failed - ret -.Llong_mode_assertion_failed: - call .Lassert_cpu_supports_long_mode_fail_get_ip -.Lassert_cpu_supports_long_mode_fail_get_ip: - pop %eax - lea (mesage_long_mode_not_supported - .Lassert_cpu_supports_long_mode_fail_get_ip)(%eax), %eax + .set MULTIBOOT2_MAGIC, 0x36d76289 + cmp $MULTIBOOT2_MAGIC, %eax + je 1f + lea (message_not_loaded_by_multiboot2 - 0b)(%esi), %eax push %eax call _panic +1: + pie_function_end /** - * Assert that the CPU supports the CPUID instruction. + * @brief Store the multiboot 2 information pointer in the global memory. + * + * @return void + */ +_save_multiboot_information_pointer: + pie_function_start + + lea (multiboot_information_pointer - 0b)(%esi), %eax + mov %ebx, (%eax) + + pie_function_end + +/** + * @brief Assert that the CPU supports the CPUID instruction. * * The primary way to check for support of the instruction is to flip the ID * bin in EFLAGS and then check if this changed was accepted. If so, the CPU * supports the CPUID instruction, otherwise it most-likely doesn't. */ -assert_cpuid_instruction_is_supported: +_assert_cpuid_instruction_is_supported: + pie_function_start + pushfl pop %eax mov %eax, %ecx @@ -271,52 +273,100 @@ assert_cpuid_instruction_is_supported: popfl cmp %ecx, %eax - je .Lcpuid_assertion_fail - ret -.Lcpuid_assertion_fail: - call .Lassert_cpuid_instruction_is_supported_fail_get_ip -.Lassert_cpuid_instruction_is_supported_fail_get_ip: - pop %eax - lea (message_cpuid_instruction_no_supported - .Lassert_cpuid_instruction_is_supported_fail_get_ip)(%eax), %eax + jne 1f + lea (message_cpuid_instruction_no_supported - 0b)(%esi), %eax push %eax call _panic +1: + pie_function_end + /** - * Assert that we were loaded by a Multiboot 2 compliant bootloader. - * - * This assertion will panic the system if the magic signature was not found. - * If we were loaded my an appropriate bootloader, this function also saves - * the provided MBI pointer to `multiboot_information_pointer`. + * @brief Assert that the CPU supports going into long mode. */ -assert_loaded_by_multiboot2_loader: - cmp $0x36d76289, %eax /* Check if we received the - expected magic */ - jne .Lmultiboot2_assertion_fail /* Panic otherwise */ - call .Lassert_loaded_by_multiboot2_loader_get_ip -.Lassert_loaded_by_multiboot2_loader_get_ip: - pop %eax - lea (multiboot_information_pointer - .Lassert_loaded_by_multiboot2_loader_get_ip)(%eax), %eax - mov %ebx, (%eax) /* Store the MBI pointer */ - ret -.Lmultiboot2_assertion_fail: - call .Lassert_loaded_by_multiboot2_loader_fail_get_ip -.Lassert_loaded_by_multiboot2_loader_fail_get_ip: - pop %eax - lea (message_not_loaded_by_multiboot2 - .Lassert_loaded_by_multiboot2_loader_fail_get_ip)(%eax), %eax +_assert_cpu_supports_long_mode: + pie_function_start + + mov $0x80000000, %eax + cpuid + cmp $0x80000001, %eax + jb 1f + + mov $0x80000001, %eax + cpuid + test $(1 << 29), %edx + jnz 2f +1: + lea (message_long_mode_not_supported - 0b)(%esi), %eax push %eax call _panic +2: + pie_function_end /** - * Enable paging. + * @brief Prepare a recursive page map hierarchy + * + * 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. + * + * @return void + */ +_prepare_page_maps: + pie_function_start + push %ebx + + .set HUGE_PAGES_TO_MAP, 16 + + /* Map the P4 table recursively */ + lea (page_map_level_4 - 0b)(%esi), %eax + mov %eax, %ebx + or $0b11, %ebx + mov %ebx, (511 * 8)(%eax) + + /* Add an entry to the PML4, pointing to the PML3 */ + lea (page_map_level_3 - 0b)(%esi), %ebx + or $0b11, %ebx + mov %ebx, (((0x0000000000100000 >> 39) & 0x1ff) * 8)(%eax) + + /* Add an entry to the PML3, pointing to the PML2 */ + lea (page_map_level_3 - 0b)(%esi), %eax + lea (page_map_level_2 - 0b)(%esi), %ebx + or $0b11, %ebx + mov %ebx, (((0x0000000000100000 >> 30) & 0x1ff) * 8)(%eax) + + /* Add entries for huge pages to the PML2 */ + push %edi + lea (page_map_level_2 - 0b)(%esi), %ebx + mov $HUGE_PAGES_TO_MAP, %edi + xor %ecx, %ecx + +1: + mov $(1 << 21), %eax + mul %ecx + or $0b10000011, %eax + mov %eax, (%ebx, %ecx, 8) + + inc %ecx + cmp %edi, %ecx + jne 1b + + pop %edi + pop %ebx + pie_function_end + +/** + * @p Enable memory virtualization via paging. * * Note: This routine expects for there to be a valid set of page maps already * set up for use. - */ -enable_paging: - call .Lenable_paging_get_ip -.Lenable_paging_get_ip: - pop %eax -lea (page_map_level_4 - .Lenable_paging_get_ip)(%eax), %eax + * + * @return void + */For +_enable_paging: + pie_function_start + + lea (page_map_level_4 - 0b)(%esi), %eax mov %eax, %cr3 /* Enable Physical Address Extension */ @@ -335,12 +385,14 @@ lea (page_map_level_4 - .Lenable_paging_get_ip)(%eax), %eax or $(1 << 31), %eax mov %eax, %cr0 - ret + pie_function_end /** - * Enable use of SSE instructions. + * @brief Enable use of SSE instructions. */ -enable_sse: +_enable_sse: + function_start + mov %cr0, %eax and $0xfffffffb, %eax or $0x00000002, %eax @@ -350,57 +402,26 @@ enable_sse: or $(3 << 9), %eax mov %eax, %cr4 - ret + function_end /** - * Prepare the page maps. + * @brief Prepare a new GTD and load make it active. * - * 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. + * @return void */ -prepare_page_maps: - call .Lprepare_page_maps_get_ip -.Lprepare_page_maps_get_ip: - pop %edi - /* Map the P4 table recursively */ - lea (page_map_level_4 - .Lprepare_page_maps_get_ip)(%edi), %eax - mov %eax, %ebx - or $0b11, %eax /* Write present + writable flags into eax register */ - mov %eax, (511 * 8)(%ebx) - - /* Add an entry to the PML4, pointing to the PML3 */ - lea (page_map_level_3 - .Lprepare_page_maps_get_ip)(%edi), %eax - lea (page_map_level_4 - .Lprepare_page_maps_get_ip)(%edi), %ebx - or $0x3, %eax - mov %eax, (((0x0000000000100000 >> 39) & 0x1ff) * 8)(%ebx) - - /* Add an entry to the PML3, pointing to the PML2 */ - lea (page_map_level_2 - .Lprepare_page_maps_get_ip)(%edi), %eax - lea (page_map_level_3 - .Lprepare_page_maps_get_ip)(%edi), %ebx - or $0x3, %eax - mov %eax, (((0x0000000000100000 >> 30) & 0x1ff) * 8)(%ebx) - - xor %ecx, %ecx - - push %esi - lea (_end_linear - .Lprepare_page_maps_get_ip)(%edi), %esi - shr $21, %esi - add $2, %esi +_reload_gdt: + pie_function_start -.Lmap_pages: - lea (page_map_level_2 - .Lprepare_page_maps_get_ip)(%edi), %ebx - mov $(1 << 21), %eax - mul %ecx - or $((1 << 0) | (1 << 1) | (1 << 7)), %eax - mov %eax, (%ebx,%ecx,8) + sub $10, %esp + lea (global_descriptor_table - 0b)(%esi), %eax + movw $(global_descriptor_table_end - global_descriptor_table -1), (%esp) + mov %eax, 2(%esp) + movl $0, 6(%esp) - inc %ecx - cmp %esi, %ecx - jne .Lmap_pages + lgdt (%esp) + add $10, %esp - pop %esi - ret + pie_function_end .section .boot_text, "ax", @progbits .code64 @@ -413,12 +434,9 @@ _transition_to_long_mode: mov %rax, %fs mov %rax, %gs - leaq vga_buffer_pointer(%rip), %rax - movl $0xb8000, (%rax) - xor %rax, %rax call _init call main - call halt + call _halt |