mirror of
https://github.com/RGBCube/serenity
synced 2025-05-31 03:58:12 +00:00
acf8f2a2a3
The kernel doesn't currently boot when using an address other than 0xc0000000 because the page tables aren't set up properly for that but this at least lets us build the kernel.
594 lines
14 KiB
ArmAsm
594 lines
14 KiB
ArmAsm
#define _BOOTLOADER
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#include <AK/Platform.h>
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#include <Kernel/Sections.h>
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.code32
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.section .stack, "aw", @nobits
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stack_bottom:
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.skip 32768
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stack_top:
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.global kernel_cmdline
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kernel_cmdline:
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.skip 4096
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.section .page_tables, "aw", @nobits
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.align 4096
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#if ARCH(X86_64)
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.global boot_pml4t
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boot_pml4t:
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.skip 4096
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#endif
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.global boot_pdpt
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boot_pdpt:
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.skip 4096
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.global boot_pd0
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boot_pd0:
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.skip 4096
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.global boot_pd3
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boot_pd3:
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.skip 4096
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.global boot_pd0_pt0
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boot_pd0_pt0:
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.skip 4096 * 4
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.global boot_pd3_pts
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boot_pd3_pts:
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.skip 4096 * 16
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.global boot_pd3_pt1023
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boot_pd3_pt1023:
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.skip 4096
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.section .boot_text, "ax"
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.global start
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.type start, @function
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.extern init
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.type init, @function
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.extern multiboot_info_ptr
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.type multiboot_info_ptr, @object
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/*
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construct the following (64-bit PML4T) page table layout:
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(the PML4T part is not used for 32-bit x86)
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pml4t:
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0: pdpt (0-512GB)
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pdpt
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0: boot_pd0 (0-1GB)
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1: n/a (1-2GB)
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2: n/a (2-3GB)
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3: boot_pd3 (3-4GB)
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boot_pd0 : 512 pde's
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0: boot_pd0_pt0 (0-2MB) (id 512 4KB pages)
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boot_pd3 : 512 pde's
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0: boot_pd3_pts[0] (3072-3074MB) (pseudo 512 4KB pages)
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1: boot_pd3_pts[1] (3074-3076MB) (pseudo 512 4KB pages)
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2: boot_pd3_pts[2] (3076-3078MB) (pseudo 512 4KB pages)
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3: boot_pd3_pts[3] (3078-3080MB) (pseudo 512 4KB pages)
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4: boot_pd3_pts[4] (3080-3082MB) (pseudo 512 4KB pages)
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5: boot_pd3_pts[5] (3082-3084MB) (pseudo 512 4KB pages)
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6: boot_pd3_pts[6] (3084-3086MB) (pseudo 512 4KB pages)
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7: boot_pd3_pts[7] (3086-3088MB) (pseudo 512 4KB pages)
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8: boot_pd3_pts[8] (3088-3090MB) (pseudo 512 4KB pages)
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9: boot_pd3_pts[9] (3090-3076MB) (pseudo 512 4KB pages)
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10: boot_pd3_pts[10] (3092-3094MB) (pseudo 512 4KB pages)
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11: boot_pd3_pts[11] (3094-3096MB) (pseudo 512 4KB pages)
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12: boot_pd3_pts[12] (3096-3098MB) (pseudo 512 4KB pages)
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13: boot_pd3_pts[13] (3098-3100MB) (pseudo 512 4KB pages)
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14: boot_pd3_pts[14] (3100-3102MB) (pseudo 512 4KB pages)
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15: boot_pd3_pts[15] (3102-3104MB) (pseudo 512 4KB pages)
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16: boot_pd3_pt1023 (4094-4096MB) (for page table mappings)
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the 9 page tables each contain 512 pte's that map individual 4KB pages
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*/
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#if ARCH(X86_64)
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gdt64:
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.quad 0
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gdt64code:
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.quad (1<<43) | (1<<44) | (1<<47) | (1<<53) /* executable, code segment, present, 64-bit */
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.global gdt64ptr
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gdt64ptr:
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.short . - gdt64 - 1
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.quad gdt64
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.global code64_sel
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.set code64_sel, gdt64code - gdt64
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#endif
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start:
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jmp real_start
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/*
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this function assumes that paging is disabled (or everything is mapped 1:1)
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param 1: pointer to string ended with null terminator (C string)
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*/
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print_and_halt:
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/* from now on, we don't really care about booting because we are missing required CPU features such as PAE or long mode.
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the flow from now is like so:
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1. Copy all necessary parts to low memory section in RAM
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2. Jump to that section
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3. In that section we do:
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a. exit protected mode to pure 16 bit real mode
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b. load the "<missing feature> is not supported" String, call the BIOS print to screen service
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c. halt
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*/
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.equ COPIED_STRING_LOCATION, 0x400
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.equ GDT_REAL_MODE_LOCATION, 0x45000
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.equ EXITING_PROTECTED_MODE_CODE_LOCATION, 0x10000
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.equ REAL_MODE_CODE, 0x500
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.equ PROTECTED_MODE_16_BIT_CODE, 0x600
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mov %esp, %ebp
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mov 4(%ebp), %edi
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/* Copy string to low memory section */
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mov %edi, %esi
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xor %ecx, %ecx
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pushl %eax
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pushl %edi
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check_string_length:
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movb (%edi), %ah
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cmp $0, %ah
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je check_string_length_exit
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inc %ecx
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inc %edi
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jmp check_string_length
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check_string_length_exit:
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popl %edi
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popl %eax
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/* source address of the code is ESI */
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movw %cx, (COPIED_STRING_LOCATION)
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mov $COPIED_STRING_LOCATION + 2, %edi /* destination address of the code */
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rep movsb
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/* Copy gdt_table_real_mode to low memory section */
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movl $(gdt_table_real_mode - KERNEL_BASE), %eax
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movl $(gdt_table_real_mode_end - KERNEL_BASE), %ebx
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movl %ebx, %ecx
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sub %eax, %ecx
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mov %eax, %esi /* source address of the code */
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mov $GDT_REAL_MODE_LOCATION, %edi /* destination address of the code */
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rep movsb
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/* Copy protected_mode_16_bit to real_mode to low memory section */
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movl $(protected_mode_16_bit - KERNEL_BASE), %eax
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movl $(real_mode - KERNEL_BASE), %ebx
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movl %ebx, %ecx
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sub %eax, %ecx
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mov %eax, %esi /* source address of the code */
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mov $PROTECTED_MODE_16_BIT_CODE, %edi /* destination address of the code */
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rep movsb
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/* Copy real_mode to end_of_print_and_halt_function to low memory section */
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movl $(real_mode - KERNEL_BASE), %eax
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movl $(end_of_print_and_halt_function - KERNEL_BASE), %ebx
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movl %ebx, %ecx
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sub %eax, %ecx
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mov %eax, %esi /* source address of the code */
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mov $REAL_MODE_CODE, %edi /* destination address of the code */
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rep movsb
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/* Copy all opcodes from exiting_real_mode label to protected_mode_16_bit label to low memory RAM */
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movl $(exiting_real_mode - KERNEL_BASE), %eax
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movl $(protected_mode_16_bit - KERNEL_BASE), %ebx
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movl %ebx, %ecx
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sub %eax, %ecx
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mov %eax, %esi /* source address of the code */
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mov $EXITING_PROTECTED_MODE_CODE_LOCATION, %edi /* destination address of the code */
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pushl %edi
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rep movsb
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popl %edi
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pushl %edi
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ret
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gdt_table_real_mode:
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.quad 0 /* Empty entry */
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.short 0xffff
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.short 0
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.byte 0
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.byte 0b10011010
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.byte 0b00001111
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.byte 0x0
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.short 0xffff
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.short 0
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.byte 0
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.byte 0b10010010
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.byte 0b00001111
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.byte 0x0
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gdt_table_real_mode_end:
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no_long_mode_string:
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.asciz "Your computer does not support long mode (64-bit mode). Halting!"
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no_pae_string:
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.asciz "Your computer does not support PAE. Halting!"
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kernel_image_too_big_string:
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.asciz "Error: Kernel Image too big for memory slot. Halting!"
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/*
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This part is completely standalone - it doesn't involve any location from this
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near code. It uses arbitrary locations in the low memory section of the RAM.
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We don't really worry about where are these locations, because we only want to quickly
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print a string and halt.
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*/
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.code32
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exiting_real_mode:
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/* Build IDT pointer and load it */
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mov $0x50000, %eax
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pushl %eax
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movl $0x3ff, 0(%eax)
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add $2, %eax
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movl $0, 0(%eax)
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popl %eax
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lidt (%eax)
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/* Build GDT pointer and load it */
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mov $0x40000, %eax
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pushl %eax
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movl $32, 0(%eax)
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add $2, %eax
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movl $GDT_REAL_MODE_LOCATION, 0(%eax)
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popl %eax
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lgdt (%eax)
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/* far jump to protected_mode_16_bit in 0x5000 */
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pushw $8
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push $PROTECTED_MODE_16_BIT_CODE
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lret
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hlt
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.code16
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protected_mode_16_bit:
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xor %eax, %eax
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movl $0x10, %eax
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movw %ax, %ds
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and $0xFE, %al /* switch to pure real mode */
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mov %eax, %cr0
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mov $0x10, %eax
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movl %eax, %cr0
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pushw $0
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push $REAL_MODE_CODE
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lret
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hlt
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real_mode:
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movw $0x7000, %ax
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movl $0x0000, %esp
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movw %ax, %ss
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xor %ax, %ax
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movw %ax, %ds
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movw %ax, %es
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movw %ax, %fs
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movw %ax, %gs
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mov $0x3, %ax
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int $0x10
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movb $0x13, %ah
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movb $0x0, %bh
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movb $0xf, %bl
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movw (COPIED_STRING_LOCATION), %cx
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movw $0, %dx
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movw $COPIED_STRING_LOCATION + 2, %bp
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int $0x10
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movl $0xdeadcafe, %ebx
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cli
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hlt
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end_of_print_and_halt_function:
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.code32
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real_start:
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cli
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cld
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mov $(end_of_kernel_image - KERNEL_BASE), %esi
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cmp $KERNEL_PD_OFFSET, %esi
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jbe kernel_not_too_large
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movl $(kernel_image_too_big_string - KERNEL_BASE), %esi
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pushl %esi
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call print_and_halt
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/* We should not return, but just in case, halt */
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hlt
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kernel_not_too_large:
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/* test for PAE presence, save the most important registers from corruption */
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pushl %eax
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pushl %edx
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pushl %ebx
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movl $0x1, %eax /* PAE presence is in CPUID input 0x1 */
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cpuid
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testl $(1 << 6), %edx /* Test if the PAE-bit, which is bit 6, is set in the edx register. */
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jnz pae_supported /* If the bit is not set, there is no PAE capability. */
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/* Since there is no PAE capability, halt with an error message */
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movl $(no_pae_string - KERNEL_BASE), %esi
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pushl %esi
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call print_and_halt
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/* We should not return, but just in case, halt */
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hlt
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#if ARCH(X86_64)
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pae_supported:
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movl $0x80000001, %eax
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cpuid
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testl $(1 << 29), %edx /* Test if the LM-bit, which is bit 29, is set in the edx register. */
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jnz long_mode_supported /* If LM-bit is not enabled, there is no long mode. */
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/* Since there is no long mode, halt with an error message */
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movl $(no_long_mode_string - KERNEL_BASE), %esi
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pushl %esi
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call print_and_halt
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/* We should not return, but just in case, halt */
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hlt
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/* If both PAE and long mode is supported, continue with booting the system */
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long_mode_supported:
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/* restore the pushed registers and continue with booting */
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popl %ebx
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popl %edx
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popl %eax
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#else
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/* If PAE is supported, continue with booting the system */
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pae_supported:
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/* restore the pushed registers and continue with booting */
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popl %ebx
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popl %edx
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popl %eax
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#endif
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/* We don't know where the bootloader might have put the command line.
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* It might be at an inconvenient location that we're not about to map,
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* so let's just copy it to a convenient location while we have the whole
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* memory space identity-mapped anyway. :^)
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*/
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movl %ebx, %esi
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addl $16, %esi
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movl (%esi), %esi
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movl $1024, %ecx
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movl $(kernel_cmdline - KERNEL_BASE), %edi
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rep movsl
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#if ARCH(X86_64)
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/* clear pml4t */
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movl $(boot_pml4t - KERNEL_BASE), %edi
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movl $1024, %ecx
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xorl %eax, %eax
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rep stosl
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/* set up pml4t[0] */
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movl $(boot_pml4t - KERNEL_BASE), %edi
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movl $(boot_pdpt - KERNEL_BASE), 0(%edi)
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/* R/W + Present */
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orl $0x3, 0(%edi)
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#endif
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/* clear pdpt */
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movl $(boot_pdpt - KERNEL_BASE), %edi
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movl $1024, %ecx
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xorl %eax, %eax
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rep stosl
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/* set up pdpt[0] and pdpt[3] */
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movl $(boot_pdpt - KERNEL_BASE), %edi
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#if ARCH(X86_64)
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movl $((boot_pd0 - KERNEL_BASE) + 3), 0(%edi)
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movl $((boot_pd3 - KERNEL_BASE) + 3), 24(%edi)
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#else
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movl $((boot_pd0 - KERNEL_BASE) + 1), 0(%edi)
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movl $((boot_pd3 - KERNEL_BASE) + 1), 24(%edi)
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#endif
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/* clear pd0 */
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movl $(boot_pd0 - KERNEL_BASE), %edi
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movl $1024, %ecx
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xorl %eax, %eax
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rep stosl
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/* clear pd3 */
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movl $(boot_pd3 - KERNEL_BASE), %edi
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movl $1024, %ecx
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xorl %eax, %eax
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rep stosl
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/* clear pd0's pt's */
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movl $(boot_pd0_pt0 - KERNEL_BASE), %edi
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movl $(1024 * 4), %ecx
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xorl %eax, %eax
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rep stosl
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/* clear pd3's pt's */
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movl $(boot_pd3_pts - KERNEL_BASE), %edi
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movl $(1024 * 17), %ecx
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xorl %eax, %eax
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rep stosl
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/* add boot_pd0_pt0 to boot_pd0 */
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movl $(boot_pd0 - KERNEL_BASE), %edi
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movl $(boot_pd0_pt0 - KERNEL_BASE), %eax
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movl %eax, 0(%edi)
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/* R/W + Present */
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orl $0x3, 0(%edi)
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/* add boot_pd3_pts to boot_pd3 */
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movl $16, %ecx
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movl $(boot_pd3 - KERNEL_BASE), %edi
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movl $(boot_pd3_pts - KERNEL_BASE), %eax
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1:
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movl %eax, 0(%edi)
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/* R/W + Present */
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orl $0x3, 0(%edi)
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addl $8, %edi
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addl $4096, %eax
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loop 1b
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/* identity map the 0 to 2MB range */
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movl $512, %ecx
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movl $(boot_pd0_pt0 - KERNEL_BASE), %edi
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xorl %eax, %eax
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1:
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movl %eax, 0(%edi)
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/* R/W + Present */
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orl $0x3, 0(%edi)
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addl $8, %edi
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addl $4096, %eax
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loop 1b
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/* pseudo identity map the 3072-3104MB range */
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movl $(512 * 16), %ecx
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movl $(boot_pd3_pts - KERNEL_BASE), %edi
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xorl %eax, %eax
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1:
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movl %eax, 0(%edi)
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/* R/W + Present */
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orl $0x3, 0(%edi)
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addl $8, %edi
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addl $4096, %eax
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loop 1b
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/* create an empty page table for the top 2MB at the 4GB mark */
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movl $(boot_pd3 - KERNEL_BASE), %edi
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movl $(boot_pd3_pt1023 - KERNEL_BASE), 4088(%edi)
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orl $0x3, 4088(%edi)
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movl $0, 4092(%edi)
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#if ARCH(X86_64)
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/* point CR3 to PML4T */
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movl $(boot_pml4t - KERNEL_BASE), %eax
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#else
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/* point CR3 to PDPT */
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movl $(boot_pdpt - KERNEL_BASE), %eax
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#endif
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movl %eax, %cr3
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/* enable PAE + PSE */
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movl %cr4, %eax
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orl $0x60, %eax
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movl %eax, %cr4
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#if ARCH(X86_64)
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1:
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/* Enter Long-mode! ref(https://wiki.osdev.org/Setting_Up_Long_Mode)*/
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mov $0xC0000080, %ecx /* Set the C-register to 0xC0000080, which is the EFER MSR.*/
|
|
rdmsr /* Read from the model-specific register.*/
|
|
or $(1 << 8), %eax /* Set the LM-bit which is the 9th bit (bit 8).*/
|
|
wrmsr /* Write to the model-specific register.*/
|
|
#endif
|
|
|
|
/* enable PG */
|
|
movl %cr0, %eax
|
|
orl $0x80000000, %eax
|
|
movl %eax, %cr0
|
|
|
|
/* set up stack */
|
|
mov $(stack_top - KERNEL_BASE), %esp
|
|
and $-16, %esp
|
|
|
|
#if ARCH(X86_64)
|
|
/* Now we are in 32-bit compatibility mode, We still need to load a 64-bit GDT */
|
|
mov $(gdt64ptr - KERNEL_BASE), %eax
|
|
lgdt (%eax)
|
|
ljmpl $code64_sel, $(1f - KERNEL_BASE)
|
|
|
|
.code64
|
|
1:
|
|
movl %ebx, %ebx
|
|
movabs $KERNEL_BASE, %rax
|
|
addq %rax, %rbx
|
|
movabs $multiboot_info_ptr, %rax
|
|
movq %rbx, (%rax)
|
|
|
|
movabs $gdt64ptr, %rax
|
|
lgdt (%rax)
|
|
movabs $1f, %rax
|
|
jmp *%rax
|
|
|
|
1:
|
|
movabs $KERNEL_BASE, %rax
|
|
addq %rax, %rsp
|
|
|
|
mov $0, %ax
|
|
mov %ax, %ss
|
|
mov %ax, %ds
|
|
mov %ax, %es
|
|
mov %ax, %fs
|
|
mov %ax, %gs
|
|
|
|
mov %cr3, %rax
|
|
mov %rax, %cr3
|
|
|
|
#else
|
|
addl $KERNEL_BASE, %ebx
|
|
movl %ebx, multiboot_info_ptr
|
|
|
|
/* jmp to an address above the 3GB mark */
|
|
movl $1f, %eax
|
|
jmp *%eax
|
|
1:
|
|
add $KERNEL_BASE, %esp
|
|
|
|
movl %cr3, %eax
|
|
movl %eax, %cr3
|
|
#endif
|
|
|
|
/* unmap the 0-1MB range, which isn't used after jmp-ing up here */
|
|
movl $256, %ecx
|
|
movl $(boot_pd0_pt0 - KERNEL_BASE), %edi
|
|
xorl %eax, %eax
|
|
|
|
1:
|
|
movl %eax, 0(%edi)
|
|
addl $8, %edi
|
|
loop 1b
|
|
|
|
#if ARCH(X86_64)
|
|
movabs $init, %rax
|
|
call *%rax
|
|
add $4, %rsp
|
|
#else
|
|
call init
|
|
add $4, %esp
|
|
#endif
|
|
|
|
cli
|
|
loop:
|
|
hlt
|
|
jmp loop
|