This commit fixes some instances of uninitialized memory. In addition, the bootstrap tables for x64 are moved around a bit, in this awful game of placing stuff where it won't collide with grub.
183 lines
4.8 KiB
ArmAsm
183 lines
4.8 KiB
ArmAsm
/******************************************************************************
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COPYRIGHT(C) JONAS 'SORTIE' TERMANSEN 2011.
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This file is part of Sortix.
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Sortix is free software: you can redistribute it and/or modify it under the
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terms of the GNU General Public License as published by the Free Software
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Foundation, either version 3 of the License, or (at your option) any later
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version.
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Sortix is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY# without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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details.
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You should have received a copy of the GNU General Public License along
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with Sortix. If not, see <http://www.gnu.org/licenses/>.
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boot.s
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Bootstraps the kernel and passes over control from the boot-loader to the
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kernel main function. It also jumps into long mode!
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******************************************************************************/
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.globl start, _start
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.section .text
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.text 0x100000
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.type _start, @function
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.code32
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start:
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_start:
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jmp multiboot_entry
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# Align 32 bits boundary.
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.align 4
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# Multiboot header.
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multiboot_header:
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# Magic.
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.long 0x1BADB002
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# Flags.
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.long 0x00000003
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# Checksum.
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.long -(0x1BADB002 + 0x00000003)
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multiboot_entry:
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# We got our multiboot information in various registers. But we are going
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# to need these registers. But where can we store them then? Oh hey, let's
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# store then in the code already run!
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# Store the pointer to the Multiboot information structure.
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mov %ebx, 0x100000
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# Store the magic value.
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mov %eax, 0x100004
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# Clear the first $0xE000 bytes following 0x21000.
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movl $0x21000, %edi
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mov %edi, %cr3
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xorl %eax, %eax
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movl $0xE000, %ecx
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rep stosl
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movl %cr3, %edi
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# Set the initial page tables.
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# Note that we OR with 0x7 here to allow user-space access, except in the
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# first 2 MiB. We also do this with 0x200 to allow forking the page.
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# Page-Map Level 4
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movl $0x22207, (%edi)
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addl $0x1000, %edi
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# Page-Directory Pointer Table
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movl $0x23207, (%edi)
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addl $0x1000, %edi
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# Page-Directory (no user-space access here)
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movl $0x24203, (%edi) # (First 2 MiB)
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movl $0x25203, 8(%edi) # (Second 2 MiB)
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addl $0x1000, %edi
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# Page-Table
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# Memory map the first 4 MiB.
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movl $0x3, %ebx
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movl $1024, %ecx
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SetEntry:
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mov %ebx, (%edi)
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add $0x1000, %ebx
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add $8, %edi
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loop SetEntry
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# Enable PAE.
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mov %cr4, %eax
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orl $0x20, %eax
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mov %eax, %cr4
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# Enable long mode.
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mov $0xC0000080, %ecx
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rdmsr
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orl $0x100, %eax
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wrmsr
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# Enable paging and enter long mode (still 32-bit)
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mov %cr0, %eax
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orl $0x80000000, %eax
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mov %eax, %cr0
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# Load the long mode GDT.
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mov GDTPointer, %eax
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lgdtl GDTPointer
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# Now use the 64-bit code segment, and we are in full 64-bit mode.
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ljmp $0x10, $Realm64
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.code64
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Realm64:
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# Now, set up the other segment registers.
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cli
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mov $0x18, %ax
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mov %ax, %ds
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mov %ax, %es
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mov %ax, %fs
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mov %ax, %gs
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# Alright, that was the bootstrap code. Now begin preparing to run the
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# actual 64-bit kernel.
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jmp Main
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.section .data
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GDT64: # Global Descriptor Table (64-bit).
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GDTNull: # The null descriptor.
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.word 0 # Limit (low).
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.word 0 # Base (low).
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.byte 0 # Base (middle)
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.byte 0 # Access.
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.byte 0 # Granularity.
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.byte 0 # Base (high).
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GDTUnused: # The null descriptor.
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.word 0 # Limit (low).
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.word 0 # Base (low).
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.byte 0 # Base (middle)
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.byte 0 # Access.
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.byte 0 # Granularity.
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.byte 0 # Base (high).
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GDTCode: # The code descriptor.
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.word 0xFFFF # Limit (low).
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.word 0 # Base (low).
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.byte 0 # Base (middle)
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.byte 0x9A # Access.
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.byte 0xAF # Granularity.
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.byte 0 # Base (high).
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GDTData: # The data descriptor.
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.word 0xFFFF # Limit (low).
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.word 0 # Base (low).
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.byte 0 # Base (middle)
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.byte 0x92 # Access.
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.byte 0x8F # Granularity.
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.byte 0 # Base (high).
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GDTPointer: # The GDT-pointer.
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.word GDTPointer - GDT64 - 1 # Limit.
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.long GDT64 # Base.
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.long 0
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Main:
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# Copy the character B onto the screen so we know it works.
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movq $0x242, %r15
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movq %r15, %rax
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movw %ax, 0xB8000
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# Load the pointer to the Multiboot information structure.
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mov 0x100000, %ebx
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# Load the magic value.
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mov 0x100004, %eax
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jmp beginkernel
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