Added build system and some core boot files
This commit is contained in:
213
arch/x86_64/start_32.S
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213
arch/x86_64/start_32.S
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@@ -0,0 +1,213 @@
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.set ALIGN, 1 << 0
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.set MEMINFO, 1 << 1
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.set VIDMODE, 1 << 2
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.set FLAGS, ALIGN | MEMINFO
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.set MAGIC, 0x1BADB002
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.set CHECKSUM, -(MAGIC + FLAGS)
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/* the amount of memory to allocate for bootstrap page directories. */
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#define BOOTSTRAP_PDIR_SIZE 0x1000
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.extern start_64 # defined in start_64.S
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.code32
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.section .boot.rodata, "a", @progbits
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no_long_mode_err:
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.asciz "This system is not 64-bit. Press any key to reboot."
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unsupported_cpu_err:
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.asciz "Your CPU is not supported by Magenta. Press any key to reboot."
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.section .boot.bss, "aw", @nobits
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bootstrap_pml4t: # a single PML4T
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.skip 0x1000
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bootstrap_pdpt: # a single PDPT
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.skip 0x1000
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bootstrap_pdir_buf: # a buffer of page directories. each pdir entry can be used to map 2MB of virtual memory.
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.skip BOOTSTRAP_PDIR_SIZE
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bootstrap_stack_bottom:
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.skip 0x1000
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bootstrap_stack_top:
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.section .boot.text, "ax", @progbits
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.align 4
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.long MAGIC
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.long FLAGS
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.long CHECKSUM
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# Print an error message and wait for RETURN if the system's CPU doesn't support long mode.
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no_long_mode:
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# print error message
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mov $no_long_mode_err, %esi
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mov $0xb8000, %edi
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1:
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movsb
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movb $12, (%edi)
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incl %edi
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cmpb $0, (%esi)
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jne 1b
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2:
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inb $0x64, %al
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test $0x01, %al
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jz 3f
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inb $0x60, %al
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jmp 2b
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3:
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inb $0x64, %al
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test $0x01, %al
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jz 3b
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int $0xff
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cli
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hlt
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# Print an error message and wait for RETURN if the system's CPU isn't supported.
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unsupported_cpu:
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# print error message
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mov $unsupported_cpu_err, %esi
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mov $0xb8000, %edi
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1:
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movsb
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movb $12, (%edi)
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incl %edi
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cmpb $0, (%esi)
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jne 1b
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2:
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inb $0x64, %al
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test $0x01, %al
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jz 3f
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inb $0x60, %al
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jmp 2b
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3:
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inb $0x64, %al
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test $0x01, %al
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jz 3b
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int $0xff
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cli
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hlt
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init_page_tables:
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/* STEP 1: add an entry in the PML4T pointing to the PDPT.
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NOTE that we actually add two entries in the PML4T that both point to the same PDPT.
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This allows us to map the kernel at both vaddr 0x0 AND vaddr 0xffffffff80000000 using the same PDPT */
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mov $bootstrap_pml4t, %edi
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mov $bootstrap_pdpt, %esi
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# in %ESI, build a PML4T entry containing the base address of the PDPT
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xor $0xFFF, %esi
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or $0x3, %esi
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# add the PML4T entries at PML4T[0] and PML4T[511]
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mov %esi, (%edi)
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add $0xFF8, %edi
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mov %esi, (%edi)
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/* STEP 2: initialise the PDPT.
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We need to create an entry in the PDPT for every page directory we intend to use. */
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# BOOTSTRAP_PDIR_SIZE contains the total size of the page directory buffer.
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# use it to calculate the number of page directories we're using.
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mov $0, %edx
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mov $BOOTSTRAP_PDIR_SIZE, %eax
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mov $0x1000, %ebx
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idiv %ebx
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mov $bootstrap_pdpt, %edi
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mov $bootstrap_pdir_buf, %esi
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/* %ESI is a pointer into the pagedir buffer.
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%EDI is a pointer into the PDPT.
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%EAX is the total number of page directories.
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%EBX is where we build the PDPT entry. */
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1:
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mov %esi, %ebx
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xor $0xFFF, %ebx
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or $0x3, %ebx
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# skip the first 4 bytes of the 8-byte entry, leaving them zero.
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add $0x4, %edi
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mov %ebx, (%edi)
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add $0x1000, %esi
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add $0x4, %edi
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sub $0x1, %eax
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cmp $0x0, %eax
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jne 1b
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/* STEP 3: initialise the page directories.
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Each page directory can be used to map 2MiB of virtual memory.
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The exact number of page directories in use is determined by BOOTSTRAP_PDIR_SIZE */
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/* the total number of page directory entries is stored in %EAX */
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mov $0, %edx
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mov $BOOTSTRAP_PDIR_SIZE, %eax
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mov $0x8, %ebx
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idiv %ebx
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mov $0x0, %esi
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mov $bootstrap_pdir_buf, %edi
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/* %EDI is a pointer into the pagedir buffer.
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%ESI is the physical address being mapped. must be a multiple of 2MiB.
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%EAX is the total number of page directories.
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%EBX is where we build the pagedir entry. */
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2:
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mov %esi, %ebx
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xor $0xFFF, %ebx
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or $0x3, %ebx
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# skip the first 4 bytes of the 8-byte entry, leaving them zero.
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add $0x4, %edi
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mov %ebx, (%edi)
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add $0x200000, %esi
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add $0x4, %edi
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dec %eax
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jnz 2b
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ret
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long_mode_switch:
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ret
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.global _start
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.type _start, @function
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_start:
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mov $bootstrap_stack_top, %esp
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push %ebx # store the pointer to the multiboot info block.
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# check if long mode is supported
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movl $0x80000000, %eax # Extended-function 80000000h.
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cpuid # Is largest extended function
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cmpl $0x80000000, %eax # any function > 80000000h?
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jbe no_long_mode # If not, no long mode.
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movl $0x80000001, %eax # Extended-function 80000001h.
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cpuid # Now EDX = extended-features flags.
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btl $29, %edx # Test if long mode is supported.
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jnc no_long_mode # Exit if not supported.
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movl $1, %eax
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cpuid
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btl $3, %edx
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mov $0xb8000, %eax
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movb $76, (%eax)
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inc %eax
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movb $0xF, (%eax)
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call init_page_tables
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call long_mode_switch # calls start_64, does not return
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cli
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hlt
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