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Simplify bootloader GDT

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This commit is contained in:
Jeremy Soller 2016-09-12 15:49:54 -06:00
parent 6d675fc43a
commit 6560cc653b
1 changed files with 6 additions and 74 deletions
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80
bootloader/x86_64/startup-x86_64.asm
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@ -1,6 +1,7 @@
trampoline: trampoline:
.ready: dq 0 .ready: dq 0
.cpu_id: dq 0 .cpu_id: dq 0
.page_table: dq 0
.stack_start: dq 0 .stack_start: dq 0
.stack_end: dq 0 .stack_end: dq 0
.code: dq 0 .code: dq 0
@ -133,13 +134,14 @@ long_mode_ap:
mov ss, rax mov ss, rax
mov rdi, [trampoline.cpu_id] mov rdi, [trampoline.cpu_id]
mov rsi, [trampoline.stack_start] mov rsi, [trampoline.page_table]
mov rdx, [trampoline.stack_end] mov rdx, [trampoline.stack_start]
mov rcx, [trampoline.stack_end]
lea rsp, [rdx - 256] lea rsp, [rcx - 256]
mov qword [trampoline.ready], 1
mov rax, [trampoline.code] mov rax, [trampoline.code]
mov qword [trampoline.ready], 1
jmp rax jmp rax
gdtr: gdtr:
@ -171,74 +173,4 @@ istruc GDTEntry
at GDTEntry.baseh, db 0 at GDTEntry.baseh, db 0
iend iend
.user_code equ $ - gdt
istruc GDTEntry
at GDTEntry.limitl, dw 0
at GDTEntry.basel, dw 0
at GDTEntry.basem, db 0
at GDTEntry.attribute, db attrib.present | attrib.ring3 | attrib.user | attrib.code
at GDTEntry.flags__limith, db flags.long_mode
at GDTEntry.baseh, db 0
iend
.user_data equ $ - gdt
istruc GDTEntry
at GDTEntry.limitl, dw 0
at GDTEntry.basel, dw 0
at GDTEntry.basem, db 0
; AMD System Programming Manual states that the writeable bit is ignored in long mode, but ss can not be set to this descriptor without it
at GDTEntry.attribute, db attrib.present | attrib.ring3 | attrib.user | attrib.writable
at GDTEntry.flags__limith, db 0
at GDTEntry.baseh, db 0
iend
.user_tls equ $ - gdt
istruc GDTEntry
at GDTEntry.limitl, dw 0
at GDTEntry.basel, dw 0
at GDTEntry.basem, db 0
; AMD System Programming Manual states that the writeable bit is ignored in long mode, but ss can not be set to this descriptor without it
at GDTEntry.attribute, db attrib.present | attrib.ring3 | attrib.user | attrib.writable
at GDTEntry.flags__limith, db 0
at GDTEntry.baseh, db 0
iend
.tss equ $ - gdt
istruc GDTEntry
at GDTEntry.limitl, dw (tss.end - tss) & 0xFFFF
at GDTEntry.basel, dw (tss-$$+0x7C00) & 0xFFFF
at GDTEntry.basem, db ((tss-$$+0x7C00) >> 16) & 0xFF
at GDTEntry.attribute, db attrib.present | attrib.ring3 | attrib.tssAvailabe64
at GDTEntry.flags__limith, db ((tss.end - tss) >> 16) & 0xF
at GDTEntry.baseh, db ((tss-$$+0x7C00) >> 24) & 0xFF
iend
dq 0 ;tss descriptors are extended to 16 Bytes
.end equ $ - gdt .end equ $ - gdt
struc TSS
.reserved1 resd 1 ;The previous TSS - if we used hardware task switching this would form a linked list.
.rsp0 resq 1 ;The stack pointer to load when we change to kernel mode.
.rsp1 resq 1 ;everything below here is unused now..
.rsp2 resq 1
.reserved2 resd 1
.reserved3 resd 1
.ist1 resq 1
.ist2 resq 1
.ist3 resq 1
.ist4 resq 1
.ist5 resq 1
.ist6 resq 1
.ist7 resq 1
.reserved4 resd 1
.reserved5 resd 1
.reserved6 resw 1
.iomap_base resw 1
endstruc
tss:
istruc TSS
at TSS.rsp0, dd 0x800000 - 128
at TSS.iomap_base, dw 0xFFFF
iend
.end: