diff options
Diffstat (limited to 'purgatory/arch/x86_64/entry64-32.S')
| -rw-r--r-- | purgatory/arch/x86_64/entry64-32.S | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/purgatory/arch/x86_64/entry64-32.S b/purgatory/arch/x86_64/entry64-32.S new file mode 100644 index 0000000..f2b6377 --- /dev/null +++ b/purgatory/arch/x86_64/entry64-32.S @@ -0,0 +1,164 @@ +/* + * purgatory: setup code + * + * Copyright (C) 2003,2004 Eric Biederman (ebiederm@xmission.com) + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation (version 2 of the License). + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +.data + .equ MSR_K6_EFER, 0xC0000080 + .equ EFER_LME, 0x00000100 + .equ X86_CR4_PAE, 0x00000020 + .equ CR0_PG, 0x80000000 + + .text + .balign 16 + .globl entry32, entry32_regs +entry32: + .code64 + + /* Setup the 4G offset of entry32 lm_exit code segment */ + movq $0x00CF9A000000ffff, %rax + + leaq entry32(%rip), %rbx /* Low 24 bits */ + andq $0xffffff, %rbx + shlq $16, %rbx + orq %rbx, %rax + + leaq entry32(%rip), %rbx /* High 8 bits */ + movq $0xff000000, %rdx + andq %rdx, %rbx + shlq $32, %rbx + orq %rbx, %rax + + movq %rax, (gdt + 0x20)(%rip) + + /* Setup a gdt that is generally usefully */ + lgdt gdt(%rip) + + /* Setup the far pointer to the entry point */ + movl eip(%rip), %eax + movl %eax, entry32_addr(%rip) + + /* Switch to 32bit compatiblity mode */ + ljmp *lm_exit_addr(%rip) +lm_exit: + .code32 + + /* Disable paging */ + movl %cr0, %eax + andl $~CR0_PG, %eax + movl %eax, %cr0 + + /* Disable long mode */ + movl $MSR_K6_EFER, %ecx + rdmsr + andl $~EFER_LME, %eax + wrmsr + + /* Disable PAE */ + xorl %eax, %eax + movl %eax, %cr4 + + /* load the data segments */ + movl $0x18, %eax /* data segment */ + movl %eax, %ds + movl %eax, %es + movl %eax, %ss + movl %eax, %fs + movl %eax, %gs + + /* Load the registers */ + movl %cs:eax - entry32, %eax + movl %cs:ecx - entry32, %ecx + movl %cs:edx - entry32, %edx + movl %cs:esi - entry32, %esi + movl %cs:edi - entry32, %edi + movl %cs:esp - entry32, %esp + movl %cs:ebp - entry32, %ebp + movl %cs:ebx - entry32, %ebx + + /* Jump to the loaded image */ + ljmp *%cs:entry32_addr - entry32 + + .section ".data" + .balign 16 +gdt: /* 0x00 unusable segment + * 0x08 unused + * so use them as the gdt ptr + */ + .word gdt_end - gdt - 1 + .quad gdt + .word 0, 0, 0 + + /* Documented linux kernel segments */ + /* 0x10 4GB flat code segment */ + .word 0xFFFF, 0x0000, 0x9A00, 0x00CF + /* 0x18 4GB flat data segment */ + .word 0xFFFF, 0x0000, 0x9200, 0x00CF + + /* 0x20 4GB flat code segment base at entry32 */ + .word 0xFFFF, 0x0000, 0x9A00, 0x0CF + /* 0x28 dummy */ + .word 0x0000, 0x0000, 0x0000, 0x000 + /* 0x30 dummy */ + .word 0x0000, 0x0000, 0x0000, 0x000 + /* 0x38 dummy */ + .word 0x0000, 0x0000, 0x0000, 0x000 + /* 0x40 dummy */ + .word 0x0000, 0x0000, 0x0000, 0x000 + /* 0x48 dummy */ + .word 0x0000, 0x0000, 0x0000, 0x000 + /* 0x50 dummy */ + .word 0x0000, 0x0000, 0x0000, 0x000 + /* 0x58 dummy */ + .word 0x0000, 0x0000, 0x0000, 0x000 + + /* Segments used by the 2.5.x kernel */ + /* 0x60 4GB flat code segment */ + .word 0xFFFF, 0x0000, 0x9A00, 0x00CF + /* 0x68 4GB flat data segment */ + .word 0xFFFF, 0x0000, 0x9200, 0x00CF +gdt_end: + + .section ".rodata" + .balign 4 +lm_exit_addr: + .long lm_exit - entry32 + .long 0x20 + + .section ".data" + .balign 4 +entry32_addr: + .long 0x00000000 + .long 0x10 + + .section ".rodata" + .balign 4 +entry32_regs: +eax: .long 0x00000000 +ebx: .long 0x00000000 +ecx: .long 0x00000000 +edx: .long 0x00000000 +esi: .long 0x00000000 +edi: .long 0x00000000 +esp: .long 0x00000000 +ebp: .long 0x00000000 +eip: .quad entry16 /* low 32 bits address + * high 32bits zeros + * uses 64bit reloc + */ + .size entry32_regs, (. - 4) - entry32_regs + |