250 lines
4.5 KiB
ArmAsm
250 lines
4.5 KiB
ArmAsm
/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2009 Free Software Foundation, Inc.
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*
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* GRUB is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GRUB is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <grub/symbol.h>
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#include <grub/i386/memory.h>
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#ifdef BACKWARD
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#define RELOCATOR_VARIABLE(x) VARIABLE(grub_relocator32_backward_ ## x)
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#else
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#define RELOCATOR_VARIABLE(x) VARIABLE(grub_relocator32_forward_ ## x)
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#endif
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#ifdef __x86_64__
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#define RAX %rax
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#define RCX %rcx
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#define RDX %rdx
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#define RDI %rdi
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#define RSI %rdi
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#else
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#define RAX %eax
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#define RCX %ecx
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#define RDX %edx
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#define RDI %edi
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#define RSI %esi
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#endif
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/* The code segment of the protected mode. */
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#define CODE_SEGMENT 0x10
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/* The data segment of the protected mode. */
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#define DATA_SEGMENT 0x18
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.p2align 4 /* force 16-byte alignment */
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RELOCATOR_VARIABLE(start)
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#ifdef BACKWARD
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LOCAL(base):
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#endif
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cli
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#ifndef __x86_64__
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/* mov imm32, %eax */
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.byte 0xb8
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RELOCATOR_VARIABLE(dest)
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.long 0
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movl %eax, %edi
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/* mov imm32, %eax */
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.byte 0xb8
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RELOCATOR_VARIABLE(src)
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.long 0
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movl %eax, %esi
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/* mov imm32, %ecx */
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.byte 0xb9
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RELOCATOR_VARIABLE(size)
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.long 0
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#else
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xorq %rax, %rax
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/* mov imm32, %eax */
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.byte 0xb8
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RELOCATOR_VARIABLE(dest)
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.long 0
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movq %rax, %rdi
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/* mov imm64, %rax */
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.byte 0x48
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.byte 0xb8
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RELOCATOR_VARIABLE(src)
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.long 0, 0
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movq %rax, %rsi
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xorq %rcx, %rcx
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/* mov imm32, %ecx */
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.byte 0xb9
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RELOCATOR_VARIABLE(size)
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.long 0
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#endif
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mov RDI, RAX
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#ifdef BACKWARD
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add RCX, RSI
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add RDX, RDI
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#endif
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#ifndef BACKWARD
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add RCX, RAX
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#endif
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add $0x3, RCX
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shr $2, RCX
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#ifdef BACKWARD
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/* Backward movsl is implicitly off-by-four. compensate that. */
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sub $4, RSI
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sub $4, RDI
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/* Backward copy. */
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std
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rep
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movsl
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#else
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/* Forward copy. */
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cld
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rep
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movsl
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#endif
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/* %rax contains now our new 'base'. */
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mov RAX, RSI
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add $(LOCAL(cont0) - LOCAL(base)), RAX
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jmp *RAX
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LOCAL(cont0):
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lea (LOCAL(cont1) - LOCAL(base)) (RSI, 1), RAX
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movl %eax, (LOCAL(jump_vector) - LOCAL(base)) (RSI, 1)
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lea (LOCAL(gdt) - LOCAL(base)) (RSI, 1), RAX
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mov RAX, (LOCAL(gdt_addr) - LOCAL(base)) (RSI, 1)
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/* Switch to compatibility mode. */
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lgdt (LOCAL(gdtdesc) - LOCAL(base)) (RSI, 1)
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/* Update %cs. Thanks to David Miller for pointing this mistake out. */
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ljmp *(LOCAL(jump_vector) - LOCAL(base)) (RSI, 1)
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LOCAL(cont1):
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.code32
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/* Update other registers. */
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movl $DATA_SEGMENT, %eax
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movl %eax, %ds
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movl %eax, %es
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movl %eax, %fs
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movl %eax, %gs
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movl %eax, %ss
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/* Disable paging. */
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movl %cr0, %eax
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andl $(~GRUB_MEMORY_CPU_CR0_PAGING_ON), %eax
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movl %eax, %cr0
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/* Disable amd64. */
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movl $GRUB_MEMORY_CPU_AMD64_MSR, %ecx
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rdmsr
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andl $(~GRUB_MEMORY_CPU_AMD64_MSR_ON), %eax
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wrmsr
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/* Turn off PAE. */
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movl %cr4, %eax
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andl $GRUB_MEMORY_CPU_CR4_PAE_ON, %eax
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movl %eax, %cr4
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jmp LOCAL(cont2)
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LOCAL(cont2):
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.code32
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/* mov imm32, %eax */
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.byte 0xb8
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RELOCATOR_VARIABLE (esp)
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.long 0
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movl %eax, %esp
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/* mov imm32, %eax */
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.byte 0xb8
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RELOCATOR_VARIABLE (eax)
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.long 0
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/* mov imm32, %ebx */
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.byte 0xbb
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RELOCATOR_VARIABLE (ebx)
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.long 0
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/* mov imm32, %ecx */
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.byte 0xb9
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RELOCATOR_VARIABLE (ecx)
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.long 0
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/* mov imm32, %edx */
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.byte 0xba
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RELOCATOR_VARIABLE (edx)
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.long 0
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/* Cleared direction flag is of no problem with any current
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payload and makes this implementation easier. */
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cld
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.byte 0xea
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RELOCATOR_VARIABLE (eip)
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.long 0
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.word CODE_SEGMENT
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/* GDT. Copied from loader/i386/linux.c. */
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.p2align 4
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LOCAL(gdt):
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/* NULL. */
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.byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
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/* Reserved. */
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.byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
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/* Code segment. */
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.byte 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x9A, 0xCF, 0x00
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/* Data segment. */
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.byte 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x92, 0xCF, 0x00
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.p2align 4
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LOCAL(gdtdesc):
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.word 0x27
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LOCAL(gdt_addr):
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#ifdef __x86_64__
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/* Filled by the code. */
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.quad 0
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#else
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/* Filled by the code. */
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.long 0
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#endif
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.p2align 4
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LOCAL(jump_vector):
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/* Jump location. Is filled by the code */
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.long 0
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.long CODE_SEGMENT
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#ifndef BACKWARD
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LOCAL(base):
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#endif
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RELOCATOR_VARIABLE(end)
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