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65 lines
1.7 KiB
65 lines
1.7 KiB
20 years ago
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/*
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*
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* Trampoline.S Derived from Setup.S by Linus Torvalds
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*
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* 4 Jan 1997 Michael Chastain: changed to gnu as.
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*
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* Entry: CS:IP point to the start of our code, we are
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* in real mode with no stack, but the rest of the
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* trampoline page to make our stack and everything else
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* is a mystery.
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*
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* In fact we don't actually need a stack so we don't
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* set one up.
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*
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* On entry to trampoline_data, the processor is in real mode
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* with 16-bit addressing and 16-bit data. CS has some value
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* and IP is zero. Thus, data addresses need to be absolute
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* (no relocation) and are taken with regard to r_base.
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*
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* If you work on this file, check the object module with objdump
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* --full-contents --reloc to make sure there are no relocation
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* entries. For the GDT entry we do hand relocation in smpboot.c
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* because of 64bit linker limitations.
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*/
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#include <linux/linkage.h>
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#include <asm/segment.h>
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#include <asm/page.h>
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.data
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.code16
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ENTRY(trampoline_data)
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r_base = .
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wbinvd
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mov %cs, %ax # Code and data in the same place
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mov %ax, %ds
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cli # We should be safe anyway
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movl $0xA5A5A5A5, trampoline_data - r_base
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# write marker for master knows we're running
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lidt idt_48 - r_base # load idt with 0, 0
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lgdt gdt_48 - r_base # load gdt with whatever is appropriate
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xor %ax, %ax
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inc %ax # protected mode (PE) bit
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lmsw %ax # into protected mode
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# flaush prefetch and jump to startup_32 in arch/x86_64/kernel/head.S
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ljmpl $__KERNEL32_CS, $(startup_32-__START_KERNEL_map)
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# Careful these need to be in the same 64K segment as the above;
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idt_48:
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.word 0 # idt limit = 0
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.word 0, 0 # idt base = 0L
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gdt_48:
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.short __KERNEL32_CS + 7 # gdt limit
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.long cpu_gdt_table-__START_KERNEL_map
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.globl trampoline_end
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trampoline_end:
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