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/*
*
* Trampoline.S Derived from Setup.S by Linus Torvalds
*
* 4 Jan 1997 Michael Chastain: changed to gnu as.
*
* This is only used for booting secondary CPUs in SMP machine
*
* Entry: CS:IP point to the start of our code, we are
* in real mode with no stack, but the rest of the
* trampoline page to make our stack and everything else
* is a mystery.
*
* We jump into arch/x86/kernel/head_32.S.
*
* On entry to trampoline_data, the processor is in real mode
* with 16-bit addressing and 16-bit data. CS has some value
* and IP is zero. Thus, we load CS to the physical segment
* of the real mode code before doing anything further.
*
* The structure real_mode_header includes entries that need
* to be set up before executing this code:
*
* startup_32_smp
* boot_gdt
*/
#include <linux/linkage.h>
#include <linux/init.h>
#include <asm/segment.h>
#include <asm/page_types.h>
.text
.code16
.globl trampoline_data
.balign PAGE_SIZE
trampoline_data:
wbinvd # Needed for NUMA-Q should be harmless for others
.byte 0xea # ljmpw
.word 1f # Offset
.word real_mode_seg # Segment
1:
mov %cs, %ax # Code and data in the same place
mov %ax, %ds
cli # We should be safe anyway
movl $0xA5A5A5A5, trampoline_status
# write marker for master knows we're running
/* GDT tables in non default location kernel can be beyond 16MB and
* lgdt will not be able to load the address as in real mode default
* operand size is 16bit. Use lgdtl instead to force operand size
* to 32 bit.
*/
lidtl boot_idt_descr # load idt with 0, 0
lgdtl boot_gdt_descr # load gdt with whatever is appropriate
xor %ax, %ax
inc %ax # protected mode (PE) bit
lmsw %ax # into protected mode
# flush prefetch and jump to startup_32_smp in arch/i386/kernel/head.S
ljmpl *(startup_32_smp)
.data
.globl startup_32_smp, boot_gdt, trampoline_status
boot_gdt_descr:
.word __BOOT_DS + 7 # gdt limit
boot_gdt:
.long 0 # gdt base
boot_idt_descr:
.word 0 # idt limit = 0
.long 0 # idt base = 0L
trampoline_status:
.long 0
startup_32_smp:
.long 0x00000000
.word __BOOT_CS, 0
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