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1da177e4 LT |
1 | /* |
2 | * | |
3 | * Trampoline.S Derived from Setup.S by Linus Torvalds | |
4 | * | |
5 | * 4 Jan 1997 Michael Chastain: changed to gnu as. | |
6 | * | |
7 | * This is only used for booting secondary CPUs in SMP machine | |
8 | * | |
9 | * Entry: CS:IP point to the start of our code, we are | |
10 | * in real mode with no stack, but the rest of the | |
11 | * trampoline page to make our stack and everything else | |
12 | * is a mystery. | |
13 | * | |
94a8a7ac | 14 | * We jump into arch/x86/kernel/head_32.S. |
1da177e4 LT |
15 | * |
16 | * On entry to trampoline_data, the processor is in real mode | |
17 | * with 16-bit addressing and 16-bit data. CS has some value | |
18 | * and IP is zero. Thus, data addresses need to be absolute | |
19 | * (no relocation) and are taken with regard to r_base. | |
20 | * | |
21 | * If you work on this file, check the object module with | |
22 | * objdump --reloc to make sure there are no relocation | |
23 | * entries except for: | |
24 | * | |
25 | * TYPE VALUE | |
26 | * R_386_32 startup_32_smp | |
52de74dd | 27 | * R_386_32 boot_gdt |
1da177e4 LT |
28 | */ |
29 | ||
30 | #include <linux/linkage.h> | |
31 | #include <asm/segment.h> | |
0341c14d | 32 | #include <asm/page_types.h> |
1da177e4 | 33 | |
1119a33a VG |
34 | /* We can free up trampoline after bootup if cpu hotplug is not supported. */ |
35 | #ifndef CONFIG_HOTPLUG_CPU | |
4c01f23b | 36 | .section ".cpuinit.data","aw",@progbits |
121d7bf5 JB |
37 | #else |
38 | .section .rodata,"a",@progbits | |
1119a33a VG |
39 | #endif |
40 | ||
1da177e4 LT |
41 | .code16 |
42 | ||
43 | ENTRY(trampoline_data) | |
44 | r_base = . | |
45 | wbinvd # Needed for NUMA-Q should be harmless for others | |
46 | mov %cs, %ax # Code and data in the same place | |
47 | mov %ax, %ds | |
48 | ||
49 | cli # We should be safe anyway | |
50 | ||
51 | movl $0xA5A5A5A5, trampoline_data - r_base | |
52 | # write marker for master knows we're running | |
53 | ||
54 | /* GDT tables in non default location kernel can be beyond 16MB and | |
55 | * lgdt will not be able to load the address as in real mode default | |
56 | * operand size is 16bit. Use lgdtl instead to force operand size | |
57 | * to 32 bit. | |
58 | */ | |
59 | ||
52de74dd SD |
60 | lidtl boot_idt_descr - r_base # load idt with 0, 0 |
61 | lgdtl boot_gdt_descr - r_base # load gdt with whatever is appropriate | |
1da177e4 LT |
62 | |
63 | xor %ax, %ax | |
64 | inc %ax # protected mode (PE) bit | |
65 | lmsw %ax # into protected mode | |
66 | # flush prefetch and jump to startup_32_smp in arch/i386/kernel/head.S | |
67 | ljmpl $__BOOT_CS, $(startup_32_smp-__PAGE_OFFSET) | |
68 | ||
69 | # These need to be in the same 64K segment as the above; | |
70 | # hence we don't use the boot_gdt_descr defined in head.S | |
52de74dd | 71 | boot_gdt_descr: |
1da177e4 | 72 | .word __BOOT_DS + 7 # gdt limit |
52de74dd | 73 | .long boot_gdt - __PAGE_OFFSET # gdt base |
1da177e4 | 74 | |
52de74dd | 75 | boot_idt_descr: |
1da177e4 LT |
76 | .word 0 # idt limit = 0 |
77 | .long 0 # idt base = 0L | |
78 | ||
79 | .globl trampoline_end | |
80 | trampoline_end: |