Commit | Line | Data |
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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 | * | |
14 | * In fact we don't actually need a stack so we don't | |
15 | * set one up. | |
16 | * | |
17 | * We jump into the boot/compressed/head.S code. So you'd | |
18 | * better be running a compressed kernel image or you | |
19 | * won't get very far. | |
20 | * | |
21 | * On entry to trampoline_data, the processor is in real mode | |
22 | * with 16-bit addressing and 16-bit data. CS has some value | |
23 | * and IP is zero. Thus, data addresses need to be absolute | |
24 | * (no relocation) and are taken with regard to r_base. | |
25 | * | |
26 | * If you work on this file, check the object module with | |
27 | * objdump --reloc to make sure there are no relocation | |
28 | * entries except for: | |
29 | * | |
30 | * TYPE VALUE | |
31 | * R_386_32 startup_32_smp | |
32 | * R_386_32 boot_gdt_table | |
33 | */ | |
34 | ||
35 | #include <linux/linkage.h> | |
36 | #include <asm/segment.h> | |
37 | #include <asm/page.h> | |
38 | ||
39 | .data | |
40 | ||
1119a33a VG |
41 | /* We can free up trampoline after bootup if cpu hotplug is not supported. */ |
42 | #ifndef CONFIG_HOTPLUG_CPU | |
43 | .section ".init.data","aw",@progbits | |
44 | #endif | |
45 | ||
1da177e4 LT |
46 | .code16 |
47 | ||
48 | ENTRY(trampoline_data) | |
49 | r_base = . | |
50 | wbinvd # Needed for NUMA-Q should be harmless for others | |
51 | mov %cs, %ax # Code and data in the same place | |
52 | mov %ax, %ds | |
53 | ||
54 | cli # We should be safe anyway | |
55 | ||
56 | movl $0xA5A5A5A5, trampoline_data - r_base | |
57 | # write marker for master knows we're running | |
58 | ||
59 | /* GDT tables in non default location kernel can be beyond 16MB and | |
60 | * lgdt will not be able to load the address as in real mode default | |
61 | * operand size is 16bit. Use lgdtl instead to force operand size | |
62 | * to 32 bit. | |
63 | */ | |
64 | ||
65 | lidtl boot_idt - r_base # load idt with 0, 0 | |
66 | lgdtl boot_gdt - r_base # load gdt with whatever is appropriate | |
67 | ||
68 | xor %ax, %ax | |
69 | inc %ax # protected mode (PE) bit | |
70 | lmsw %ax # into protected mode | |
71 | # flush prefetch and jump to startup_32_smp in arch/i386/kernel/head.S | |
72 | ljmpl $__BOOT_CS, $(startup_32_smp-__PAGE_OFFSET) | |
73 | ||
74 | # These need to be in the same 64K segment as the above; | |
75 | # hence we don't use the boot_gdt_descr defined in head.S | |
76 | boot_gdt: | |
77 | .word __BOOT_DS + 7 # gdt limit | |
78 | .long boot_gdt_table-__PAGE_OFFSET # gdt base | |
79 | ||
80 | boot_idt: | |
81 | .word 0 # idt limit = 0 | |
82 | .long 0 # idt base = 0L | |
83 | ||
84 | .globl trampoline_end | |
85 | trampoline_end: |