| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 | |
| 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 | |
| 60 | lidtl boot_idt - r_base # load idt with 0, 0 |
| 61 | lgdtl boot_gdt - r_base # load gdt with whatever is appropriate |
| 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 |
| 71 | boot_gdt: |
| 72 | .word __BOOT_DS + 7 # gdt limit |
| 73 | .long boot_gdt_table-__PAGE_OFFSET # gdt base |
| 74 | |
| 75 | boot_idt: |
| 76 | .word 0 # idt limit = 0 |
| 77 | .long 0 # idt base = 0L |
| 78 | |
| 79 | .globl trampoline_end |
| 80 | trampoline_end: |