3 * Trampoline.S Derived from Setup.S by Linus Torvalds
5 * 4 Jan 1997 Michael Chastain: changed to gnu as.
7 * This is only used for booting secondary CPUs in SMP machine
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
14 * In fact we don't actually need a stack so we don't
17 * We jump into the boot/compressed/head.S code. So you'd
18 * better be running a compressed kernel image or you
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.
26 * If you work on this file, check the object module with
27 * objdump --reloc to make sure there are no relocation
31 * R_386_32 startup_32_smp
32 * R_386_32 boot_gdt_table
35 #include <linux/linkage.h>
36 #include <asm/segment.h>
43 ENTRY(trampoline_data)
45 wbinvd # Needed for NUMA-Q should be harmless for others
46 mov %cs, %ax # Code and data in the same place
49 cli # We should be safe anyway
51 movl $0xA5A5A5A5, trampoline_data - r_base
52 # write marker for master knows we're running
54 lidt boot_idt - r_base # load idt with 0, 0
55 lgdt boot_gdt - r_base # load gdt with whatever is appropriate
58 inc %ax # protected mode (PE) bit
59 lmsw %ax # into protected mode
60 # flush prefetch and jump to startup_32_smp in arch/i386/kernel/head.S
61 ljmpl $__BOOT_CS, $(startup_32_smp-__PAGE_OFFSET)
63 # These need to be in the same 64K segment as the above;
64 # hence we don't use the boot_gdt_descr defined in head.S
66 .word __BOOT_DS + 7 # gdt limit
67 .long boot_gdt_table-__PAGE_OFFSET # gdt base
70 .word 0 # idt limit = 0
71 .long 0 # idt base = 0L