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 * We jump into arch/x86/kernel/head_32.S.
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.
21 * If you work on this file, check the object module with
22 * objdump --reloc to make sure there are no relocation
26 * R_386_32 startup_32_smp
30 #include <linux/linkage.h>
31 #include <linux/init.h>
32 #include <asm/segment.h>
33 #include <asm/page_types.h>
37 .section ".x86_trampoline","a"
41 ENTRY(trampoline_data)
43 wbinvd # Needed for NUMA-Q should be harmless for others
44 mov %cs, %ax # Code and data in the same place
47 cli # We should be safe anyway
49 movl $0xA5A5A5A5, trampoline_status - r_base
50 # write marker for master knows we're running
52 /* GDT tables in non default location kernel can be beyond 16MB and
53 * lgdt will not be able to load the address as in real mode default
54 * operand size is 16bit. Use lgdtl instead to force operand size
58 lidtl boot_idt_descr - r_base # load idt with 0, 0
59 lgdtl boot_gdt_descr - r_base # load gdt with whatever is appropriate
62 inc %ax # protected mode (PE) bit
63 lmsw %ax # into protected mode
64 # flush prefetch and jump to startup_32_smp in arch/i386/kernel/head.S
65 ljmpl $__BOOT_CS, $(startup_32_smp-__PAGE_OFFSET)
67 # These need to be in the same 64K segment as the above;
68 # hence we don't use the boot_gdt_descr defined in head.S
70 .word __BOOT_DS + 7 # gdt limit
71 .long boot_gdt - __PAGE_OFFSET # gdt base
74 .word 0 # idt limit = 0
75 .long 0 # idt base = 0L
77 ENTRY(trampoline_status)
83 #endif /* CONFIG_SMP */