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Diffstat (limited to 'arch/x86_64/kernel/trampoline.S')
| -rw-r--r-- | arch/x86_64/kernel/trampoline.S | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/arch/x86_64/kernel/trampoline.S b/arch/x86_64/kernel/trampoline.S new file mode 100644 index 00000000000..6d9c9a8e7d0 --- /dev/null +++ b/arch/x86_64/kernel/trampoline.S @@ -0,0 +1,64 @@ +/* + * + * Trampoline.S Derived from Setup.S by Linus Torvalds + * + * 4 Jan 1997 Michael Chastain: changed to gnu as. + * + * Entry: CS:IP point to the start of our code, we are + * in real mode with no stack, but the rest of the + * trampoline page to make our stack and everything else + * is a mystery. + * + * In fact we don't actually need a stack so we don't + * set one up. + * + * On entry to trampoline_data, the processor is in real mode + * with 16-bit addressing and 16-bit data. CS has some value + * and IP is zero. Thus, data addresses need to be absolute + * (no relocation) and are taken with regard to r_base. + * + * If you work on this file, check the object module with objdump + * --full-contents --reloc to make sure there are no relocation + * entries. For the GDT entry we do hand relocation in smpboot.c + * because of 64bit linker limitations. + */ + +#include <linux/linkage.h> +#include <asm/segment.h> +#include <asm/page.h> + +.data + +.code16 + +ENTRY(trampoline_data) +r_base = . + wbinvd + mov %cs, %ax # Code and data in the same place + mov %ax, %ds + + cli # We should be safe anyway + + movl $0xA5A5A5A5, trampoline_data - r_base + # write marker for master knows we're running + + lidt idt_48 - r_base # load idt with 0, 0 + lgdt gdt_48 - r_base # load gdt with whatever is appropriate + + xor %ax, %ax + inc %ax # protected mode (PE) bit + lmsw %ax # into protected mode + # flaush prefetch and jump to startup_32 in arch/x86_64/kernel/head.S + ljmpl $__KERNEL32_CS, $(startup_32-__START_KERNEL_map) + + # Careful these need to be in the same 64K segment as the above; +idt_48: + .word 0 # idt limit = 0 + .word 0, 0 # idt base = 0L + +gdt_48: + .short __KERNEL32_CS + 7 # gdt limit + .long cpu_gdt_table-__START_KERNEL_map + +.globl trampoline_end +trampoline_end: |