1/* 2 * 3 * Trampoline.S Derived from Setup.S by Linus Torvalds 4 * 5 * 4 Jan 1997 Michael Chastain: changed to gnu as. 6 * 15 Sept 2005 Eric Biederman: 64bit PIC support 7 * 8 * Entry: CS:IP point to the start of our code, we are 9 * in real mode with no stack, but the rest of the 10 * trampoline page to make our stack and everything else 11 * is a mystery. 12 * 13 * On entry to trampoline_data, the processor is in real mode 14 * with 16-bit addressing and 16-bit data. CS has some value 15 * and IP is zero. Thus, data addresses need to be absolute 16 * (no relocation) and are taken with regard to r_base. 17 * 18 * With the addition of trampoline_level4_pgt this code can 19 * now enter a 64bit kernel that lives at arbitrary 64bit 20 * physical addresses. 21 * 22 * If you work on this file, check the object module with objdump 23 * --full-contents --reloc to make sure there are no relocation 24 * entries. 25 */ 26 27#include <linux/linkage.h> 28#include <linux/init.h> 29#include <asm/pgtable_types.h> 30#include <asm/page_types.h> 31#include <asm/msr.h> 32#include <asm/segment.h> 33#include <asm/processor-flags.h> 34 35#ifdef CONFIG_ACPI_SLEEP 36.section .rodata, "a", @progbits 37#else 38/* We can free up the trampoline after bootup if cpu hotplug is not supported. */ 39__CPUINITRODATA 40#endif 41.code16 42 43ENTRY(trampoline_data) 44r_base = . 45 cli # We should be safe anyway 46 wbinvd 47 mov %cs, %ax # Code and data in the same place 48 mov %ax, %ds 49 mov %ax, %es 50 mov %ax, %ss 51 52 53 movl $0xA5A5A5A5, trampoline_data - r_base 54 # write marker for master knows we're running 55 56 # Setup stack 57 movw $(trampoline_stack_end - r_base), %sp 58 59 call verify_cpu # Verify the cpu supports long mode 60 testl %eax, %eax # Check for return code 61 jnz no_longmode 62 63 mov %cs, %ax 64 movzx %ax, %esi # Find the 32bit trampoline location 65 shll $4, %esi 66 67 # Fixup the vectors 68 addl %esi, startup_32_vector - r_base 69 addl %esi, startup_64_vector - r_base 70 addl %esi, tgdt + 2 - r_base # Fixup the gdt pointer 71 72 /* 73 * GDT tables in non default location kernel can be beyond 16MB and 74 * lgdt will not be able to load the address as in real mode default 75 * operand size is 16bit. Use lgdtl instead to force operand size 76 * to 32 bit. 77 */ 78 79 lidtl tidt - r_base # load idt with 0, 0 80 lgdtl tgdt - r_base # load gdt with whatever is appropriate 81 82 mov $X86_CR0_PE, %ax # protected mode (PE) bit 83 lmsw %ax # into protected mode 84 85 # flush prefetch and jump to startup_32 86 ljmpl *(startup_32_vector - r_base) 87 88 .code32 89 .balign 4 90startup_32: 91 movl $__KERNEL_DS, %eax # Initialize the %ds segment register 92 movl %eax, %ds 93 94 movl $X86_CR4_PAE, %eax 95 movl %eax, %cr4 # Enable PAE mode 96 97 # Setup trampoline 4 level pagetables 98 leal (trampoline_level4_pgt - r_base)(%esi), %eax 99 movl %eax, %cr3 100 101 movl $MSR_EFER, %ecx 102 movl $(1 << _EFER_LME), %eax # Enable Long Mode 103 xorl %edx, %edx 104 wrmsr 105 106 # Enable paging and in turn activate Long Mode 107 # Enable protected mode 108 movl $(X86_CR0_PG | X86_CR0_PE), %eax 109 movl %eax, %cr0 110 111 /* 112 * At this point we're in long mode but in 32bit compatibility mode 113 * with EFER.LME = 1, CS.L = 0, CS.D = 1 (and in turn 114 * EFER.LMA = 1). Now we want to jump in 64bit mode, to do that we use 115 * the new gdt/idt that has __KERNEL_CS with CS.L = 1. 116 */ 117 ljmp *(startup_64_vector - r_base)(%esi) 118 119 .code64 120 .balign 4 121startup_64: 122 # Now jump into the kernel using virtual addresses 123 movq $secondary_startup_64, %rax 124 jmp *%rax 125 126 .code16 127no_longmode: 128 hlt 129 jmp no_longmode 130#include "verify_cpu_64.S" 131 132 # Careful these need to be in the same 64K segment as the above; 133tidt: 134 .word 0 # idt limit = 0 135 .word 0, 0 # idt base = 0L 136 137 # Duplicate the global descriptor table 138 # so the kernel can live anywhere 139 .balign 4 140tgdt: 141 .short tgdt_end - tgdt # gdt limit 142 .long tgdt - r_base 143 .short 0 144 .quad 0x00cf9b000000ffff # __KERNEL32_CS 145 .quad 0x00af9b000000ffff # __KERNEL_CS 146 .quad 0x00cf93000000ffff # __KERNEL_DS 147tgdt_end: 148 149 .balign 4 150startup_32_vector: 151 .long startup_32 - r_base 152 .word __KERNEL32_CS, 0 153 154 .balign 4 155startup_64_vector: 156 .long startup_64 - r_base 157 .word __KERNEL_CS, 0 158 159trampoline_stack: 160 .org 0x1000 161trampoline_stack_end: 162ENTRY(trampoline_level4_pgt) 163 .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE 164 .fill 510,8,0 165 .quad level3_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE 166 167ENTRY(trampoline_end) 168