diff options
Diffstat (limited to 'arch/x86/kernel/trampoline_64.S')
| -rw-r--r-- | arch/x86/kernel/trampoline_64.S | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/arch/x86/kernel/trampoline_64.S b/arch/x86/kernel/trampoline_64.S new file mode 100644 index 00000000000..607983b0d27 --- /dev/null +++ b/arch/x86/kernel/trampoline_64.S @@ -0,0 +1,166 @@ +/* + * + * Trampoline.S Derived from Setup.S by Linus Torvalds + * + * 4 Jan 1997 Michael Chastain: changed to gnu as. + * 15 Sept 2005 Eric Biederman: 64bit PIC support + * + * 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. + * + * With the addition of trampoline_level4_pgt this code can + * now enter a 64bit kernel that lives at arbitrary 64bit + * physical addresses. + * + * If you work on this file, check the object module with objdump + * --full-contents --reloc to make sure there are no relocation + * entries. + */ + +#include <linux/linkage.h> +#include <asm/pgtable.h> +#include <asm/page.h> +#include <asm/msr.h> +#include <asm/segment.h> + +.data + +.code16 + +ENTRY(trampoline_data) +r_base = . + cli # We should be safe anyway + wbinvd + mov %cs, %ax # Code and data in the same place + mov %ax, %ds + mov %ax, %es + mov %ax, %ss + + + movl $0xA5A5A5A5, trampoline_data - r_base + # write marker for master knows we're running + + # Setup stack + movw $(trampoline_stack_end - r_base), %sp + + call verify_cpu # Verify the cpu supports long mode + testl %eax, %eax # Check for return code + jnz no_longmode + + mov %cs, %ax + movzx %ax, %esi # Find the 32bit trampoline location + shll $4, %esi + + # Fixup the vectors + addl %esi, startup_32_vector - r_base + addl %esi, startup_64_vector - r_base + addl %esi, tgdt + 2 - r_base # Fixup the gdt pointer + + /* + * GDT tables in non default location kernel can be beyond 16MB and + * lgdt will not be able to load the address as in real mode default + * operand size is 16bit. Use lgdtl instead to force operand size + * to 32 bit. + */ + + lidtl tidt - r_base # load idt with 0, 0 + lgdtl tgdt - r_base # load gdt with whatever is appropriate + + xor %ax, %ax + inc %ax # protected mode (PE) bit + lmsw %ax # into protected mode + + # flush prefetch and jump to startup_32 + ljmpl *(startup_32_vector - r_base) + + .code32 + .balign 4 +startup_32: + movl $__KERNEL_DS, %eax # Initialize the %ds segment register + movl %eax, %ds + + xorl %eax, %eax + btsl $5, %eax # Enable PAE mode + movl %eax, %cr4 + + # Setup trampoline 4 level pagetables + leal (trampoline_level4_pgt - r_base)(%esi), %eax + movl %eax, %cr3 + + movl $MSR_EFER, %ecx + movl $(1 << _EFER_LME), %eax # Enable Long Mode + xorl %edx, %edx + wrmsr + + xorl %eax, %eax + btsl $31, %eax # Enable paging and in turn activate Long Mode + btsl $0, %eax # Enable protected mode + movl %eax, %cr0 + + /* + * At this point we're in long mode but in 32bit compatibility mode + * with EFER.LME = 1, CS.L = 0, CS.D = 1 (and in turn + * EFER.LMA = 1). Now we want to jump in 64bit mode, to do that we use + * the new gdt/idt that has __KERNEL_CS with CS.L = 1. + */ + ljmp *(startup_64_vector - r_base)(%esi) + + .code64 + .balign 4 +startup_64: + # Now jump into the kernel using virtual addresses + movq $secondary_startup_64, %rax + jmp *%rax + + .code16 +no_longmode: + hlt + jmp no_longmode +#include "verify_cpu_64.S" + + # Careful these need to be in the same 64K segment as the above; +tidt: + .word 0 # idt limit = 0 + .word 0, 0 # idt base = 0L + + # Duplicate the global descriptor table + # so the kernel can live anywhere + .balign 4 +tgdt: + .short tgdt_end - tgdt # gdt limit + .long tgdt - r_base + .short 0 + .quad 0x00cf9b000000ffff # __KERNEL32_CS + .quad 0x00af9b000000ffff # __KERNEL_CS + .quad 0x00cf93000000ffff # __KERNEL_DS +tgdt_end: + + .balign 4 +startup_32_vector: + .long startup_32 - r_base + .word __KERNEL32_CS, 0 + + .balign 4 +startup_64_vector: + .long startup_64 - r_base + .word __KERNEL_CS, 0 + +trampoline_stack: + .org 0x1000 +trampoline_stack_end: +ENTRY(trampoline_level4_pgt) + .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE + .fill 510,8,0 + .quad level3_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE + +ENTRY(trampoline_end) |