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+/*
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+ *
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+ * Trampoline.S Derived from Setup.S by Linus Torvalds
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+ *
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+ * 4 Jan 1997 Michael Chastain: changed to gnu as.
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+ * 15 Sept 2005 Eric Biederman: 64bit PIC support
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+ *
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+ * Entry: CS:IP point to the start of our code, we are
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+ * in real mode with no stack, but the rest of the
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+ * trampoline page to make our stack and everything else
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+ * is a mystery.
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+ *
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+ * On entry to trampoline_data, the processor is in real mode
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+ * with 16-bit addressing and 16-bit data. CS has some value
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+ * and IP is zero. Thus, data addresses need to be absolute
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+ * (no relocation) and are taken with regard to r_base.
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+ *
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+ * With the addition of trampoline_level4_pgt this code can
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+ * now enter a 64bit kernel that lives at arbitrary 64bit
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+ * physical addresses.
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+ *
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+ * If you work on this file, check the object module with objdump
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+ * --full-contents --reloc to make sure there are no relocation
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+ * entries.
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+ */
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+
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+#include <linux/linkage.h>
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+#include <linux/init.h>
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+#include <asm/pgtable_types.h>
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+#include <asm/page_types.h>
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+#include <asm/msr.h>
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+#include <asm/segment.h>
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+#include <asm/processor-flags.h>
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+
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+ .text
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+ .balign PAGE_SIZE
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+ .code16
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+
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+ENTRY(trampoline_data)
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+ cli # We should be safe anyway
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+ wbinvd
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+
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+ .byte 0xea # ljmpw
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+ .word 1f # Offset
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+ .word real_mode_seg # Segment
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+1:
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+ mov %cs, %ax # Code and data in the same place
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+ mov %ax, %ds
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+ mov %ax, %es
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+ mov %ax, %ss
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+
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+ movl $0xA5A5A5A5, trampoline_status
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+ # write marker for master knows we're running
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+
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+ # Setup stack
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+ movw $trampoline_stack_end, %sp
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+
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+ call verify_cpu # Verify the cpu supports long mode
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+ testl %eax, %eax # Check for return code
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+ jnz no_longmode
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+
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+ /*
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+ * GDT tables in non default location kernel can be beyond 16MB and
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+ * lgdt will not be able to load the address as in real mode default
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+ * operand size is 16bit. Use lgdtl instead to force operand size
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+ * to 32 bit.
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+ */
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+
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+ lidtl tidt # load idt with 0, 0
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+ lgdtl tgdt # load gdt with whatever is appropriate
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+
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+ mov $X86_CR0_PE, %ax # protected mode (PE) bit
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+ lmsw %ax # into protected mode
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+
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+ # flush prefetch and jump to startup_32
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+ ljmpl *(startup_32_vector)
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+
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+no_longmode:
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+ hlt
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+ jmp no_longmode
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+#include "../kernel/verify_cpu.S"
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+
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+ .code32
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+ .balign 4
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+ENTRY(startup_32)
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+ movl $__KERNEL_DS, %eax # Initialize the %ds segment register
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+ movl %eax, %ds
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+
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+ movl $X86_CR4_PAE, %eax
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+ movl %eax, %cr4 # Enable PAE mode
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+
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+ movl pa_startup_64_smp, %esi
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+ movl pa_startup_64_smp_high, %edi
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+
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+ # Setup trampoline 4 level pagetables
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+ leal pa_trampoline_level4_pgt, %eax
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+ movl %eax, %cr3
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+
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+ movl $MSR_EFER, %ecx
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+ movl $(1 << _EFER_LME), %eax # Enable Long Mode
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+ xorl %edx, %edx
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+ wrmsr
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+
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+ # Enable paging and in turn activate Long Mode
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+ # Enable protected mode
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+ movl $(X86_CR0_PG | X86_CR0_PE), %eax
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+ movl %eax, %cr0
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+
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+ /*
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+ * At this point we're in long mode but in 32bit compatibility mode
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+ * with EFER.LME = 1, CS.L = 0, CS.D = 1 (and in turn
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+ * EFER.LMA = 1). Now we want to jump in 64bit mode, to do that we use
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+ * the new gdt/idt that has __KERNEL_CS with CS.L = 1.
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+ */
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+ ljmpl *(pa_startup_64_vector)
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+
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+ .code64
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+ .balign 4
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+ENTRY(startup_64)
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+ # Now jump into the kernel using virtual addresses
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+ movl %edi, %eax
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+ shlq $32, %rax
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+ addl %esi, %eax
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+ jmp *%rax
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+
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+ # Careful these need to be in the same 64K segment as the above;
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+tidt:
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+ .word 0 # idt limit = 0
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+ .word 0, 0 # idt base = 0L
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+
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+ # Duplicate the global descriptor table
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+ # so the kernel can live anywhere
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+ .balign 4
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+ .globl tgdt
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+tgdt:
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+ .short tgdt_end - tgdt # gdt limit
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+ .long pa_tgdt
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+ .short 0
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+ .quad 0x00cf9b000000ffff # __KERNEL32_CS
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+ .quad 0x00af9b000000ffff # __KERNEL_CS
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+ .quad 0x00cf93000000ffff # __KERNEL_DS
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+tgdt_end:
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+
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+ .balign 4
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+startup_32_vector:
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+ .long pa_startup_32
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+ .word __KERNEL32_CS, 0
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+
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+ .balign 4
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+ .globl startup_64_vector
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+startup_64_vector:
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+ .long pa_startup_64
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+ .word __KERNEL_CS, 0
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+
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+ .data
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+
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+ .balign 4
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+ENTRY(trampoline_status)
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+ .long 0
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+
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+trampoline_stack:
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+ .org 0x1000
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+trampoline_stack_end:
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+
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+ .globl level3_ident_pgt
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+ .globl level3_kernel_pgt
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+ENTRY(trampoline_level4_pgt)
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+ level3_ident_pgt: .quad 0
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+ .fill 510,8,0
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+ level3_kernel_pgt: .quad 0
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+
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+ .globl startup_64_smp
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+ .globl startup_64_smp_high
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+startup_64_smp: .long 0
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+startup_64_smp_high: .long 0
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Jarkko Sakkinen