| /* |
| * linux/boot/head.S |
| * |
| * Copyright (C) 1991, 1992, 1993 Linus Torvalds |
| */ |
| |
| /* |
| * head.S contains the 32-bit startup code. |
| * |
| * NOTE!!! Startup happens at absolute address 0x00001000, which is also where |
| * the page directory will exist. The startup code will be overwritten by |
| * the page directory. [According to comments etc elsewhere on a compressed |
| * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC] |
| * |
| * Page 0 is deliberately kept safe, since System Management Mode code in |
| * laptops may need to access the BIOS data stored there. This is also |
| * useful for future device drivers that either access the BIOS via VM86 |
| * mode. |
| */ |
| |
| /* |
| * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996 |
| */ |
| .code32 |
| .text |
| |
| #include <linux/linkage.h> |
| #include <asm/segment.h> |
| #include <asm/pgtable.h> |
| #include <asm/page.h> |
| #include <asm/msr.h> |
| |
| .section ".text.head" |
| .code32 |
| .globl startup_32 |
| |
| startup_32: |
| cld |
| cli |
| movl $(__KERNEL_DS), %eax |
| movl %eax, %ds |
| movl %eax, %es |
| movl %eax, %ss |
| |
| /* Calculate the delta between where we were compiled to run |
| * at and where we were actually loaded at. This can only be done |
| * with a short local call on x86. Nothing else will tell us what |
| * address we are running at. The reserved chunk of the real-mode |
| * data at 0x34-0x3f are used as the stack for this calculation. |
| * Only 4 bytes are needed. |
| */ |
| leal 0x40(%esi), %esp |
| call 1f |
| 1: popl %ebp |
| subl $1b, %ebp |
| |
| /* setup a stack and make sure cpu supports long mode. */ |
| movl $user_stack_end, %eax |
| addl %ebp, %eax |
| movl %eax, %esp |
| |
| call verify_cpu |
| testl %eax, %eax |
| jnz no_longmode |
| |
| /* Compute the delta between where we were compiled to run at |
| * and where the code will actually run at. |
| */ |
| /* %ebp contains the address we are loaded at by the boot loader and %ebx |
| * contains the address where we should move the kernel image temporarily |
| * for safe in-place decompression. |
| */ |
| |
| #ifdef CONFIG_RELOCATABLE |
| movl %ebp, %ebx |
| addl $(LARGE_PAGE_SIZE -1), %ebx |
| andl $LARGE_PAGE_MASK, %ebx |
| #else |
| movl $CONFIG_PHYSICAL_START, %ebx |
| #endif |
| |
| /* Replace the compressed data size with the uncompressed size */ |
| subl input_len(%ebp), %ebx |
| movl output_len(%ebp), %eax |
| addl %eax, %ebx |
| /* Add 8 bytes for every 32K input block */ |
| shrl $12, %eax |
| addl %eax, %ebx |
| /* Add 32K + 18 bytes of extra slack and align on a 4K boundary */ |
| addl $(32768 + 18 + 4095), %ebx |
| andl $~4095, %ebx |
| |
| /* |
| * Prepare for entering 64 bit mode |
| */ |
| |
| /* Load new GDT with the 64bit segments using 32bit descriptor */ |
| leal gdt(%ebp), %eax |
| movl %eax, gdt+2(%ebp) |
| lgdt gdt(%ebp) |
| |
| /* Enable PAE mode */ |
| xorl %eax, %eax |
| orl $(1 << 5), %eax |
| movl %eax, %cr4 |
| |
| /* |
| * Build early 4G boot pagetable |
| */ |
| /* Initialize Page tables to 0*/ |
| leal pgtable(%ebx), %edi |
| xorl %eax, %eax |
| movl $((4096*6)/4), %ecx |
| rep stosl |
| |
| /* Build Level 4 */ |
| leal pgtable + 0(%ebx), %edi |
| leal 0x1007 (%edi), %eax |
| movl %eax, 0(%edi) |
| |
| /* Build Level 3 */ |
| leal pgtable + 0x1000(%ebx), %edi |
| leal 0x1007(%edi), %eax |
| movl $4, %ecx |
| 1: movl %eax, 0x00(%edi) |
| addl $0x00001000, %eax |
| addl $8, %edi |
| decl %ecx |
| jnz 1b |
| |
| /* Build Level 2 */ |
| leal pgtable + 0x2000(%ebx), %edi |
| movl $0x00000183, %eax |
| movl $2048, %ecx |
| 1: movl %eax, 0(%edi) |
| addl $0x00200000, %eax |
| addl $8, %edi |
| decl %ecx |
| jnz 1b |
| |
| /* Enable the boot page tables */ |
| leal pgtable(%ebx), %eax |
| movl %eax, %cr3 |
| |
| /* Enable Long mode in EFER (Extended Feature Enable Register) */ |
| movl $MSR_EFER, %ecx |
| rdmsr |
| btsl $_EFER_LME, %eax |
| wrmsr |
| |
| /* Setup for the jump to 64bit mode |
| * |
| * When the jump is performend we will be in long mode but |
| * in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1 |
| * (and in turn EFER.LMA = 1). To jump into 64bit mode we use |
| * the new gdt/idt that has __KERNEL_CS with CS.L = 1. |
| * We place all of the values on our mini stack so lret can |
| * used to perform that far jump. |
| */ |
| pushl $__KERNEL_CS |
| leal startup_64(%ebp), %eax |
| pushl %eax |
| |
| /* Enter paged protected Mode, activating Long Mode */ |
| movl $0x80000001, %eax /* Enable Paging and Protected mode */ |
| movl %eax, %cr0 |
| |
| /* Jump from 32bit compatibility mode into 64bit mode. */ |
| lret |
| |
| no_longmode: |
| /* This isn't an x86-64 CPU so hang */ |
| 1: |
| hlt |
| jmp 1b |
| |
| #include "../../kernel/verify_cpu.S" |
| |
| /* Be careful here startup_64 needs to be at a predictable |
| * address so I can export it in an ELF header. Bootloaders |
| * should look at the ELF header to find this address, as |
| * it may change in the future. |
| */ |
| .code64 |
| .org 0x200 |
| ENTRY(startup_64) |
| /* We come here either from startup_32 or directly from a |
| * 64bit bootloader. If we come here from a bootloader we depend on |
| * an identity mapped page table being provied that maps our |
| * entire text+data+bss and hopefully all of memory. |
| */ |
| |
| /* Setup data segments. */ |
| xorl %eax, %eax |
| movl %eax, %ds |
| movl %eax, %es |
| movl %eax, %ss |
| |
| /* Compute the decompressed kernel start address. It is where |
| * we were loaded at aligned to a 2M boundary. %rbp contains the |
| * decompressed kernel start address. |
| * |
| * If it is a relocatable kernel then decompress and run the kernel |
| * from load address aligned to 2MB addr, otherwise decompress and |
| * run the kernel from CONFIG_PHYSICAL_START |
| */ |
| |
| /* Start with the delta to where the kernel will run at. */ |
| #ifdef CONFIG_RELOCATABLE |
| leaq startup_32(%rip) /* - $startup_32 */, %rbp |
| addq $(LARGE_PAGE_SIZE - 1), %rbp |
| andq $LARGE_PAGE_MASK, %rbp |
| movq %rbp, %rbx |
| #else |
| movq $CONFIG_PHYSICAL_START, %rbp |
| movq %rbp, %rbx |
| #endif |
| |
| /* Replace the compressed data size with the uncompressed size */ |
| movl input_len(%rip), %eax |
| subq %rax, %rbx |
| movl output_len(%rip), %eax |
| addq %rax, %rbx |
| /* Add 8 bytes for every 32K input block */ |
| shrq $12, %rax |
| addq %rax, %rbx |
| /* Add 32K + 18 bytes of extra slack and align on a 4K boundary */ |
| addq $(32768 + 18 + 4095), %rbx |
| andq $~4095, %rbx |
| |
| /* Copy the compressed kernel to the end of our buffer |
| * where decompression in place becomes safe. |
| */ |
| leaq _end(%rip), %r8 |
| leaq _end(%rbx), %r9 |
| movq $_end /* - $startup_32 */, %rcx |
| 1: subq $8, %r8 |
| subq $8, %r9 |
| movq 0(%r8), %rax |
| movq %rax, 0(%r9) |
| subq $8, %rcx |
| jnz 1b |
| |
| /* |
| * Jump to the relocated address. |
| */ |
| leaq relocated(%rbx), %rax |
| jmp *%rax |
| |
| .section ".text" |
| relocated: |
| |
| /* |
| * Clear BSS |
| */ |
| xorq %rax, %rax |
| leaq _edata(%rbx), %rdi |
| leaq _end(%rbx), %rcx |
| subq %rdi, %rcx |
| cld |
| rep |
| stosb |
| |
| /* Setup the stack */ |
| leaq user_stack_end(%rip), %rsp |
| |
| /* zero EFLAGS after setting rsp */ |
| pushq $0 |
| popfq |
| |
| /* |
| * Do the decompression, and jump to the new kernel.. |
| */ |
| pushq %rsi # Save the real mode argument |
| movq %rsi, %rdi # real mode address |
| leaq _heap(%rip), %rsi # _heap |
| leaq input_data(%rip), %rdx # input_data |
| movl input_len(%rip), %eax |
| movq %rax, %rcx # input_len |
| movq %rbp, %r8 # output |
| call decompress_kernel |
| popq %rsi |
| |
| |
| /* |
| * Jump to the decompressed kernel. |
| */ |
| jmp *%rbp |
| |
| .data |
| gdt: |
| .word gdt_end - gdt |
| .long gdt |
| .word 0 |
| .quad 0x0000000000000000 /* NULL descriptor */ |
| .quad 0x00af9a000000ffff /* __KERNEL_CS */ |
| .quad 0x00cf92000000ffff /* __KERNEL_DS */ |
| gdt_end: |
| .bss |
| /* Stack for uncompression */ |
| .balign 4 |
| user_stack: |
| .fill 4096,4,0 |
| user_stack_end: |
