diff options
Diffstat (limited to 'arch/x86/boot/compressed/head_64.S')
| -rw-r--r-- | arch/x86/boot/compressed/head_64.S | 311 |
1 files changed, 311 insertions, 0 deletions
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S new file mode 100644 index 000000000000..49467640751f --- /dev/null +++ b/arch/x86/boot/compressed/head_64.S @@ -0,0 +1,311 @@ +/* + * 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 0x1e4 (defined as a scratch field) are used as the stack + * for this calculation. Only 4 bytes are needed. + */ + leal (0x1e4+4)(%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_64.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 + movl %eax, %fs + movl %eax, %gs + lldt %ax + movl $0x20, %eax + ltr %ax + + /* 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 */ + .quad 0x0080890000000000 /* TS descriptor */ + .quad 0x0000000000000000 /* TS continued */ +gdt_end: + .bss +/* Stack for uncompression */ + .balign 4 +user_stack: + .fill 4096,4,0 +user_stack_end: |