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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 | /* -*- linux-c -*- ------------------------------------------------------- * * * Copyright (C) 1991, 1992 Linus Torvalds * Copyright 2007 rPath, Inc. - All Rights Reserved * * This file is part of the Linux kernel, and is made available under * the terms of the GNU General Public License version 2. * * ----------------------------------------------------------------------- */ /* * Prepare the machine for transition to protected mode. */ #include "boot.h" #include <asm/segment.h> /* * Invoke the realmode switch hook if present; otherwise * disable all interrupts. */ static void realmode_switch_hook(void) { if (boot_params.hdr.realmode_swtch) { asm volatile("lcallw *%0" : : "m" (boot_params.hdr.realmode_swtch) : "eax", "ebx", "ecx", "edx"); } else { asm volatile("cli"); outb(0x80, 0x70); /* Disable NMI */ io_delay(); } } /* * A zImage kernel is loaded at 0x10000 but wants to run at 0x1000. * A bzImage kernel is loaded and runs at 0x100000. */ static void move_kernel_around(void) { /* Note: rely on the compile-time option here rather than the LOADED_HIGH flag. The Qemu kernel loader unconditionally sets the loadflags to zero. */ #ifndef __BIG_KERNEL__ u16 dst_seg, src_seg; u32 syssize; dst_seg = 0x1000 >> 4; src_seg = 0x10000 >> 4; syssize = boot_params.hdr.syssize; /* Size in 16-byte paragraphs */ while (syssize) { int paras = (syssize >= 0x1000) ? 0x1000 : syssize; int dwords = paras << 2; asm volatile("pushw %%es ; " "pushw %%ds ; " "movw %1,%%es ; " "movw %2,%%ds ; " "xorw %%di,%%di ; " "xorw %%si,%%si ; " "rep;movsl ; " "popw %%ds ; " "popw %%es" : "+c" (dwords) : "r" (dst_seg), "r" (src_seg) : "esi", "edi"); syssize -= paras; dst_seg += paras; src_seg += paras; } #endif } /* * Disable all interrupts at the legacy PIC. */ static void mask_all_interrupts(void) { outb(0xff, 0xa1); /* Mask all interrupts on the secondary PIC */ io_delay(); outb(0xfb, 0x21); /* Mask all but cascade on the primary PIC */ io_delay(); } /* * Reset IGNNE# if asserted in the FPU. */ static void reset_coprocessor(void) { outb(0, 0xf0); io_delay(); outb(0, 0xf1); io_delay(); } /* * Set up the GDT */ struct gdt_ptr { u16 len; u32 ptr; } __attribute__((packed)); static void setup_gdt(void) { /* There are machines which are known to not boot with the GDT being 8-byte unaligned. Intel recommends 16 byte alignment. */ static const u64 boot_gdt[] __attribute__((aligned(16))) = { /* CS: code, read/execute, 4 GB, base 0 */ [GDT_ENTRY_BOOT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff), /* DS: data, read/write, 4 GB, base 0 */ [GDT_ENTRY_BOOT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff), /* TSS: 32-bit tss, 104 bytes, base 4096 */ /* We only have a TSS here to keep Intel VT happy; we don't actually use it for anything. */ [GDT_ENTRY_BOOT_TSS] = GDT_ENTRY(0x0089, 4096, 103), }; /* Xen HVM incorrectly stores a pointer to the gdt_ptr, instead of the gdt_ptr contents. Thus, make it static so it will stay in memory, at least long enough that we switch to the proper kernel GDT. */ static struct gdt_ptr gdt; gdt.len = sizeof(boot_gdt)-1; gdt.ptr = (u32)&boot_gdt + (ds() << 4); asm volatile("lgdtl %0" : : "m" (gdt)); } /* * Set up the IDT */ static void setup_idt(void) { static const struct gdt_ptr null_idt = {0, 0}; asm volatile("lidtl %0" : : "m" (null_idt)); } /* * Actual invocation sequence */ void go_to_protected_mode(void) { /* Hook before leaving real mode, also disables interrupts */ realmode_switch_hook(); /* Move the kernel/setup to their final resting places */ move_kernel_around(); /* Enable the A20 gate */ if (enable_a20()) { puts("A20 gate not responding, unable to boot...\n"); die(); } /* Reset coprocessor (IGNNE#) */ reset_coprocessor(); /* Mask all interrupts in the PIC */ mask_all_interrupts(); /* Actual transition to protected mode... */ setup_idt(); setup_gdt(); protected_mode_jump(boot_params.hdr.code32_start, (u32)&boot_params + (ds() << 4)); } |