1 /* -*- linux-c -*- ------------------------------------------------------- * 2 * 3 * Copyright (C) 1991, 1992 Linus Torvalds 4 * Copyright 2007 rPath, Inc. - All Rights Reserved 5 * 6 * This file is part of the Linux kernel, and is made available under 7 * the terms of the GNU General Public License version 2. 8 * 9 * ----------------------------------------------------------------------- */ 10 11 /* 12 * arch/i386/boot/pm.c 13 * 14 * Prepare the machine for transition to protected mode. 15 */ 16 17 #include "boot.h" 18 #include <asm/segment.h> 19 20 /* 21 * Invoke the realmode switch hook if present; otherwise 22 * disable all interrupts. 23 */ 24 static void realmode_switch_hook(void) 25 { 26 if (boot_params.hdr.realmode_swtch) { 27 asm volatile("lcallw *%0" 28 : : "m" (boot_params.hdr.realmode_swtch) 29 : "eax", "ebx", "ecx", "edx"); 30 } else { 31 asm volatile("cli"); 32 outb(0x80, 0x70); /* Disable NMI */ 33 io_delay(); 34 } 35 } 36 37 /* 38 * A zImage kernel is loaded at 0x10000 but wants to run at 0x1000. 39 * A bzImage kernel is loaded and runs at 0x100000. 40 */ 41 static void move_kernel_around(void) 42 { 43 /* Note: rely on the compile-time option here rather than 44 the LOADED_HIGH flag. The Qemu kernel loader unconditionally 45 sets the loadflags to zero. */ 46 #ifndef __BIG_KERNEL__ 47 u16 dst_seg, src_seg; 48 u32 syssize; 49 50 dst_seg = 0x1000 >> 4; 51 src_seg = 0x10000 >> 4; 52 syssize = boot_params.hdr.syssize; /* Size in 16-byte paragraphs */ 53 54 while (syssize) { 55 int paras = (syssize >= 0x1000) ? 0x1000 : syssize; 56 int dwords = paras << 2; 57 58 asm volatile("pushw %%es ; " 59 "pushw %%ds ; " 60 "movw %1,%%es ; " 61 "movw %2,%%ds ; " 62 "xorw %%di,%%di ; " 63 "xorw %%si,%%si ; " 64 "rep;movsl ; " 65 "popw %%ds ; " 66 "popw %%es" 67 : "+c" (dwords) 68 : "r" (dst_seg), "r" (src_seg) 69 : "esi", "edi"); 70 71 syssize -= paras; 72 dst_seg += paras; 73 src_seg += paras; 74 } 75 #endif 76 } 77 78 /* 79 * Disable all interrupts at the legacy PIC. 80 */ 81 static void mask_all_interrupts(void) 82 { 83 outb(0xff, 0xa1); /* Mask all interrupts on the secondary PIC */ 84 io_delay(); 85 outb(0xfb, 0x21); /* Mask all but cascade on the primary PIC */ 86 io_delay(); 87 } 88 89 /* 90 * Reset IGNNE# if asserted in the FPU. 91 */ 92 static void reset_coprocessor(void) 93 { 94 outb(0, 0xf0); 95 io_delay(); 96 outb(0, 0xf1); 97 io_delay(); 98 } 99 100 /* 101 * Set up the GDT 102 */ 103 #define GDT_ENTRY(flags,base,limit) \ 104 (((u64)(base & 0xff000000) << 32) | \ 105 ((u64)flags << 40) | \ 106 ((u64)(limit & 0x00ff0000) << 32) | \ 107 ((u64)(base & 0x00ffff00) << 16) | \ 108 ((u64)(limit & 0x0000ffff))) 109 110 struct gdt_ptr { 111 u16 len; 112 u32 ptr; 113 } __attribute__((packed)); 114 115 static void setup_gdt(void) 116 { 117 /* There are machines which are known to not boot with the GDT 118 being 8-byte unaligned. Intel recommends 16 byte alignment. */ 119 static const u64 boot_gdt[] __attribute__((aligned(16))) = { 120 /* CS: code, read/execute, 4 GB, base 0 */ 121 [GDT_ENTRY_BOOT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff), 122 /* DS: data, read/write, 4 GB, base 0 */ 123 [GDT_ENTRY_BOOT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff), 124 }; 125 /* Xen HVM incorrectly stores a pointer to the gdt_ptr, instead 126 of the gdt_ptr contents. Thus, make it static so it will 127 stay in memory, at least long enough that we switch to the 128 proper kernel GDT. */ 129 static struct gdt_ptr gdt; 130 131 gdt.len = sizeof(boot_gdt)-1; 132 gdt.ptr = (u32)&boot_gdt + (ds() << 4); 133 134 asm volatile("lgdtl %0" : : "m" (gdt)); 135 } 136 137 /* 138 * Set up the IDT 139 */ 140 static void setup_idt(void) 141 { 142 static const struct gdt_ptr null_idt = {0, 0}; 143 asm volatile("lidtl %0" : : "m" (null_idt)); 144 } 145 146 /* 147 * Actual invocation sequence 148 */ 149 void go_to_protected_mode(void) 150 { 151 /* Hook before leaving real mode, also disables interrupts */ 152 realmode_switch_hook(); 153 154 /* Move the kernel/setup to their final resting places */ 155 move_kernel_around(); 156 157 /* Enable the A20 gate */ 158 if (enable_a20()) { 159 puts("A20 gate not responding, unable to boot...\n"); 160 die(); 161 } 162 163 /* Reset coprocessor (IGNNE#) */ 164 reset_coprocessor(); 165 166 /* Mask all interrupts in the PIC */ 167 mask_all_interrupts(); 168 169 /* Actual transition to protected mode... */ 170 setup_idt(); 171 setup_gdt(); 172 protected_mode_jump(boot_params.hdr.code32_start, 173 (u32)&boot_params + (ds() << 4)); 174 } 175