diff options
Diffstat (limited to 'arch/i386/boot/pm.c')
| -rw-r--r-- | arch/i386/boot/pm.c | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/arch/i386/boot/pm.c b/arch/i386/boot/pm.c new file mode 100644 index 00000000000..3fa53e15ed7 --- /dev/null +++ b/arch/i386/boot/pm.c @@ -0,0 +1,170 @@ +/* -*- 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. + * + * ----------------------------------------------------------------------- */ + +/* + * arch/i386/boot/pm.c + * + * 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) + : "rm" (dst_seg), "rm" (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 seconday 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 + */ +#define GDT_ENTRY(flags,base,limit) \ + (((u64)(base & 0xff000000) << 32) | \ + ((u64)flags << 40) | \ + ((u64)(limit & 0x00ff0000) << 32) | \ + ((u64)(base & 0x00ffff00) << 16) | \ + ((u64)(limit & 0x0000ffff))) + +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), + }; + 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)); +} |