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![Graeme Russ](/assets/img/avatar_default.png)
Linux has C macros and code to load the GTD after switching to Protected Mode. Using these greatly simplifies the assembler code
150 lines
4.1 KiB
C
150 lines
4.1 KiB
C
/*
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* (C) Copyright 2002
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* Daniel Engström, Omicron Ceti AB, daniel@omicron.se.
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*
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* (C) Copyright 2002
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* Sysgo Real-Time Solutions, GmbH <www.elinos.com>
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* Marius Groeger <mgroeger@sysgo.de>
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*
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* (C) Copyright 2002
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* Sysgo Real-Time Solutions, GmbH <www.elinos.com>
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* Alex Zuepke <azu@sysgo.de>
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*
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* See file CREDITS for list of people who contributed to this
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* project.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*/
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/*
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* CPU specific code
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*/
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#include <common.h>
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#include <command.h>
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#include <asm/interrupt.h>
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/* Constructor for a conventional segment GDT (or LDT) entry */
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/* This is a macro so it can be used in initializers */
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#define GDT_ENTRY(flags, base, limit) \
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((((base) & 0xff000000ULL) << (56-24)) | \
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(((flags) & 0x0000f0ffULL) << 40) | \
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(((limit) & 0x000f0000ULL) << (48-16)) | \
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(((base) & 0x00ffffffULL) << 16) | \
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(((limit) & 0x0000ffffULL)))
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/* Simple and small GDT entries for booting only */
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#define GDT_ENTRY_32BIT_CS 2
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#define GDT_ENTRY_32BIT_DS (GDT_ENTRY_32BIT_CS + 1)
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#define GDT_ENTRY_16BIT_CS (GDT_ENTRY_32BIT_DS + 1)
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#define GDT_ENTRY_16BIT_DS (GDT_ENTRY_16BIT_CS + 1)
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/*
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* Set up the GDT
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*/
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struct gdt_ptr {
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u16 len;
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u32 ptr;
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} __attribute__((packed));
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static void reload_gdt(void)
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{
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/* There are machines which are known to not boot with the GDT
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being 8-byte unaligned. Intel recommends 16 byte alignment. */
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static const u64 boot_gdt[] __attribute__((aligned(16))) = {
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/* CS: code, read/execute, 4 GB, base 0 */
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[GDT_ENTRY_32BIT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff),
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/* DS: data, read/write, 4 GB, base 0 */
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[GDT_ENTRY_32BIT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
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/* 16-bit CS: code, read/execute, 64 kB, base 0 */
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[GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x109b, 0, 0x0ffff),
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/* 16-bit DS: data, read/write, 64 kB, base 0 */
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[GDT_ENTRY_16BIT_DS] = GDT_ENTRY(0x1093, 0, 0x0ffff),
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};
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static struct gdt_ptr gdt;
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gdt.len = sizeof(boot_gdt)-1;
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gdt.ptr = (u32)&boot_gdt;
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asm volatile("lgdtl %0\n" \
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"movl $((2+1)*8), %%ecx\n" \
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"movl %%ecx, %%ds\n" \
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"movl %%ecx, %%es\n" \
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"movl %%ecx, %%fs\n" \
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"movl %%ecx, %%gs\n" \
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"movl %%ecx, %%ss" \
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: : "m" (gdt) : "ecx");
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}
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int cpu_init_f(void)
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{
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/* initialize FPU, reset EM, set MP and NE */
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asm ("fninit\n" \
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"movl %cr0, %eax\n" \
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"andl $~0x4, %eax\n" \
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"orl $0x22, %eax\n" \
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"movl %eax, %cr0\n" );
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return 0;
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}
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int cpu_init_r(void)
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{
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reload_gdt();
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/* Initialize core interrupt and exception functionality of CPU */
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cpu_init_interrupts ();
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return 0;
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}
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int do_reset(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
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{
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printf ("resetting ...\n");
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udelay(50000); /* wait 50 ms */
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disable_interrupts();
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reset_cpu(0);
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/*NOTREACHED*/
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return 0;
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}
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void flush_cache (unsigned long dummy1, unsigned long dummy2)
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{
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asm("wbinvd\n");
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return;
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}
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void __attribute__ ((regparm(0))) generate_gpf(void);
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/* segment 0x70 is an arbitrary segment which does not exist */
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asm(".globl generate_gpf\n"
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".hidden generate_gpf\n"
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".type generate_gpf, @function\n"
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"generate_gpf:\n"
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"ljmp $0x70, $0x47114711\n");
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void __reset_cpu(ulong addr)
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{
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printf("Resetting using i386 Triple Fault\n");
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set_vector(13, generate_gpf); /* general protection fault handler */
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set_vector(8, generate_gpf); /* double fault handler */
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generate_gpf(); /* start the show */
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}
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void reset_cpu(ulong addr) __attribute__((weak, alias("__reset_cpu")));
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