src/arch/i386/boot/tables.c

#include <console/console.h>
#include <cpu/cpu.h>
#include <boot/tables.h>
#include <boot/linuxbios_tables.h>
#include <arch/pirq_routing.h>
#include <arch/smp/mpspec.h>
#include <arch/acpi.h>
#include "linuxbios_table.h"

// Global Descriptor Table, defined in c_start.S
extern uint8_t gdt;
extern uint8_t gdt_end;

/* i386 lgdt argument */
struct gdtarg {
    unsigned short limit;
    unsigned int base;
} __attribute__((packed));

// Copy GDT to new location and reload it
// 2003-07 by SONE Takeshi
// Ported from Etherboot to LinuxBIOS 2005-08 by Steve Magnani
void move_gdt(unsigned long newgdt)
{
	uint16_t num_gdt_bytes = &gdt_end - &gdt;
    struct gdtarg gdtarg;

    printk_debug("Moving GDT to %#lx...", newgdt);
    memcpy((void*)newgdt, &gdt, num_gdt_bytes);
    gdtarg.base = newgdt;
    gdtarg.limit = num_gdt_bytes - 1;
    __asm__ __volatile__ ("lgdt %0\n\t" : : "m" (gdtarg));
    printk_debug("ok\n");
}

struct lb_memory *write_tables(void)
{
	unsigned long low_table_start, low_table_end;
	unsigned long rom_table_start, rom_table_end;

	rom_table_start = 0xf0000;
	rom_table_end =   0xf0000;
	/* Start low addr at 16 bytes instead of 0 because of a buglet
	 * in the generic linux unzip code, as it tests for the a20 line.
	 */
	low_table_start = 0;
	low_table_end = 16;

	post_code(0x9a);

	/* This table must be betweeen 0xf0000 & 0x100000 */
	rom_table_end = write_pirq_routing_table(rom_table_end);
	rom_table_end = (rom_table_end + 1023) & ~1023;

	/* copy the smp block to address 0 */
	post_code(0x96);

	/* The smp table must be in 0-1K, 639K-640K, or 960K-1M */
	low_table_end = write_smp_table(low_table_end);

	/* Write ACPI tables */
	/* write them in the rom area because DSDT can be large (8K on epia-m) which
	 * pushes linuxbios table out of first 4K if set up in low table area 
         */

	rom_table_end = write_acpi_tables(rom_table_end);
	rom_table_end = (rom_table_end+1023) & ~1023;

	/* Don't write anything in the traditional x86 BIOS data segment */
	if (low_table_end < 0x500) {
		low_table_end = 0x500;
	}

	// Relocate the GDT to reserved memory, so it won't get clobbered
	move_gdt(low_table_end);
	low_table_end += &gdt_end - &gdt;

	/* The linuxbios table must be in 0-4K or 960K-1M */
	write_linuxbios_table(
			      low_table_start, low_table_end,
			      rom_table_start >> 10, rom_table_end >> 10);

	return get_lb_mem();
}