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/* Segmentation of the i386 architecture.
*
* 2003-07 by SONE Takeshi
*/
#include "config.h"
#include "kernel/kernel.h"
#include "libopenbios/sys_info.h"
#include "relocate.h"
#include "segment.h"
#define printf printk
#ifdef CONFIG_DEBUG_BOOT
#define debug printk
#else
#define debug(x...)
#endif
/* i386 lgdt argument */
struct gdtarg {
unsigned short limit;
unsigned int base;
} __attribute__((packed));
/* How far the virtual address (used in C) is different from physical
* address. Since we start in flat mode, the initial value is zero. */
unsigned long virt_offset = 0;
/* GDT, the global descriptor table */
struct segment_desc gdt[NUM_SEG] = {
/* 0x00: null segment */
{0, 0, 0, 0, 0, 0},
/* 0x08: flat code segment */
{0xffff, 0, 0, 0x9f, 0xcf, 0},
/* 0x10: flat data segment */
{0xffff, 0, 0, 0x93, 0xcf, 0},
/* 0x18: code segment for relocated execution */
{0xffff, 0, 0, 0x9f, 0xcf, 0},
/* 0x20: data segment for relocated execution */
{0xffff, 0, 0, 0x93, 0xcf, 0},
};
void relocate(struct sys_info *info)
{
int i;
unsigned long prog_addr;
unsigned long prog_size;
unsigned long addr, new_base;
unsigned long long segsize;
unsigned long new_offset;
unsigned d0, d1, d2;
struct gdtarg gdtarg;
#define ALIGNMENT 16
prog_addr = virt_to_phys(&_start);
prog_size = virt_to_phys(&_end) - virt_to_phys(&_start);
debug("Current location: %#lx-%#lx\n", prog_addr, prog_addr+prog_size-1);
new_base = 0;
for (i = 0; i < info->n_memranges; i++) {
if (info->memrange[i].base >= 1ULL<<32)
continue;
segsize = info->memrange[i].size;
if (info->memrange[i].base + segsize > 1ULL<<32)
segsize = (1ULL<<32) - info->memrange[i].base;
if (segsize < prog_size+ALIGNMENT)
continue;
addr = info->memrange[i].base + segsize - prog_size;
addr &= ~(ALIGNMENT-1);
if (addr >= prog_addr && addr < prog_addr + prog_size)
continue;
if (prog_addr >= addr && prog_addr < addr + prog_size)
continue;
if (addr > new_base)
new_base = addr;
}
if (new_base == 0) {
printf("Can't find address to relocate\n");
return;
}
debug("Relocating to %#lx-%#lx... ",
new_base, new_base + prog_size - 1);
/* New virtual address offset */
new_offset = new_base - (unsigned long) &_start;
/* Tweak the GDT */
gdt[RELOC_CODE].base_0 = (unsigned short) new_offset;
gdt[RELOC_CODE].base_16 = (unsigned char) (new_offset>>16);
gdt[RELOC_CODE].base_24 = (unsigned char) (new_offset>>24);
gdt[RELOC_DATA].base_0 = (unsigned short) new_offset;
gdt[RELOC_DATA].base_16 = (unsigned char) (new_offset>>16);
gdt[RELOC_DATA].base_24 = (unsigned char) (new_offset>>24);
/* Load new GDT and reload segments */
gdtarg.base = new_offset + (unsigned long) gdt;
gdtarg.limit = GDT_LIMIT;
__asm__ __volatile__ (
"rep; movsb\n\t" /* copy everything */
"lgdt %3\n\t"
"ljmp %4, $1f\n1:\t"
"movw %5, %%ds\n\t"
"movw %5, %%es\n\t"
"movw %5, %%fs\n\t"
"movw %5, %%gs\n\t"
"movw %5, %%ss\n"
: "=&S" (d0), "=&D" (d1), "=&c" (d2)
: "m" (gdtarg), "n" (RELOC_CS), "q" ((unsigned short) RELOC_DS),
"0" (&_start), "1" (new_base), "2" (prog_size));
virt_offset = new_offset;
debug("ok\n");
}
#if 0
/* Copy GDT to new location and reload it */
void move_gdt(unsigned long newgdt)
{
struct gdtarg gdtarg;
debug("Moving GDT to %#lx...", newgdt);
memcpy(phys_to_virt(newgdt), gdt, sizeof gdt);
gdtarg.base = newgdt;
gdtarg.limit = GDT_LIMIT;
debug("reloading GDT...");
__asm__ __volatile__ ("lgdt %0\n\t" : : "m" (gdtarg));
debug("reloading CS for fun...");
__asm__ __volatile__ ("ljmp %0, $1f\n1:" : : "n" (RELOC_CS));
debug("ok\n");
}
#endif
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