Skip to content

Commit

Permalink
Use an option rom instead of boot sector for -kernel
Browse files Browse the repository at this point in the history 
Generate an option rom instead of using a hijacked boot sector for kernel
booting.  This just requires adding a small option ROM header and a few more
instructions to the boot sector to take over the int19 vector and run our
boot code.

A disk is no longer needed when using -kernel on x86.

Signed-off-by: Anthony Liguori <[email protected]>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5650 c046a42c-6fe2-441c-8c8c-71466251a162
  • Loading branch information
aliguori committed Nov 8, 2008
1 parent 6223246 commit 4fc9af5
Show file tree
Hide file tree
Showing 4 changed files with 50 additions and 58 deletions.
32 changes: 0 additions & 32 deletions block.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -527,14 +527,6 @@ int bdrv_read(BlockDriverState *bs, int64_t sector_num,
if (!drv)
return -ENOMEDIUM;

if (sector_num == 0 && bs->boot_sector_enabled && nb_sectors > 0) {
memcpy(buf, bs->boot_sector_data, 512);
sector_num++;
nb_sectors--;
buf += 512;
if (nb_sectors == 0)
return 0;
}
if (drv->bdrv_pread) {
int ret, len;
len = nb_sectors * 512;
Expand Down Expand Up @@ -567,9 +559,6 @@ int bdrv_write(BlockDriverState *bs, int64_t sector_num,
return -ENOMEDIUM;
if (bs->read_only)
return -EACCES;
if (sector_num == 0 && bs->boot_sector_enabled && nb_sectors > 0) {
memcpy(bs->boot_sector_data, buf, 512);
}
if (drv->bdrv_pwrite) {
int ret, len;
len = nb_sectors * 512;
Expand Down Expand Up @@ -750,16 +739,6 @@ void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr)
*nb_sectors_ptr = length;
}

/* force a given boot sector. */
void bdrv_set_boot_sector(BlockDriverState *bs, const uint8_t *data, int size)
{
bs->boot_sector_enabled = 1;
if (size > 512)
size = 512;
memcpy(bs->boot_sector_data, data, size);
memset(bs->boot_sector_data + size, 0, 512 - size);
}

void bdrv_set_geometry_hint(BlockDriverState *bs,
int cyls, int heads, int secs)
{
Expand Down Expand Up @@ -1155,14 +1134,6 @@ BlockDriverAIOCB *bdrv_aio_read(BlockDriverState *bs, int64_t sector_num,
if (!drv)
return NULL;

/* XXX: we assume that nb_sectors == 0 is suppored by the async read */
if (sector_num == 0 && bs->boot_sector_enabled && nb_sectors > 0) {
memcpy(buf, bs->boot_sector_data, 512);
sector_num++;
nb_sectors--;
buf += 512;
}

ret = drv->bdrv_aio_read(bs, sector_num, buf, nb_sectors, cb, opaque);

if (ret) {
Expand All @@ -1185,9 +1156,6 @@ BlockDriverAIOCB *bdrv_aio_write(BlockDriverState *bs, int64_t sector_num,
return NULL;
if (bs->read_only)
return NULL;
if (sector_num == 0 && bs->boot_sector_enabled && nb_sectors > 0) {
memcpy(bs->boot_sector_data, buf, 512);
}

ret = drv->bdrv_aio_write(bs, sector_num, buf, nb_sectors, cb, opaque);

Expand Down
1 change: 0 additions & 1 deletion block.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -79,7 +79,6 @@ int bdrv_truncate(BlockDriverState *bs, int64_t offset);
int64_t bdrv_getlength(BlockDriverState *bs);
void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr);
int bdrv_commit(BlockDriverState *bs);
void bdrv_set_boot_sector(BlockDriverState *bs, const uint8_t *data, int size);
/* async block I/O */
typedef struct BlockDriverAIOCB BlockDriverAIOCB;
typedef void BlockDriverCompletionFunc(void *opaque, int ret);
Expand Down
3 changes: 0 additions & 3 deletions block_int.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -104,9 +104,6 @@ struct BlockDriverState {
BlockDriver *drv; /* NULL means no media */
void *opaque;

int boot_sector_enabled;
uint8_t boot_sector_data[512];

char filename[1024];
char backing_file[1024]; /* if non zero, the image is a diff of
this file image */
Expand Down
72 changes: 50 additions & 22 deletions hw/pc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -438,30 +438,45 @@ static void bochs_bios_init(void)

/* Generate an initial boot sector which sets state and jump to
a specified vector */
static void generate_bootsect(uint32_t gpr[8], uint16_t segs[6], uint16_t ip)
static void generate_bootsect(uint8_t *option_rom,
uint32_t gpr[8], uint16_t segs[6], uint16_t ip)
{
uint8_t bootsect[512], *p;
uint8_t rom[512], *p, *reloc;
uint8_t sum;
int i;
int hda;

hda = drive_get_index(IF_IDE, 0, 0);
if (hda == -1) {
fprintf(stderr, "A disk image must be given for 'hda' when booting "
"a Linux kernel\n(if you really don't want it, use /dev/zero)\n");
exit(1);
}
memset(rom, 0, sizeof(rom));

p = rom;
/* Make sure we have an option rom signature */
*p++ = 0x55;
*p++ = 0xaa;

memset(bootsect, 0, sizeof(bootsect));
/* ROM size in sectors*/
*p++ = 1;

/* Copy the MSDOS partition table if possible */
bdrv_read(drives_table[hda].bdrv, 0, bootsect, 1);
/* Hook int19 */

/* Make sure we have a partition signature */
bootsect[510] = 0x55;
bootsect[511] = 0xaa;
*p++ = 0x50; /* push ax */
*p++ = 0x1e; /* push ds */
*p++ = 0x31; *p++ = 0xc0; /* xor ax, ax */
*p++ = 0x8e; *p++ = 0xd8; /* mov ax, ds */

*p++ = 0xc7; *p++ = 0x06; /* movvw _start,0x64 */
*p++ = 0x64; *p++ = 0x00;
reloc = p;
*p++ = 0x00; *p++ = 0x00;

*p++ = 0x8c; *p++ = 0x0e; /* mov cs,0x66 */
*p++ = 0x66; *p++ = 0x00;

*p++ = 0x1f; /* pop ds */
*p++ = 0x58; /* pop ax */
*p++ = 0xcb; /* lret */

/* Actual code */
p = bootsect;
*reloc = (p - rom);

*p++ = 0xfa; /* CLI */
*p++ = 0xfc; /* CLD */

Expand Down Expand Up @@ -491,7 +506,13 @@ static void generate_bootsect(uint32_t gpr[8], uint16_t segs[6], uint16_t ip)
*p++ = segs[1]; /* CS */
*p++ = segs[1] >> 8;

bdrv_set_boot_sector(drives_table[hda].bdrv, bootsect, sizeof(bootsect));
/* sign rom */
sum = 0;
for (i = 0; i < (sizeof(rom) - 1); i++)
sum += rom[i];
rom[sizeof(rom) - 1] = -sum;

memcpy(option_rom, rom, sizeof(rom));
}

static long get_file_size(FILE *f)
Expand All @@ -508,7 +529,8 @@ static long get_file_size(FILE *f)
return size;
}

static void load_linux(const char *kernel_filename,
static void load_linux(uint8_t *option_rom,
const char *kernel_filename,
const char *initrd_filename,
const char *kernel_cmdline)
{
Expand Down Expand Up @@ -658,7 +680,7 @@ static void load_linux(const char *kernel_filename,
memset(gpr, 0, sizeof gpr);
gpr[4] = cmdline_addr-real_addr-16; /* SP (-16 is paranoia) */

generate_bootsect(gpr, seg, 0);
generate_bootsect(option_rom, gpr, seg, 0);
}

static void main_cpu_reset(void *opaque)
Expand Down Expand Up @@ -862,6 +884,15 @@ static void pc_init1(ram_addr_t ram_size, int vga_ram_size,
int size, offset;

offset = 0;
if (linux_boot) {
option_rom_offset = qemu_ram_alloc(TARGET_PAGE_SIZE);
load_linux(phys_ram_base + option_rom_offset,
kernel_filename, initrd_filename, kernel_cmdline);
cpu_register_physical_memory(0xd0000, TARGET_PAGE_SIZE,
option_rom_offset | IO_MEM_ROM);
offset = TARGET_PAGE_SIZE;
}

for (i = 0; i < nb_option_roms; i++) {
size = get_image_size(option_rom[i]);
if (size < 0) {
Expand Down Expand Up @@ -891,9 +922,6 @@ static void pc_init1(ram_addr_t ram_size, int vga_ram_size,

bochs_bios_init();

if (linux_boot)
load_linux(kernel_filename, initrd_filename, kernel_cmdline);

cpu_irq = qemu_allocate_irqs(pic_irq_request, NULL, 1);
i8259 = i8259_init(cpu_irq[0]);
ferr_irq = i8259[13];
Expand Down

0 comments on commit 4fc9af5

Please sign in to comment.