/*
* Generate sector extents
*/
static void generate_extents(struct syslinux_extent _slimg *ex, int nptrs,
const sector_t *sectp, int nsect)
{
uint32_t addr = 0x8000; /* ldlinux.sys starts loading here */
uint32_t base;
sector_t sect, lba;
unsigned int len;
base = addr;
len = 0;
lba = 0;
memset_sl(ex, 0, nptrs * sizeof *ex);
while (nsect) {
sect = *sectp++;
if (len) {
uint32_t xbytes = (len + 1) * SECTOR_SIZE;
if (sect == lba + len && xbytes < 65536 &&
((addr ^ (base + xbytes - 1)) & 0xffff0000) == 0) {
/* We can add to the current extent */
len++;
goto next;
}
set_64_sl(&ex->lba, lba);
set_16_sl(&ex->len, len);
ex++;
}
base = addr;
lba = sect;
len = 1;
next:
addr += SECTOR_SIZE;
nsect--;
}
if (len) {
set_64_sl(&ex->lba, lba);
set_16_sl(&ex->len, len);
ex++;
}
}
/*
* This patches the boot sector and the beginning of ldlinux.sys
* based on an ldlinux.sys sector map passed in. Typically this is
* handled by writing ldlinux.sys, mapping it, and then overwrite it
* with the patched version. If this isn't safe to do because of
* an OS which does block reallocation, then overwrite it with
* direct access since the location is known.
*
* Returns the number of modified bytes in ldlinux.sys if successful,
* otherwise -1.
*/
int syslinux_patch(const sector_t *sectp, int nsectors,
int stupid, int raid_mode,
const char *subdir, const char *subvol)
{
struct patch_area *patcharea;
struct ext_patch_area *epa;
struct syslinux_extent *ex;
uint32_t *wp;
int nsect = ((boot_image_len + SECTOR_SIZE - 1) >> SECTOR_SHIFT) + 2;
uint32_t csum;
int i, dw, nptrs;
struct fat_boot_sector *sbs = (struct fat_boot_sector *)boot_sector;
uint64_t *advptrs;
if (nsectors < nsect)
return -1; /* The actual file is too small for content */
/* Search for LDLINUX_MAGIC to find the patch area */
for (wp = (uint32_t *)boot_image; get_32_sl(wp) != LDLINUX_MAGIC;
wp++)
;
patcharea = (struct patch_area *)wp;
epa = ptr(boot_image, &patcharea->epaoffset);
/* First sector need pointer in boot sector */
set_32(ptr(sbs, &epa->sect1ptr0), sectp[0]);
set_32(ptr(sbs, &epa->sect1ptr1), sectp[0] >> 32);
sectp++;
/* Handle RAID mode */
if (raid_mode) {
/* Patch in INT 18h = CD 18 */
set_16(ptr(sbs, &epa->raidpatch), 0x18CD);
}
/* Set up the totals */
dw = boot_image_len >> 2; /* COMPLETE dwords, excluding ADV */
set_16_sl(&patcharea->data_sectors, nsect - 2); /* Not including ADVs */
set_16_sl(&patcharea->adv_sectors, 2); /* ADVs need 2 sectors */
set_32_sl(&patcharea->dwords, dw);
/* Handle Stupid mode */
if (stupid) {
/* Access only one sector at a time */
set_16_sl(&patcharea->maxtransfer, 1);
}
/* Set the sector extents */
ex = ptr(boot_image, &epa->secptroffset);
nptrs = get_16_sl(&epa->secptrcnt);
if (nsect > nptrs) {
/* Not necessarily an error in this case, but a general problem */
fprintf(stderr, "Insufficient extent space, build error!\n");
exit(1);
}
/* -1 for the pointer in the boot sector, -2 for the two ADVs */
generate_extents(ex, nptrs, sectp, nsect-1-2);
/* ADV pointers */
advptrs = ptr(boot_image, &epa->advptroffset);
set_64_sl(&advptrs[0], sectp[nsect-1-2]);
set_64_sl(&advptrs[1], sectp[nsect-1-1]);
/* Poke in the base directory path */
if (subdir) {
int sublen = strlen(subdir) + 1;
if (get_16_sl(&epa->dirlen) < sublen) {
fprintf(stderr, "Subdirectory path too long... aborting install!\n");
exit(1);
}
memcpy_to_sl(ptr(boot_image, &epa->diroffset), subdir, sublen);
}
/* Poke in the subvolume information */
if (subvol) {
int sublen = strlen(subvol) + 1;
if (get_16_sl(&epa->subvollen) < sublen) {
fprintf(stderr, "Subvol name too long... aborting install!\n");
exit(1);
}
memcpy_to_sl(ptr(boot_image, &epa->subvoloffset), subvol, sublen);
}
/* Now produce a checksum */
set_32_sl(&patcharea->checksum, 0);
csum = LDLINUX_MAGIC;
for (i = 0, wp = (uint32_t *)boot_image; i < dw; i++, wp++)
csum -= get_32_sl(wp); /* Negative checksum */
set_32_sl(&patcharea->checksum, csum);
/*
* Assume all bytes modified. This can be optimized at the expense
* of keeping track of what the highest modified address ever was.
*/
return dw << 2;
}
