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-rw-r--r--syslxmod.c194
1 files changed, 121 insertions, 73 deletions
diff --git a/syslxmod.c b/syslxmod.c
index 9a1087e9..8599625a 100644
--- a/syslxmod.c
+++ b/syslxmod.c
@@ -20,48 +20,74 @@
#include <stdio.h>
#include <inttypes.h>
#include <string.h>
+#include <stddef.h>
#include "syslinux.h"
#define LDLINUX_MAGIC 0x3eb202fe
enum bs_offsets {
- bsJump = 0x00,
- bsOemName = 0x03,
- bsBytesPerSec = 0x0b,
- bsSecPerClust = 0x0d,
- bsResSectors = 0x0e,
- bsFATs = 0x10,
- bsRootDirEnts = 0x11,
- bsSectors = 0x13,
- bsMedia = 0x15,
- bsFATsecs = 0x16,
- bsSecPerTrack = 0x18,
- bsHeads = 0x1a,
- bsHiddenSecs = 0x1c,
- bsHugeSectors = 0x20,
- bsDriveNumber = 0x24,
- bsReserved1 = 0x25,
- bsBootSignature = 0x26,
- bsVolumeID = 0x27,
- bsVolumeLabel = 0x2b,
- bsFileSysType = 0x36,
- bsCode = 0x3e,
+ bsJump = 0x00,
+ bsOemName = 0x03,
+ bsBytesPerSec = 0x0b,
+ bsSecPerClust = 0x0d,
+ bsResSectors = 0x0e,
+ bsFATs = 0x10,
+ bsRootDirEnts = 0x11,
+ bsSectors = 0x13,
+ bsMedia = 0x15,
+ bsFATsecs = 0x16,
+ bsSecPerTrack = 0x18,
+ bsHeads = 0x1a,
+ bsHiddenSecs = 0x1c,
+ bsHugeSectors = 0x20,
+
+ /* FAT12/16 only */
+ bs16DriveNumber = 0x24,
+ bs16Reserved1 = 0x25,
+ bs16BootSignature = 0x26,
+ bs16VolumeID = 0x27,
+ bs16VolumeLabel = 0x2b,
+ bs16FileSysType = 0x36,
+ bs16Code = 0x3e,
+
+ /* FAT32 only */
+ bs32FATSz32 = 36,
+ bs32ExtFlags = 40,
+ bs32FSVer = 42,
+ bs32RootClus = 44,
+ bs32FSInfo = 48,
+ bs32BkBootSec = 50,
+ bs32Reserved = 52,
+ bs32DriveNumber = 64,
+ bs32Reserved1 = 65,
+ bs32BootSignature = 66,
+ bs32VolumeID = 67,
+ bs32VolumeLabel = 71,
+ bs32FileSysType = 82,
+ bs32Code = 90,
+
bsSignature = 0x1fe
};
#define bsHead bsJump
#define bsHeadLen (bsOemName-bsHead)
-#define bsCodeLen (bsSignature-bsCode)
+#define bsCode bs32Code /* The common safe choice */
+#define bsCodeLen (bsSignature-bs32Code)
/*
* Access functions for littleendian numbers, possibly misaligned.
*/
+static inline uint8_t get_8(const unsigned char *p)
+{
+ return *(const uint8_t *)p;
+}
+
static inline uint16_t get_16(const unsigned char *p)
{
#if defined(__i386__) || defined(__x86_64__)
/* Littleendian and unaligned-capable */
- return *(uint16_t *)p;
+ return *(const uint16_t *)p;
#else
return (uint16_t)p[0] + ((uint16_t)p[1] << 8);
#endif
@@ -71,7 +97,7 @@ static inline uint32_t get_32(const unsigned char *p)
{
#if defined(__i386__) || defined(__x86_64__)
/* Littleendian and unaligned-capable */
- return *(uint32_t *)p;
+ return *(const uint32_t *)p;
#else
return (uint32_t)p[0] + ((uint32_t)p[1] << 8) +
((uint32_t)p[2] << 16) + ((uint32_t)p[3] << 24);
@@ -119,65 +145,87 @@ void syslinux_make_bootsect(void *bs)
/*
* Check to see that what we got was indeed an MS-DOS boot sector/superblock;
- * Return 0 if bad and 1 if OK.
+ * Return NULL if OK and otherwise an error message;
*/
-int syslinux_check_bootsect(const void *bs, const char **errmsg)
+const char *syslinux_check_bootsect(const void *bs)
{
int veryold;
- unsigned int sectors, clusters;
+ int sectorsize;
+ long long sectors, fatsectors, dsectors;
+ long long clusters;
+ int rootdirents, clustersize;
const unsigned char *sectbuf = bs;
- *errmsg = 0;
-
- /*** FIX: Handle FAT32 ***/
+ veryold = 0;
- if ( sectbuf[bsBootSignature] == 0x29 ) {
- /* It's DOS, and it has all the new nice fields */
-
- veryold = 0;
-
- sectors = get_16(sectbuf+bsSectors);
- sectors = sectors ? sectors : get_32(sectbuf+bsHugeSectors);
- clusters = sectors / sectbuf[bsSecPerClust];
-
- if ( !memcmp(sectbuf+bsFileSysType, "FAT12 ", 8) ) {
- if ( clusters > 4086 ) {
- *errmsg = "FAT12 but claims more than 4086 clusters";
- return 0;
- }
- } else if ( !memcmp(sectbuf+bsFileSysType, "FAT16 ", 8) ) {
- if ( clusters <= 4086 ) {
- *errmsg = "FAT16 but claims less than 4086 clusters";
- return 0;
+ /* Must be 0xF0 or 0xF8..0xFF */
+ if ( get_8(sectbuf+bsMedia) != 0xF0 &&
+ get_8(sectbuf+bsMedia) < 0xF8 )
+ goto invalid;
+
+ sectorsize = get_16(sectbuf+bsBytesPerSec);
+ if ( sectorsize == 512 )
+ ; /* ok */
+ else if ( sectorsize == 1024 || sectorsize == 2048 || sectorsize == 4096 )
+ return "only 512-byte sectors are supported";
+ else
+ goto invalid;
+
+ clustersize = get_8(sectbuf+bsSecPerClust);
+ if ( clustersize == 0 || (clustersize & (clustersize-1)) )
+ goto invalid; /* Must be nonzero and a power of 2 */
+
+ sectors = get_16(sectbuf+bsSectors);
+ sectors = sectors ? sectors : get_32(sectbuf+bsHugeSectors);
+
+ dsectors = sectors - get_16(sectbuf+bsResSectors);
+
+ fatsectors = get_16(sectbuf+bsFATsecs);
+ fatsectors = fatsectors ? fatsectors : get_32(sectbuf+bs32FATSz32);
+ fatsectors *= get_8(sectbuf+bsFATs);
+ dsectors -= fatsectors;
+
+ rootdirents = get_16(sectbuf+bsRootDirEnts);
+ dsectors -= (rootdirents+sectorsize/32-1)/sectorsize;
+
+ if ( dsectors < 0 || fatsectors == 0 )
+ goto invalid;
+
+ clusters = dsectors/clustersize;
+
+ if ( clusters < 0xFFF5 ) {
+ /* FAT12 or FAT16 */
+
+ if ( !get_16(sectbuf+bsFATsecs) )
+ goto invalid;
+
+ if ( get_8(sectbuf+bs16BootSignature) == 0x29 ) {
+ if ( !memcmp(sectbuf+bs16FileSysType, "FAT12 ", 8) ) {
+ if ( clusters >= 4085 )
+ return "more than 4084 clusters but claims FAT12";
+ } else if ( !memcmp(sectbuf+bs16FileSysType, "FAT16 ", 8) ) {
+ if ( clusters < 4085 )
+ return "less than 4084 clusters but claims FAT16";
+ } else if ( memcmp(sectbuf+bs16FileSysType, "FAT ", 8) ) {
+ static char fserr[] = "filesystem type \"????????\" not supported";
+ memcpy(fserr+17, sectbuf+bs16FileSysType, 8);
+ return fserr;
}
- } else if ( !memcmp(sectbuf+bsFileSysType, "FAT ", 8) ) {
- /* OS/2 sets up the filesystem as just `FAT'. */
- } else {
- static char fserr[] = "filesystem type \"????????\" not supported";
- memcpy(fserr+17, sectbuf+bsFileSysType, 8);
- *errmsg = fserr;
- return 0;
}
+ } else if ( clusters < 0x0FFFFFF5 ) {
+ /* FAT32 */
+ /* Moving the FileSysType and BootSignature was a lovely stroke of M$ idiocy */
+ if ( get_8(sectbuf+bs32BootSignature) != 0x29 ||
+ !memcmp(sectbuf+bs32FileSysType, "FAT32 ", 8) )
+ goto invalid;
} else {
- veryold = 1;
-
- if ( sectbuf[bsSecPerClust] & (sectbuf[bsSecPerClust] - 1) ||
- sectbuf[bsSecPerClust] == 0 ) {
- *errmsg = "this doesn't look like a FAT filesystem";
- return 0;
- }
-
- sectors = get_16(sectbuf+bsSectors);
- sectors = sectors ? sectors : get_32(sectbuf+bsHugeSectors);
- clusters = sectors / sectbuf[bsSecPerClust];
- }
-
- if ( get_16(sectbuf+bsBytesPerSec) != 512 ) {
- *errmsg = "sector sizes other than 512 not supported";
- return 0;
+ goto invalid;
}
+
+ return NULL;
- return 1;
+ invalid:
+ return "this doesn't look like a valid FAT filesystem";
}
/*
@@ -231,6 +279,6 @@ int syslinux_patch(const uint32_t *sectors, int nsectors)
set_32(patcharea+4, csum);
- return 0;
+ return 0;
}