core: handle more than 32K of code for disk-based derivatives

Handle more than 32K worth of code for disk-based derivatives.  We do
this by allowing the sector pointers to overflow past sector 1; this
is OK because we limit a run to be based on only the pointers that we
have read so far.

XXX: This is implemented for EXTLINUX, but breaks SYSLINUX.  Need to
update (and unify!) the SYSLINUX installers to cope.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

2 files changed, 80 insertions, 11 deletions

diff --git a/libinstaller/setadv.c b/libinstaller/setadv.c
index c768d1b1..c57f0974 100644
--- a/libinstaller/setadv.c
+++ b/libinstaller/setadv.c
@@ -36,14 +36,14 @@ static void cleanup_adv(unsigned char *advbuf)
   uint32_t csum;
 
   /* Make sure both copies agree, and update the checksum */
-  set_32(advbuf, ADV_MAGIC1);
+  set_32((uint32_t *)advbuf, ADV_MAGIC1);
 
   csum = ADV_MAGIC2;
   for (i = 8; i < ADV_SIZE-4; i += 4)
-    csum -= get_32(advbuf+i);
+    csum -= get_32((uint32_t *)(advbuf+i));
 
-  set_32(advbuf+4, csum);
-  set_32(advbuf+ADV_SIZE-4, ADV_MAGIC3);
+  set_32((uint32_t *)(advbuf+4), csum);
+  set_32((uint32_t *)(advbuf+ADV_SIZE-4), ADV_MAGIC3);
 
   memcpy(advbuf+ADV_SIZE, advbuf, ADV_SIZE);
 }
@@ -130,12 +130,13 @@ static int adv_consistent(const unsigned char *p)
   int i;
   uint32_t csum;
 
-  if (get_32(p) != ADV_MAGIC1 || get_32(p+ADV_SIZE-4) != ADV_MAGIC3)
+  if (get_32((uint32_t *)p) != ADV_MAGIC1 ||
+      get_32((uint32_t *)(p+ADV_SIZE-4)) != ADV_MAGIC3)
     return 0;
 
   csum = 0;
   for (i = 4; i < ADV_SIZE-4; i += 4)
-    csum += get_32(p+i);
+    csum += get_32((uint32_t *)(p+i));
 
   return csum == ADV_MAGIC2;
 }
diff --git a/libinstaller/syslxint.h b/libinstaller/syslxint.h
index 120026de..3cecf3c0 100644
--- a/libinstaller/syslxint.h
+++ b/libinstaller/syslxint.h
@@ -18,12 +18,12 @@
 /*
  * Access functions for littleendian numbers, possibly misaligned.
  */
-static inline uint8_t get_8(const unsigned char *p)
+static inline uint8_t get_8(const uint8_t *p)
 {
   return *(const uint8_t *)p;
 }
 
-static inline uint16_t get_16(const unsigned char *p)
+static inline uint16_t get_16(const uint16_t *p)
 {
 #if defined(__i386__) || defined(__x86_64__)
   /* Littleendian and unaligned-capable */
@@ -33,7 +33,7 @@ static inline uint16_t get_16(const unsigned char *p)
 #endif
 }
 
-static inline uint32_t get_32(const unsigned char *p)
+static inline uint32_t get_32(const uint32_t *p)
 {
 #if defined(__i386__) || defined(__x86_64__)
   /* Littleendian and unaligned-capable */
@@ -44,7 +44,7 @@ static inline uint32_t get_32(const unsigned char *p)
 #endif
 }
 
-static inline void set_16(unsigned char *p, uint16_t v)
+static inline void set_16(uint16_t *p, uint16_t v)
 {
 #if defined(__i386__) || defined(__x86_64__)
   /* Littleendian and unaligned-capable */
@@ -55,7 +55,7 @@ static inline void set_16(unsigned char *p, uint16_t v)
 #endif
 }
 
-static inline void set_32(unsigned char *p, uint32_t v)
+static inline void set_32(uint32_t *p, uint32_t v)
 {
 #if defined(__i386__) || defined(__x86_64__)
   /* Littleendian and unaligned-capable */
@@ -71,4 +71,72 @@ static inline void set_32(unsigned char *p, uint32_t v)
 #define SECTOR_SHIFT	9	/* 512-byte sectors */
 #define SECTOR_SIZE	(1 << SECTOR_SHIFT)
 
+#define LDLINUX_MAGIC	0x3eb202fe
+
+/* Patch area for disk-based installers */
+struct patch_area {
+  uint32_t magic;		/* LDLINUX_MAGIC */
+  uint32_t instance;		/* Per-version value */
+  uint16_t data_sectors;
+  uint16_t adv_sectors;
+  uint32_t dwords;
+  uint32_t checksum;
+  uint32_t currentdir;
+  uint16_t secptroffset;
+  uint16_t secptrcnt;
+};
+
+  /* FAT bootsector format, also used by other disk-based derivatives */
+struct boot_sector {
+  uint8_t	bsJump[3];
+  char		bsOemName[8];
+  uint16_t	bsBytesPerSec;
+  uint8_t	bsSecPerClust;
+  uint16_t	bsResSectors;
+  uint8_t	bsFATs;
+  uint16_t	bsRootDirEnts;
+  uint16_t	bsSectors;
+  uint8_t	bsMedia;
+  uint16_t	bsFATsecs;
+  uint16_t	bsSecPerTrack;
+  uint16_t	bsHeads;
+  uint32_t	bsHiddenSecs;
+  uint32_t	bsHugeSectors;
+
+  union {
+    struct {
+      uint8_t	DriveNumber;
+      uint8_t	Reserved1;
+      uint8_t	BootSignature;
+      uint32_t	VolumeID;
+      char	VolumeLabel[11];
+      char	FileSysType[8];
+      uint8_t	Code[442];
+    }  __attribute__((packed)) bs16;
+    struct {
+      uint32_t	FATSz32;
+      uint16_t	ExtFlags;
+      uint16_t	FSVer;
+      uint32_t	RootClus;
+      uint16_t	FSInfo;
+      uint16_t	BkBootSec;
+      uint8_t	DriveNumber;
+      uint8_t	Reserved1;
+      uint8_t	BootSignature;
+      uint32_t	VolumeID;
+      char	VolumeLabel[11];
+      char	FileSysType[8];
+      uint8_t	Code[414];
+    } __attribute__((packed)) bs32;
+  } __attribute__((packed));
+
+  uint32_t	NextSector;	/* Pointer to the first unused sector */
+  uint16_t	MaxTransfer;	/* Max sectors per transfer */
+  uint16_t	bsSignature;
+} __attribute__((packed));
+
+#define bsHead      bsJump
+#define bsHeadLen   offsetof(struct boot_sector, bsJump)
+#define bsCode	    bs32.Code	/* The common safe choice */
+
 #endif /* SYSLXINT_H */