[boot] Stamp start sector offset into boot sector for MBR boots

bootblocks/boot_sect.S

@@ -68,21 +68,6 @@ floppy_table:
 
 entry1:
 #endif
-
-	// instructions through _next0 not needed for floppy, only MBR boot
-	cld
-	cmp $0x4c65,%ax			// coming from ELKS MBR?
-	jnz _next0
-	mov 8(%si),%ax			// get MBR start sector from partion table at DS:SI
-	mov 10(%si),%si
-	push %cs
-	pop %es
-	mov $BOOTADDR+sect_offset,%di
-	stosw
-	xchg %ax,%si
-	stosw
-_next0:
-
 	// Get the memory size
 	// TODO: optional BIOS INT 12h
 
@@ -559,16 +544,17 @@ msg_error:
 msg_reboot:
 	.asciz "Press key\r\n"
 
+	.global end_of_code
+end_of_code:
+//------------------------------------------------------------------------------
+
 #ifndef BOOT_FAT
+	.org 0x1F3              // Fixed address of sect_offset for MINIX boot sector
 	.global sect_offset
 sect_offset:
 	.long 0
 #endif
 
-	.global last_code
-last_code:
-//------------------------------------------------------------------------------
-
 // ELKS disk parameter structure
 // For future expansion, fields should be added at the _front_ of structure
 

bootblocks/mbr.S

@@ -110,7 +110,6 @@ sector_loaded:
 
 	mov	drive_num,%dh	// Restore DH drive number for VBR
 	mov	%si,%bp		// LILO says some BBs use bp rather than si
-	mov	$0x4c65,%ax	// 'eL' ELKS magic number
 
 	ljmp	$0,$BOOTADDR	// Jump to VBR boot sector
 

elks/tools/setboot/setboot.c

@@ -3,7 +3,7 @@
  *
  * 7 Feb 2020 Greg Haerr <[email protected]>
  *
- * Usage: setboot <image> [-F] [-{B,P}<sectors>,<heads>[,<tracks>]] [<input_boot_sector>]
+ * Usage: setboot <image> [-F] [-S{m,f}] [-{B,P}<sectors>,<heads>[,<tracks>]] [<input_boot_sector>]
  *
  *	setboot writes image after optionally reading an input boot sector and
  *		optionally modifying boot sector disk parameters passed as parameters.
@@ -33,11 +33,18 @@
 #define ELKS_BPB_SecPerTrk	0x1F9		/* offset of sectors per track (byte)*/
 #define ELKS_BPB_NumHeads	0x1FA		/* offset of number of heads (byte)*/
 
+/* MINIX-only offsets*/
+#define MINIX_SectOffset	0x1F3		/* offset of partition start sector (long)*/
+
 /* FAT BPB start and end offsets*/
 #define FATBPB_START	11				/* start at bytes per sector*/
 #define FATBPB_END		61				/* through end of file system type*/
 
+/* FAT-only offsets*/
+#define FAT_BPB_SectOffset	0x1C		/* offset of partition start sector (long) */
+
 static unsigned int SecPerTrk, NumHeads, NumTracks;
+static unsigned long StartSector;
 
 struct partition
 {
@@ -75,6 +82,7 @@ static void writePartition(unsigned char *buf)
 	p->cyl = 0;
 	p->start_sect = 1;			/* zero-relative start sector here*/
 #endif
+	StartSector = p->start_sect;
 	p->sys_ind = 0x80;			/* ELKS, Old Minix*/
 	p->end_head = NumHeads;
 	p->end_sector = SecPerTrk | ((NumTracks >> 2) & 0xc0);
@@ -141,12 +149,14 @@ int main(int argc,char **argv)
 	int opt_new_bootsect = 0, opt_updatebpb = 0;
 	int opt_skipfatbpb = 0;
 	int opt_writepartitiontable = 0;
+	int opt_update_start_sector_minix = 0;
+	int opt_update_start_sector_fat = 0;
 	char *outfile, *infile = NULL;
 	unsigned char blk[SECT_SIZE*2];
 	unsigned char inblk[SECT_SIZE];
 
 	if (argc != 3 && argc != 4 && argc != 5)
-		fatalmsg("Usage: %s <image> [-F] [-{B,P}<sectors>,<heads>[,<tracks>]] [<input_boot_image>]\n", argv[0]);
+		fatalmsg("Usage: %s <image> [-F] [-S{m,f}] [-{B,P}<sectors>,<heads>[,<tracks>]] [<input_boot_image>]\n", argv[0]);
 
 	outfile = *++argv; argc--;
 
@@ -181,6 +191,13 @@ int main(int argc,char **argv)
 			argv++;
 			argc--;
 		}
+		else if (argv[1][1] == 'S') {	/* update start sector in ELKS boot sector*/
+			if (argv[1][2] == 'm') opt_update_start_sector_minix = 1;
+			if (argv[1][2] == 'f') opt_update_start_sector_fat = 1;
+			printf("Updating start sector in ELKS boot sector\n");
+			argv++;
+			argc--;
+		}
 	}
 	if (argc == 2) {			/* new boot sector specified*/
 		infile = *++argv;
@@ -241,6 +258,34 @@ int main(int argc,char **argv)
 			fprintf(stderr, "Warning: '%s' may not be valid bootable sector\n", infile);
 
 		if (fwrite(blk,1,count,ofp) != count) die("fwrite(%s)", infile);
+
+		if (opt_update_start_sector_minix || opt_update_start_sector_fat) {
+			if (fseek(ofp, StartSector * SECT_SIZE, SEEK_SET) != 0)
+				die("fseek(%s)", outfile);
+
+			count = fread(blk,1,SECT_SIZE,ofp);
+			if (count != SECT_SIZE)
+				die("fread(%s)", outfile);
+
+			if (opt_update_start_sector_minix) {
+				blk[MINIX_SectOffset] = (unsigned char)StartSector;
+				blk[MINIX_SectOffset+1] = (unsigned char)(StartSector >> 8);
+				blk[MINIX_SectOffset+2] = (unsigned char)(StartSector >> 16);
+				blk[MINIX_SectOffset+3] = (unsigned char)(StartSector >> 24);
+			}
+			if (opt_update_start_sector_fat) {
+				blk[FAT_BPB_SectOffset] = (unsigned char)StartSector;
+				blk[FAT_BPB_SectOffset+1] = (unsigned char)(StartSector >> 8);
+				blk[FAT_BPB_SectOffset+2] = (unsigned char)(StartSector >> 16);
+				blk[FAT_BPB_SectOffset+3] = (unsigned char)(StartSector >> 24);
+			}
+
+			if (fseek(ofp, StartSector * SECT_SIZE, SEEK_SET) != 0)
+				die("fseek(%s)", outfile);
+			if (fwrite(blk,1,SECT_SIZE,ofp) != SECT_SIZE)
+				die("fwrite(%s)", outfile);
+		}
+
 		fclose(ofp);
 		fclose(ifp);
 	} else {			/* perform BPB update only on existing boot block*/

elkscmd/sys_utils/makeboot.c

@@ -37,8 +37,8 @@
 #define ELKS_BPB_SecPerTrk	0x1F9		/* offset of sectors per track (byte)*/
 #define ELKS_BPB_NumHeads	0x1FA		/* offset of number of heads (byte)*/
 
-/* MINIX-only offsets, FIXME - SectOffset not yet standard*/
-#define MINIX_SectOffset	0x1B5		/* offset of partition start sector FIXME */
+/* MINIX-only offsets*/
+#define MINIX_SectOffset	0x1F3		/* offset of partition start sector (long)*/
 
 /* FAT BPB start and end offsets*/
 #define FATBPB_START	11				/* start at bytes per sector*/
@@ -332,17 +332,13 @@ int main(int ac, char **av)
 		return -1;
 	}
 	close(fd);
-//sync();
-//return 0;
 
-	if (mkdir(MOUNTDIR, 0777) < 0) {
-		fprintf(stderr, "Can't create temp mount point %s\n", MOUNTDIR);
-		return -1;
-	}
+	if (mkdir(MOUNTDIR, 0777) < 0)
+		fprintf(stderr, "Can't create temp mount point %s, may already exist\n", MOUNTDIR);
+
 	if (mount(targetdevice, MOUNTDIR, fstype, 0) < 0) {
 		fprintf(stderr, "Can't mount %s on %s\n", targetdevice, MOUNTDIR);
-		rmdir(MOUNTDIR);
-		return -1;
+		goto errout2;
 	}
 	if (!copyfile(SYSFILE1, MOUNTDIR SYSFILE1, 1)) {
 		fprintf(stderr, "Error copying %s\n", SYSFILE1);
@@ -360,11 +356,14 @@ int main(int ac, char **av)
 	if (umount(targetdevice) < 0)
 		fprintf(stderr, "Unmount error\n");
 	rmdir(MOUNTDIR);
+	sync();
 
 	return fstype;		/* return filesystem type (1=MINIX, 2=FAT */
 
 errout:
 	umount(targetdevice);
+errout2:
 	rmdir(MOUNTDIR);
-	return 0;
+	sync();
+	return -1;
 }

image/Makefile

@@ -138,11 +138,11 @@ hd32-fat:
 # MBR images
 hd32mbr-minix:
 	dd if=/dev/zero bs=512 count=63 | cat - hd32-minix.bin > hd32mbr-minix.bin
-	setboot hd32mbr-minix.bin -P63,16,63 $(HD_MBR_BOOT)
+	setboot hd32mbr-minix.bin -P63,16,63 -Sm $(HD_MBR_BOOT)
 
 hd32mbr-fat:
 	dd if=/dev/zero bs=512 count=63 | cat - hd32-fat.bin > hd32mbr-fat.bin
-	setboot hd32mbr-fat.bin -P63,16,63 $(HD_MBR_BOOT)
+	setboot hd32mbr-fat.bin -P63,16,63 -Sf $(HD_MBR_BOOT)
 
 # Clean target