Merge pull request #2084 from ghaerr/mbr

[boot] Fix bad MBR partition generated by setboot
ghaerr · Oct 21, 2024 · 1bcdc74 · 1bcdc74
2 parents eddf88b + 4febb81
commit 1bcdc74
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Showing 3 changed files with 10 additions and 8 deletions.
diff --git a/elks/tools/setboot/setboot.c b/elks/tools/setboot/setboot.c
@@ -78,17 +78,19 @@ static void writePartition(unsigned char *buf)
 	p->sector = 1;				/* next cylinder after MBR, standard*/
 	p->cyl = 0;
 	p->start_sect = NumTracks;	/* zero-relative start sector here*/
+	nr_sects -= SecPerTrk;
 #else
 	p->head = 0;
 	p->sector = 2;				/* next sector after MBR, non-standard*/
 	p->cyl = 0;
 	p->start_sect = 1;			/* zero-relative start sector here*/
+	nr_sects -= 1;
 #endif
 	StartSector = p->start_sect;
 	p->sys_ind = 0x80;			/* ELKS, Old Minix*/
 	p->end_head = NumHeads;
-	p->end_sector = SecPerTrk | ((NumTracks >> 2) & 0xc0);
-	p->end_cyl = NumTracks & 0xff;
+	p->end_sector = SecPerTrk | (((NumTracks-1) >> 2) & 0xc0);
+	p->end_cyl = (NumTracks-1) & 0xff;
 	p->start_sect_hi = 0;
 	p->nr_sects = nr_sects & 0xffff;
 	p->nr_sects_hi = nr_sects >> 16;

diff --git a/elkscmd/disk_utils/fdisk.c b/elkscmd/disk_utils/fdisk.c
@@ -164,8 +164,8 @@ void add_part(void)
     oset = MBR + PARTITION_START + ((part - 1) * 16);
 
     printf("Total cylinders: %d\n", geometry.cylinders);
-    for (scyl = geometry.cylinders + 1; scyl < 0 || scyl > geometry.cylinders;) {
-        printf("First cylinder (%d-%d): ", 0, geometry.cylinders);
+    for (scyl = geometry.cylinders; scyl < 0 || scyl > geometry.cylinders-1;) {
+        printf("First cylinder (%d-%d): ", 0, geometry.cylinders-1);
         fflush(stdout);
         fgets(buf, 31, stdin);
         scyl = atoi(buf);
@@ -185,8 +185,8 @@ void add_part(void)
     p.cyl       = (scyl & 0xff);
     p.sys_ind   = PARTITION_TYPE;
 
-    for (ecyl = geometry.cylinders + 1; ecyl < scyl || ecyl > geometry.cylinders;) {
-        printf("Ending cylinder (%d-%d): ", 0, geometry.cylinders);
+    for (ecyl = geometry.cylinders; ecyl < scyl || ecyl > geometry.cylinders-1;) {
+        printf("Ending cylinder (%d-%d): ", 0, geometry.cylinders-1);
         fflush(stdout);
         fgets(buf, 31, stdin);
         ecyl = atoi(buf);

diff --git a/image/Makefile b/image/Makefile
@@ -202,11 +202,11 @@ hd32-fat:
 	rm Config
 
 # MBR images
-hd32mbr-minix:
+hd32mbr-minix: hd32-minix
 	dd if=/dev/zero bs=512 count=63 | cat - hd32-minix.img > hd32mbr-minix.img
 	setboot hd32mbr-minix.img -P63,16,63 -Sm $(HD_MBR_BOOT)
 
-hd32mbr-fat:
+hd32mbr-fat: hd32-fat
 	dd if=/dev/zero bs=512 count=63 | cat - hd32-fat.img > hd32mbr-fat.img
 	setboot hd32mbr-fat.img -P63,16,63 -Sf $(HD_MBR_BOOT)