Attachment 294617 Details for Bug 432441 – Backport relevant changes from parted-1.8

[patch] Backport relevant changes from parted-1.8

parted-1.6.19-msdos-geom.patch (text/plain), 2.76 KB, created by Brad Hinson on 2008-02-12 02:02:57 UTC

(hide)

Description:

Filename:

MIME Type:

Creator: Brad Hinson

Created: 2008-02-12 02:02:57 UTC

Size: 2.76 KB

patch

obsolete

>--- parted-1.6.19/libparted/disk_dos.c.orig
>+++ parted-1.6.19/libparted/disk_dos.c
>@@ -158,6 +158,9 @@
> 
> 	PED_ASSERT (dev != NULL, return 0);
> 
>+	if (dev->sector_size != 512)
>+		return 0;
>+
> 	if (!ped_device_read (dev, &part_table, 0, 1))
> 		return 0;
> 
>@@ -484,6 +487,7 @@
> 	RawCHS* end_chs;
> 	PedSector c, h, s, a, a_;	/* start */
> 	PedSector C, H, S, A, A_;	/* end */
>+	PedSector dont_overflow, denum;
> 	PedSector cyl_size, head_size;
> 	PedSector cylinders, heads, sectors;
> 
>@@ -514,7 +518,12 @@
> 		return 0;
> 	if (c > C)
> 		return 0;
>-	if (A > MAX_CHS_CYLINDER * 255 * 63)
>+
>+	/* If no geometry is feasible, then don't even bother.
>+	 * Useful for eliminating assertions for broken partition
>+	 * tables generated by Norton Ghost et al.
>+	 */
>+	if (A > (C+1) * 255 * 63)
> 		return 0;
> 
> 	/* Not enough information.  In theory, we can do better.  Should we? */
>@@ -523,34 +532,45 @@
> 	if (C == 0)
> 		return 0;
> 
>-	/* STEP ONE: find cyl_size */
>-	if (h == 0 && c > 0) {
>-		/* If the matrix looks like this, then it's easy!
>-		 * [ c 0 ]
>-		 * [ C H ]
>-		 */
>-		cyl_size = a_ / c;
>-	} else if (h > 0) {
>-		/* if h > 0, we can do R2 -> R2 - H/h R1 to get:
>-		 *
>-		 * [ c h ] = [ a_ ]
>-		 * [ X 0 ] = [ Y ]
>-		 *
>-		 * Then, cyl_size = Y / X
>-		 *
>-		 * However, if H/h isn't an integer, this isn't going
>-		 * to work out nicely, so the partition table must
>-		 * be inconsistent.
>-		 */
>-		if (H % h != 0)
>-			return 0;
>-		if (C == H/h * c)
>-			return 0;
>-		cyl_size = (A_ - H/h * a_) / (C - H/h * c);
>-	} else {
>-		/* h == 0 && c == 0: not enough information */
>+	/* Calculate the maximum number that can be multiplied by
>+	 * any head count without overflowing a PedSector
>+	 * 2^8 = 256, 8 bits + 1(sign bit) = 9
>+	 */
>+	dont_overflow = 1;
>+	dont_overflow <<= (8*sizeof(dont_overflow)) - 9;
>+	dont_overflow--;
>+
>+	if (a_ > dont_overflow || A_ > dont_overflow)
>+		return 0;
>+
>+	/* The matrix is solved by :
>+	 *
>+	 * [ c h | a_]                  R1
>+	 * [ C H | A_]                  R2
>+	 *
>+	 * (cH - Ch) cyl_size = a_H - A_h               H R1 - h R2
>+	 * => (if cH - Ch != 0) cyl_size = (a_H - A_h) / (cH - Ch)
>+	 *
>+	 * (Hc - hC) head_size = A_c - a_C              c R2 - C R1
>+	 * => (if cH - Ch != 0) head_size = (A_c - a_C) / (cH - Ch)
>+	 *
>+	 *   But this calculation of head_size would need
>+	 *   not overflowing A_c or a_C
>+	 *   So substitution is use instead, to minimize dimension
>+	 *   of temporary results :
>+	 *
>+	 * If h != 0 : head_size = ( a_ - c cyl_size ) / h
>+	 * If H != 0 : head_size = ( A_ - C cyl_size ) / H
>+	 *
>+	 */
>+	denum = c * H - C * h;
>+	if (denum == 0)
>+		return 0;
>+
>+	cyl_size = (a_*H - A_*h) / denum;
>+	/* Check for non integer result */
>+	if (cyl_size * denum != a_*H - A_*h)
> 		return 0;
>-	}
> 
> 	PED_ASSERT (cyl_size > 0, return 0);
>  	PED_ASSERT (cyl_size <= 255 * 63, return 0);

Actions: View | Diff

Attachments on bug 432441: 294617 | 294698