[src/netbsd-1-4]: src/sbin/fdisk/mbr pullup 1.3->1.6 (fvdl)

[perry <perry%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/d1dd5e761049
branches:  netbsd-1-4
changeset: 468609:d1dd5e761049
user:      perry <perry%NetBSD.org@localhost>
date:      Sun May 02 21:30:36 1999 +0000

description:
pullup 1.3->1.6 (fvdl)

diffstat:

 sbin/fdisk/mbr/mbr.S |  100 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 97 insertions(+), 3 deletions(-)

diffs (145 lines):

diff -r 02f336a8890f -r d1dd5e761049 sbin/fdisk/mbr/mbr.S
--- a/sbin/fdisk/mbr/mbr.S      Sun May 02 21:29:41 1999 +0000
+++ b/sbin/fdisk/mbr/mbr.S      Sun May 02 21:30:36 1999 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mbr.S,v 1.3 1999/02/08 21:52:43 ws Exp $       */
+/*     $NetBSD: mbr.S,v 1.3.2.1 1999/05/02 21:30:36 perry Exp $        */
 
 /*
  * Copyright (C) 1998 Wolfgang Solfrank.
@@ -41,6 +41,48 @@
 
 #define        BOOTADDR        0x7c00
 
+/*
+ * XXX should be in an include file
+ */
+/*
+ * Register values used in the i386 instruction set
+ */
+#define AL      0
+#define BL      3
+#define CL      1
+#define DL      2
+#define AH      4
+#define BH      7
+#define CH      5
+#define DH      6
+
+#define AX      0
+#define BX      3
+#define CX      1
+#define DX      2
+#define SP      4
+#define BP      5
+#define SI      6
+#define DI      7
+
+#define SI_INDEX        4
+#define DI_INDEX        5
+#define BP_INDEX        6
+#define BX_INDEX        7
+
+#define cmpw_reg_iregoff(reg,ireg,off) \
+       .byte 0x39 ; .byte (0x40 + ireg) | (reg << 3) ; .byte off
+
+#define movb_ireg0_reg(ireg,reg) .byte 0x8a ; .byte (reg << 3) | ireg
+
+#define movb_reg_mem(reg,mem) \
+       .byte 0x88 ; .byte 0x6 | (reg << 3) ; .word mem
+#define movb_mem_reg(mem,reg) \
+       .byte 0x8a ; .byte 0x6 | (reg << 3) ; .word mem
+
+#define MINDRV 0x80
+#define MAXDRV 0x87
+
        .text
 /*
  * Move ourselves out of the way first
@@ -67,6 +109,14 @@
        .word   0
 #endif
 1:
+       cmpb    $MINDRV,%dl
+       jl      2f
+       cmpb    $MAXDRV,%dl
+       jle     3f
+2:
+       movb $0x80,%dl
+3:
+       movb_reg_mem(DL,drvno)
 /*
  * Now look for the active partition
  */
@@ -100,11 +150,52 @@
  * Active partition pointed to by si.
  * Read the first sector.
  *
- * First determine whether we have int13-extensions.
+ * First:
+ * - see what the total number of sectors is that we can address through the
+ *   normal CHS interface
+ * - if this partition needs more, determine whether we have int13-extensions.
+ *
+ * Why this extra check? Well, some BIOSes apparently report that they do
+ * int13 extensions, but fail if you actually use them (oh, great). So we
+ * try to avoid them unless really necessary.
  */
 boot:
+       movb_mem_reg(drvno, DL);
+       data32
+       xorl    %ecx,%ecx
+       data32
+       xorl    %eax,%eax
+       movb    $8,%ah
+       int     $0x13
+
+       shrl    $8,%edx
+       incl    %edx                    /* dx now has #heads */
+
+       movl    %ecx,%eax
+       andl    $0x3f,%eax              /* ax has #sectors */
+
+       movl    %ecx,%ebx
+       shrl    $8,%ecx
+       andl    $0xc0,%ebx
+       shll    $2,%ebx
+       orl     %ebx,%ecx
+       incl    %ecx                    /* cx has #cylinders */
+
+       mull    %edx                    /* h * s (will fit in 16 bits) */
+       data32
+       mull    %ecx                    /* %eax = c * h * s */
+
+       movb_mem_reg(drvno, DL)
+
+       data32
        addr32
-       movb    0(%esi), %dl            % get drive identifier
+       movl    8(%esi), %ebx
+       data32
+       cmpl    %eax, %ebx
+       data32
+       jl      noext                   /* total # chs sectors > part. start */
+
+tryext:
        data32
        push    %esi
        push    %edx
@@ -203,6 +294,7 @@
        movl    $0xaa55, %ebx
        cmpl    %eax, %ebx
        jnz     out
+       movb_mem_reg(drvno, DL)
 #ifdef ASSEMBLE_16BIT
        jmp     0:BOOTADDR
 #else
@@ -211,6 +303,8 @@
        .word   0
 #endif
 
+drvno:
+       .byte 0x80
 msinvp:
        .asciz  "Invalid partition table"
 noos: