commented, no functional changes; from Christos Zoulas

SCCS-vsn: sys/i386/stand/fdbootblk.c 7.3

diff --git a/usr/src/sys/i386/stand/fdbootblk.c b/usr/src/sys/i386/stand/fdbootblk.c
index 076ac62..d365535 100644 (file)
--- a/usr/src/sys/i386/stand/fdbootblk.c
+++ b/usr/src/sys/i386/stand/fdbootblk.c
@@ -7,29 +7,27 @@
  *
  * %sccs.include.redist.c%
  *
  *
  * %sccs.include.redist.c%
  *

- *     @(#)fdbootblk.c 7.2 (Berkeley) %G%
+ *     @(#)fdbootblk.c 7.3 (Berkeley) %G%

  */
 
 /*
  */
 
 /*

- * fdbootblk.s:
- *     Written 10/6/90 by William F. Jolitz
- *     Initial block boot for AT/386 with typical stupid NEC controller
- *     Works only with 3.5 inch diskettes that have 16 or greater sectors/side
- *
- *     Goal is to read in sucessive 7.5Kbytes of bootstrap to
- *     execute.
- *
- *     No attempt is made to handle disk errors.
+ * Initial block boot for AT/386 with typical stupid NEC controller.  Works
+ * only with 3.5 inch diskettes that have 16 or greater sectors/side.  Goal
+ * is to read in sucessive 7.5Kbytes of bootstrap to execute.  No attempt
+ * is made to handle disk errors.

  */
  */

-/*#include "/sys/i386/isa/isa.h"
-#include "/sys/i386/isa/fdreg.h"*/
-#define        NOP     jmp 1f ; nop ; 1:
-#define BIOSRELOC      0x7c00
-#define        start   0x70400
+#define        NOP             jmp 1f ; nop ; 1:
+#define        BIOSRELOC       0x7c00
+#define        start           0x70400
+
+/* Gas does not know about 16 bit opcodes... */

 
        /* step 0 force descriptors to bottom of address space */
 
 
        /* step 0 force descriptors to bottom of address space */
 

-       .byte 0xfa,0xb8,0x30,0x00,0x8e,0xd0,0xbc,0x00,0x01 #ll fb
+       .byte   0xfa                    # cli
+       .byte   0xb8, 0x30, 0x00        # mov $0x0030, %ax
+       .byte   0x8e, 0xd0              # mov %ax, %ss
+       .byte   0xbc, 0x00, 0x01        # mov $0x0100, %sp

 
        xorl    %eax,%eax
        movl    %ax,%ds
 
        xorl    %eax,%eax
        movl    %ax,%ds


@@ -37,9 +35,9 @@
 
        /* step 1 load new descriptor table */
 
 
        /* step 1 load new descriptor table */
 

-       .byte 0x2E,0x0F,1,0x16
-       .word   BIOSRELOC+0x4a  #GDTptr
-       # word aword cs lgdt GDTptr
+       .byte   0x2e                    # seg cs
+       .byte   0x0f, 0x01, 0x16        # lgdt DS:d16
+       .word   BIOSRELOC + 0x4a        # [BIOSRELOC + GDTptr]

 
        /* step 2 turn on protected mode */
 
 
        /* step 2 turn on protected mode */
 


@@ -49,42 +47,45 @@
        jmp     1f
        nop
 
        jmp     1f
        nop
 

+ 1:

        /* step 3  reload segment descriptors */
 
        /* step 3  reload segment descriptors */
 

- 1:

        xorl    %eax,%eax
        movb    $0x10,%al
        movl    %ax,%ds
        movl    %ax,%es
        movl    %ax,%ss
        word
        xorl    %eax,%eax
        movb    $0x10,%al
        movl    %ax,%ds
        movl    %ax,%es
        movl    %ax,%ss
        word

-       ljmp    $0x8,$ BIOSRELOC+0x59   /* would be nice if .-RELOC+0x7c00 worked */
+       ljmp    $0x8, $ BIOSRELOC + 0x59 # [BIOSRELOC + reloc]

 
 

- /* Global Descriptor Table contains three descriptors:
+ /* 
+  * Global Descriptor Table contains three descriptors:

   * 0x00: Null: not used
   * 0x08: Code: code segment starts at 0 and extents for 4 gigabytes
   * 0x10: Data: data segment starts at 0 and extends for 4 gigabytes
   *            (overlays code)
   */
 GDT:
   * 0x00: Null: not used
   * 0x08: Code: code segment starts at 0 and extents for 4 gigabytes
   * 0x10: Data: data segment starts at 0 and extends for 4 gigabytes
   *            (overlays code)
   */
 GDT:

-NullDesc:      .word   0,0,0,0 # null descriptor - not used
-CodeDesc:      .word   0xFFFF  # limit at maximum: (bits 15:0)
+NullDsc:.word  0,0,0,0 # null descriptor - not used
+CodeDsc:.word  0xFFFF  # limit at maximum: (bits 15:0)

        .byte   0,0,0   # base at 0: (bits 23:0)
        .byte   0x9f    # present/priv level 0/code/conforming/readable
        .byte   0xcf    # page granular/default 32-bit/limit(bits 19:16)
        .byte   0       # base at 0: (bits 31:24)
        .byte   0,0,0   # base at 0: (bits 23:0)
        .byte   0x9f    # present/priv level 0/code/conforming/readable
        .byte   0xcf    # page granular/default 32-bit/limit(bits 19:16)
        .byte   0       # base at 0: (bits 31:24)

-DataDesc:      .word   0xFFFF  # limit at maximum: (bits 15:0)
+DataDsc:.word  0xFFFF  # limit at maximum: (bits 15:0)

        .byte   0,0,0   # base at 0: (bits 23:0)
        .byte   0x93    # present/priv level 0/data/expand-up/writeable
        .byte   0xcf    # page granular/default 32-bit/limit(bits 19:16)
        .byte   0       # base at 0: (bits 31:24)
 
        .byte   0,0,0   # base at 0: (bits 23:0)
        .byte   0x93    # present/priv level 0/data/expand-up/writeable
        .byte   0xcf    # page granular/default 32-bit/limit(bits 19:16)
        .byte   0       # base at 0: (bits 31:24)
 

-/* Global Descriptor Table pointer
+/* 
+ * Global Descriptor Table pointer

  *  contains 6-byte pointer information for LGDT
  */
 GDTptr:        .word   0x17    # limit to three 8 byte selectors(null,code,data)
  *  contains 6-byte pointer information for LGDT
  */
 GDTptr:        .word   0x17    # limit to three 8 byte selectors(null,code,data)

-       .long   BIOSRELOC+0x32  # GDT -- arrgh, gas again!
-readcmd: .byte 0xe6,0,0,0,0,2,18,0x1b,0xff
+       .long   BIOSRELOC + 0x32        # [BIOSRELOC + GDT]
+
+readcmd: .byte 0xe6, 0x00, 0x00, 0x00, 0x00, 0x02, 18, 0x1b, 0xff

 
        /* step 4 relocate to final bootstrap address. */
 reloc:
 
        /* step 4 relocate to final bootstrap address. */
 reloc: