Module Name: src
Committed By: dsl
Date: Sat Oct 24 10:28:30 UTC 2009
Modified Files:
src/sys/arch/i386/stand/cdboot: cdboot.S
Log Message:
Add some illumination ...
To generate a diff of this commit:
cvs rdiff -u -r1.8 -r1.9 src/sys/arch/i386/stand/cdboot/cdboot.S
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/i386/stand/cdboot/cdboot.S
diff -u src/sys/arch/i386/stand/cdboot/cdboot.S:1.8 src/sys/arch/i386/stand/cdboot/cdboot.S:1.9
--- src/sys/arch/i386/stand/cdboot/cdboot.S:1.8 Sat May 3 13:07:31 2008
+++ src/sys/arch/i386/stand/cdboot/cdboot.S Sat Oct 24 10:28:30 2009
@@ -1,4 +1,4 @@
-/* $NetBSD: cdboot.S,v 1.8 2008/05/03 13:07:31 ad Exp $ */
+/* $NetBSD: cdboot.S,v 1.9 2009/10/24 10:28:30 dsl Exp $ */
/*-
* Copyright (c) 2005 The NetBSD Foundation, Inc.
@@ -224,6 +224,8 @@
boot_cdrom:
movw $str_banner, %si
call message
+
+/* Read volume descriptor sectors until Primary decriptor found */
movl $VD_LBA, %eax
next_block:
movb $1, %dh /* Number of sectors to read */
@@ -238,6 +240,7 @@
call message
jmp panic
+/* Read all of root directory */
pvd_found:
movw $PVD_ADDR+PVD_ROOT_DR, %bx
movl DR_EXTENT(%bx), %eax /* LBA of the root directory */
@@ -246,6 +249,8 @@
movb %dl, %dh /* ... and load it to %dh */
movl $ROOTDIR_ADDR, %ebx
call read_sectors
+
+/* Scan directory entries searching for /boot */
next_entry:
cmpb $0, DR_LEN(%bx)
jz last_entry
@@ -270,6 +275,7 @@
call message
jmp panic
+/* Found /boot, read contents to 0x1000:0 */
load_loader:
movl DR_EXTENT(%bx), %eax
movl DR_DATA_LEN(%bx), %edx
@@ -278,6 +284,8 @@
movb %dl, %dh
movl $LOADER_ADDR, %ebx
call read_sectors
+
+/* Finally call into code of /boot */
movl $boot_params, %esi /* Provide boot_params */
xorl %edx, %edx
movb boot_drive, %dl
@@ -297,8 +305,8 @@
*/
read_sectors:
pusha
- movl %eax, edd_lba /* Convert LBA to segment */
- shrl $4, %ebx
+ movl %eax, edd_lba
+ shrl $4, %ebx /* Convert buffer addr to seg:0 */
movw %bx, edd_segment
movb %dh, edd_nsecs
movb boot_drive, %dl
