[src/trunk]: src/sys/arch/i386/stand/cdboot Support reading /boot > 64k. Bas...

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

details:   https://anonhg.NetBSD.org/src/rev/ddce6acbde6a
branches:  trunk
changeset: 748447:ddce6acbde6a
user:      dsl <dsl%NetBSD.org@localhost>
date:      Sat Oct 24 11:23:06 2009 +0000

description:
Support reading /boot > 64k.  Based on the patch from Izumi Tsutsui.
Compiles but not actually tested!  Fixes PR/42202

diffstat:

 sys/arch/i386/stand/cdboot/cdboot.S |  37 ++++++++++++++++++-------------------
 1 files changed, 18 insertions(+), 19 deletions(-)

diffs (76 lines):

diff -r d50b697d7842 -r ddce6acbde6a sys/arch/i386/stand/cdboot/cdboot.S
--- a/sys/arch/i386/stand/cdboot/cdboot.S       Sat Oct 24 11:22:48 2009 +0000
+++ b/sys/arch/i386/stand/cdboot/cdboot.S       Sat Oct 24 11:23:06 2009 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: cdboot.S,v 1.9 2009/10/24 10:28:30 dsl Exp $   */
+/*     $NetBSD: cdboot.S,v 1.10 2009/10/24 11:23:06 dsl Exp $  */
 
 /*-
  * Copyright (c) 2005 The NetBSD Foundation, Inc.
@@ -33,9 +33,6 @@
  * This is a primary boot loader that loads a secondary boot loader
  * directly from CD without performing floppy/hard disk emulation as
  * described by the El Torito specification.
- *
- * TODO:
- *  - Support for loading secondary boot loader > 64kB
  */
 
 #include <machine/asm.h>
@@ -302,21 +299,34 @@
  * %eax = LBA of starting sector
  * %ebx = buffer to store sectors
  * %dh = number of sectors to read
+ *
+ * Long transfers are split onto multiple 64k reads
  */
+#define MAX_SECTORS (0x10000/BLOCK_SIZE)
 read_sectors:
-       pusha
+       pushal
        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
+1:     movb    %dh, edd_nsecs
+       cmpb    $MAX_SECTORS, %dh
+       jle     2f                      /* j if less than 64k */
+       movb    $MAX_SECTORS, edd_nsecs /* Read 16 sectors - 64k bytes */
+2:     movb    boot_drive, %dl
        movw    $edd_packet, %si
 read_again:
        movb    $0x42, %ah
+       push    %dx                     /* bios shouldn't kill %dh, but ... */
        int     $0x13
+       pop     %dx                     /* ... better safe than sorry! */
        jc      read_fail
-       popa
+       addw    $0x1000, edd_segment    /* Advance segment addr by 64k bytes */
+       addl    $MAX_SECTORS, edd_lba   /* And sector number to match */
+       sub     edd_nsecs, %dh          /* Number of sectors remaining */
+       jnz     1b                      
+       popal
        ret
+
 read_fail:
        cmpb    $ERROR_TIMEOUT, %ah
        jz      read_again
@@ -324,17 +334,6 @@
        call    message
        jmp     panic
 
-/*
- * For debugging purpose
- */
-put_char:
-       pusha
-       movb    $0x0e, %ah
-       movw    $0x0001, %bx
-       int     $0x10
-       popa
-       ret
-
 #include <message.S>
 
 edd_packet: