aboutsummaryrefslogtreecommitdiffstats
path: root/mbr
diff options
context:
space:
mode:
authorGene Cumm <gene.cumm@gmail.com>2010-11-26 13:17:55 -0500
committerGene Cumm <gene.cumm@gmail.com>2011-03-09 21:07:03 -0500
commit2bd1add73478a285a55b357703edeb7ea1e7c66e (patch)
tree986876105dda390a8ca07d536b19b418195bf0b7 /mbr
parentc9c8889ce52e2390164935539649dcc540910675 (diff)
downloadsyslinux-2bd1add73478a285a55b357703edeb7ea1e7c66e.tar.gz
syslinux-2bd1add73478a285a55b357703edeb7ea1e7c66e.tar.xz
syslinux-2bd1add73478a285a55b357703edeb7ea1e7c66e.zip
mbr_ho.bin: Fix bug in $PnP Scan; PressAnyKey; compare [ES:DI]
Also numerous uses of *w opcodes and spacing fixes
Diffstat (limited to 'mbr')
-rw-r--r--mbr/mbr_ho.S92
1 files changed, 59 insertions, 33 deletions
diff --git a/mbr/mbr_ho.S b/mbr/mbr_ho.S
index 993b0c3c..48220c21 100644
--- a/mbr/mbr_ho.S
+++ b/mbr/mbr_ho.S
@@ -33,21 +33,24 @@
* mbr_ho.S: MBR-like codeblock to display handoff data
*
* Displays the values of DL, DS, SI, the contents of [DS:SI] (16 bytes),
- * the values of ES, DI then the contents of [ES:DI] (4 bytes) then reports
- * a boot failure.
+ * the values of ES, DI, the contents of [ES:DI] (4 bytes), scans memory for
+ * $PnP then reports a boot failure.
+ *
+ * This should (hopefully) be only 8086 code
*/
-#define DEBUG_MARKER1
-#define DEBUG_START
-#define DEBUG_LOADE
-#define DEBUG_PNP
+// #define DEBUG_MARKER1 /* Insert markers in binary */
+// #define DEBUG_START /* Print entry addresses at start */
+// #define DEBUG_LOADE /* movw versus pop */
+#define DEBUG_PNP /* Scan for $PnP and show address */
+#define DEBUG_PAK /* Press Any Key before boot fail */
#ifdef DEBUG_MARKER1
.macro ASCII_MARKER1 s:vararg
- .ascii \s
+ .ascii \s
.endm
#else /* DEBUG_MARKER1 */
- .macro ASCII_MARKER1 s
+ .macro ASCII_MARKER1 s:vararg
.endm
#endif /* DEBUG_MARKER1 */
@@ -65,13 +68,20 @@
.text
entry = 0x7c00
-pnps = (entry)
-pnpi = (pnps-2)
-stack = (pnpi-2)
-e_di = (stack-2)
-e_es = (stack-4)
-e_si = (stack-6)
-e_ds = (stack-8)
+stack = (entry)
+e0_ax = (stack-2)
+e0_cx = (stack-4)
+e0_dx = (stack-6)
+e0_bx = (stack-8)
+e0_sp = (stack-10)
+e0_bp = (stack-12)
+e0_si = (stack-14)
+e0_di = (stack-16)
+e0_bot = (stack-16)
+e_di = (e0_bot-2) /* Original register values from entry point */
+e_es = (e0_bot-4)
+e_si = (e0_bot-6)
+e_ds = (e0_bot-8)
BIOS_page = 0x462
@@ -81,14 +91,15 @@ _start:
xorw %ax, %ax
movw %ax, %ss
movw $stack, %sp
- sti
- cld
+ pushaw
pushw %di /* es:di -> $PnP header */
pushw %es
pushw %si
pushw %ds
- push %cs
- pop %ds
+ sti
+ cld
+ pushw %cs
+ popw %ds
#ifdef DEBUG_START
pushw %dx
@@ -96,11 +107,10 @@ _start:
movw $(_start),%dx /* 0x0600 mbr.ld .text address */
call wrhexw
call crlf
-// movw $(entry - _start),%dx /* 0x7C00 */
call caddr
-caddr: popw %ax
- sub $(caddr - _start), %ax
- movw %ax, %dx /* Same size as pushw %ax;popw %dx */
+caddr:
+ popw %dx
+ subw $(caddr - _start), %dx
call wrhexw
call crlf
popw %dx
@@ -113,7 +123,6 @@ pr_dl: call wrstr
/* DS */
pr_ds: call wrstr
.ascii " DS: \0"
-// popw %dx
LOADE ds, dx
pushw %dx
popw %es
@@ -121,7 +130,6 @@ pr_ds: call wrstr
/* SI */
pr_si: call wrstr
.ascii " SI: \0"
-// popw %dx
LOADE si, dx
pushw %dx
popw %di
@@ -135,14 +143,12 @@ pr_si: call wrstr
/* ES */
pr_es: call wrstr
.ascii "ES: \0"
-// popw %dx
LOADE es, dx
pushw %dx
popw %es
call wrhexw
pr_di: call wrstr
.ascii " DI: \0"
-// popw %dx
LOADE di, dx
pushw %dx
popw %di
@@ -151,8 +157,19 @@ pr_di: call wrstr
/* ES:DI */ /* %es:0(%di) */
movw $4, %cx
call wrhexbses
- call crlf
+#ifdef DEBUG_PNP
+ subw $4, %si
+ es lodsw
+ cmpw $0x5024, %ax
+ jne scn_pnp
+ es lodsw
+ cmpw $0x506E, %ax
+ jne scn_pnp
+ call wrstr
+ .ascii " =$PnP\0"
+scn_pnp:
+ call crlf
/* $PnP Scan */
movw $0xf000, %dx
pushw %dx
@@ -163,10 +180,10 @@ pr_di: call wrstr
movw $0x5024, %dx
movw $0x506E, %bx
ch_pnp: es lodsw
- cmp %dx, %ax
+ cmpw %dx, %ax
jne ch_pnp_l
es lodsw
- cmp %bx, %ax
+ cmpw %bx, %ax
je pr_pnp
ch_pnp_l:
addw $14, %si
@@ -174,15 +191,18 @@ ch_pnp_l:
loopw ch_pnp
jmp end
pr_pnp:
+ pushw %si
call wrstr
.ascii "$PnP-\0"
movw %es, %dx
call wrhexw
movb $':, %al
call wrchr
- movw %si, %dx
+ popw %dx
andw $0xFFF0, %dx
call wrhexw
+#endif /* DEBUG_PNP */
+
call crlf
end:
@@ -210,8 +230,8 @@ wrstr_d:
ret
crlf:
- call wrstr
- .ascii "\r\n\0"
+ call wrstr
+ .ascii "\r\n\0"
ret
ASCII_MARKER1 "hx"
@@ -259,6 +279,12 @@ wrhexbses_l:
data:
ASCII_MARKER1 "bf"
bootfail:
+#ifdef DEBUG_PAK
+ call wrstr
+ .ascii "\r\n\r\nPress any key\r\n\0"
+ xor %ax, %ax
+ int $0x16
+#endif
int $0x18 /* Boot failure */
die:
hlt