On Wednesday, June 22, 2011 7:34:05 am Henri Hennebert wrote:
I get
LBA: 00008200
Read error: 04
Odd. Oh, I fubar'd and read the wrong thing for the sector. Also, we
should leave the EDD packet on the stack so it doesn't get trashed by
calling hex8, etc. Please try this:
Index: zfsldr.S
===================================================================
--- zfsldr.S (revision 223365)
+++ zfsldr.S (working copy)
@@ -16,7 +16,6 @@
*/
/* Memory Locations */
- .set MEM_REL,0x700 # Relocation address
.set MEM_ARG,0x900 # Arguments
.set MEM_ORG,0x7c00 # Origin
.set MEM_BUF,0x8000 # Load area
@@ -91,26 +90,18 @@ main: cld #
String ops inc
mov %cx,%ss # Set up
mov $start,%sp # stack
/*
- * Relocate ourself to MEM_REL. Since %cx == 0, the inc %ch sets
- * %cx == 0x100.
- */
- mov %sp,%si # Source
- mov $MEM_REL,%di # Destination
- incb %ch # Word count
- rep # Copy
- movsw # code
-/*
* If we are on a hard drive, then load the MBR and look for the first
* FreeBSD slice. We use the fake partition entry below that points to
* the MBR when we call nread. The first pass looks for the first active
* FreeBSD slice. The second pass looks for the first non-active FreeBSD
* slice if the first one fails.
*/
- mov $part4,%si # Partition
+ mov $part4,%si # Dummy partition
cmpb $0x80,%dl # Hard drive?
jb main.4 # No
- movb $0x1,%dh # Block count
- callw nread # Read MBR
+ xor %eax,%eax # Read MBR
+ movw $MEM_BUF,%bx # from first
+ callw nread # sector
mov $0x1,%cx # Two passes
main.1: mov $MEM_BUF+PRT_OFF,%si # Partition table
movb $0x1,%dh # Partition
@@ -161,10 +152,16 @@ main.4: xor %dx,%dx #
Partition:drive
* area and target area do not overlap.
*/
main.5: mov %dx,MEM_ARG # Save args
- movb $NSECT,%dh # Sector count
+ mov $NSECT,%cx # Sector count
movl $1024,%eax # Offset to boot2
- callw nread.1 # Read disk
-main.6: mov $MEM_BUF,%si # BTX (before reloc)
+ mov $MEM_BUF,%bx # Destination buffer
+main.6: pushal # Save params
+ callw nread # Read disk
+ popal # Restore
+ incl %eax # Update for
+ add $SIZ_SEC,%bx # next sector
+ loop main.6 # If not last, read another
+ mov $MEM_BUF,%si # BTX (before reloc)
mov 0xa(%si),%bx # Get BTX length and set
mov $NSECT*SIZ_SEC-1,%di # Size of load area (less one)
mov %di,%si # End of load
@@ -214,29 +211,35 @@ seta20.3: sti # Enable
interrupts
* packet on the stack and passes it to read.
*
* %eax - int - LBA to read in relative to partition start
+ * %es:%bx - ptr - destination address
* %dl - byte - drive to read from
- * %dh - byte - num sectors to read
* %si - ptr - MBR partition entry
*/
-nread: xor %eax,%eax # Sector offset in partition
-nread.1: xor %ecx,%ecx # Get
+nread: xor %ecx,%ecx # Get
addl 0x8(%si),%eax # LBA
adc $0,%ecx
pushl %ecx # Starting absolute block
pushl %eax # block number
push %es # Address of
- push $MEM_BUF # transfer buffer
- xor %ax,%ax # Number of
- movb %dh,%al # blocks to
- push %ax # transfer
+ push %bx # transfer buffer
+ push $0x1 # Read 1 sector
push $0x10 # Size of packet
mov %sp,%bp # Packet pointer
callw read # Read from disk
+ jc nread.1 # If error, fail
lea 0x10(%bp),%sp # Clear stack
- jnc return # If success, return
- mov $msg_read,%si # Otherwise, set the error
- # message and fall through to
- # the error routine
+ ret # If success, return
+nread.1: mov %ah,%al # Format
+ mov $read_err,%di # error
+ call hex8 # code
+ movl 0x8(%bp),%eax # Format
+ mov $lba,%di # LBA
+ call hex32
+ mov $msg_lba,%si # Display
+ call putstr # LBA
+ mov $msg_read,%si # Set the error message and
+ # fall through to the error
+ # routine
/*
* Print out the error message pointed to by %ds:(%si) followed
* by a prompt, wait for a keypress, and then reboot the machine.
@@ -259,14 +262,6 @@ putstr: lodsb # Get char
jne putstr.0 # No
/*
- * Overused return code. ereturn is used to return an error from the
- * read function. Since we assume putstr succeeds, we (ab)use the
- * same code when we return from putstr.
- */
-ereturn: movb $0x1,%ah # Invalid
- stc # argument
-return: retw # To caller
-/*
* Reads sectors from the disk. If EDD is enabled, then check if it is
* installed and use it if it is. If it is not installed or not enabled, then
* fall back to using CHS. Since we use a LBA, if we are using CHS, we have
to
@@ -294,14 +289,38 @@ read: cmpb $0x80,%dl # Hard
drive?
retw # To caller
read.1: mov $msg_chs,%si
jmp error
-msg_chs: .asciz "CHS not supported"
+/*
+ * Convert EAX, AX, or AL to hex, saving the result to [EDI].
+ */
+hex32: pushl %eax # Save
+ shrl $0x10,%eax # Do upper
+ call hex16 # 16
+ popl %eax # Restore
+hex16: call hex16.1 # Do upper 8
+hex16.1: xchgb %ah,%al # Save/restore
+hex8: push %ax # Save
+ shrb $0x4,%al # Do upper
+ call hex8.1 # 4
+ pop %ax # Restore
+hex8.1: andb $0xf,%al # Get lower 4
+ cmpb $0xa,%al # Convert
+ sbbb $0x69,%al # to hex
+ das # digit
+ orb $0x20,%al # To lower case
+ stosb # Save char
+ ret # (Recursive)
+
/* Messages */
-msg_read: .asciz "Read"
-msg_part: .asciz "Boot"
+msg_chs: .asciz "CHS not supported"
+msg_read: .ascii "Read error: "
+read_err: .asciz "XX"
+msg_lba: .ascii "LBA: "
+lba: .asciz "XXXXXXXX\r\n"
+msg_part: .asciz "Boot error"
-prompt: .asciz " error\r\n"
+prompt: .asciz "\r\n"
.org PRT_OFF,0x90
