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Only update the boot sector when there is a valid drive number provided.

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(After squeezing a few more bytes out of boot0)

Discussed With: jhb, julian
PR: 66248
Submitted By: Hans Petter Selasky
MFC After: 1 week
This commit is contained in:
peadar 2005-01-09 23:30:35 +00:00
parent 587dd95b4b
commit ec9a802b3c
1 changed files with 15 additions and 14 deletions
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29
sys/boot/i386/boot0/boot0.S
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@ -104,10 +104,15 @@ main:
* number should be used. If what the bios gives us is bad, use the '0' in
* the block instead.
*/
testb $0x20,_FLAGS(%bp) # Set number drive?
testb $0x20,_FLAGS(%bp) # Set drive number?
jnz main.1 # Yes
testb %dl,%dl # Drive number valid?
js main.2 # Possibly (0x80 set)
/*
* Only update the boot-sector when there is a valid drive number or
* the drive number is set manually.
*/
orb $0x40,_FLAGS(%bp) # Disable updates
main.1: movb _SETDRV(%bp),%dl # Drive number to use
/*
* Whatever we decided to use, now store it into the fake
@ -145,16 +150,14 @@ main.3: movb %ch,-0x4(%bx) # Zero active flag (ch == 0)
/*
* Now scan the table of known types
*/
movb $TBL1SZ,%cl # Number of entries
repne # Known
scasb # type?
jne main.4 # No
movb $TBL1SZ+1,%cl # Number of entries
repne # Locate
scasb # type
/*
* If it matches get the matching element in the next array. If it doesn't,
* we are already pointing at its first element which points to a "?".
* Get the matching element in the next array.
*/
addw $TBL1SZ,%di # Adjust
main.4: movb (%di),%cl # Partition
addw $TBL1SZ-1, %di # Adjust
movb (%di),%cl # Partition
addw %cx,%di # description
callw putx # Display it
main.5: incw %dx # Next item
@ -305,7 +308,6 @@ main.14: popw %si # Restore
/*
* Load selected bootsector to the LOAD location in RAM.
* If it fails to read or isn't marked bootable, treat it as a bad selection.
* XXX: What does %si carry?
*/
main.15: movw $LOAD,%bx # Address for read
movb $0x2,%ah # Read sector
@ -313,10 +315,8 @@ main.15: movw $LOAD,%bx # Address for read
jc main.10 # If error
cmpw $MAGIC,0x1fe(%bx) # Bootable?
jne main.10 # No
pushw %si # Save
movw $crlf,%si # Leave some
callw puts # space
popw %si # Restore
jmp *%bx # Invoke bootstrap
/*
@ -413,9 +413,9 @@ tables:
.byte 0x9f, 0xa5, 0xa6, 0xa9
/*
* These are offsets that match the known names above and point to the strings
* that will be printed.
* that will be printed. os_misc will be used if the search of the above table
* runs over.
*/
.byte os_misc-. # Unknown
.byte os_dos-. # DOS
.byte os_dos-. # DOS
.byte os_dos-. # DOS
@ -427,6 +427,7 @@ tables:
.byte os_freebsd-. # FreeBSD
.byte os_bsd-. # OpenBSD
.byte os_bsd-. # NetBSD
.byte os_misc-. # Unknown
/*
* And here are the strings themselves. 0x80 or'd into a byte indicates
* the end of the string. (not so great for Russians but...)