diff options
Diffstat (limited to 'sys')
| -rw-r--r-- | sys/boot/i386/boot0/boot0.S | 29 |
1 files changed, 15 insertions, 14 deletions
diff --git a/sys/boot/i386/boot0/boot0.S b/sys/boot/i386/boot0/boot0.S index de3ed54..0f88a6b 100644 --- a/sys/boot/i386/boot0/boot0.S +++ b/sys/boot/i386/boot0/boot0.S @@ -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...) |
