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Tweak the code to handle intercepting BIOS calls to int 0x15 to shave

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another 16 bytes off of BTX (and thus boot2):
- Compare against the value of %eax that is saved on the stack instead of
  loading it into %eax (which requires saving the current %eax on the
  stack).
- Use %ch to examine the keyboard flag state in the BIOS to see if
  Ctrl-Alt-Del is pressed instead of %al so we don't have to save %eax on
  the stack anymore.

MFC after:	1 week
This commit is contained in:
John Baldwin 2006-09-28 19:42:10 +00:00
parent 4b9657e974
commit d64e328e3c
1 changed files with 10 additions and 17 deletions
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27
sys/boot/i386/btx/btx/btx.S
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@ -657,23 +657,16 @@ v86intn: lodsb # Get int no
cmpb $0x19,%al # is it int 19?
je reboot # yes, reboot the machine
cmpb $0x15,%al # is it int 15?
jne v86intn.3 # no, skip parse
pushl %eax # stash EAX
movl 0x1c(%ebp),%eax # user's saved EAX
cmpb $0x87,%ah # is it the memcpy subfunction?
jne v86intn.1 # no, keep checking
popl %eax # get the stack straight
jmp int15_87 # it's our cue
v86intn.1: cmpw $0x4f53,%ax # is it the delete key callout?
jne v86intn.2 # no, handle the int normally
movb BDA_KEYFLAGS,%al # get the shift key state
andb $0xc,%al # mask off just Ctrl and Alt
cmpb $0xc,%al # are both Ctrl and Alt down?
jne v86intn.2 # no, handle the int normally
popl %eax # restore EAX
jmp reboot # reboot the machine
v86intn.2: popl %eax # restore EAX
v86intn.3: subl %edi,%esi # From
jne v86intn.1 # no, skip parse
cmpb $0x87,0x1d(%ebp) # is it the memcpy subfunction?
je int15_87 # yes
cmpw $0x4f53,0x1c(%ebp) # is it the delete key callout?
jne v86intn.1 # no, handle the int normally
movb BDA_KEYFLAGS,%ch # get the shift key state
andb $0xc,%ch # mask off just Ctrl and Alt
cmpb $0xc,%ch # are both Ctrl and Alt down?
je reboot # yes, reboot the machine
v86intn.1: subl %edi,%esi # From
shrl $0x4,%edi # linear
movw %dx,-0x2(%ebx) # Save flags
movw %di,-0x4(%ebx) # Save CS