// // Derived from free code by Martynas Kunigelis, // who is in no way associated with this project. // // // Keyboard interrupt hooking example. // The author is not responsible for any // damage this code could do to you or your property. // //            Martynas Kunigelis, 1996/13/05 //            e-mail:  Martynas.Kunigelis@vm.ktu.lt //		.file	"kb.s" // // externals (optional): //		.extern ___djgpp_base_address		.extern ___djgpp_ds_alias 		.extern	___djgpp_dos_sel // // public functions and variables: //		.global _keyboard_buffer		.global _keyboard_buffer_pos		.global _keyboard_init		.global _keyboard_close		.global _keyboard_chain		.text				.align 	4locking_region_start:_keyboard_buffer:	.space 	0x200, 0_keyboard_buffer_pos:	.long	0old_vector:old_vector_ofs:	.long	0old_vector_sel:	.word	0chain_flag:	.long 	1		.align	4handler_procedure: // // .. will be called every time a key is pressed/released //                    		pushl	%eax		pushl	%edx		pushw	%ds // // Load DS with our data selector // 		movw	%cs:___djgpp_ds_alias, %ds // // Read the scancode from keyboard port and update keyboard_map //		movl	_keyboard_buffer_pos, %edx		cmpl	$0x200, %edx		je	skip_buffering		inb	$0x60, %al		cmpb	$0xE0, %al		jne	normal_key		cmpl	$0x1FF, %edx		je	skip_bufferingnormal_key:		movb	%al, _keyboard_buffer(%edx)		incl	%edx		movl	%edx, _keyboard_buffer_posskip_buffering: // // Chain if flag is set, otherwise do what's necessary and return //		cmpl	$0, chain_flag		jne	handler_chain // // Acknowledge keyboard and interrupt contollers //		inb	$0x61, %al		orb	$0x80, %al		outb	%al, $0x61		andb	$0x7f, %al		outb	%al, $0x61		movb	$0x20, %al		outb	%al, $0x20		popw	%ds		popl	%edx		popl	%eax		sti		iret		.align	4handler_chain:  popw	%ds		popl	%edx		popl	%eax		ljmp	*%cs:(old_vector)locking_region_end:		.align	4_keyboard_init: // // int keyboard_init(void); // // Initializes the keyboard handler and hooks the keyboard interrupt. // Returns -1 on failure, zero on success //		pushl	%esi		pushl	%edi		pushl	%ebx // // First, we need to lock the handler and memory it touches, so // it doesn't get swapped out to disk. //		leal	locking_region_start, %ecx		leal	locking_region_end, %edi		subl	%ecx, %edi		addl	___djgpp_base_address, %ecx		shldl	$16, %ecx, %ebx		// ecx -> bx:cx		shldl	$16, %edi, %esi         // edi -> si:di		movw    $0x0600, %ax		// lock linear region		int	$0x31		jc	init_error // // Now we need to save the old interrupt vector, so we can restore // it later and also to know where to jump if chaining. //		movw	$0x0204, %ax    	// get pm int vector		movb	$0x09, %bl		int	$0x31		movw	%cx, old_vector_sel		movl	%edx, old_vector_ofs // // Make sure we chain after initialization. //		movl	$1, chain_flag // // Set the interrupt vector to point to our handler. //		movw	%cs, %cx    				leal	handler_procedure, %edx		movb	$0x09, %bl		movw	$0x0205, %ax    	// set pm int vector		int	$0x31 //* //* Actually we would have to unlock the locked region on failure //* here. But since most programs would exit with an error message //* in such case, there's no need to worry. //*init_error: // // This sets EAX to -1 if CF is set and to 0 atherwise //		movl	$0, %eax		sbbl	$0, %eax				popl	%ebx		popl	%edi		popl	%esi		ret		.align 4_keyboard_close: // // void keyboard_close(void); // // Shuts the keyboard handler down. //		pushl	%esi		pushl	%edi		pushl	%ebx // // Unlock the region we locked at initialization // 		leal	locking_region_start, %ecx		leal	locking_region_end, %edi		subl	%ecx, %edi		addl	___djgpp_base_address, %ecx		shldl	$16, %ecx, %ebx		shldl	$16, %edi, %esi		movw	$0x0601, %ax  		// unlock linear region		int	$0x31                    // // Restore the interrupt vector to its previous value //		movw	old_vector_sel, %cx		movl	old_vector_ofs, %edx		movb	$0x09, %bl		movw	$0x0205, %ax            // set pm int vector		int	$0x31		popl	%ebx		popl	%edi		popl	%esi		ret // // void keyboard_chain(int toggle); //		.align	4_keyboard_chain:		cmpl	$0, 4(%esp)		je	chain_offchain_on: // // Set the chain_flag and clear BIOS shift/ctrl/alt status bits: //		movl	$1, chain_flag		push	%es		movw	___djgpp_dos_sel, %es		andb	$0xf0, %es:0x417		pop	%es		jmp	chain_donechain_off:		movl	$0, chain_flagchain_done:     ret // //  "Hey pig, nothing's turning out the way I planned." //  - Nine Inch Nails //