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/* Project:     OSLib
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 * Description: The OS Construction Kit
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 * Date:                1.6.2000
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 * Idea by:             Luca Abeni & Gerardo Lamastra
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 *
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 * OSLib is an SO project aimed at developing a common, easy-to-use
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 * low-level infrastructure for developing OS kernels and Embedded
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 * Applications; it partially derives from the HARTIK project but it
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 * currently is independently developed.
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 *
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 * OSLib is distributed under GPL License, and some of its code has
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 * been derived from the Linux kernel source; also some important
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 * ideas come from studying the DJGPP go32 extender.
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 *
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 * We acknowledge the Linux Community, Free Software Foundation,
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 * D.J. Delorie and all the other developers who believe in the
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 * freedom of software and ideas.
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 *
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 * For legalese, check out the included GPL license.
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 */
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/*	Safe abort routine & timer asm handler	*/
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.title	"Timer.S"
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#include <ll/i386/sel.h>
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#include <ll/i386/linkage.h>
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#include <ll/i386/defs.h>
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#include <ll/sys/ll/exc.h>
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.data
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ASMFILE(TimerHandler)
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.extern JmpSel
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.extern JmpZone
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.globl SYMBOL_NAME(ll_clock)
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.globl SYMBOL_NAME(last_handler)
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		/* Used as JMP entry point to check if a real	*/
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		/* context switch is necessary			*/
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SYMBOL_NAME_LABEL(ll_clock)	.int	0
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SYMBOL_NAME_LABEL(last_handler)	.long   0
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.extern  SYMBOL_NAME(periodic_wake_up)
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.extern  SYMBOL_NAME(oneshot_wake_up)
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.text
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		.globl SYMBOL_NAME(ll_timer)
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/* This is the timer handler; it reloads for safety the DS register; this   */
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/* prevents from mess when timer interrupts linear access to memory (not in */
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/* ELF address space); then EOI is sent in order to detect timer overrun    */
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/* The high level kernel procedure wake_up() is called to perform the 	    */
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/* preeption at higher level (process descriptos); the resulting context    */
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/* if different from the old one is used to trigger the task activation.    */
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SYMBOL_NAME_LABEL(ll_timer)
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			pushal
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			pushw	%ds
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			pushw	%es
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			pushw	%fs
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			pushw	%gs
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			movw    $(X_FLATDATA_SEL),%ax
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			movw    %ax,%ds
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			movw    %ax,%es
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			/* Send EOI to master PIC		*/
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			/* to perform later the overrun test	*/
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			movb    $0x20,%al
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			movl	$0x20,%edx
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			outb    %al,%dx
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			/* Call wake_up(actual_context) */
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			movl	SYMBOL_NAME(ll_clock),%eax
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			incl 	%eax
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			movl	%eax,SYMBOL_NAME(ll_clock)
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			/* The following could be optimized a little... */
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			xorl %ebx, %ebx
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			movw %ss, %bx
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			/* We must switch to a ``safe stack'' */
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#if 0
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	/*
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	 * OK, this is the idea: in %esp we have the address of the
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	 * stack pointer in the APPLICATION address space...
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	 * We assume that address spaces are implemented through segments...
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	 * What we have to do is to add the segment base to %esp:
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	 *	- Load the GDT base in a register
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	 *	- Add DS * 8 to that value
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	 *	- Read the corresponding GDT entry (the segment descriptor)
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	 *	- Compute the base...
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	 *	It is (*p & 0xFC) | (*(p +1)  & 0x0F) << 16) | *(p + 2)
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	 */
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			movl SYMBOL_NAME(GDT_base), %edi
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			addl %ebx, %edi
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			xorl %ebx, %ebx
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			movb 7(%edi), %bh
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			movb 4(%edi), %bl
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			shl $16, %ebx
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			movw 2(%edi), %bx
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			/* Is it correct? I think so... Test it!!! */
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			addl %ebx, %esp
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			/* Save EBX for returning to our stack... */
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			movw %ds, %cx
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			movw %ss, %dx
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			movw %cx, %ss
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			pushl %ebx
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			pushl %edx
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#endif
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			cld
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			movl	SYMBOL_NAME(timermode), %eax
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			cmpl	$1, %eax
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			je	oneshot
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			call    SYMBOL_NAME(periodic_wake_up)
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			jmp	goon
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oneshot:		call    SYMBOL_NAME(oneshot_wake_up)
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goon:
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			/* This is the overrun test		 */
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			/* Do it after sending EOI to master PIC */
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			movb    $0x0A,%al
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			movl	$0x020,%edx
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			outb    %al,%dx
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			inb     %dx,%al
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			testb   $1,%al
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			jz      Timer_OK
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			movl    $(CLOCK_OVERRUN),%eax
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			pushl	%eax
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			call    SYMBOL_NAME(ll_abort)
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Timer_OK:
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#if 0
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			/* Restore ESP */
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			popl	%edx
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			popl	%ebx	/* We must subtract it from ESP...*/
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			subl	%ebx, %esp
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			movw	%dx, %ss
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#endif
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#ifdef __VIRCSW__
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			movw	SYMBOL_NAME(currCtx), %ax
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			cmpw    %ax,JmpSel
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			je      NoPreempt2
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			movw    %ax,JmpSel
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			ljmp    JmpZone  /* DISPATCH! */
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#endif
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NoPreempt2:
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			cmpl	$0, SYMBOL_NAME(last_handler)
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			je	nohandler
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			movl	SYMBOL_NAME(last_handler), %ebx
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			call	*%ebx
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nohandler:
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			popw	%gs
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			popw	%fs
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			popw	%es
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			popw	%ds
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			popal
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			iret