hi ,
plz tell me where am i going wrong in hacking timer0
first i'm setting counter0 to generate square wave at
approx 500 microsecind
set_pit_count
{
cli()
outb(0x36,0x40)
outb((char)counter&0xff)
outb((char(counter>>8)
sti():
}
i'm saving old stub's address as
void *get_old_stub(int n) //here n=32
{
cli();
struct descriptor_idt *idte=&((struct descriptor
idt*)ptr_idt_table)[n]
return((void*)(idte->offset_high<<16)+idte_offset_low))//this
returns old_stub
sti();
}
The PROBLEM is here in my calling my interrupt routine
and original stub
void stub(void)
{
asm("
.globl stub
align 4,0x90
stub:
pushal
call *func_ptr
//func_ptr=(unsigned long)&func interrupt handler i
have to invoke every 500 microsecond
popal
movb $0x20,%al
outb %al,$0x20
//sending EOI to i8253
iret
")
//in stack we have eflags,return EIP
void func(void)
{
temp_pit_counter-=1;
//required as for 500 micro second and 10 ms original
(schesuler call)
//this has value around 20 means when it is 0 i have
to call scheduler
if(!temp_pit_counter)
{
temp_pit_counter=compensation_count//reset it to 20
for next call
asm("addl $4,%esp //this is return
EIP
popal
jmp old_stub //old address
")
}
return
}
my program is not running i checked the old_stub value
with original value
all is right but my calling sequence somewhere wrong
it is giving error bad EIP value
plz help
thanks
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