+# pcboot - bootable PC demo/game kernel
+# Copyright (C) 2018 John Tsiombikas <nuclear@member.fsf.org>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY, without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <https://www.gnu.org/licenses/>.
+
.data
.align 4
.short 0
out %al, $0x20
pop %eax
iret
-
+
+/* special case for IRQ 7 and IRQ 15, to catch spurious interrupts */
+ .set PIC1_CMD, 0x20
+ .set PIC2_CMD, 0xa0
+ .set OCW2_EOI, 0x20
+ .set OCW3_ISR, 0x0b
+
+ .extern intr_entry_irq7
+ .global irq7_entry_check_spurious
+irq7_entry_check_spurious:
+ push %eax
+ mov $OCW3_ISR, %al
+ out %al, $PIC1_CMD
+ in $PIC1_CMD, %al
+ and $0x80, %al
+ pop %eax
+ jnz intr_entry_irq7
+ iret
+
+ .extern intr_entry_irq15
+ .global irq15_entry_check_spurious
+irq15_entry_check_spurious:
+ push %eax
+ mov $OCW3_ISR, %al
+ out %al, $PIC2_CMD
+ in $PIC2_CMD, %al
+ and $0x80, %al
+ jnz 0f
+ # it was spurious, send EOI to master PIC and iret
+ mov $OCW2_EOI, %al
+ out %al, $PIC1_CMD
+ pop %eax
+ iret
+0: pop %eax
+ jmp intr_entry_irq15
+
/* XXX not necessary for now, just leaving it in in case it's useful
* down the road.