kernel/isr: improve interrupt handling code

On the assembly side, ensure the stack frame looks always the same, by pushing
a fake "error code" for the interrupts that don't generate one.

On the C side, use a struct instead of magic indices into an "array", and
make it consistent with the current style.

1 files changed, 38 insertions, 23 deletions

diff --git a/src/kernel/arch/amd64/interrupts/isr.c b/src/kernel/arch/amd64/interrupts/isr.c
index dd97fd4..bf84c5c 100644
--- a/src/kernel/arch/amd64/interrupts/isr.c
+++ b/src/kernel/arch/amd64/interrupts/isr.c
@@ -8,29 +8,48 @@
 #include <stdint.h>
 
 enum {
-	NMI = 0x02,
-	GP_FAULT = 0x0d,
-	PAGE_FAULT = 0x0e,
+	Nmi = 0x02,
+	GpFault = 0x0d,
+	PageFault = 0x0e,
 };
 
+typedef struct {
+	uint64_t ip, cs, flags;
+	/* only valid if switching from/into user mode */
+	uint64_t sp, ss;
+} IretFrame;
+
 void (*irq_fn[16])(void) = {0};
 
-static void log_interrupt(int interrupt, uint64_t *stackframe) {
+static uint64_t
+getcr2(void)
+{
+	uint64_t cr2;
+	asm("mov %%cr2, %0" : "=r"(cr2));
+	return cr2;
+}
+
+static void
+log_interrupt(uint8_t inr, void *stackframe)
+{
+	IretFrame *iret = stackframe;
+	uint64_t *errcode = ((uint64_t*)stackframe) - 1;
 	kprintf("interrupt %d, rip = k/%08x, cs 0x%x, code 0x%x\n",
-			interrupt, stackframe[0], stackframe[1], stackframe[-1]);
-	if ((stackframe[1] & 0x3) == 0) {
-		uint64_t *stack = (void*)stackframe[3];
-		kprintf("kernel rip = %p, *rip = %p\n", stack, *stack);
+			inr, iret->ip, iret->cs, *errcode);
+	if ((iret->cs & 0x3) == 0) { /* ring 0? */
+		uint64_t *stack = (void*)iret->sp;
+		kprintf("kernel rsp = %p, *rsp = %p\n", stack, *stack);
 	}
-	if (interrupt == PAGE_FAULT) {
-		uint64_t addr = 0x69;
-		asm("mov %%cr2, %0" : "=r"(addr));
-		kprintf("addr 0x%x\n", addr);
+	if (inr == PageFault) {
+		kprintf("addr 0x%x\n", getcr2());
 	}
 }
 
-void isr_stage3(uint8_t interrupt, uint64_t *stackframe) {
-	uint8_t irqn = interrupt - IRQ_IBASE;
+void
+isr_stage3(uint8_t inr, void *stackframe)
+{
+	IretFrame *iret = stackframe;
+	uint8_t irqn = inr - IRQ_IBASE;
 	if (irqn < 16) {
 		if (irq_fn[irqn]) {
 			irq_fn[irqn]();
@@ -39,21 +58,17 @@ void isr_stage3(uint8_t interrupt, uint64_t *stackframe) {
 		}
 	}
 
-	if (interrupt == NMI) { /* print some debugging information */
-		log_interrupt(interrupt, stackframe);
+	if (inr == Nmi) { /* print some debugging information */
+		log_interrupt(inr, stackframe);
 		mem_debugprint();
 		return;
 	}
 
-	if (interrupt == PAGE_FAULT || interrupt == GP_FAULT) {
-		stackframe++;
-	}
-
-	if ((stackframe[1] & 0x3) == 0) { /* in kernel */
-		log_interrupt(interrupt, stackframe);
+	if ((iret->cs & 0x3) == 0) { /* ring 0? */
+		log_interrupt(inr, stackframe);
 		cpu_halt();
 	} else { /* in user */
-		proc_kill(proc_cur, interrupt);
+		proc_kill(proc_cur, inr);
 		proc_switch_any();
 	}
 }