From 4f0922e34a02e0b988d45cfbf647b25c735340c7 Mon Sep 17 00:00:00 2001
From: Adrien Bourmault <neox@os-k.eu>
Date: Sat, 8 Feb 2020 00:30:09 +0100
Subject: [PATCH] Spurious exception now detected and handled

---
 kaleid/kernel/ke/idt.c | 49 ++++++++++++++++++++++++++----------------
 1 file changed, 30 insertions(+), 19 deletions(-)

diff --git a/kaleid/kernel/ke/idt.c b/kaleid/kernel/ke/idt.c
index d67ebb9..9e0460c 100644
--- a/kaleid/kernel/ke/idt.c
+++ b/kaleid/kernel/ke/idt.c
@@ -32,6 +32,7 @@
 IdtEntry_t idt[256] = { 0 };
 IdtPtr_t _KeIdtPtr;
 bool KeIdtIsInitialized = 0;
+ulong KeSpuriousCount = 0;
 
 static ISRList_t isrList = { 0 };
 
@@ -73,7 +74,6 @@ static char *ExceptionsChar[32] = {
 static void EnablePIC(void);
 static void EarlyExceptionHandler(ISRFrame_t *regs);
 static void DoubleFaultHandler(ISRFrame_t *regs);
-static void SpuriousChkHandler(ISRFrame_t *regs);
 
 //
 // Registers an isr with his IRQ to handle driver interrupts
@@ -158,7 +158,7 @@ void KeSetupIDT(void)
     // Set IDT IRQs Gates
     KeSetIDTGate(0x20, (ulong)isr32, codeSeg, 0x8E, 0);
     KeSetIDTGate(0x21, (ulong)isr33, codeSeg, 0x8E, 3);
-    KeSetIDTGate(0x22, (ulong)isr34, codeSeg, 0x8E, 3);
+    KeSetIDTGate(0x22, (ulong)isr34, codeSeg, 0x8E, 3); // NEVER RAISED : cascaded
     KeSetIDTGate(0x23, (ulong)isr35, codeSeg, 0x8E, 3);
     KeSetIDTGate(0x24, (ulong)isr36, codeSeg, 0x8E, 3);
     KeSetIDTGate(0x25, (ulong)isr37, codeSeg, 0x8E, 3);
@@ -182,7 +182,6 @@ void KeSetupIDT(void)
 
     KeRegisterISR(KeBrkDumpRegisters, 0x3);
     KeRegisterISR(DoubleFaultHandler, 0x8);
-    KeRegisterISR(SpuriousChkHandler, 0x27);
 
     // Load IDT
     KeLoadIDT();
@@ -219,12 +218,12 @@ static void EnablePIC(void)
     IoWriteByteOnPort(0xa0, 0x11);
 
     // Set ICW2 (IRQ base offsets)
-    IoWriteByteOnPort(0x21, 0x20); //0x20 is the first free interrupt for IRQ0
-    IoWriteByteOnPort(0xa1, 0x28); // PIC2 is offseted to 0x28
+    IoWriteByteOnPort(0x21, 0x20);  // 0x20 is the first free interrupt for IRQ0
+    IoWriteByteOnPort(0xa1, 0x28);  // PIC2 is offseted to 0x28
 
     // Set ICW3
-    IoWriteByteOnPort(0x21, 0x4);
-    IoWriteByteOnPort(0xa1, 0x2);
+    IoWriteByteOnPort(0x21, 0x4);   // A slave exists
+    IoWriteByteOnPort(0xa1, 0x2);   // You're a slave
 
     // Set ICW4
     IoWriteByteOnPort(0x21, 0x1);
@@ -254,7 +253,7 @@ void KeMaskIRQ(uchar isr)
     uchar port;
     uchar value;
 
-    if(isr < 0x8) {
+    if(isr < 8) {
         port = 0x21;
     } else {
         port = 0xA1;
@@ -295,20 +294,40 @@ void KeDisableNMI(void)
     DebugLog("NMI Interrupts disabled\n");
 }
 
+
+//
+// Get the content of a register of the PIC. Parameter is a ocw3 command :
+//      - 0x0a : read the IRR
+//      - 0x0b : read the ISR
+//
+static inline ushort KeGetIrqRegister(int ocw3)
+{
+    IoWriteByteOnPort(0x20, ocw3);
+    IoWriteByteOnPort(0xA0, ocw3);
+    return ((IoReadByteFromPort(0xA0) << 8) | IoReadByteFromPort(0x20)); // We MUST read the COMMAND PORT
+}
+
+
 //
 // The main ISR handler
 //
 void _KeHandleISR(ISRFrame_t *regs)
 {
-    /* if ((!regs) || (!regs->rip)) */
-    /*     KeStartPanic("[ISR ?] Unknown ISR Exception Abort\n"); */
-
     if ((regs->intNo >= 0x15) && (regs->intNo <= 0x1D))
         return; // INTEL RESERVED
 
     if ((regs->intNo == 0x0F) || (regs->intNo == 0x1F))
         return; // INTEL RESERVED
 
+   if (!(KeGetIrqRegister(0x0b) & (1<<(regs->intNo - 0x20)))) {
+       bprintf(BStdDbg, "[%d]\tISR 0x%x SPURIOUS\n",
+               KeGetTicks(),
+               regs->intNo
+               );
+       KeSpuriousCount++;
+       return;
+   }
+
     for (int i = 0; i < isrList.n; i++) {
         if (regs->intNo == isrList.entry[i].isrNo) {
             isrList.entry[i].isr(regs);
@@ -345,14 +364,6 @@ static void EarlyExceptionHandler(ISRFrame_t *regs)
     KeHaltCPU();
 }
 
-//
-// Spurious interruption check
-//
-void SpuriousChkHandler(ISRFrame_t *regs)
-{
-    // XXX;
-}
-
 //
 // Double Fault handling and stack overflow detection
 //