s/IRQ_OFFSET/T_IRQ0/: it's a trap number, not an irq number.

move the SYSCALL number up, so does not overlap the IRQ traps.

trap.c

@@ -45,7 +45,7 @@ trap(struct trapframe *tf)
   }
 
   switch(tf->trapno){
-  case IRQ_OFFSET + IRQ_TIMER:
+  case T_IRQ0 + IRQ_TIMER:
     if(cpu() == 0){
       acquire(&tickslock);
       ticks++;
@@ -54,20 +54,20 @@ trap(struct trapframe *tf)
     }
     lapiceoi();
     break;
-  case IRQ_OFFSET + IRQ_IDE:
+  case T_IRQ0 + IRQ_IDE:
     ideintr();
     lapiceoi();
     break;
-  case IRQ_OFFSET + IRQ_KBD:
+  case T_IRQ0 + IRQ_KBD:
     kbdintr();
     lapiceoi();
     break;
-  case IRQ_OFFSET + IRQ_COM1:
+  case T_IRQ0 + IRQ_COM1:
     uartintr();
     lapiceoi();
     break;
-  case IRQ_OFFSET + 7:
-  case IRQ_OFFSET + IRQ_SPURIOUS:
+  case T_IRQ0 + 7:
+  case T_IRQ0 + IRQ_SPURIOUS:
     cprintf("cpu%d: spurious interrupt at %x:%x\n",
             cpu(), tf->cs, tf->eip);
     lapiceoi();
@@ -94,7 +94,7 @@ trap(struct trapframe *tf)
 
   // Force process to give up CPU on clock tick.
   // If interrupts were on while locks held, would need to check nlock.
-  if(cp && cp->state == RUNNING && tf->trapno == IRQ_OFFSET+IRQ_TIMER)
+  if(cp && cp->state == RUNNING && tf->trapno == T_IRQ0+IRQ_TIMER)
     yield();
 
   // Check if the process has been killed since we yielded

traps.h

@@ -24,10 +24,10 @@
 
 // These are arbitrarily chosen, but with care not to overlap
 // processor defined exceptions or interrupt vectors.
-#define T_SYSCALL       48      // system call
+#define T_SYSCALL       64     // system call
 #define T_DEFAULT      500      // catchall
 
-#define IRQ_OFFSET      32      // IRQ 0 corresponds to int IRQ_OFFSET
+#define T_IRQ0          32      // IRQ 0 corresponds to int T_IRQ
 
 #define IRQ_TIMER        0
 #define IRQ_KBD          1
@@ -35,3 +35,4 @@
 #define IRQ_IDE         14
 #define IRQ_ERROR       19
 #define IRQ_SPURIOUS    31
+