fix compiler warnings

arch/at91sam3x8e/interrupt.c

@@ -28,7 +28,9 @@ void arch_irq_invoke(enum irqno irqno)
 			REG_SCB_ICSR = REG_SCB_ICSR_PENDSTSET_BIT;
 			break;
 
-		/* TODO: Implement the rest of interrupts < 0 */
+		default:
+			/* TODO: Implement the rest of interrupts < 0 */
+			break;
 		}
 	} else {
 		REG_NVIC_ISPR((uint32_t)irqno >> 5) = 1 << ( ((uint32_t)irqno) & 0x1F );

arch/at91sam3x8e/sched.c

@@ -64,8 +64,8 @@ void arch_sched_process_init(struct process *process, void (*entry)(void))
 
 	memset(regs, 0, sizeof(*regs));
 	regs->hw.pc = entry;
-	regs->hw.psr = 0x01000000;
-	regs->sw.lr = 0xFFFFFFF9;
+	regs->hw.psr = 0x01000000U;
+	regs->sw.lr = (void *)0xFFFFFFF9U;
 }
 
 void sched_switch_early(enum proc_state state)

kernel/sched.c

@@ -102,7 +102,7 @@ struct process *sched_process_create(void (*entry)(void))
 	}
 
 	proc->pid = pid;
-	proc->stack_bottom = &_estack - (pid * CONFIG_STACKSZ);
+	proc->stack_bottom = &_estack - (pid * (signed)CONFIG_STACKSZ);
 	proc->lastexec = 0;
 	proc->sleep_usecs = 0;
 	proc->state = PROC_QUEUE;