Some machine specific code for reading and writing registers

riscv.h

@@ -1,8 +1,73 @@
+#ifndef RISCV_KERNEL_H
+#define RISCV_KERNEL_H
+
 #include <types.h>
 
+// Supervisor Status Register, sstatus
+
+/** Supervisor Previous Privilege */
+#define SSTATUS_SPP (1L << 8) // Previous mode, 1=Supervisor, 0=User
+
+/** Supervisor Previous Interrupt Enable */
+#define SSTATUS_SPIE (1L << 5)
+
+/** User Previous Interrupt Enable */
+#define SSTATUS_UPIE (1L << 4)
+
+/** Supervisor Interrupt Enable */
+#define SSTATUS_SIE (1L << 1)
+
+/** User Interrupt Enable */
+#define SSTATUS_UIE (1L << 0)
+
+/** Page Table Entry Type */
+typedef u64 pte_t;
+
+/** Page Table Type */
+typedef u64 *pagetable_t; // 512 PTEs
+
 /** Returns the current hart id */
 static inline u64 r_mhartid() {
     u64 x;
     asm volatile("csrr %0, mhartid" : "=r"(x));
     return x;
 }
+
+/** Read thread pointer */
+static inline u64 r_tp() {
+    u64 x;
+    asm volatile("mv %0, tp" : "=r"(x));
+    return x;
+}
+
+/**
+ * Read the value of the sstatus register.
+ * (Supervisor Status Register)
+ */
+static inline u64 r_sstatus() {
+    u64 x;
+    asm volatile("csrr %0, sstatus" : "=r"(x));
+    return x;
+}
+
+/**
+ * Write a value to the sstatus register.
+ * (Supervisor Status Register)
+ */
+static inline void w_sstatus(u64 x) {
+    asm volatile("csrw sstatus, %0" : : "r"(x));
+}
+
+/** Enable device interrupts */
+static inline void intr_on() { w_sstatus(r_sstatus() | SSTATUS_SIE); }
+
+/** Disable device interrupts */
+static inline void intr_off() { w_sstatus(r_sstatus() & ~SSTATUS_SIE); }
+
+/** Are device interrupts enabled? */
+static inline int intr_get() {
+    u64 x = r_sstatus();
+    return (x & SSTATUS_SIE) != 0;
+}
+
+#endif