thermosphere: add in basic hypervisor skeleton

thermosphere/src/regs.h

@@ -0,0 +1,62 @@
+/**
+ * Thermosphère: register access primitives
+ * Copyright (c) Kate J. Temkin <k@ktemkin.com>
+ */
+
+#ifndef __REGS_H__
+#define __REGS_H__
+
+/**
+ * Access to system registers.
+ */
+#define WRITE_SYSREG(sysreg, val, type) \
+    asm volatile ("msr        "#sysreg", %0\n" : : "r"((type)(val)))
+#define READ_SYSREG(sysreg, val, type) \
+    asm volatile ("mrs        %0, "#sysreg"\n" : "=r"((type)(val)))
+
+#define READ_SYSREG_32(sysreg, val)   READ_SYSREG(sysreg, val, uint32_t)
+#define WRITE_SYSREG_32(sysreg, val)  WRITE_SYSREG(sysreg, val, uint32_t)
+
+#define READ_SYSREG_64(sysreg, val)   READ_SYSREG(sysreg, val, uint64_t)
+#define WRITE_SYSREG_64(sysreg, val)  WRITE_SYSREG(sysreg, val, uint64_t)
+
+
+/**
+ * Returns the system's current Execution Level (EL).
+ */
+inline static uint32_t get_current_el(void) {
+    uint32_t val;
+
+    // Read the CurrentEl register, and extract the bits that tell us our EL.
+    READ_SYSREG_32(CurrentEl, val);
+    return val >> 2;
+}
+
+/**
+ * Sets the base address of the EL2 exception table.
+ */
+inline static void set_vbar_el2(void * address) {
+    WRITE_SYSREG_64(vbar_el2, (uint64_t)address);
+}
+
+
+/**
+ * Sets the address to 'return to' when leaving EL2.
+ */
+inline static void set_elr_el2(void * address) {
+    WRITE_SYSREG_64(elr_el2, (uint64_t)address);
+}
+
+
+/**
+ * Returns the MMU status bit from the SCTLR register.
+ */
+inline static uint32_t get_el2_mmu_status(void) {
+    uint32_t val;
+
+    // Read the CurrentEl register, and extract the bits that tell us our EL.
+    READ_SYSREG_32(sctlr_el2, val);
+    return val & 1;
+}
+
+#endif