/**
 * 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