HelenOS sources

root/boot/arch/riscv64/src/asm.S

#
# Copyright (c) 2016 Martin Decky
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# - Redistributions of source code must retain the above copyright
#   notice, this list of conditions and the following disclaimer.
# - Redistributions in binary form must reproduce the above copyright
#   notice, this list of conditions and the following disclaimer in the
#   documentation and/or other materials provided with the distribution.
# - The name of the author may not be used to endorse or promote products
#   derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#

#include <abi/asmtool.h>
#include <arch/arch.h>
#include <arch/mm.h>

#define MCOUNTEREN_CY_MASK  0x00000001
#define MCOUNTEREN_TM_MASK  0x00000002
#define MCOUNTEREN_IR_MASK  0x00000004

#define MSTATUS_MPP_MASK        0x00001800
#define MSTATUS_MPP_USER        0x00000000
#define MSTATUS_MPP_SUPERVISOR  0x00000800
#define MSTATUS_MPP_MACHINE     0x00001800

#define MSTATUS_SUM_MASK        0x00040000

#define SATP_PFN_MASK  0x00000fffffffffff

#define SATP_MODE_MASK  0xf000000000000000
#define SATP_MODE_BARE  0x0000000000000000
#define SATP_MODE_SV39  0x8000000000000000
#define SATP_MODE_SV48  0x9000000000000000

.section BOOTSTRAP

.org DEFAULT_MTVEC + TRAP_VECTOR_RESET
SYMBOL(start)
        /* Set up machine state */
        li x1, 0
        li x2, 0
        li x3, 0
        li x4, 0
        li x5, 0
        li x6, 0
        li x7, 0
        li x8, 0
        li x9, 0
        li x10, 0
        li x11, 0
        li x12, 0
        li x13, 0
        li x14, 0
        li x15, 0
        li x16, 0
        li x17, 0
        li x18, 0
        li x19, 0
        li x20, 0
        li x21, 0
        li x22, 0
        li x23, 0
        li x24, 0
        li x25, 0
        li x26, 0
        li x27, 0
        li x28, 0
        li x29, 0
        li x30, 0
        li x31, 0

        /* Set up stack, create stack frame */
        la sp, boot_stack + BOOT_STACK_SIZE
        addi sp, sp, -16

        j bootstrap

.text

FUNCTION_BEGIN(jump_to_kernel)
        /* Enable performance counters access in supervisor mode */
        csrsi mcounteren, MCOUNTEREN_CY_MASK | MCOUNTEREN_TM_MASK | MCOUNTEREN_IR_MASK

        /* Setup SV48 paging for supervisor mode */
        la t0, ptl_0
        srli t0, t0, 12

        li t1, SATP_PFN_MASK
        and t0, t0, t1

        li t1, SATP_MODE_SV48
        or t0, t0, t1

        csrw sptbr, t0

        /* Jump to supervisor mode */
        csrr t0, mstatus

        li t1, ~MSTATUS_MPP_MASK
        and t0, t0, t1

        /*
         * TODO: Enable running with Supervisor User Mode
         * access disabled.
         */
        li t1, MSTATUS_MPP_SUPERVISOR | MSTATUS_SUM_MASK
        or t0, t0, t1

        csrw mstatus, t0

        /* Entry point address is in a1. */
        mv ra, a1
        csrw mepc, ra

        mret
FUNCTION_END(jump_to_kernel)

FUNCTION_BEGIN(halt)
        j halt
FUNCTION_END(halt)

.data

.align PAGE_WIDTH
SYMBOL(boot_stack)
        .space BOOT_STACK_SIZE

.section .pt, "aw", @progbits

.align PAGE_WIDTH
SYMBOL(ptl_0)
        .fill 256, 8, 0
        /* Identity mapping for [0; 512G) */
        .quad 0 + (PTL_DIRTY | PTL_ACCESSED | PTL_EXECUTABLE | PTL_WRITABLE | PTL_READABLE | PTL_VALID)
        .fill 255, 8, 0