.option norvc
.option norelax

.section .text
.globl _start
.globl vm_boot

# --------------------------------------------------
# Entry point
# --------------------------------------------------
_start:
vm_boot:
    # Only hart 0
    csrr    a0, mhartid
    bnez    a0, hang.   

    # --------------------------------------------------
    # Build page table entries
    # --------------------------------------------------

    # root_pt[0] -> l1_pt
    la      t0, l1_pt
    srli    t0, t0, 12
    slli    t0, t0, 10
    ori     t0, t0, 0x1          # V
    la      t1, root_pt
    sd      t0, 0(t1)

    # l1_pt[0] -> l0_pt
    la      t0, l0_pt
    srli    t0, t0, 12
    slli    t0, t0, 10
    ori     t0, t0, 0x1          # V
    la      t1, l1_pt
    sd      t0, 0(t1)

    # l0_pt[0] -> identity RWX mapping
    li      t0, (1<<0)|(1<<1)|(1<<2)|(1<<3)|(1<<4)|(1<<6)
    la      t1, l0_pt
    sd      t0, 0(t1)

    # --------------------------------------------------
    # Enable Sv39 paging
    # --------------------------------------------------

    la      t0, root_pt
    srli    t0, t0, 12            # PPN
    li      t1, (8 << 60)          # MODE = Sv39
    or      t0, t0, t1
    csrw    satp, t0
    sfence.vma zero, zero

    # Signal success
    la      t0, tohost
    li      t1, 1
    sd      t1, 0(t0)

hang:
    wfi
    j hang

# --------------------------------------------------
# Required ISA test symbols
# --------------------------------------------------

.globl exit
exit:
    j exit

# --------------------------------------------------
# Data section (NO .bss)
# --------------------------------------------------

.section .data
.align 3

.globl tohost
.globl fromhost
tohost:
    .dword 0
fromhost:
    .dword 0

# --------------------------------------------------
# Page tables (must be in .data)
# --------------------------------------------------

.align 12
root_pt:
    .zero 4096

.align 12
l1_pt:
    .zero 4096

.align 12
l0_pt:
    .zero 4096