debug/programs/mprv.S

   1 #include "../../env/encoding.h"
   2 #define PGSHIFT         12
   3
   4         .global         main
   5
   6         .section        .text
   7 main:
   8         # Set up a page table entry that maps 0x0... to 0x8...
   9         la      t0, page_table
  10         srli    t0, t0, PGSHIFT
  11         csrw    CSR_SPTBR, t0
  12
  13         # update mstatus
  14         csrr    t1, CSR_MSTATUS
  15 #if XLEN == 32
  16         li      t0, (MSTATUS_MPRV | (VM_SV32 << 24))
  17 #else
  18         li      t0, (MSTATUS_MPRV | (VM_SV39 << 24))
  19 #endif
  20         #li      t0, ((VM_SV39 << 24))
  21         or      t1, t0, t1
  22         csrw    CSR_MSTATUS, t1
  23
  24         la      t0, (loop - 0x80000000)
  25         csrw    CSR_MEPC, t0
  26
  27         # Exit supervisor mode, entering user mode at loop.
  28         mret
  29
  30 loop:
  31         la      t0, data
  32         lw      t1, 0(t0)
  33         j       loop
  34
  35         .section        .data
  36 data:
  37         .word   0xbead
  38
  39         .balign 0x1000
  40 page_table:
  41 #if XLEN == 32
  42         .word   ((0x80000000 >> 2) | PTE_V | PTE_R | PTE_W | PTE_X | PTE_G | PTE_U)
  43 #else
  44         .word   ((0x80000000 >> 2) | PTE_V | PTE_R | PTE_W | PTE_X | PTE_G | PTE_U)
  45         .word   0
  46 #endif